{-# LANGUAGE LambdaCase #-}
{-
ToDo [Oct 2013]
~~~~~~~~~~~~~~~
1. Nuke ForceSpecConstr for good (it is subsumed by GHC.Types.SPEC in ghc-prim)
2. Nuke NoSpecConstr


(c) The GRASP/AQUA Project, Glasgow University, 1992-1998

\section[SpecConstr]{Specialise over constructors}
-}



{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

module GHC.Core.Opt.SpecConstr(
        specConstrProgram,
        SpecConstrAnnotation(..),
        SpecFailWarning(..)
    ) where

import GHC.Prelude

import GHC.Driver.DynFlags ( DynFlags(..), GeneralFlag( Opt_SpecConstrKeen )
                          , gopt, hasPprDebug )

import GHC.Core
import GHC.Core.Subst
import GHC.Core.Utils
import GHC.Core.Unfold
import GHC.Core.Opt.Simplify.Inline
import GHC.Core.FVs     ( exprsFreeVarsList, exprFreeVars )
import GHC.Core.Opt.Monad
import GHC.Core.Opt.WorkWrap.Utils
import GHC.Core.Opt.OccurAnal( BinderSwapDecision(..), scrutOkForBinderSwap )
import GHC.Core.DataCon
import GHC.Core.Class( classTyVars )
import GHC.Core.Coercion hiding( substCo )
import GHC.Core.Rules
import GHC.Core.Predicate ( typeDeterminesValue )
import GHC.Core.Type     hiding ( substTy )
import GHC.Core.TyCon   (TyCon, tyConName )
import GHC.Core.Multiplicity
import GHC.Core.Ppr     ( pprParendExpr )
import GHC.Core.Make    ( mkImpossibleExpr )

import GHC.Unit.Module
import GHC.Unit.Module.ModGuts

import GHC.Types.Error (MessageClass(..), Severity(..), DiagnosticReason(WarningWithoutFlag), ResolvedDiagnosticReason (..))
import GHC.Types.Literal ( litIsLifted )
import GHC.Types.Id
import GHC.Types.Id.Info ( IdDetails(..) )
import GHC.Types.Id.Make ( voidArgId, voidPrimId )
import GHC.Types.Var.Env
import GHC.Types.Var.Set
import GHC.Types.Name
import GHC.Types.Tickish
import GHC.Types.Basic
import GHC.Types.Demand
import GHC.Types.Cpr
import GHC.Types.Unique.Supply
import GHC.Types.Unique.FM
import GHC.Types.Unique( hasKey )

import GHC.Data.Maybe     ( orElse, catMaybes, isJust, isNothing )
import GHC.Data.FastString

import GHC.Utils.Misc
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Utils.Constants (debugIsOn)
import GHC.Utils.Monad

import GHC.Builtin.Names ( specTyConKey )

import GHC.Exts( SpecConstrAnnotation(..) )
import GHC.Serialized   ( deserializeWithData )

import Control.Monad
import Data.List ( sortBy, partition, dropWhileEnd, mapAccumL )
import Data.Maybe( mapMaybe )
import Data.Ord( comparing )
import Data.Tuple

{-
-----------------------------------------------------
                        Game plan
-----------------------------------------------------

Consider
        drop n []     = []
        drop 0 xs     = []
        drop n (x:xs) = drop (n-1) xs

After the first time round, we could pass n unboxed.  This happens in
numerical code too.  Here's what it looks like in Core:

        drop n xs = case xs of
                      []     -> []
                      (y:ys) -> case n of
                                  I# n# -> case n# of
                                             0 -> []
                                             _ -> drop (I# (n# -# 1#)) xs

Notice that the recursive call has an explicit constructor as argument.
Noticing this, we can make a specialised version of drop

        RULE: drop (I# n#) xs ==> drop' n# xs

        drop' n# xs = let n = I# n# in ...orig RHS...

Now the simplifier will apply the specialisation in the rhs of drop', giving

        drop' n# xs = case xs of
                      []     -> []
                      (y:ys) -> case n# of
                                  0 -> []
                                  _ -> drop' (n# -# 1#) xs

Much better!

We'd also like to catch cases where a parameter is carried along unchanged,
but evaluated each time round the loop:

        f i n = if i>0 || i>n then i else f (i*2) n

Here f isn't strict in n, but we'd like to avoid evaluating it each iteration.
In Core, by the time we've w/wd (f is strict in i) we get

        f i# n = case i# ># 0 of
                   False -> I# i#
                   True  -> case n of { I# n# ->
                            case i# ># n# of
                                False -> I# i#
                                True  -> f (i# *# 2#) n

At the call to f, we see that the argument, n is known to be (I# n#),
and n is evaluated elsewhere in the body of f, so we can play the same
trick as above.


Note [Reboxing]
~~~~~~~~~~~~~~~
We must be careful not to allocate the same constructor twice.  Consider
        f p = (...(case p of (a,b) -> e)...p...,
               ...let t = (r,s) in ...t...(f t)...)
At the recursive call to f, we can see that t is a pair.  But we do NOT want
to make a specialised copy:
        f' a b = let p = (a,b) in (..., ...)
because now t is allocated by the caller, then r and s are passed to the
recursive call, which allocates the (r,s) pair again.

This happens if
  (a) the argument p is used in other than a case-scrutinisation way.
  (b) the argument to the call is not a 'fresh' tuple; you have to
        look into its unfolding to see that it's a tuple

Hence the "OR" part of Note [Good arguments] below.

ALTERNATIVE 2: pass both boxed and unboxed versions.  This no longer saves
allocation, but does perhaps save evals. In the RULE we'd have
something like

  f (I# x#) = f' (I# x#) x#

If at the call site the (I# x) was an unfolding, then we'd have to
rely on CSE to eliminate the duplicate allocation.... This alternative
doesn't look attractive enough to pursue.

ALTERNATIVE 3: ignore the reboxing problem.  The trouble is that
the conservative reboxing story prevents many useful functions from being
specialised.  Example:
        foo :: Maybe Int -> Int -> Int
        foo   (Just m) 0 = 0
        foo x@(Just m) n = foo x (n-m)
Here the use of 'x' will clearly not require boxing in the specialised function.

The strictness analyser has the same problem, in fact.  Example:
        f p@(a,b) = ...
If we pass just 'a' and 'b' to the worker, it might need to rebox the
pair to create (a,b).  A more sophisticated analysis might figure out
precisely the cases in which this could happen, but the strictness
analyser does no such analysis; it just passes 'a' and 'b', and hopes
for the best.

So my current choice is to make SpecConstr similarly aggressive, and
ignore the bad potential of reboxing.


Note [Good arguments]
~~~~~~~~~~~~~~~~~~~~~
So we look for

* A self-recursive function.  Ignore mutual recursion for now,
  because it's less common, and the code is simpler for self-recursion.

* EITHER

   a) At a recursive call, one or more parameters is an explicit
      constructor application
        AND
      That same parameter is scrutinised by a case somewhere in
      the RHS of the function

  OR

    b) At a recursive call, one or more parameters has an unfolding
       that is an explicit constructor application
        AND
      That same parameter is scrutinised by a case somewhere in
      the RHS of the function
        AND
      Those are the only uses of the parameter (see Note [Reboxing])


What to abstract over
~~~~~~~~~~~~~~~~~~~~~
There's a bit of a complication with type arguments.  If the call
site looks like

        f p = ...f ((:) [a] x xs)...

then our specialised function look like

        f_spec x xs = let p = (:) [a] x xs in ....as before....

This only makes sense if either
  a) the type variable 'a' is in scope at the top of f, or
  b) the type variable 'a' is an argument to f (and hence fs)

Actually, (a) may hold for value arguments too, in which case
we may not want to pass them.  Suppose 'x' is in scope at f's
defn, but xs is not.  Then we'd like

        f_spec xs = let p = (:) [a] x xs in ....as before....

Similarly (b) may hold too.  If x is already an argument at the
call, no need to pass it again.

Finally, if 'a' is not in scope at the call site, we could abstract
it as we do the term variables:

        f_spec a x xs = let p = (:) [a] x xs in ...as before...

So the grand plan is:

        * abstract the call site to a constructor-only pattern
          e.g.  C x (D (f p) (g q))  ==>  C s1 (D s2 s3)

        * Find the free variables of the abstracted pattern

        * Pass these variables, less any that are in scope at
          the fn defn.  But see Note [Shadowing in SpecConstr] below.


NOTICE that we only abstract over variables that are not in scope,
so we're in no danger of shadowing variables used in "higher up"
in f_spec's RHS.


Note [Shadowing in SpecConstr]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In this pass we gather up usage information that may mention variables
that are bound between the usage site and the definition site; or (more
seriously) may be bound to something different at the definition site.
For example:

        f x = letrec g y v = let x = ...
                             in ...(g (a,b) x)...

Since 'x' is in scope at the call site, we may make a rewrite rule that
looks like
        RULE forall a,b. g (a,b) x = ...
But this rule will never match, because it's really a different 'x' at
the call site -- and that difference will be manifest by the time the
simplifier gets to it.  [A worry: the simplifier doesn't *guarantee*
no-shadowing, so perhaps it may not be distinct?]

Anyway, the rule isn't actually wrong, it's just not useful.  One possibility
is to run deShadowBinds before running SpecConstr, but instead we run the
simplifier.  That gives the simplest possible program for SpecConstr to
chew on; and it virtually guarantees no shadowing.

Note [Specialising for constant parameters]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This one is about specialising on a *constant* (but not necessarily
constructor) argument

    foo :: Int -> (Int -> Int) -> Int
    foo 0 f = 0
    foo m f = foo (f m) (+1)

It produces

    lvl_rmV :: GHC.Base.Int -> GHC.Base.Int
    lvl_rmV =
      \ (ds_dlk :: GHC.Base.Int) ->
        case ds_dlk of wild_alH { GHC.Base.I# x_alG ->
        GHC.Base.I# (GHC.Prim.+# x_alG 1)

    T.$wfoo :: GHC.Prim.Int# -> (GHC.Base.Int -> GHC.Base.Int) ->
    GHC.Prim.Int#
    T.$wfoo =
      \ (ww_sme :: GHC.Prim.Int#) (w_smg :: GHC.Base.Int -> GHC.Base.Int) ->
        case ww_sme of ds_Xlw {
          __DEFAULT ->
        case w_smg (GHC.Base.I# ds_Xlw) of w1_Xmo { GHC.Base.I# ww1_Xmz ->
        T.$wfoo ww1_Xmz lvl_rmV
        };
          0 -> 0
        }

The recursive call has lvl_rmV as its argument, so we could create a specialised copy
with that argument baked in; that is, not passed at all.   Now it can perhaps be inlined.

When is this worth it?  Call the constant 'lvl'
- If 'lvl' has an unfolding that is a constructor, see if the corresponding
  parameter is scrutinised anywhere in the body.

- If 'lvl' has an unfolding that is a inlinable function, see if the corresponding
  parameter is applied (...to enough arguments...?)

  Also do this is if the function has RULES?

Also

Note [Specialising for lambda parameters]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    foo :: Int -> (Int -> Int) -> Int
    foo 0 f = 0
    foo m f = foo (f m) (\n -> n-m)

This is subtly different from the previous one in that we get an
explicit lambda as the argument:

    T.$wfoo :: GHC.Prim.Int# -> (GHC.Base.Int -> GHC.Base.Int) ->
    GHC.Prim.Int#
    T.$wfoo =
      \ (ww_sm8 :: GHC.Prim.Int#) (w_sma :: GHC.Base.Int -> GHC.Base.Int) ->
        case ww_sm8 of ds_Xlr {
          __DEFAULT ->
        case w_sma (GHC.Base.I# ds_Xlr) of w1_Xmf { GHC.Base.I# ww1_Xmq ->
        T.$wfoo
          ww1_Xmq
          (\ (n_ad3 :: GHC.Base.Int) ->
             case n_ad3 of wild_alB { GHC.Base.I# x_alA ->
             GHC.Base.I# (GHC.Prim.-# x_alA ds_Xlr)
             })
        };
          0 -> 0
        }

I wonder if SpecConstr couldn't be extended to handle this? After all,
lambda is a sort of constructor for functions and perhaps it already
has most of the necessary machinery?

Furthermore, there's an immediate win, because you don't need to allocate the lambda
at the call site; and if perchance it's called in the recursive call, then you
may avoid allocating it altogether.  Just like for constructors.

Looks cool, but probably rare...but it might be easy to implement.


Note [SpecConstr for casts]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
    data family T a :: *
    data instance T Int = T Int

    foo n = ...
       where
         go (T 0) = 0
         go (T n) = go (T (n-1))

The recursive call ends up looking like
        go (T (I# ...) `cast` g)
So we want to spot the constructor application inside the cast.
That's why we have the Cast case in argToPat

Note [Seeding recursive groups]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
For a recursive group that is either
  * nested, or
  * top-level, but with no exported Ids
we can see all the calls to the function, so we seed the specialisation
loop from the calls in the body, and /not/ from the calls in the RHS.
Consider:

  bar m n = foo n (n,n) (n,n) (n,n) (n,n)
   where
     foo n p q r s
       | n == 0    = m
       | n > 3000  = case p of { (p1,p2) -> foo (n-1) (p2,p1) q r s }
       | n > 2000  = case q of { (q1,q2) -> foo (n-1) p (q2,q1) r s }
       | n > 1000  = case r of { (r1,r2) -> foo (n-1) p q (r2,r1) s }
       | otherwise = case s of { (s1,s2) -> foo (n-1) p q r (s2,s1) }

If we start with the RHSs of 'foo', we get lots and lots of specialisations,
most of which are not needed.  But if we start with the (single) call
in the rhs of 'bar' we get exactly one fully-specialised copy, and all
the recursive calls go to this fully-specialised copy. Indeed, the original
function is later collected as dead code.  This is very important in
specialising the loops arising from stream fusion, for example in NDP where
we were getting literally hundreds of (mostly unused) specialisations of
a local function.

In a case like the above we end up never calling the original un-specialised
function.  (Although we still leave its code around just in case.)

Wrinkles

* Boring calls. If we find any boring calls in the body, including
  *unsaturated* ones, such as
      letrec foo x y = ....foo...
      in map foo xs
  then we will end up calling the un-specialised function, so then we
  *should* use the calls in the un-specialised RHS as seeds.  We call
  these "boring call patterns", and callsToNewPats reports if it finds
  any of these.  Then 'specialise' unleashes the usage info from the
  un-specialised RHS.

* Exported Ids. `specialise` /also/ unleashes `si_mb_unspec`
  for exported Ids.  That way we are sure to generate usage info from
  the /un-specialised/ RHS of an exported function.

More precisely:

* Always start from the calls in the body of the let or (for top level)
  calls in the rest of the module.  See the body_calls in the call to
  `specialise` in `specNonRec`, and to `go` in `specRec`.

* si_mb_unspec holds the usage from the unspecialised RHS.
  See `initSpecInfo`.

* `specialise` will unleash si_mb_unspec, if
  - `callsToNewPats` reports "boring calls found", or
  - this is a top-level exported Id.

Historical note.  At an earlier point, if a top-level Id was exported,
we used only seeds from the RHS, and /not/from the body. But Dimitrios
had an example where using call patterns from the body (the other defns
in the module) was crucial.  And doing so improved nofib allocation results:
    multiplier: 4%   better
    minimax:    2.8% better
In any case, it is easier to do!

Note [Do not specialise diverging functions]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Specialising a function that just diverges is a waste of code.
Furthermore, it broke GHC (simpl014) thus:
   {-# STR Sb #-}
   f = \x. case x of (a,b) -> f x
If we specialise f we get
   f = \x. case x of (a,b) -> fspec a b
But fspec doesn't have decent strictness info.  As it happened,
(f x) :: IO t, so the state hack applied and we eta expanded fspec,
and hence f.  But now f's strictness is less than its arity, which
breaks an invariant.


Note [Forcing specialisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
With stream fusion and in other similar cases, we want to fully
specialise some (but not necessarily all!) loops regardless of their
size and the number of specialisations.

We allow a library to do this, in one of two ways (one which is
deprecated):

  1) Add a parameter of type GHC.Types.SPEC (from ghc-prim) to the loop body.

  2) (Deprecated) Annotate a type with ForceSpecConstr from GHC.Exts,
     and then add *that* type as a parameter to the loop body

The reason #2 is deprecated is because it requires GHCi, which isn't
available for things like a cross compiler using stage1.

Here's a (simplified) example from the `vector` package. You may bring
the special 'force specialization' type into scope by saying:

  import GHC.Types (SPEC(..))

or by defining your own type (again, deprecated):

  data SPEC = SPEC | SPEC2
  {-# ANN type SPEC ForceSpecConstr #-}

(Note this is the exact same definition of GHC.Types.SPEC, just
without the annotation.)

After that, you say:

  foldl :: (a -> b -> a) -> a -> Stream b -> a
  {-# INLINE foldl #-}
  foldl f z (Stream step s _) = foldl_loop SPEC z s
    where
      foldl_loop !sPEC z s = case step s of
                              Yield x s' -> foldl_loop sPEC (f z x) s'
                              Skip       -> foldl_loop sPEC z s'
                              Done       -> z

SpecConstr will spot the SPEC parameter and always fully specialise
foldl_loop. Note that

  * We have to prevent the SPEC argument from being removed by
    w/w which is why (a) SPEC is a sum type, and (b) we have to seq on
    the SPEC argument.

  * And lastly, the SPEC argument is ultimately eliminated by
    SpecConstr itself so there is no runtime overhead.

This is all quite ugly; we ought to come up with a better design.

ForceSpecConstr arguments are spotted in scExpr' and scTopBinds which then set
sc_force to True when calling specLoop. This flag does four things:

(FS1) Ignore specConstrThreshold, to specialise functions of arbitrary size
        (see scTopBind)
(FS2) Ignore specConstrCount, to make arbitrary numbers of specialisations
        (see specialise)
(FS3) Specialise even for arguments that are not scrutinised in the loop
        (see argToPat; #4448)
(FS4) Only specialise on recursive types a finite number of times
        (see sc_recursive; #5550; Note [Limit recursive specialisation])
(FS5) Use a different restriction on the maximum number of arguments which
        the optimisation will specialise. We tried removing the limit on worker
        args for forced specs (#14003) but this caused issues when specializing
        code for large data structures (#25197).
        This is handled by `too_many_worker_args` in `callsToNewPats`

The flag holds only for specialising a single binding group, and NOT
for nested bindings.  (So really it should be passed around explicitly
and not stored in ScEnv.)  #14379 turned out to be caused by
   f SPEC x = let g1 x = ...
              in ...
We force-specialise f (because of the SPEC), but that generates a specialised
copy of g1 (as well as the original).  Alas g1 has a nested binding g2; and
in each copy of g1 we get an unspecialised and specialised copy of g2; and so
on. Result, exponential.  So the force-spec flag now only applies to one
level of bindings at a time.

Mechanism for this one-level-only thing:

 - Switch it on at the call to specRec, in scExpr and scTopBinds
 - Switch it off when doing the RHSs;
   this can be done very conveniently in decreaseSpecCount

What alternatives did I consider?

* Annotating the loop itself doesn't work because (a) it is local and
  (b) it will be w/w'ed and having w/w propagating annotations somehow
  doesn't seem like a good idea. The types of the loop arguments
  really seem to be the most persistent thing.

* Annotating the types that make up the loop state doesn't work,
  either, because (a) it would prevent us from using types like Either
  or tuples here, (b) we don't want to restrict the set of types that
  can be used in Stream states and (c) some types are fixed by the
  user (e.g., the accumulator here) but we still want to specialise as
  much as possible.

Alternatives to ForceSpecConstr
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Instead of giving the loop an extra argument of type SPEC, we
also considered *wrapping* arguments in SPEC, thus
  data SPEC a = SPEC a | SPEC2

  loop = \arg -> case arg of
                     SPEC state ->
                        case state of (x,y) -> ... loop (SPEC (x',y')) ...
                        S2 -> error ...
The idea is that a SPEC argument says "specialise this argument
regardless of whether the function case-analyses it".  But this
doesn't work well:
  * SPEC must still be a sum type, else the strictness analyser
    eliminates it
  * But that means that 'loop' won't be strict in its real payload
This loss of strictness in turn screws up specialisation, because
we may end up with calls like
   loop (SPEC (case z of (p,q) -> (q,p)))
Without the SPEC, if 'loop' were strict, the case would move out
and we'd see loop applied to a pair. But if 'loop' isn't strict
this doesn't look like a specialisable call.

Note [Limit recursive specialisation]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is possible for ForceSpecConstr to cause an infinite loop of specialisation.
Because there is no limit on the number of specialisations, a recursive call with
a recursive constructor as an argument (for example, list cons) will generate
a specialisation for that constructor. If the resulting specialisation also
contains a recursive call with the constructor, this could proceed indefinitely.

For example, if ForceSpecConstr is on:
  loop :: [Int] -> [Int] -> [Int]
  loop z []         = z
  loop z (x:xs)     = loop (x:z) xs
this example will create a specialisation for the pattern
  loop (a:b) c      = loop' a b c

  loop' a b []      = (a:b)
  loop' a b (x:xs)  = loop (x:(a:b)) xs
and a new pattern is found:
  loop (a:(b:c)) d  = loop'' a b c d
which can continue indefinitely.

Roman's suggestion to fix this was to stop after a couple of times on recursive types,
but still specialising on non-recursive types as much as possible.

To implement this, we count the number of times we have gone round the
"specialise recursively" loop ('go' in 'specRec').  Once have gone round
more than N times (controlled by -fspec-constr-recursive=N) we check

  - If sc_force is off, and sc_count is (Just max) then we don't
    need to do anything: trim_pats will limit the number of specs

  - Otherwise check if any function has now got more than (sc_count env)
    specialisations.  If sc_count is "no limit" then we arbitrarily
    choose 10 as the limit (ugh).

See #5550.   Also #13623, where this test had become over-aggressive,
and we lost a wonderful specialisation that we really wanted!

Note [NoSpecConstr]
~~~~~~~~~~~~~~~~~~~
The ignoreDataCon stuff allows you to say
    {-# ANN type T NoSpecConstr #-}
to mean "don't specialise on arguments of this type".  It was added
before we had ForceSpecConstr.  Lacking ForceSpecConstr we specialised
regardless of size; and then we needed a way to turn that *off*.  Now
that we have ForceSpecConstr, this NoSpecConstr is probably redundant.
(Used only for PArray, TODO: remove?)

Note [SpecConstr and strict fields]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We treat strict fields in SpecConstr the same way we do in W/W.
That is we make the specialized function strict in arguments
representing strict fields. See Note [Call-by-value for worker args]
for why we do this.

(SCF1) The arg_id might be an /imported/ Id like M.foo_acf (see #24944).
  We don't want to make
     case M.foo_acf of M.foo_acf { DEFAULT -> blah }
  because the binder of a case-expression should never be imported.  Rather,
  we must localise it thus:
     case M.foo_acf of foo_acf { DEFAULT -> blah }
  We keep the same unique, so in the next round of simplification we'll replace
  any M.foo_acf's in `blah` by `foo_acf`.

  c.f. Note [Localise pattern binders] in GHC.HsToCore.Utils.

Note [Specialising on dictionaries]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In #21386, SpecConstr saw this call:

   $wgo 100# @.. ($fMonadStateT @.. @.. $fMonadIdentity)

where $wgo :: Int# -> forall m. Monad m => blah

You might think that the type-class Specialiser would have specialised
this, but there are good reasons why not: the Specialiser ran too early.
But regardless, SpecConstr can and should!  It's easy:

* isValue: treat ($fblah d1 .. dn)
  like a constructor application.

* scApp: treat (op_sel d), a class method selection,
  like a case expression

* Float that dictionary application to top level, thus
    lvl = $fMonadStateT @.. @.. $fMonadIdentity
  so the call looks like
    ($wgo 100# @.. lvl)

  Why? This way dictionaries will appear as top level binders which we
  can trivially match in rules.  (CSE runs before SpecConstr, so we
  may hope to common-up duplicate top-level dictionaries.)
  For the floating part, see the "Arguments" case of Note
  [Floating to the top] in GHC.Core.Opt.SetLevels.

  We could be more clever, perhaps, and generate a RULE like
     $wgo _  @.. ($fMonadStateT @.. @.. $fMonadIdentity) = $s$wgo ...
  but that would mean making argToPat able to spot dfun applications as
  well as constructor applications.

Wrinkles:

* This should all work perfectly fine for newtype classes.  Mind you,
  currently newtype classes are inlined fairly agressively, but we
  may change that. And it would take extra code to exclude them, as
  well as being unnecessary.

* In isValue, we (mis-) use LambdaVal for this ($fblah d1 .. dn)
  because ConVal requires us to list the data constructor and
  fields, and that is (a) inconvenient and (b) unnecessary for
  class methods.

-----------------------------------------------------
                Stuff not yet handled
-----------------------------------------------------

Here are notes arising from Roman's work that I don't want to lose.

Example 1
~~~~~~~~~
    data T a = T !a

    foo :: Int -> T Int -> Int
    foo 0 t = 0
    foo x t | even x    = case t of { T n -> foo (x-n) t }
            | otherwise = foo (x-1) t

SpecConstr does no specialisation, because the second recursive call
looks like a boxed use of the argument.  A pity.

    $wfoo_sFw :: GHC.Prim.Int# -> T.T GHC.Base.Int -> GHC.Prim.Int#
    $wfoo_sFw =
      \ (ww_sFo [Just L] :: GHC.Prim.Int#) (w_sFq [Just L] :: T.T GHC.Base.Int) ->
         case ww_sFo of ds_Xw6 [Just L] {
           __DEFAULT ->
                case GHC.Prim.remInt# ds_Xw6 2 of wild1_aEF [Dead Just A] {
                  __DEFAULT -> $wfoo_sFw (GHC.Prim.-# ds_Xw6 1) w_sFq;
                  0 ->
                    case w_sFq of wild_Xy [Just L] { T.T n_ad5 [Just U(L)] ->
                    case n_ad5 of wild1_aET [Just A] { GHC.Base.I# y_aES [Just L] ->
                    $wfoo_sFw (GHC.Prim.-# ds_Xw6 y_aES) wild_Xy
                    } } };
           0 -> 0

Example 2
~~~~~~~~~
    data a :*: b = !a :*: !b
    data T a = T !a

    foo :: (Int :*: T Int) -> Int
    foo (0 :*: t) = 0
    foo (x :*: t) | even x    = case t of { T n -> foo ((x-n) :*: t) }
                  | otherwise = foo ((x-1) :*: t)

Very similar to the previous one, except that the parameters are now in
a strict tuple. Before SpecConstr, we have

    $wfoo_sG3 :: GHC.Prim.Int# -> T.T GHC.Base.Int -> GHC.Prim.Int#
    $wfoo_sG3 =
      \ (ww_sFU [Just L] :: GHC.Prim.Int#) (ww_sFW [Just L] :: T.T
    GHC.Base.Int) ->
        case ww_sFU of ds_Xws [Just L] {
          __DEFAULT ->
        case GHC.Prim.remInt# ds_Xws 2 of wild1_aEZ [Dead Just A] {
          __DEFAULT ->
            case ww_sFW of tpl_B2 [Just L] { T.T a_sFo [Just A] ->
            $wfoo_sG3 (GHC.Prim.-# ds_Xws 1) tpl_B2             -- $wfoo1
            };
          0 ->
            case ww_sFW of wild_XB [Just A] { T.T n_ad7 [Just S(L)] ->
            case n_ad7 of wild1_aFd [Just L] { GHC.Base.I# y_aFc [Just L] ->
            $wfoo_sG3 (GHC.Prim.-# ds_Xws y_aFc) wild_XB        -- $wfoo2
            } } };
          0 -> 0 }

We get two specialisations:
"SC:$wfoo1" [0] __forall {a_sFB :: GHC.Base.Int sc_sGC :: GHC.Prim.Int#}
                  Foo.$wfoo sc_sGC (Foo.T @ GHC.Base.Int a_sFB)
                  = Foo.$s$wfoo1 a_sFB sc_sGC ;
"SC:$wfoo2" [0] __forall {y_aFp :: GHC.Prim.Int# sc_sGC :: GHC.Prim.Int#}
                  Foo.$wfoo sc_sGC (Foo.T @ GHC.Base.Int (GHC.Base.I# y_aFp))
                  = Foo.$s$wfoo y_aFp sc_sGC ;

But perhaps the first one isn't good.  After all, we know that tpl_B2 is
a T (I# x) really, because T is strict and Int has one constructor.  (We can't
unbox the strict fields, because T is polymorphic!)

************************************************************************
*                                                                      *
\subsection{Top level wrapper stuff}
*                                                                      *
************************************************************************
-}

specConstrProgram :: ModGuts -> CoreM ModGuts
specConstrProgram :: ModGuts -> CoreM ModGuts
specConstrProgram ModGuts
guts
  = do { env0 <- ModGuts -> CoreM ScEnv
initScEnv ModGuts
guts
       ; us   <- getUniqueSupplyM
       ; let (_usg, binds', warnings) = initUs_ us $
                              scTopBinds env0 (mg_binds guts)

       ; when (not (null warnings)) $ msg specConstr_warn_class (warn_msg warnings)

       ; return (guts { mg_binds = binds' }) }

  where
    specConstr_warn_class :: MessageClass
specConstr_warn_class = Severity
-> ResolvedDiagnosticReason -> Maybe DiagnosticCode -> MessageClass
MCDiagnostic Severity
SevWarning (DiagnosticReason -> ResolvedDiagnosticReason
ResolvedDiagnosticReason DiagnosticReason
WarningWithoutFlag) Maybe DiagnosticCode
forall a. Maybe a
Nothing
    warn_msg :: SpecFailWarnings -> SDoc
    warn_msg :: [SpecFailWarning] -> SDoc
warn_msg [SpecFailWarning]
warnings = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"SpecConstr encountered one or more function(s) with a SPEC argument that resulted in too many arguments," SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$
                        String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"which resulted in no specialization being generated for these functions:" SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$
                        Int -> SDoc -> SDoc
nest Int
2 ([SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat ((SpecFailWarning -> SDoc) -> [SpecFailWarning] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map SpecFailWarning -> SDoc
forall a. Outputable a => a -> SDoc
ppr [SpecFailWarning]
warnings)) SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$
                        (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"If this is expected you might want to increase -fmax-forced-spec-args to force specialization anyway.")
scTopBinds :: ScEnv -> [InBind] -> UniqSM (ScUsage, [OutBind], [SpecFailWarning])
scTopBinds :: ScEnv
-> [OutBind] -> UniqSM (ScUsage, [OutBind], [SpecFailWarning])
scTopBinds ScEnv
_env []     = (ScUsage, [OutBind], [SpecFailWarning])
-> UniqSM (ScUsage, [OutBind], [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, [], [])
scTopBinds ScEnv
env  (OutBind
b:[OutBind]
bs) = do { (usg, b', bs', warnings) <- TopLevelFlag
-> ScEnv
-> OutBind
-> (ScEnv -> UniqSM (ScUsage, [OutBind], [SpecFailWarning]))
-> UniqSM (ScUsage, [OutBind], [OutBind], [SpecFailWarning])
forall a.
TopLevelFlag
-> ScEnv
-> OutBind
-> (ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning]))
-> UniqSM (ScUsage, [OutBind], a, [SpecFailWarning])
scBind TopLevelFlag
TopLevel ScEnv
env OutBind
b ((ScEnv -> UniqSM (ScUsage, [OutBind], [SpecFailWarning]))
 -> UniqSM (ScUsage, [OutBind], [OutBind], [SpecFailWarning]))
-> (ScEnv -> UniqSM (ScUsage, [OutBind], [SpecFailWarning]))
-> UniqSM (ScUsage, [OutBind], [OutBind], [SpecFailWarning])
forall a b. (a -> b) -> a -> b
$
                                                (\ScEnv
env -> ScEnv
-> [OutBind] -> UniqSM (ScUsage, [OutBind], [SpecFailWarning])
scTopBinds ScEnv
env [OutBind]
bs)
                            ; return (usg, b' ++ bs', warnings) }

{-
************************************************************************
*                                                                      *
\subsection{Environment: goes downwards}
*                                                                      *
************************************************************************

Note [ConVal work-free-ness]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The sc_vals field keeps track of in-scope value bindings, and is used in
two ways:

(1) To do case-of-known-constructor in a case expression.  E.g. if sc_vals
    includes [x :-> ConVal Just e], then we can simplify
      case x of Just y -> ...
    with the case-of-known-constructor transformation. (Yes this is
    done by the Simplifier, but SpecConstr creates new opportunities when
    it makes a specialised RHS for a function.)

    For (1) it is crucial that the arguments are /work-free/; see (CV1)
    below.

(2) To figure out call pattresns. E.g. if sc_vals includes
    [x :-> ConVal Just e], and we have call (f x), then we might want
    to specialise `f (Just _)`

    For (2) it is /not/ important that the constructor arguments are work-free;
    indeed, it would be bad to insist on that. For example
       let x = Just <expensive>
       in ....(f x)...
    Here we want to specialise for `f (Just _)`, and we won't do so if we
    don't allow [x :-> ConVal Just e] into the environment.  Does this ever happen?
    Yes: see #24282.

    (Yes, the Simplifier will ANF that let-binding, but SpecConstr can
    make more: see (CV1) for an example.)

Wrinkle:

(CV1) Why is work-free-ness important for (1)?  In the example in (1) above, of `e` is
      expensive, we do /not/ want to simplify
         case x of { Just y -> ... }  ==>   let y = e in ...
      because the x-binding still exists and we've now duplicated `e`.

      This seldom happens because let-bound constructor applications are ANF-ised, but
      it can happen as a result of on-the-fly transformations in SpecConstr itself.
      Here is #7865:

              let { a'_shr =
                      case xs_af8 of _ {
                        [] -> acc_af6;
                        : ds_dgt [Dmd=<L,A>] ds_dgu [Dmd=<L,A>] ->
                          (expensive x_af7, x_af7
                      } } in
              let { ds_sht =
                      case a'_shr of _ { (p'_afd, q'_afe) ->
                      TSpecConstr_DoubleInline.recursive
                        (GHC.Types.: @ GHC.Types.Int x_af7 wild_X6) (q'_afe, p'_afd)
                      } } in

      When processed knowing that xs_af8 was bound to a cons, we simplify to
         a'_shr = (expensive x_af7, x_af7)
      and we do NOT want to inline that at the occurrence of a'_shr in ds_sht.
      (There are other occurrences of a'_shr.)  No no no.

      It would be possible to do some on-the-fly ANF-ising, so that a'_shr turned
      into a work-free value again, thus
         a1 = expensive x_af7
         a'_shr = (a1, x_af7)
      but that's more work, so until its shown to be important I'm going to
      leave it for now.

Note [Making SpecConstr keener]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this, in (perf/should_run/T9339)
   last (filter odd [1..1000])

After optimisation, including SpecConstr, we get:
   f :: Int# -> Int -> Int
   f x y = case remInt# x 2# of
             __DEFAULT -> case x of
                            __DEFAULT -> f (+# wild_Xp 1#) (I# x)
                            1000000# -> ...
             0# -> case x of
                     __DEFAULT -> f (+# wild_Xp 1#) y
                    1000000#   -> y

Not good!  We build an (I# x) box every time around the loop.
SpecConstr (as described in the paper) does not specialise f, despite
the call (f ... (I# x)) because 'y' is not scrutinised in the body.
But it is much better to specialise f for the case where the argument
is of form (I# x); then we build the box only when returning y, which
is on the cold path.

Another example:

   f x = ...(g x)....

Here 'x' is not scrutinised in f's body; but if we did specialise 'f'
then the call (g x) might allow 'g' to be specialised in turn.

So sc_keen controls whether or not we take account of whether argument is
scrutinised in the body.  True <=> ignore that, and specialise whenever
the function is applied to a data constructor.
-}

-- | Options for Specializing over constructors in Core.
data SpecConstrOpts = SpecConstrOpts
  { SpecConstrOpts -> Int
sc_max_args  :: !Int
  -- ^ The threshold at which a worker-wrapper transformation used as part of
  -- this pass will no longer happen, measured in the number of arguments.

  , SpecConstrOpts -> Int
sc_max_forced_args  :: !Int
  -- ^ The threshold at which a worker-wrapper transformation used as part of
  -- this pass will no longer happen even if a SPEC arg was used to force
  -- specialization. Measured in the number of arguments.
  -- See Note [Forcing specialisation]

  , SpecConstrOpts -> Bool
sc_debug     :: !Bool
  -- ^ Whether to print debug information

  , SpecConstrOpts -> UnfoldingOpts
sc_uf_opts   :: !UnfoldingOpts
  -- ^ Unfolding options

  , SpecConstrOpts -> Module
sc_module    :: !Module
  -- ^ The name of the module being processed

  , SpecConstrOpts -> Maybe Int
sc_size      :: !(Maybe Int)
  -- ^ Size threshold: Nothing => no limit

  , SpecConstrOpts -> Maybe Int
sc_count     :: !(Maybe Int)
  -- ^ Max # of specialisations for any one function. Nothing => no limit.
  -- See Note [Avoiding exponential blowup] and decreaseSpecCount

  , SpecConstrOpts -> Int
sc_recursive :: !Int
  -- ^ Max # of specialisations over recursive type. Stops
  -- ForceSpecConstr from diverging.

  , SpecConstrOpts -> Bool
sc_keen      :: !Bool
  -- ^ Specialise on arguments that are known constructors, even if they are
  -- not scrutinised in the body. See Note [Making SpecConstr keener].
  }

data ScEnv = SCE { ScEnv -> SpecConstrOpts
sc_opts      :: !SpecConstrOpts,
                   ScEnv -> Bool
sc_force     :: Bool,        -- Force specialisation?
                                                -- See Note [Forcing specialisation]

                   ScEnv -> Subst
sc_subst     :: Subst,       -- Current substitution
                                                -- Maps InIds to OutExprs

                   ScEnv -> HowBoundEnv
sc_how_bound :: HowBoundEnv,
                        -- Binds interesting non-top-level variables
                        -- Domain is OutVars (*after* applying the substitution)

                   ScEnv -> ValueEnv
sc_vals      :: ValueEnv,
                        -- Domain is OutIds (*after* applying the substitution)
                        -- Used even for top-level bindings (but not imported ones)

                   ScEnv -> UniqFM Name SpecConstrAnnotation
sc_annotations :: UniqFM Name SpecConstrAnnotation
             }

---------------------
type HowBoundEnv = VarEnv HowBound      -- Domain is OutVars

---------------------
type ValueEnv = IdEnv Value            -- Domain is OutIds

data Value = ConVal            -- Constructor application
                  Bool             -- True <=> all args are work-free
                                   --      See Note [ConVal work-free-ness]
                  AltCon           -- Never DEFAULT
                  [CoreArg]        -- Saturates the constructor
           | LambdaVal         -- Inlinable lambdas or PAPs

instance Outputable Value where
   ppr :: Value -> SDoc
ppr Value
LambdaVal            = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"<Lambda>"
   ppr (ConVal Bool
wf AltCon
con [Expr Id]
args)
     | [Expr Id] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Expr Id]
args = AltCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr AltCon
con
     | Bool
otherwise = SDoc -> SDoc
forall doc. IsLine doc => doc -> doc
parens (AltCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr AltCon
con SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc
braces SDoc
pp_wf SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> [Expr Id] -> SDoc
forall a. Outputable a => [a] -> SDoc
interpp'SP [Expr Id]
args)
     where
       pp_wf :: SDoc
pp_wf | Bool
wf        = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"wf"
             | Bool
otherwise = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"not-wf"


---------------------
initScOpts :: DynFlags -> Module -> SpecConstrOpts
initScOpts :: DynFlags -> Module -> SpecConstrOpts
initScOpts DynFlags
dflags Module
this_mod = SpecConstrOpts
        { sc_max_args :: Int
sc_max_args    = DynFlags -> Int
maxWorkerArgs DynFlags
dflags,
          sc_max_forced_args :: Int
sc_max_forced_args = DynFlags -> Int
maxForcedSpecArgs DynFlags
dflags,
          sc_debug :: Bool
sc_debug       = DynFlags -> Bool
hasPprDebug DynFlags
dflags,
          sc_uf_opts :: UnfoldingOpts
sc_uf_opts     = DynFlags -> UnfoldingOpts
unfoldingOpts DynFlags
dflags,
          sc_module :: Module
sc_module      = Module
this_mod,
          sc_size :: Maybe Int
sc_size        = DynFlags -> Maybe Int
specConstrThreshold DynFlags
dflags,
          sc_count :: Maybe Int
sc_count       = DynFlags -> Maybe Int
specConstrCount     DynFlags
dflags,
          sc_recursive :: Int
sc_recursive   = DynFlags -> Int
specConstrRecursive DynFlags
dflags,
          sc_keen :: Bool
sc_keen        = GeneralFlag -> DynFlags -> Bool
gopt GeneralFlag
Opt_SpecConstrKeen DynFlags
dflags
        }

initScEnv :: ModGuts -> CoreM ScEnv
initScEnv :: ModGuts -> CoreM ScEnv
initScEnv ModGuts
guts
  = do { dflags    <- CoreM DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; (_, anns) <- getFirstAnnotations deserializeWithData guts
       ; this_mod  <- getModule
       ; return (SCE { sc_opts        = initScOpts dflags this_mod,
                       sc_force       = False,
                       sc_subst       = init_subst,
                       sc_how_bound   = emptyVarEnv,
                       sc_vals        = emptyVarEnv,
                       sc_annotations = anns }) }
  where
    init_subst :: Subst
init_subst = InScopeSet -> Subst
mkEmptySubst (InScopeSet -> Subst) -> InScopeSet -> Subst
forall a b. (a -> b) -> a -> b
$ [OutBind] -> InScopeSet
mkInScopeSetBndrs (ModGuts -> [OutBind]
mg_binds ModGuts
guts)
        -- Acccount for top-level bindings that are not in dependency order;
        -- see Note [Glomming] in GHC.Core.Opt.OccurAnal
        -- Easiest thing is to bring all the top level binders into scope at once,
        -- as if  at once, as if all the top-level decls were mutually recursive.

data HowBound = RecFun  -- These are the recursive functions for which
                        -- we seek interesting call patterns

              | RecArg  -- These are those functions' arguments, or their sub-components;
                        -- we gather occurrence information for these

instance Outputable HowBound where
  ppr :: HowBound -> SDoc
ppr HowBound
RecFun = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"RecFun"
  ppr HowBound
RecArg = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"RecArg"

scForce :: ScEnv -> Bool -> ScEnv
scForce :: ScEnv -> Bool -> ScEnv
scForce ScEnv
env Bool
b = ScEnv
env { sc_force = b }

lookupHowBound :: ScEnv -> OutId -> Maybe HowBound
lookupHowBound :: ScEnv -> Id -> Maybe HowBound
lookupHowBound ScEnv
env Id
id = HowBoundEnv -> Id -> Maybe HowBound
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv (ScEnv -> HowBoundEnv
sc_how_bound ScEnv
env) Id
id

scSubstId :: ScEnv -> InId -> OutExpr
scSubstId :: ScEnv -> Id -> Expr Id
scSubstId ScEnv
env Id
v = HasDebugCallStack => Subst -> Id -> Expr Id
Subst -> Id -> Expr Id
lookupIdSubst (ScEnv -> Subst
sc_subst ScEnv
env) Id
v




-- The !subst ensures that we force the selection `(sc_subst env)`, which avoids
-- retaining all of `env` when we only need `subst`.  The `Solo` means that the
-- substitution itself is lazy, because that type is often discarded.
-- The callers of `scSubstTy` always force the result (to unpack the `Solo`)
-- so we get the desired effect: we leave a thunk, but retain only the subst,
-- not the whole env.
--
-- Fully forcing the result of `scSubstTy` regresses performance (#22102)
scSubstTy :: ScEnv -> InType -> Solo OutType
scSubstTy :: ScEnv -> InType -> Solo InType
scSubstTy ScEnv
env InType
ty =
  let !subst :: Subst
subst = ScEnv -> Subst
sc_subst ScEnv
env
  in InType -> Solo InType
forall a. a -> Solo a
MkSolo (Subst -> InType -> InType
substTyUnchecked Subst
subst InType
ty)

scSubstCo :: ScEnv -> Coercion -> Coercion
scSubstCo :: ScEnv -> Coercion -> Coercion
scSubstCo ScEnv
env Coercion
co = HasDebugCallStack => Subst -> Coercion -> Coercion
Subst -> Coercion -> Coercion
substCo (ScEnv -> Subst
sc_subst ScEnv
env) Coercion
co

zapScSubst :: ScEnv -> ScEnv
zapScSubst :: ScEnv -> ScEnv
zapScSubst ScEnv
env = ScEnv
env { sc_subst = zapSubst (sc_subst env) }

extendScInScope :: ScEnv -> [Var] -> ScEnv
        -- Bring the quantified variables into scope
extendScInScope :: ScEnv -> [Id] -> ScEnv
extendScInScope ScEnv
env [Id]
qvars
  = ScEnv
env { sc_subst = extendSubstInScopeList (sc_subst env) qvars }

        -- Extend the substitution
extendScSubst :: ScEnv -> Var -> OutExpr -> ScEnv
extendScSubst :: ScEnv -> Id -> Expr Id -> ScEnv
extendScSubst ScEnv
env Id
var Expr Id
expr = ScEnv
env { sc_subst = extendSubst (sc_subst env) var expr }

extendScSubstList :: ScEnv -> [(Var,OutExpr)] -> ScEnv
extendScSubstList :: ScEnv -> [(Id, Expr Id)] -> ScEnv
extendScSubstList ScEnv
env [(Id, Expr Id)]
prs = ScEnv
env { sc_subst = extendSubstList (sc_subst env) prs }

extendHowBound :: ScEnv -> [Var] -> HowBound -> ScEnv
extendHowBound :: ScEnv -> [Id] -> HowBound -> ScEnv
extendHowBound ScEnv
env [Id]
bndrs HowBound
how_bound
  = ScEnv
env { sc_how_bound = extendVarEnvList (sc_how_bound env)
                            [(bndr,how_bound) | bndr <- bndrs] }

extendBndrsWith :: HowBound -> ScEnv -> [Var] -> (ScEnv, [Var])
extendBndrsWith :: HowBound -> ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrsWith HowBound
how_bound ScEnv
env [Id]
bndrs
  = (ScEnv
env { sc_subst = subst', sc_how_bound = hb_env' }, [Id]
bndrs')
  where
    (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substBndrs (ScEnv -> Subst
sc_subst ScEnv
env) [Id]
bndrs
    hb_env' :: HowBoundEnv
hb_env' = ScEnv -> HowBoundEnv
sc_how_bound ScEnv
env HowBoundEnv -> [(Id, HowBound)] -> HowBoundEnv
forall a. VarEnv a -> [(Id, a)] -> VarEnv a
`extendVarEnvList`
                    [(Id
bndr,HowBound
how_bound) | Id
bndr <- [Id]
bndrs']

extendBndrWith :: HowBound -> ScEnv -> Var -> (ScEnv, Var)
extendBndrWith :: HowBound -> ScEnv -> Id -> (ScEnv, Id)
extendBndrWith HowBound
how_bound ScEnv
env Id
bndr
  = (ScEnv
env { sc_subst = subst', sc_how_bound = hb_env' }, Id
bndr')
  where
    (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr (ScEnv -> Subst
sc_subst ScEnv
env) Id
bndr
    hb_env' :: HowBoundEnv
hb_env' = HowBoundEnv -> Id -> HowBound -> HowBoundEnv
forall a. VarEnv a -> Id -> a -> VarEnv a
extendVarEnv (ScEnv -> HowBoundEnv
sc_how_bound ScEnv
env) Id
bndr' HowBound
how_bound

extendRecBndrs :: ScEnv -> [Var] -> (ScEnv, [Var])
extendRecBndrs :: ScEnv -> [Id] -> (ScEnv, [Id])
extendRecBndrs ScEnv
env [Id]
bndrs  = (ScEnv
env { sc_subst = subst' }, [Id]
bndrs')
                      where
                        (Subst
subst', [Id]
bndrs') = Subst -> [Id] -> (Subst, [Id])
forall (f :: * -> *).
Traversable f =>
Subst -> f Id -> (Subst, f Id)
substRecBndrs (ScEnv -> Subst
sc_subst ScEnv
env) [Id]
bndrs

extendBndrs :: ScEnv -> [Var] -> (ScEnv, [Var])
extendBndrs :: ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrs ScEnv
env [Id]
bndrs = (ScEnv -> Id -> (ScEnv, Id)) -> ScEnv -> [Id] -> (ScEnv, [Id])
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env [Id]
bndrs

extendBndr :: ScEnv -> Var -> (ScEnv, Var)
extendBndr :: ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env Id
bndr  = (ScEnv
env { sc_subst = subst' }, Id
bndr')
                     where
                       (Subst
subst', Id
bndr') = Subst -> Id -> (Subst, Id)
substBndr (ScEnv -> Subst
sc_subst ScEnv
env) Id
bndr

extendValEnv :: ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv :: ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env Id
id Maybe Value
mb_val
  = case Maybe Value
mb_val of
      Maybe Value
Nothing -> ScEnv
env
      Just Value
cv -> ScEnv
env { sc_vals = extendVarEnv (sc_vals env) id cv }

extendCaseBndrs :: ScEnv -> OutExpr -> OutId -> AltCon -> [Var] -> (ScEnv, [Var])
-- When we encounter
--      case scrut of b
--          C x y -> ...
-- we want to bind b, to (C x y)
-- NB1: Extends only the sc_vals part of the envt
-- NB2: Kill the dead-ness info on the pattern binders x,y, since
--      they are potentially made alive by the [b -> C x y] binding
extendCaseBndrs :: ScEnv -> Expr Id -> Id -> AltCon -> [Id] -> (ScEnv, [Id])
extendCaseBndrs ScEnv
env Expr Id
scrut Id
case_bndr AltCon
con [Id]
alt_bndrs
   = (ScEnv
env2, [Id]
alt_bndrs')
 where
   live_case_bndr :: Bool
live_case_bndr = Bool -> Bool
not (Id -> Bool
isDeadBinder Id
case_bndr)
   env1 :: ScEnv
env1 | DoBinderSwap Id
v MCoercion
mco <- Expr Id -> BinderSwapDecision
scrutOkForBinderSwap Expr Id
scrut
        , MCoercion -> Bool
isReflMCo MCoercion
mco  = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env Id
v Maybe Value
cval
        | Bool
otherwise      = ScEnv
env  -- See Note [Add scrutinee to ValueEnv too]
   env2 :: ScEnv
env2 | Bool
live_case_bndr = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env1 Id
case_bndr Maybe Value
cval
        | Bool
otherwise      = ScEnv
env1

   alt_bndrs' :: [Id]
alt_bndrs' | case Expr Id
scrut of { Var {} -> Bool
True; Expr Id
_ -> Bool
live_case_bndr }
              = (Id -> Id) -> [Id] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map Id -> Id
zap [Id]
alt_bndrs
              | Bool
otherwise
              = [Id]
alt_bndrs

   cval :: Maybe Value
cval = case AltCon
con of
                AltCon
DEFAULT    -> Maybe Value
forall a. Maybe a
Nothing
                LitAlt {}  -> Value -> Maybe Value
forall a. a -> Maybe a
Just (Bool -> AltCon -> [Expr Id] -> Value
ConVal Bool
True AltCon
con [])
                DataAlt {} -> Value -> Maybe Value
forall a. a -> Maybe a
Just (Bool -> AltCon -> [Expr Id] -> Value
ConVal Bool
True AltCon
con [Expr Id]
vanilla_args)
                      where
                        vanilla_args :: [Expr Id]
vanilla_args = (InType -> Expr Id) -> [InType] -> [Expr Id]
forall a b. (a -> b) -> [a] -> [b]
map InType -> Expr Id
forall b. InType -> Expr b
Type (HasDebugCallStack => InType -> [InType]
InType -> [InType]
tyConAppArgs (Id -> InType
idType Id
case_bndr)) [Expr Id] -> [Expr Id] -> [Expr Id]
forall a. [a] -> [a] -> [a]
++
                                       [Id] -> [Expr Id]
forall b. [Id] -> [Expr b]
varsToCoreExprs [Id]
alt_bndrs

   zap :: Id -> Id
zap Id
v | Id -> Bool
isTyVar Id
v = Id
v                -- See NB2 above
         | Bool
otherwise = Id -> Id
zapIdOccInfo Id
v


decreaseSpecCount :: ScEnv -> Int -> ScEnv
-- See Note [Avoiding exponential blowup]
decreaseSpecCount :: ScEnv -> Int -> ScEnv
decreaseSpecCount ScEnv
env Int
_n_specs
  = ScEnv
env { sc_force = False   -- See Note [Forcing specialisation]
        , sc_opts = opts { sc_count = case sc_count opts of
                             Maybe Int
Nothing -> Maybe Int
forall a. Maybe a
Nothing
                             Just Int
n  -> Int -> Maybe Int
forall a. a -> Maybe a
Just (Int -> Maybe Int) -> Int -> Maybe Int
forall a b. (a -> b) -> a -> b
$! Int -> Int
forall {a}. Integral a => a -> a
dec Int
n
            }
        }
  where
    opts :: SpecConstrOpts
opts  = ScEnv -> SpecConstrOpts
sc_opts ScEnv
env
    dec :: a -> a
dec a
n = a
n a -> a -> a
forall a. Integral a => a -> a -> a
`div` a
2  -- See Note [Avoiding exponential blowup]

    -- Or:   n `div` (n_specs + 1)
    -- See the historical note part of Note [Avoiding exponential blowup]
    -- The "+1" takes account of the original function;

---------------------------------------------------
-- See Note [Forcing specialisation]
ignoreType    :: ScEnv -> Type   -> Bool
ignoreDataCon  :: ScEnv -> DataCon -> Bool
forceSpecBndr :: ScEnv -> Var    -> Bool

ignoreDataCon :: ScEnv -> DataCon -> Bool
ignoreDataCon ScEnv
env DataCon
dc = ScEnv -> TyCon -> Bool
ignoreTyCon ScEnv
env (DataCon -> TyCon
dataConTyCon DataCon
dc)

ignoreType :: ScEnv -> InType -> Bool
ignoreType ScEnv
env InType
ty
  = case InType -> Maybe TyCon
tyConAppTyCon_maybe InType
ty of
      Just TyCon
tycon -> ScEnv -> TyCon -> Bool
ignoreTyCon ScEnv
env TyCon
tycon
      Maybe TyCon
_          -> Bool
False

ignoreTyCon :: ScEnv -> TyCon -> Bool
ignoreTyCon :: ScEnv -> TyCon -> Bool
ignoreTyCon ScEnv
env TyCon
tycon
  = UniqFM Name SpecConstrAnnotation
-> Name -> Maybe SpecConstrAnnotation
forall key elt. Uniquable key => UniqFM key elt -> key -> Maybe elt
lookupUFM (ScEnv -> UniqFM Name SpecConstrAnnotation
sc_annotations ScEnv
env) (TyCon -> Name
tyConName TyCon
tycon) Maybe SpecConstrAnnotation -> Maybe SpecConstrAnnotation -> Bool
forall a. Eq a => a -> a -> Bool
== SpecConstrAnnotation -> Maybe SpecConstrAnnotation
forall a. a -> Maybe a
Just SpecConstrAnnotation
NoSpecConstr

forceSpecBndr :: ScEnv -> Id -> Bool
forceSpecBndr ScEnv
env Id
var = ScEnv -> InType -> Bool
forceSpecFunTy ScEnv
env (InType -> Bool) -> (Id -> InType) -> Id -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ([Id], InType) -> InType
forall a b. (a, b) -> b
snd (([Id], InType) -> InType)
-> (Id -> ([Id], InType)) -> Id -> InType
forall b c a. (b -> c) -> (a -> b) -> a -> c
. InType -> ([Id], InType)
splitForAllTyCoVars (InType -> ([Id], InType))
-> (Id -> InType) -> Id -> ([Id], InType)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Id -> InType
varType (Id -> Bool) -> Id -> Bool
forall a b. (a -> b) -> a -> b
$ Id
var

forceSpecFunTy :: ScEnv -> Type -> Bool
forceSpecFunTy :: ScEnv -> InType -> Bool
forceSpecFunTy ScEnv
env = (InType -> Bool) -> [InType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ScEnv -> InType -> Bool
forceSpecArgTy ScEnv
env) ([InType] -> Bool) -> (InType -> [InType]) -> InType -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (Scaled InType -> InType) -> [Scaled InType] -> [InType]
forall a b. (a -> b) -> [a] -> [b]
map Scaled InType -> InType
forall a. Scaled a -> a
scaledThing ([Scaled InType] -> [InType])
-> (InType -> [Scaled InType]) -> InType -> [InType]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. ([Scaled InType], InType) -> [Scaled InType]
forall a b. (a, b) -> a
fst (([Scaled InType], InType) -> [Scaled InType])
-> (InType -> ([Scaled InType], InType))
-> InType
-> [Scaled InType]
forall b c a. (b -> c) -> (a -> b) -> a -> c
. InType -> ([Scaled InType], InType)
splitFunTys

forceSpecArgTy :: ScEnv -> Type -> Bool
forceSpecArgTy :: ScEnv -> InType -> Bool
forceSpecArgTy ScEnv
env InType
ty
  | InType -> Bool
isFunTy InType
ty
  = Bool
False

  | Just (TyCon
tycon, [InType]
tys) <- HasDebugCallStack => InType -> Maybe (TyCon, [InType])
InType -> Maybe (TyCon, [InType])
splitTyConApp_maybe InType
ty
  = TyCon
tycon TyCon -> Unique -> Bool
forall a. Uniquable a => a -> Unique -> Bool
`hasKey` Unique
specTyConKey
    Bool -> Bool -> Bool
|| UniqFM Name SpecConstrAnnotation
-> Name -> Maybe SpecConstrAnnotation
forall key elt. Uniquable key => UniqFM key elt -> key -> Maybe elt
lookupUFM (ScEnv -> UniqFM Name SpecConstrAnnotation
sc_annotations ScEnv
env) (TyCon -> Name
tyConName TyCon
tycon) Maybe SpecConstrAnnotation -> Maybe SpecConstrAnnotation -> Bool
forall a. Eq a => a -> a -> Bool
== SpecConstrAnnotation -> Maybe SpecConstrAnnotation
forall a. a -> Maybe a
Just SpecConstrAnnotation
ForceSpecConstr
    Bool -> Bool -> Bool
|| (InType -> Bool) -> [InType] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ScEnv -> InType -> Bool
forceSpecArgTy ScEnv
env) [InType]
tys

forceSpecArgTy ScEnv
_ InType
_ = Bool
False

{-
Note [Add scrutinee to ValueEnv too]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this:
   case x of y
     (a,b) -> case b of c
                I# v -> ...(f y)...
By the time we get to the call (f y), the ValueEnv
will have a binding for y, and for c
    y -> (a,b)
    c -> I# v
BUT that's not enough!  Looking at the call (f y) we
see that y is pair (a,b), but we also need to know what 'b' is.
So in extendCaseBndrs we must *also* add the binding
   b -> I# v
else we lose a useful specialisation for f.  This is necessary even
though the simplifier has systematically replaced uses of 'x' with 'y'
and 'b' with 'c' in the code.  The use of 'b' in the ValueEnv came
from outside the case.  See #4908 for the live example.

It's very like the binder-swap story, so we use scrutOkForBinderSwap
to identify suitable scrutinees -- but only if there is no cast
(isReflMCo) because that's all that the ValueEnv allows.

Note [Avoiding exponential blowup]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The sc_count field of the ScEnv says how many times we are prepared to
duplicate a single function.  But we must take care with recursive
specialisations.  Consider

        let $j1 = let $j2 = let $j3 = ...
                            in
                            ...$j3...
                  in
                  ...$j2...
        in
        ...$j1...

If we specialise $j1 then in each specialisation (as well as the original)
we can specialise $j2, and similarly $j3.  Even if we make just *one*
specialisation of each, because we also have the original we'll get 2^n
copies of $j3, which is not good.

So when recursively specialising we divide the sc_count (the maximum
number of specialisations, in the ScEnv) by two.  You might think that
gives us n*(n/2)*(n/4)... copies of the innnermost thing, which is
still exponential the depth.  But we use integer division, rounding
down, so if the starting sc_count is 3, we'll get 3 -> 1 -> 0, and
stop.  In fact, simply subtracting 1 would be good enough, for the same
reason.

Historical note: in the past we divided by (n_specs+1), where n_specs
is the number of specialisations at this level; but that gets us down
to zero jolly quickly, which I found led to some regressions.  (An
example is nofib/spectral/fibheaps, the getMin' function inside the
outer function $sfibToList, which has several interesting call
patterns.)

************************************************************************
*                                                                      *
\subsection{Usage information: flows upwards}
*                                                                      *
************************************************************************
-}

data ScUsage
   = SCU {
        ScUsage -> CallEnv
scu_calls :: CallEnv,           -- Calls
                                        -- The functions are a subset of the
                                        --      RecFuns in the ScEnv

        ScUsage -> IdEnv ArgOcc
scu_occs :: !(IdEnv ArgOcc)     -- Information on argument occurrences
     }                                  -- The domain is OutIds

type CallEnv = IdEnv [Call]  -- Domain is OutIds
data Call    = Call OutId [CoreArg] ValueEnv
        -- The arguments of the call, together with the
        -- env giving the constructor bindings at the call site
        -- We keep the function mainly for debug output
        --
        -- The call is not necessarily saturated; we just put
        -- in however many args are visible at the call site

instance Outputable ScUsage where
  ppr :: ScUsage -> SDoc
ppr (SCU { scu_calls :: ScUsage -> CallEnv
scu_calls = CallEnv
calls, scu_occs :: ScUsage -> IdEnv ArgOcc
scu_occs = IdEnv ArgOcc
occs })
    = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"SCU" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc
braces ([SDoc] -> SDoc
forall doc. IsLine doc => [doc] -> doc
sep [ String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"calls =" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> CallEnv -> SDoc
forall a. Outputable a => a -> SDoc
ppr CallEnv
calls
                                 , String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"occs =" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> IdEnv ArgOcc -> SDoc
forall a. Outputable a => a -> SDoc
ppr IdEnv ArgOcc
occs ])

instance Outputable Call where
  ppr :: Call -> SDoc
ppr (Call Id
fn [Expr Id]
args ValueEnv
_) = Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
fn SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> [SDoc] -> SDoc
forall doc. IsLine doc => [doc] -> doc
fsep ((Expr Id -> SDoc) -> [Expr Id] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map Expr Id -> SDoc
forall b. OutputableBndr b => Expr b -> SDoc
pprParendExpr [Expr Id]
args)

nullUsage :: ScUsage
nullUsage :: ScUsage
nullUsage = SCU { scu_calls :: CallEnv
scu_calls = CallEnv
forall a. VarEnv a
emptyVarEnv, scu_occs :: IdEnv ArgOcc
scu_occs = IdEnv ArgOcc
forall a. VarEnv a
emptyVarEnv }

combineCalls :: CallEnv -> CallEnv -> CallEnv
combineCalls :: CallEnv -> CallEnv -> CallEnv
combineCalls = ([Call] -> [Call] -> [Call]) -> CallEnv -> CallEnv -> CallEnv
forall a. (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
plusVarEnv_C [Call] -> [Call] -> [Call]
forall a. [a] -> [a] -> [a]
(++)

delCallsFor :: ScUsage -> [Var] -> ScUsage
delCallsFor :: ScUsage -> [Id] -> ScUsage
delCallsFor ScUsage
env [Id]
bndrs = ScUsage
env { scu_calls = scu_calls env `delVarEnvList` bndrs }

combineUsage :: ScUsage -> ScUsage -> ScUsage
combineUsage :: ScUsage -> ScUsage -> ScUsage
combineUsage ScUsage
u1 ScUsage
u2 = SCU { scu_calls :: CallEnv
scu_calls = CallEnv -> CallEnv -> CallEnv
combineCalls (ScUsage -> CallEnv
scu_calls ScUsage
u1) (ScUsage -> CallEnv
scu_calls ScUsage
u2),
                           scu_occs :: IdEnv ArgOcc
scu_occs  = (ArgOcc -> ArgOcc -> ArgOcc)
-> IdEnv ArgOcc -> IdEnv ArgOcc -> IdEnv ArgOcc
forall a. (a -> a -> a) -> VarEnv a -> VarEnv a -> VarEnv a
plusVarEnv_C ArgOcc -> ArgOcc -> ArgOcc
combineOcc (ScUsage -> IdEnv ArgOcc
scu_occs ScUsage
u1) (ScUsage -> IdEnv ArgOcc
scu_occs ScUsage
u2) }

combineUsages :: [ScUsage] -> ScUsage
combineUsages :: [ScUsage] -> ScUsage
combineUsages [] = ScUsage
nullUsage
combineUsages [ScUsage]
us = (ScUsage -> ScUsage -> ScUsage) -> [ScUsage] -> ScUsage
forall a. (a -> a -> a) -> [a] -> a
forall (t :: * -> *) a. Foldable t => (a -> a -> a) -> t a -> a
foldr1 ScUsage -> ScUsage -> ScUsage
combineUsage [ScUsage]
us

lookupOccs :: ScUsage -> [OutVar] -> (ScUsage, [ArgOcc])
lookupOccs :: ScUsage -> [Id] -> (ScUsage, [ArgOcc])
lookupOccs (SCU { scu_calls :: ScUsage -> CallEnv
scu_calls = CallEnv
sc_calls, scu_occs :: ScUsage -> IdEnv ArgOcc
scu_occs = IdEnv ArgOcc
sc_occs }) [Id]
bndrs
  = (SCU {scu_calls :: CallEnv
scu_calls = CallEnv
sc_calls, scu_occs :: IdEnv ArgOcc
scu_occs = IdEnv ArgOcc -> [Id] -> IdEnv ArgOcc
forall a. VarEnv a -> [Id] -> VarEnv a
delVarEnvList IdEnv ArgOcc
sc_occs [Id]
bndrs},
     [IdEnv ArgOcc -> Id -> Maybe ArgOcc
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv IdEnv ArgOcc
sc_occs Id
b Maybe ArgOcc -> ArgOcc -> ArgOcc
forall a. Maybe a -> a -> a
`orElse` ArgOcc
NoOcc | Id
b <- [Id]
bndrs])

data ArgOcc = NoOcc     -- Doesn't occur at all; or a type argument
            | UnkOcc    -- Used in some unknown way

            | ScrutOcc  -- See Note [ScrutOcc]
                 (DataConEnv [ArgOcc])
                     -- [ArgOcc]: how the sub-components are used

deadArgOcc :: ArgOcc -> Bool
deadArgOcc :: ArgOcc -> Bool
deadArgOcc (ScrutOcc {}) = Bool
False
deadArgOcc ArgOcc
UnkOcc        = Bool
False
deadArgOcc ArgOcc
NoOcc         = Bool
True

specialisableArgOcc :: ArgOcc -> Bool
-- | Does this occurrence represent one worth specializing for.
specialisableArgOcc :: ArgOcc -> Bool
specialisableArgOcc ArgOcc
UnkOcc        = Bool
False
specialisableArgOcc ArgOcc
NoOcc         = Bool
False
specialisableArgOcc (ScrutOcc {}) = Bool
True


{- Note [ScrutOcc]
~~~~~~~~~~~~~~~~~~
An occurrence of ScrutOcc indicates that the thing, or a `cast` version of the thing,
is *only* taken apart or applied.

  Functions, literal: ScrutOcc emptyUFM
  Data constructors:  ScrutOcc subs,

where (subs :: UniqFM [ArgOcc]) gives usage of the *pattern-bound* components,
The domain of the UniqFM is the Unique of the data constructor

The [ArgOcc] is the occurrences of the *pattern-bound* components
of the data structure.  E.g.
        data T a = forall b. MkT a b (b->a)
A pattern binds b, x::a, y::b, z::b->a, but not 'a'!

-}

instance Outputable ArgOcc where
  ppr :: ArgOcc -> SDoc
ppr (ScrutOcc DataConEnv [ArgOcc]
xs) = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"scrut-occ" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> DataConEnv [ArgOcc] -> SDoc
forall a. Outputable a => a -> SDoc
ppr DataConEnv [ArgOcc]
xs
  ppr ArgOcc
UnkOcc        = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"unk-occ"
  ppr ArgOcc
NoOcc         = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"no-occ"

evalScrutOcc :: ArgOcc
-- We use evalScrutOcc for
--   - mkVarUsage: applied functions
--   - scApp: dicts that are the argument of a classop
evalScrutOcc :: ArgOcc
evalScrutOcc = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
forall {k} (key :: k) elt. UniqFM key elt
emptyUFM

-- Experimentally, this version of combineOcc makes ScrutOcc "win", so
-- that if the thing is scrutinised anywhere then we get to see that
-- in the overall result, even if it's also used in a boxed way
-- This might be too aggressive; see Note [Reboxing] Alternative 3
combineOcc :: ArgOcc -> ArgOcc -> ArgOcc
combineOcc :: ArgOcc -> ArgOcc -> ArgOcc
combineOcc ArgOcc
NoOcc         ArgOcc
occ           = ArgOcc
occ
combineOcc ArgOcc
occ           ArgOcc
NoOcc         = ArgOcc
occ
combineOcc (ScrutOcc DataConEnv [ArgOcc]
xs) (ScrutOcc DataConEnv [ArgOcc]
ys) = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc (([ArgOcc] -> [ArgOcc] -> [ArgOcc])
-> DataConEnv [ArgOcc]
-> DataConEnv [ArgOcc]
-> DataConEnv [ArgOcc]
forall {k} elt (key :: k).
(elt -> elt -> elt)
-> UniqFM key elt -> UniqFM key elt -> UniqFM key elt
plusUFM_C [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs DataConEnv [ArgOcc]
xs DataConEnv [ArgOcc]
ys)
combineOcc ArgOcc
UnkOcc        (ScrutOcc DataConEnv [ArgOcc]
ys) = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
ys
combineOcc (ScrutOcc DataConEnv [ArgOcc]
xs) ArgOcc
UnkOcc        = DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc DataConEnv [ArgOcc]
xs
combineOcc ArgOcc
UnkOcc        ArgOcc
UnkOcc        = ArgOcc
UnkOcc

combineOccs :: [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs :: [ArgOcc] -> [ArgOcc] -> [ArgOcc]
combineOccs [ArgOcc]
xs [ArgOcc]
ys = String
-> (ArgOcc -> ArgOcc -> ArgOcc) -> [ArgOcc] -> [ArgOcc] -> [ArgOcc]
forall a b c.
HasDebugCallStack =>
String -> (a -> b -> c) -> [a] -> [b] -> [c]
zipWithEqual String
"combineOccs" ArgOcc -> ArgOcc -> ArgOcc
combineOcc [ArgOcc]
xs [ArgOcc]
ys

setScrutOcc :: ScEnv -> ScUsage -> OutExpr -> ArgOcc -> ScUsage
-- _Overwrite_ the occurrence info for the scrutinee, if the scrutinee
-- is a variable, and an interesting variable
setScrutOcc :: ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg (Cast Expr Id
e Coercion
_) ArgOcc
occ      = ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg Expr Id
e ArgOcc
occ
setScrutOcc ScEnv
env ScUsage
usg (Tick CoreTickish
_ Expr Id
e) ArgOcc
occ      = ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
usg Expr Id
e ArgOcc
occ
setScrutOcc ScEnv
env ScUsage
usg (Var Id
v)    ArgOcc
occ
  | Just HowBound
RecArg <- ScEnv -> Id -> Maybe HowBound
lookupHowBound ScEnv
env Id
v = ScUsage
usg { scu_occs = extendVarEnv (scu_occs usg) v occ }
  | Bool
otherwise                           = ScUsage
usg
setScrutOcc ScEnv
_env ScUsage
usg Expr Id
_other ArgOcc
_occ        -- Catch-all
  = ScUsage
usg

{-
************************************************************************
*                                                                      *
\subsection{The main recursive function}
*                                                                      *
************************************************************************

The main recursive function gathers up usage information, and
creates specialised versions of functions.
-}

scBind :: TopLevelFlag -> ScEnv -> InBind
       -> (ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning]))   -- Specialise the scope of the binding
       -> UniqSM (ScUsage, [OutBind], a, [SpecFailWarning])
scBind :: forall a.
TopLevelFlag
-> ScEnv
-> OutBind
-> (ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning]))
-> UniqSM (ScUsage, [OutBind], a, [SpecFailWarning])
scBind TopLevelFlag
top_lvl ScEnv
env (NonRec Id
bndr Expr Id
rhs) ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning])
do_body
  | Id -> Bool
isTyVar Id
bndr         -- Type-lets may be created by doBeta
  = do { (final_usage, body', warnings) <- ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning])
do_body (ScEnv -> Id -> Expr Id -> ScEnv
extendScSubst ScEnv
env Id
bndr Expr Id
rhs)
       ; return (final_usage, [], body', warnings) }

  | Bool -> Bool
not (TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl)  -- Nested non-recursive value binding
    -- See Note [Specialising local let bindings]
  = do  { let (ScEnv
body_env, Id
bndr') = ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env Id
bndr
              -- Not necessary at top level; but here we are nested

        ; (rhs_info, rhs_ws)  <- ScEnv -> (Id, Expr Id) -> UniqSM (RhsInfo, [SpecFailWarning])
scRecRhs ScEnv
env (Id
bndr',Expr Id
rhs)

        ; let body_env2 = ScEnv -> [Id] -> HowBound -> ScEnv
extendHowBound ScEnv
body_env [Id
bndr'] HowBound
RecFun
              rhs'      = RhsInfo -> Expr Id
ri_new_rhs RhsInfo
rhs_info
              body_env3 = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
body_env2 Id
bndr' (ValueEnv -> Expr Id -> Maybe Value
isValue (ScEnv -> ValueEnv
sc_vals ScEnv
env) Expr Id
rhs')

        ; (body_usg, body', warnings_body) <- do_body body_env3

          -- Now make specialised copies of the binding,
          -- based on calls in body_usg
        ; (spec_usg, specs, warnings_bnd) <- specNonRec env (scu_calls body_usg) rhs_info
          -- NB: For non-recursive bindings we inherit sc_force flag from
          -- the parent function (see Note [Forcing specialisation])

        -- Specialized + original binding
        ; let spec_bnds  = [Id -> Expr Id -> OutBind
forall b. b -> Expr b -> Bind b
NonRec Id
b Expr Id
r | (Id
b,Expr Id
r) <- RhsInfo -> SpecInfo -> [(Id, Expr Id)]
ruleInfoBinds RhsInfo
rhs_info SpecInfo
specs]
              bind_usage = (ScUsage
body_usg ScUsage -> [Id] -> ScUsage
`delCallsFor` [Id
bndr'])
                           ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
spec_usg -- Note [spec_usg includes rhs_usg]

        ; return (bind_usage, spec_bnds, body', mconcat [warnings_bnd, warnings_body, rhs_ws])
        }

  | Bool
otherwise  -- Top-level, non-recursive value binding
    -- At top level we do not specialise non-recursive bindings; that
    -- is, we do not call specNonRec, passing the calls from the body.
    -- The original paper only specialised /recursive/ bindings, but
    -- we later started specialising nested non-recursive bindings:
    -- see Note [Specialising local let bindings]
    --
    -- I tried always specialising non-recursive top-level bindings too,
    -- but found some regressions (see !8135).  So I backed off.
  = do { (rhs_usage, rhs', ws_rhs)   <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env Expr Id
rhs

       -- At top level, we've already put all binders into scope; see initScEnv
       -- Hence no need to call `extendBndr`. But we still want to
       -- extend the `ValueEnv` to record the value of this binder.
       ; let body_env = ScEnv -> Id -> Maybe Value -> ScEnv
extendValEnv ScEnv
env Id
bndr (ValueEnv -> Expr Id -> Maybe Value
isValue (ScEnv -> ValueEnv
sc_vals ScEnv
env) Expr Id
rhs')
       ; (body_usage, body', body_warnings) <- do_body body_env

       ; return (rhs_usage `combineUsage` body_usage, [NonRec bndr rhs'], body', body_warnings ++ ws_rhs) }

scBind TopLevelFlag
top_lvl ScEnv
env (Rec [(Id, Expr Id)]
prs) ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning])
do_body
  | TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl
  , Just Int
threshold <- SpecConstrOpts -> Maybe Int
sc_size (ScEnv -> SpecConstrOpts
sc_opts ScEnv
env)
  , Bool -> Bool
not Bool
force_spec -- See Note [Forcing specialisation], point (FS1)
  , Bool -> Bool
not ((Expr Id -> Bool) -> [Expr Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all (UnfoldingOpts -> Int -> Expr Id -> Bool
couldBeSmallEnoughToInline (SpecConstrOpts -> UnfoldingOpts
sc_uf_opts (ScEnv -> SpecConstrOpts
sc_opts ScEnv
env)) Int
threshold) [Expr Id]
rhss)
  = -- Do no specialisation if the RHSs are too big
    -- ToDo: I'm honestly not sure of the rationale of this size-testing, nor
    --       why it only applies at top level. But that's the way it has been
    --       for a while. See #21456.
    do  { (body_usg, body', warnings_body) <- ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning])
do_body ScEnv
rhs_env2
        ; (rhs_usgs, rhss', rhs_ws) <- mapAndUnzip3M (scExpr env) rhss
        ; let all_usg = ([ScUsage] -> ScUsage
combineUsages [ScUsage]
rhs_usgs ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
body_usg)
                        ScUsage -> [Id] -> ScUsage
`delCallsFor` [Id]
bndrs'
              bind'   = [(Id, Expr Id)] -> OutBind
forall b. [(b, Expr b)] -> Bind b
Rec ([Id]
bndrs' [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Expr Id]
rhss')
        ; return (all_usg, [bind'], body', warnings_body ++ concat rhs_ws) }

  | Bool
otherwise
  = do  { (rhs_infos, rhs_wss) <- ((Id, Expr Id) -> UniqSM (RhsInfo, [SpecFailWarning]))
-> [(Id, Expr Id)] -> UniqSM ([RhsInfo], [[SpecFailWarning]])
forall (m :: * -> *) a b c.
Applicative m =>
(a -> m (b, c)) -> [a] -> m ([b], [c])
mapAndUnzipM (ScEnv -> (Id, Expr Id) -> UniqSM (RhsInfo, [SpecFailWarning])
scRecRhs ScEnv
rhs_env2) ([Id]
bndrs' [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Expr Id]
rhss)
        ; let rhs_ws = [[SpecFailWarning]] -> [SpecFailWarning]
forall a. Monoid a => [a] -> a
mconcat [[SpecFailWarning]]
rhs_wss
        ; (body_usg, body', warnings_body) <- do_body rhs_env2

        ; (spec_usg, specs, spec_ws) <- specRec (scForce rhs_env2 force_spec)
                                          (scu_calls body_usg) rhs_infos
                -- Do not unconditionally generate specialisations from rhs_usgs
                -- Instead use them only if we find an unspecialised call
                -- See Note [Seeding recursive groups]

        ; let all_usg = (ScUsage
spec_usg ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
body_usg)  -- Note [spec_usg includes rhs_usg]
                        ScUsage -> [Id] -> ScUsage
`delCallsFor` [Id]
bndrs'
              bind'   = [(Id, Expr Id)] -> OutBind
forall b. [(b, Expr b)] -> Bind b
Rec ([[(Id, Expr Id)]] -> [(Id, Expr Id)]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat (String
-> (RhsInfo -> SpecInfo -> [(Id, Expr Id)])
-> [RhsInfo]
-> [SpecInfo]
-> [[(Id, Expr Id)]]
forall a b c.
HasDebugCallStack =>
String -> (a -> b -> c) -> [a] -> [b] -> [c]
zipWithEqual String
"scExpr'" RhsInfo -> SpecInfo -> [(Id, Expr Id)]
ruleInfoBinds [RhsInfo]
rhs_infos [SpecInfo]
specs))
                        -- zipWithEqual: length of returned [SpecInfo]
                        -- should be the same as incoming [RhsInfo]

        ; return (all_usg, [bind'], body', mconcat [warnings_body,rhs_ws,spec_ws]) }
  where
    ([Id]
bndrs,[Expr Id]
rhss) = [(Id, Expr Id)] -> ([Id], [Expr Id])
forall a b. [(a, b)] -> ([a], [b])
unzip [(Id, Expr Id)]
prs
    force_spec :: Bool
force_spec   = (Id -> Bool) -> [Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any (ScEnv -> Id -> Bool
forceSpecBndr ScEnv
env) [Id]
bndrs    -- Note [Forcing specialisation]

    (ScEnv
rhs_env1,[Id]
bndrs') | TopLevelFlag -> Bool
isTopLevel TopLevelFlag
top_lvl = (ScEnv
env, [Id]
bndrs)
                      | Bool
otherwise          = ScEnv -> [Id] -> (ScEnv, [Id])
extendRecBndrs ScEnv
env [Id]
bndrs
       -- At top level, we've already put all binders into scope; see initScEnv

    rhs_env2 :: ScEnv
rhs_env2 = ScEnv -> [Id] -> HowBound -> ScEnv
extendHowBound ScEnv
rhs_env1 [Id]
bndrs' HowBound
RecFun

{- Note [Specialising local let bindings]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It is not uncommon to find this

   let $j = \x. <blah> in ...$j True...$j True...

Here $j is an arbitrary let-bound function, but it often comes up for
join points.  We might like to specialise $j for its call patterns.
Notice the difference from a letrec, where we look for call patterns
in the *RHS* of the function.  Here we look for call patterns in the
*body* of the let.

At one point I predicated this on the RHS mentioning the outer
recursive function, but that's not essential and might even be
harmful.  I'm not sure.
-}

withWarnings :: SpecFailWarnings -> (ScUsage, CoreExpr, SpecFailWarnings) -> (ScUsage, CoreExpr, SpecFailWarnings)
withWarnings :: [SpecFailWarning]
-> (ScUsage, Expr Id, [SpecFailWarning])
-> (ScUsage, Expr Id, [SpecFailWarning])
withWarnings [SpecFailWarning]
ws (ScUsage
use,Expr Id
expr,[SpecFailWarning]
ws2) = (ScUsage
use,Expr Id
expr,[SpecFailWarning]
ws [SpecFailWarning] -> [SpecFailWarning] -> [SpecFailWarning]
forall a. [a] -> [a] -> [a]
++ [SpecFailWarning]
ws2)

------------------------
scExpr, scExpr' :: ScEnv -> CoreExpr -> UniqSM (ScUsage, CoreExpr, SpecFailWarnings)
        -- The unique supply is needed when we invent
        -- a new name for the specialised function and its args

scExpr :: ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env Expr Id
e = ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr' ScEnv
env Expr Id
e

scExpr' :: ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr' ScEnv
env (Var Id
v)      = case ScEnv -> Id -> Expr Id
scSubstId ScEnv
env Id
v of
                            Var Id
v' -> (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScEnv -> Id -> [Expr Id] -> ScUsage
mkVarUsage ScEnv
env Id
v' [], Id -> Expr Id
forall b. Id -> Expr b
Var Id
v', [])
                            Expr Id
e'     -> ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr (ScEnv -> ScEnv
zapScSubst ScEnv
env) Expr Id
e'

scExpr' ScEnv
env (Type InType
t)     =
  let !(MkSolo InType
ty') = ScEnv -> InType -> Solo InType
scSubstTy ScEnv
env InType
t
  in (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, InType -> Expr Id
forall b. InType -> Expr b
Type InType
ty', [])
scExpr' ScEnv
env (Coercion Coercion
c) = (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, Coercion -> Expr Id
forall b. Coercion -> Expr b
Coercion (ScEnv -> Coercion -> Coercion
scSubstCo ScEnv
env Coercion
c), [])
scExpr' ScEnv
_   e :: Expr Id
e@(Lit {})   = (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, Expr Id
e, [])
scExpr' ScEnv
env (Tick CoreTickish
t Expr Id
e)   = do (usg, e', ws) <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env Expr Id
e
                              return (usg, Tick (scTickish env t) e', ws)
scExpr' ScEnv
env (Cast Expr Id
e Coercion
co)  = do (usg, e', ws) <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env Expr Id
e
                              return (usg, mkCast e' (scSubstCo env co), ws)
                              -- Important to use mkCast here
                              -- See Note [SpecConstr call patterns]
scExpr' ScEnv
env e :: Expr Id
e@(App Expr Id
_ Expr Id
_)  = ScEnv
-> (Expr Id, [Expr Id])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scApp ScEnv
env (Expr Id -> (Expr Id, [Expr Id])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs Expr Id
e)
scExpr' ScEnv
env (Lam Id
b Expr Id
e)    = do let (ScEnv
env', Id
b') = ScEnv -> Id -> (ScEnv, Id)
extendBndr ScEnv
env Id
b
                              (usg, e', ws) <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env' Expr Id
e
                              return (usg, Lam b' e', ws)

scExpr' ScEnv
env (Let OutBind
bind Expr Id
body)
  = do { (final_usage, binds', body', ws) <- TopLevelFlag
-> ScEnv
-> OutBind
-> (ScEnv -> UniqSM (ScUsage, Expr Id, [SpecFailWarning]))
-> UniqSM (ScUsage, [OutBind], Expr Id, [SpecFailWarning])
forall a.
TopLevelFlag
-> ScEnv
-> OutBind
-> (ScEnv -> UniqSM (ScUsage, a, [SpecFailWarning]))
-> UniqSM (ScUsage, [OutBind], a, [SpecFailWarning])
scBind TopLevelFlag
NotTopLevel ScEnv
env OutBind
bind ((ScEnv -> UniqSM (ScUsage, Expr Id, [SpecFailWarning]))
 -> UniqSM (ScUsage, [OutBind], Expr Id, [SpecFailWarning]))
-> (ScEnv -> UniqSM (ScUsage, Expr Id, [SpecFailWarning]))
-> UniqSM (ScUsage, [OutBind], Expr Id, [SpecFailWarning])
forall a b. (a -> b) -> a -> b
$
                                         (\ScEnv
env -> ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env Expr Id
body)
       ; return (final_usage, mkLets binds' body', ws) }

scExpr' ScEnv
env (Case Expr Id
scrut Id
b InType
ty [Alt Id]
alts)
  = do  { (scrut_usg, scrut', ws) <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env Expr Id
scrut
        ; case isValue (sc_vals env) scrut' of
                Just (ConVal Bool
args_are_work_free AltCon
con [Expr Id]
args)
                   | Bool
args_are_work_free -> AltCon
-> [Expr Id]
-> Expr Id
-> [SpecFailWarning]
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
sc_con_app AltCon
con [Expr Id]
args Expr Id
scrut' [SpecFailWarning]
ws
                     -- Don't duplicate work!!  #7865
                     -- See Note [ConVal work-free-ness] (1)
                Maybe Value
_other -> ScUsage
-> Expr Id
-> [SpecFailWarning]
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
sc_vanilla ScUsage
scrut_usg Expr Id
scrut' [SpecFailWarning]
ws
        }
  where
    sc_con_app :: AltCon
-> [Expr Id]
-> Expr Id
-> [SpecFailWarning]
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
sc_con_app AltCon
con [Expr Id]
args Expr Id
scrut' [SpecFailWarning]
ws  -- Known constructor; simplify
     = do { let Alt AltCon
_ [Id]
bs Expr Id
rhs = AltCon -> [Alt Id] -> Maybe (Alt Id)
forall b. AltCon -> [Alt b] -> Maybe (Alt b)
findAlt AltCon
con [Alt Id]
alts
                                  Maybe (Alt Id) -> Alt Id -> Alt Id
forall a. Maybe a -> a -> a
`orElse` AltCon -> [Id] -> Expr Id -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
DEFAULT [] (InType -> String -> Expr Id
mkImpossibleExpr InType
ty String
"SpecConstr")
                alt_env' :: ScEnv
alt_env'     = ScEnv -> [(Id, Expr Id)] -> ScEnv
extendScSubstList ScEnv
env ((Id
b,Expr Id
scrut') (Id, Expr Id) -> [(Id, Expr Id)] -> [(Id, Expr Id)]
forall a. a -> [a] -> [a]
: [Id]
bs [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` AltCon -> [Expr Id] -> [Expr Id]
trimConArgs AltCon
con [Expr Id]
args)
          ; (use',expr',ws_new) <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
alt_env' Expr Id
rhs
          ; return (use',expr',ws ++ ws_new) }

    sc_vanilla :: ScUsage
-> Expr Id
-> [SpecFailWarning]
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
sc_vanilla ScUsage
scrut_usg Expr Id
scrut' [SpecFailWarning]
ws -- Normal case
     = do { let (ScEnv
alt_env,Id
b') = HowBound -> ScEnv -> Id -> (ScEnv, Id)
extendBndrWith HowBound
RecArg ScEnv
env Id
b
                        -- Record RecArg for the components

          ; (alt_usgs, alt_occs, alts', ws_alts) <- (Alt Id -> UniqSM (ScUsage, ArgOcc, Alt Id, [SpecFailWarning]))
-> [Alt Id]
-> UniqSM ([ScUsage], [ArgOcc], [Alt Id], [[SpecFailWarning]])
forall (m :: * -> *) a b c d e.
Monad m =>
(a -> m (b, c, d, e)) -> [a] -> m ([b], [c], [d], [e])
mapAndUnzip4M (ScEnv
-> Expr Id
-> Id
-> Alt Id
-> UniqSM (ScUsage, ArgOcc, Alt Id, [SpecFailWarning])
sc_alt ScEnv
alt_env Expr Id
scrut' Id
b') [Alt Id]
alts

          ; let scrut_occ  = (ArgOcc -> ArgOcc -> ArgOcc) -> ArgOcc -> [ArgOcc] -> ArgOcc
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr ArgOcc -> ArgOcc -> ArgOcc
combineOcc ArgOcc
NoOcc [ArgOcc]
alt_occs
                scrut_usg' = ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
scrut_usg Expr Id
scrut' ArgOcc
scrut_occ
                -- The combined usage of the scrutinee is given
                -- by scrut_occ, which is passed to setScrutOcc, which
                -- in turn treats a bare-variable scrutinee specially
          ; let !(MkSolo ty') = scSubstTy env ty

          ; return (foldr combineUsage scrut_usg' alt_usgs,
                    Case scrut' b' ty'  alts', ws ++ concat ws_alts) }

    single_alt :: Bool
single_alt = [Alt Id] -> Bool
forall a. [a] -> Bool
isSingleton [Alt Id]
alts

    sc_alt :: ScEnv
-> Expr Id
-> Id
-> Alt Id
-> UniqSM (ScUsage, ArgOcc, Alt Id, [SpecFailWarning])
sc_alt ScEnv
env Expr Id
scrut' Id
b' (Alt AltCon
con [Id]
bs Expr Id
rhs)
     = do { let (ScEnv
env1, [Id]
bs1) = HowBound -> ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrsWith HowBound
RecArg ScEnv
env [Id]
bs
                (ScEnv
env2, [Id]
bs2) = ScEnv -> Expr Id -> Id -> AltCon -> [Id] -> (ScEnv, [Id])
extendCaseBndrs ScEnv
env1 Expr Id
scrut' Id
b' AltCon
con [Id]
bs1
          ; (usg, rhs', ws) <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env2 Expr Id
rhs
          ; let (usg', b_occ:arg_occs) = lookupOccs usg (b':bs2)
                scrut_occ = case AltCon
con of
                               DataAlt DataCon
dc -- See Note [Do not specialise evals]
                                  | Bool -> Bool
not (Bool
single_alt Bool -> Bool -> Bool
&& (ArgOcc -> Bool) -> [ArgOcc] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all ArgOcc -> Bool
deadArgOcc [ArgOcc]
arg_occs)
                                  -> DataConEnv [ArgOcc] -> ArgOcc
ScrutOcc (DataCon -> [ArgOcc] -> DataConEnv [ArgOcc]
forall key elt. Uniquable key => key -> elt -> UniqFM key elt
unitUFM DataCon
dc [ArgOcc]
arg_occs)
                               AltCon
_  -> ArgOcc
UnkOcc
          ; return (usg', b_occ `combineOcc` scrut_occ, Alt con bs2 rhs', ws) }


-- | Substitute the free variables captured by a breakpoint.
-- Variables are dropped if they have a non-variable substitution, like in
-- 'GHC.Opt.Specialise.specTickish'.
scTickish :: ScEnv -> CoreTickish -> CoreTickish
scTickish :: ScEnv -> CoreTickish -> CoreTickish
scTickish SCE {sc_subst :: ScEnv -> Subst
sc_subst = Subst
subst} = Subst -> CoreTickish -> CoreTickish
substTickish Subst
subst

{- Note [Do not specialise evals]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   f x y = case x of I# _ ->
           if y>1 then f x (y-1) else x

Here `x` is scrutinised by a case, but only in an eval-like way; the
/component/ of the I# is unused.  We don't want to specialise this
function, even if we find a call (f (I# z)), because nothing is gained
  * No case branches are discarded
  * No allocation in removed
The specialised version would take an unboxed Int#, pass it along,
and rebox it at the end.

In fact this can cause significant regression.  In #21763 we had:
like
  f = ... case x of x' { I# n ->
          join j y = rhs
          in ...jump j x'...

Now if we specialise `j` for the argument `I# n`, we'll end up reboxing
it in `j`, without even removing an allocation from the call site.

Reboxing is always a worry.  But here we can ameliorate the problem as
follows.

* In scExpr (Case ...), for a /single-alternative/ case expression, in
  which the pattern binders are all unused, we build a UnkOcc for
  the scrutinee, not one that maps the data constructor; we don't treat
  this occurrence as a reason for specialisation.

* Conveniently, SpecConstr is doing its own occurrence analysis, so
  the "unused" bit is just looking for NoOcc

* Note that if we have
    f x = case x of { True -> e1; False -> e2 }
  then even though the pattern binders are unused (there are none), it is
  still worth specialising on x. Hence the /single-alternative/ guard.
-}

scApp :: ScEnv -> (InExpr, [InExpr]) -> UniqSM (ScUsage, CoreExpr, SpecFailWarnings)

scApp :: ScEnv
-> (Expr Id, [Expr Id])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scApp ScEnv
env (Var Id
fn, [Expr Id]
args)        -- Function is a variable
  = Bool
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a. HasCallStack => Bool -> a -> a
assert (Bool -> Bool
not ([Expr Id] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Expr Id]
args)) (UniqSM (ScUsage, Expr Id, [SpecFailWarning])
 -> UniqSM (ScUsage, Expr Id, [SpecFailWarning]))
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a b. (a -> b) -> a -> b
$
    do  { args_w_usgs <- (Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning]))
-> [Expr Id] -> UniqSM [(ScUsage, Expr Id, [SpecFailWarning])]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env) [Expr Id]
args
        ; let (arg_usgs, args', arg_ws) = unzip3 args_w_usgs
              arg_usg = [ScUsage] -> ScUsage
combineUsages [ScUsage]
arg_usgs
              arg_w = [[SpecFailWarning]] -> [SpecFailWarning]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[SpecFailWarning]]
arg_ws
        ; case scSubstId env fn of
            fn' :: Expr Id
fn'@(Lam {}) -> [SpecFailWarning]
-> (ScUsage, Expr Id, [SpecFailWarning])
-> (ScUsage, Expr Id, [SpecFailWarning])
withWarnings [SpecFailWarning]
arg_w ((ScUsage, Expr Id, [SpecFailWarning])
 -> (ScUsage, Expr Id, [SpecFailWarning]))
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr (ScEnv -> ScEnv
zapScSubst ScEnv
env) (Expr Id -> [Expr Id] -> Expr Id
doBeta Expr Id
fn' [Expr Id]
args')
                        -- Do beta-reduction and try again

            Var Id
fn' -> (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
arg_usg' ScUsage -> ScUsage -> ScUsage
`combineUsage` ScEnv -> Id -> [Expr Id] -> ScUsage
mkVarUsage ScEnv
env Id
fn' [Expr Id]
args',
                               Expr Id -> [Expr Id] -> Expr Id
forall b. Expr b -> [Expr b] -> Expr b
mkApps (Id -> Expr Id
forall b. Id -> Expr b
Var Id
fn') [Expr Id]
args', [SpecFailWarning]
arg_w )
               where
                 -- arg_usg': see Note [Specialising on dictionaries]
                 arg_usg' :: ScUsage
arg_usg' | Just Class
cls <- Id -> Maybe Class
isClassOpId_maybe Id
fn'
                          , Expr Id
dict_arg : [Expr Id]
_ <- [Id] -> [Expr Id] -> [Expr Id]
forall b a. [b] -> [a] -> [a]
dropList (Class -> [Id]
classTyVars Class
cls) [Expr Id]
args'
                          = ScEnv -> ScUsage -> Expr Id -> ArgOcc -> ScUsage
setScrutOcc ScEnv
env ScUsage
arg_usg Expr Id
dict_arg ArgOcc
evalScrutOcc
                          | Bool
otherwise
                          = ScUsage
arg_usg

            Expr Id
other_fn' -> (ScUsage, Expr Id, [SpecFailWarning])
-> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
arg_usg, Expr Id -> [Expr Id] -> Expr Id
forall b. Expr b -> [Expr b] -> Expr b
mkApps Expr Id
other_fn' [Expr Id]
args', [SpecFailWarning]
arg_w) }
                -- NB: doing this ignores any usage info from the substituted
                --     function, but I don't think that matters.  If it does
                --     we can fix it.
  where
    doBeta :: OutExpr -> [OutExpr] -> OutExpr
    doBeta :: Expr Id -> [Expr Id] -> Expr Id
doBeta (Lam Id
bndr Expr Id
body) (Expr Id
arg : [Expr Id]
args) = OutBind -> Expr Id -> Expr Id
forall b. Bind b -> Expr b -> Expr b
Let (Id -> Expr Id -> OutBind
forall b. b -> Expr b -> Bind b
NonRec Id
bndr Expr Id
arg) (Expr Id -> [Expr Id] -> Expr Id
doBeta Expr Id
body [Expr Id]
args)
    doBeta Expr Id
fn              [Expr Id]
args         = Expr Id -> [Expr Id] -> Expr Id
forall b. Expr b -> [Expr b] -> Expr b
mkApps Expr Id
fn [Expr Id]
args

-- The function is almost always a variable, but not always.
-- In particular, if this pass follows float-in,
-- which it may, we can get
--      (let f = ...f... in f) arg1 arg2
scApp ScEnv
env (Expr Id
other_fn, [Expr Id]
args)
  = do  { (fn_usg,   fn', fn_ws)   <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
env Expr Id
other_fn
        ; (arg_usgs, args', arg_ws) <- mapAndUnzip3M (scExpr env) args
        ; return (combineUsages arg_usgs `combineUsage` fn_usg, mkApps fn' args', combineSpecWarning fn_ws (concat arg_ws)) }

----------------------
mkVarUsage :: ScEnv -> Id -> [CoreExpr] -> ScUsage
mkVarUsage :: ScEnv -> Id -> [Expr Id] -> ScUsage
mkVarUsage ScEnv
env Id
fn [Expr Id]
args
  = case ScEnv -> Id -> Maybe HowBound
lookupHowBound ScEnv
env Id
fn of
        Just HowBound
RecFun -> SCU { scu_calls :: CallEnv
scu_calls = Id -> [Call] -> CallEnv
forall a. Id -> a -> VarEnv a
unitVarEnv Id
fn [Id -> [Expr Id] -> ValueEnv -> Call
Call Id
fn [Expr Id]
args (ScEnv -> ValueEnv
sc_vals ScEnv
env)]
                           , scu_occs :: IdEnv ArgOcc
scu_occs  = IdEnv ArgOcc
forall a. VarEnv a
emptyVarEnv }
        Just HowBound
RecArg -> SCU { scu_calls :: CallEnv
scu_calls = CallEnv
forall a. VarEnv a
emptyVarEnv
                           , scu_occs :: IdEnv ArgOcc
scu_occs  = Id -> ArgOcc -> IdEnv ArgOcc
forall a. Id -> a -> VarEnv a
unitVarEnv Id
fn ArgOcc
arg_occ }
        Maybe HowBound
Nothing     -> ScUsage
nullUsage
  where
    arg_occ :: ArgOcc
arg_occ | [Expr Id] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Expr Id]
args = ArgOcc
UnkOcc
            | Bool
otherwise = ArgOcc
evalScrutOcc

----------------------
scRecRhs :: ScEnv -> (OutId, InExpr) -> UniqSM (RhsInfo, SpecFailWarnings)
scRecRhs :: ScEnv -> (Id, Expr Id) -> UniqSM (RhsInfo, [SpecFailWarning])
scRecRhs ScEnv
env (Id
bndr,Expr Id
rhs)
  = do  { let ([Id]
arg_bndrs,Expr Id
body)       = Expr Id -> ([Id], Expr Id)
forall b. Expr b -> ([b], Expr b)
collectBinders Expr Id
rhs
              (ScEnv
body_env, [Id]
arg_bndrs') = HowBound -> ScEnv -> [Id] -> (ScEnv, [Id])
extendBndrsWith HowBound
RecArg ScEnv
env [Id]
arg_bndrs
        ; (body_usg, body', body_ws)         <- ScEnv -> Expr Id -> UniqSM (ScUsage, Expr Id, [SpecFailWarning])
scExpr ScEnv
body_env Expr Id
body
        ; let (rhs_usg, arg_occs)    = lookupOccs body_usg arg_bndrs'
        ; return (RI { ri_rhs_usg = rhs_usg
                     , ri_fn = bndr, ri_new_rhs = mkLams arg_bndrs' body'
                     , ri_lam_bndrs = arg_bndrs, ri_lam_body = body
                     , ri_arg_occs = arg_occs }, body_ws) }
                -- The arg_occs says how the visible,
                -- lambda-bound binders of the RHS are used
                -- (including the TyVar binders)
                -- Two pats are the same if they match both ways

----------------------
ruleInfoBinds :: RhsInfo -> SpecInfo -> [(Id,CoreExpr)]
ruleInfoBinds :: RhsInfo -> SpecInfo -> [(Id, Expr Id)]
ruleInfoBinds (RI { ri_fn :: RhsInfo -> Id
ri_fn = Id
fn, ri_new_rhs :: RhsInfo -> Expr Id
ri_new_rhs = Expr Id
new_rhs })
              (SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
specs })
  = [(Id
id,Expr Id
rhs) | OS { os_id :: OneSpec -> Id
os_id = Id
id, os_rhs :: OneSpec -> Expr Id
os_rhs = Expr Id
rhs } <- [OneSpec]
specs] [(Id, Expr Id)] -> [(Id, Expr Id)] -> [(Id, Expr Id)]
forall a. [a] -> [a] -> [a]
++
              -- First the specialised bindings

    [(Id
fn Id -> [CoreRule] -> Id
`addIdSpecialisations` [CoreRule]
rules, Expr Id
new_rhs)]
              -- And now the original binding
  where
    rules :: [CoreRule]
rules = [CoreRule
r | OS { os_rule :: OneSpec -> CoreRule
os_rule = CoreRule
r } <- [OneSpec]
specs]

{-
************************************************************************
*                                                                      *
                The specialiser itself
*                                                                      *
************************************************************************
-}

data RhsInfo
  = RI { RhsInfo -> Id
ri_fn :: OutId                 -- The binder
       , RhsInfo -> Expr Id
ri_new_rhs :: OutExpr          -- The specialised RHS (in current envt)
       , RhsInfo -> ScUsage
ri_rhs_usg :: ScUsage          -- Usage info from specialising RHS

       , RhsInfo -> [Id]
ri_lam_bndrs :: [InVar]       -- The *original* RHS (\xs.body)
       , RhsInfo -> Expr Id
ri_lam_body  :: InExpr        --   Note [Specialise original body]
       , RhsInfo -> [ArgOcc]
ri_arg_occs  :: [ArgOcc]      -- Info on how the xs occur in body
    }

data SpecInfo       -- Info about specialisations for a particular Id
  = SI { SpecInfo -> [OneSpec]
si_specs :: [OneSpec]          -- The specialisations we have
                                        -- generated for this function

       , SpecInfo -> Int
si_n_specs :: Int              -- Length of si_specs; used for numbering them

       , SpecInfo -> Maybe ScUsage
si_mb_unspec :: Maybe ScUsage  -- Just cs  => we have not yet used calls in the
       }                                --             from calls in the *original* RHS as
                                        --             seeds for new specialisations;
                                        --             if you decide to do so, here is the
                                        --             RHS usage (which has not yet been
                                        --             unleashed)
                                        -- Nothing => we have
                                        -- See Note [Seeding recursive groups]
                                        -- See Note [spec_usg includes rhs_usg]

        -- One specialisation: Rule plus definition
data OneSpec =
  OS { OneSpec -> CallPat
os_pat  :: CallPat    -- Call pattern that generated this specialisation
     , OneSpec -> CoreRule
os_rule :: CoreRule   -- Rule connecting original id with the specialisation
     , OneSpec -> Id
os_id   :: OutId      -- Spec id
     , OneSpec -> Expr Id
os_rhs  :: OutExpr }  -- Spec rhs

initSpecInfo :: RhsInfo -> SpecInfo
initSpecInfo :: RhsInfo -> SpecInfo
initSpecInfo (RI { ri_rhs_usg :: RhsInfo -> ScUsage
ri_rhs_usg = ScUsage
rhs_usg })
  = SI { si_specs :: [OneSpec]
si_specs = [], si_n_specs :: Int
si_n_specs = Int
0, si_mb_unspec :: Maybe ScUsage
si_mb_unspec = ScUsage -> Maybe ScUsage
forall a. a -> Maybe a
Just ScUsage
rhs_usg }
    -- si_mb_unspec: add in rhs_usg if there are any boring calls,
    --               or if the bndr is exported

----------------------
specNonRec :: ScEnv
           -> CallEnv         -- Calls in body
           -> RhsInfo         -- Structure info usage info for un-specialised RHS
           -> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])       -- Usage from RHSs (specialised and not)
                                               --     plus details of specialisations

specNonRec :: ScEnv
-> CallEnv
-> RhsInfo
-> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])
specNonRec ScEnv
env CallEnv
body_calls RhsInfo
rhs_info
  = ScEnv
-> CallEnv
-> RhsInfo
-> SpecInfo
-> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])
specialise ScEnv
env CallEnv
body_calls RhsInfo
rhs_info (RhsInfo -> SpecInfo
initSpecInfo RhsInfo
rhs_info)

----------------------
specRec :: ScEnv
        -> CallEnv                         -- Calls in body
        -> [RhsInfo]                       -- Structure info and usage info for un-specialised RHSs
        -> UniqSM (ScUsage, [SpecInfo], SpecFailWarnings)
                                           -- Usage from all RHSs (specialised and not)
                                           --     plus details of specialisations

specRec :: ScEnv
-> CallEnv
-> [RhsInfo]
-> UniqSM (ScUsage, [SpecInfo], [SpecFailWarning])
specRec ScEnv
env CallEnv
body_calls [RhsInfo]
rhs_infos
  = Int
-> CallEnv
-> ScUsage
-> [SpecInfo]
-> [SpecFailWarning]
-> UniqSM (ScUsage, [SpecInfo], [SpecFailWarning])
go Int
1 CallEnv
body_calls ScUsage
nullUsage ((RhsInfo -> SpecInfo) -> [RhsInfo] -> [SpecInfo]
forall a b. (a -> b) -> [a] -> [b]
map RhsInfo -> SpecInfo
initSpecInfo [RhsInfo]
rhs_infos) []
    -- body_calls: see Note [Seeding recursive groups]
    -- NB: 'go' always calls 'specialise' once, which in turn unleashes
    --     si_mb_unspec if there are any boring calls in body_calls,
    --     or if any of the Id(s) are exported
  where
    opts :: SpecConstrOpts
opts = ScEnv -> SpecConstrOpts
sc_opts ScEnv
env

    -- Loop, specialising, until you get no new specialisations
    go, go_again :: Int   -- Which iteration of the "until no new specialisations"
                          -- loop we are on; first iteration is 1
                 -> CallEnv   -- Seed calls
                              -- Two accumulating parameters:
                 -> ScUsage      -- Usage from earlier specialisations
                 -> [SpecInfo]   -- Details of specialisations so far
                 -> SpecFailWarnings -- Warnings so far
                 -> UniqSM (ScUsage, [SpecInfo], SpecFailWarnings)
    go :: Int
-> CallEnv
-> ScUsage
-> [SpecInfo]
-> [SpecFailWarning]
-> UniqSM (ScUsage, [SpecInfo], [SpecFailWarning])
go Int
n_iter CallEnv
seed_calls ScUsage
usg_so_far [SpecInfo]
spec_infos [SpecFailWarning]
ws_so_far
      = -- pprTrace "specRec3" (vcat [ text "bndrs" <+> ppr (map ri_fn rhs_infos)
        --                           , text "iteration" <+> int n_iter
        --                          , text "spec_infos" <+> ppr (map (map os_pat . si_specs) spec_infos)
        --                    ]) $
        do  { specs_w_usg <- (RhsInfo
 -> SpecInfo -> UniqSM (ScUsage, SpecInfo, [SpecFailWarning]))
-> [RhsInfo]
-> [SpecInfo]
-> UniqSM [(ScUsage, SpecInfo, [SpecFailWarning])]
forall (m :: * -> *) a b c.
Applicative m =>
(a -> b -> m c) -> [a] -> [b] -> m [c]
zipWithM (ScEnv
-> CallEnv
-> RhsInfo
-> SpecInfo
-> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])
specialise ScEnv
env CallEnv
seed_calls) [RhsInfo]
rhs_infos [SpecInfo]
spec_infos

            ; let (extra_usg_s, all_spec_infos, extra_ws ) = unzip3 specs_w_usg
                  extra_usg = [ScUsage] -> ScUsage
combineUsages [ScUsage]
extra_usg_s
                  all_usg   = ScUsage
usg_so_far ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
extra_usg
                  new_calls = ScUsage -> CallEnv
scu_calls ScUsage
extra_usg
            ; go_again n_iter new_calls all_usg all_spec_infos (ws_so_far ++ concat extra_ws) }

    -- go_again deals with termination
    go_again :: Int
-> CallEnv
-> ScUsage
-> [SpecInfo]
-> [SpecFailWarning]
-> UniqSM (ScUsage, [SpecInfo], [SpecFailWarning])
go_again Int
n_iter CallEnv
seed_calls ScUsage
usg_so_far [SpecInfo]
spec_infos [SpecFailWarning]
ws_so_far
      | CallEnv -> Bool
forall a. VarEnv a -> Bool
isEmptyVarEnv CallEnv
seed_calls
      = (ScUsage, [SpecInfo], [SpecFailWarning])
-> UniqSM (ScUsage, [SpecInfo], [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg_so_far, [SpecInfo]
spec_infos, [SpecFailWarning]
ws_so_far)

      -- Limit recursive specialisation
      -- See Note [Limit recursive specialisation]
      | Int
n_iter Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> SpecConstrOpts -> Int
sc_recursive SpecConstrOpts
opts  -- Too many iterations of the 'go' loop
      , ScEnv -> Bool
sc_force ScEnv
env Bool -> Bool -> Bool
|| Maybe Int -> Bool
forall a. Maybe a -> Bool
isNothing (SpecConstrOpts -> Maybe Int
sc_count SpecConstrOpts
opts)
           -- If both of these are false, the sc_count
           -- threshold will prevent non-termination
           -- See Note [Forcing specialisation], point (FS4) and (FS2)
      , (SpecInfo -> Bool) -> [SpecInfo] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any ((Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
the_limit) (Int -> Bool) -> (SpecInfo -> Int) -> SpecInfo -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. SpecInfo -> Int
si_n_specs) [SpecInfo]
spec_infos
      = -- Give up on specialisation, but don't forget to include the rhs_usg
        -- for the unspecialised function, since it may now be called
        -- pprTrace "specRec2" (ppr (map (map os_pat . si_specs) spec_infos)) $
        let rhs_usgs :: ScUsage
rhs_usgs = [ScUsage] -> ScUsage
combineUsages ((SpecInfo -> Maybe ScUsage) -> [SpecInfo] -> [ScUsage]
forall a b. (a -> Maybe b) -> [a] -> [b]
mapMaybe SpecInfo -> Maybe ScUsage
si_mb_unspec [SpecInfo]
spec_infos)
        in (ScUsage, [SpecInfo], [SpecFailWarning])
-> UniqSM (ScUsage, [SpecInfo], [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
usg_so_far ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
rhs_usgs, [SpecInfo]
spec_infos, [SpecFailWarning]
ws_so_far)

      | Bool
otherwise
      = Int
-> CallEnv
-> ScUsage
-> [SpecInfo]
-> [SpecFailWarning]
-> UniqSM (ScUsage, [SpecInfo], [SpecFailWarning])
go (Int
n_iter Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1) CallEnv
seed_calls ScUsage
usg_so_far [SpecInfo]
spec_infos [SpecFailWarning]
ws_so_far

    -- See Note [Limit recursive specialisation]
    the_limit :: Int
the_limit = case SpecConstrOpts -> Maybe Int
sc_count SpecConstrOpts
opts of
                  Maybe Int
Nothing  -> Int
10    -- Ugh!
                  Just Int
max -> Int
max

----------------------
specialise
   :: ScEnv
   -> CallEnv                     -- Info on newly-discovered calls to this function
   -> RhsInfo
   -> SpecInfo                    -- Original RHS plus patterns dealt with
   -> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])  -- New specialised versions and their usage

-- See Note [spec_usg includes rhs_usg]

-- Note: this only generates *specialised* bindings
-- The original binding is added by ruleInfoBinds
--
-- Note: the rhs here is the optimised version of the original rhs
-- So when we make a specialised copy of the RHS, we're starting
-- from an RHS whose nested functions have been optimised already.

specialise :: ScEnv
-> CallEnv
-> RhsInfo
-> SpecInfo
-> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])
specialise ScEnv
env CallEnv
bind_calls (RI { ri_fn :: RhsInfo -> Id
ri_fn = Id
fn, ri_lam_bndrs :: RhsInfo -> [Id]
ri_lam_bndrs = [Id]
arg_bndrs
                              , ri_lam_body :: RhsInfo -> Expr Id
ri_lam_body = Expr Id
body, ri_arg_occs :: RhsInfo -> [ArgOcc]
ri_arg_occs = [ArgOcc]
arg_occs })
               spec_info :: SpecInfo
spec_info@(SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
specs, si_n_specs :: SpecInfo -> Int
si_n_specs = Int
spec_count
                             , si_mb_unspec :: SpecInfo -> Maybe ScUsage
si_mb_unspec = Maybe ScUsage
mb_unspec })
  | Id -> Bool
isDeadEndId Id
fn  -- Note [Do not specialise diverging functions]
                    -- /and/ do not generate specialisation seeds from its RHS
  = -- pprTrace "specialise bot" (ppr fn) $
    (ScUsage, SpecInfo, [SpecFailWarning])
-> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, SpecInfo
spec_info, [])

  | Bool -> Bool
not (Activation -> Bool
isNeverActive (Id -> Activation
idInlineActivation Id
fn))
      -- See Note [Transfer activation]
      -- Don't specialise OPAQUE things, see Note [OPAQUE pragma].
      -- Since OPAQUE things are always never-active (see
      -- GHC.Parser.PostProcess.mkOpaquePragma) this guard never fires for
      -- OPAQUE things.
  , Bool -> Bool
not ([Id] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [Id]
arg_bndrs)                         -- Only specialise functions
  , Just [Call]
all_calls <- CallEnv -> Id -> Maybe [Call]
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv CallEnv
bind_calls Id
fn -- Some calls to it
  = -- pprTrace "specialise entry {" (ppr fn <+> ppr all_calls) $
    do  { (boring_call, pats_discarded, new_pats, warnings)
             <- ScEnv
-> Id
-> SpecInfo
-> [ArgOcc]
-> [Call]
-> UniqSM (Bool, Bool, [CallPat], [SpecFailWarning])
callsToNewPats ScEnv
env Id
fn SpecInfo
spec_info [ArgOcc]
arg_occs [Call]
all_calls

        ; let n_pats = [CallPat] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [CallPat]
new_pats
--        ; when (not (null new_pats) || isJust mb_unspec) $
--          pprTraceM "specialise" (vcat [ ppr fn <+> text "with" <+> int n_pats <+> text "good patterns"
--                                       , text "boring_call:" <+> ppr boring_call
--                                       , text "pats_discarded:" <+> ppr pats_discarded
--                                       , text "old spec_count" <+> ppr spec_count
--                                       , text "spec count limit" <+> ppr (sc_count (sc_opts env))
--                                       , text "mb_unspec" <+> ppr (isJust mb_unspec)
--                                       , text "arg_occs" <+> ppr arg_occs
--                                       , text "new_pats" <+> ppr new_pats])

        ; let spec_env = ScEnv -> Int -> ScEnv
decreaseSpecCount ScEnv
env Int
n_pats
        ; (spec_usgs, new_specs, new_wss) <- mapAndUnzip3M (spec_one spec_env fn arg_bndrs body)
                                                 (new_pats `zip` [spec_count..])
                -- See Note [Specialise original body]

        ; let spec_usg = [ScUsage] -> ScUsage
combineUsages [ScUsage]
spec_usgs

              unspec_rhs_needed = Bool
pats_discarded Bool -> Bool -> Bool
|| Bool
boring_call Bool -> Bool -> Bool
|| Id -> Bool
isExportedId Id
fn

              -- If there were any boring calls among the seeds (= all_calls), then those
              -- calls will call the un-specialised function.  So we should use the seeds
              -- from the _unspecialised_ function's RHS, which are in mb_unspec, by returning
              -- then in new_usg.
              (new_usg, mb_unspec') = case mb_unspec of
                  Just ScUsage
rhs_usg | Bool
unspec_rhs_needed
                               -> (ScUsage
spec_usg ScUsage -> ScUsage -> ScUsage
`combineUsage` ScUsage
rhs_usg, Maybe ScUsage
forall a. Maybe a
Nothing)
                  Maybe ScUsage
_            -> (ScUsage
spec_usg,                      Maybe ScUsage
mb_unspec)

--        ; pprTraceM "specialise return }" $
--          vcat [ ppr fn
--               , text "unspec_rhs_needed:" <+> ppr unspec_rhs_needed
--               , text "new calls:" <+> ppr (scu_calls new_usg)]

        ; return (new_usg, SI { si_specs     = new_specs ++ specs
                              , si_n_specs   = spec_count + n_pats
                              , si_mb_unspec = mb_unspec' }
                 ,warnings ++ concat new_wss) }

  | Bool
otherwise  -- No calls, inactive, or not a function
               -- Behave as if there was a single, boring call
  = -- pprTrace "specialise inactive" (ppr fn $$ ppr mb_unspec) $
    case Maybe ScUsage
mb_unspec of    -- Behave as if there was a single, boring call
      Just ScUsage
rhs_usg -> (ScUsage, SpecInfo, [SpecFailWarning])
-> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
rhs_usg, SpecInfo
spec_info { si_mb_unspec = Nothing }, [])
                         -- See Note [spec_usg includes rhs_usg]
      Maybe ScUsage
Nothing      -> (ScUsage, SpecInfo, [SpecFailWarning])
-> UniqSM (ScUsage, SpecInfo, [SpecFailWarning])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (ScUsage
nullUsage, SpecInfo
spec_info, [])


---------------------
spec_one :: ScEnv
         -> OutId       -- Function
         -> [InVar]     -- Lambda-binders of RHS; should match patterns
         -> InExpr      -- Body of the original function
         -> (CallPat, Int)
         -> UniqSM (ScUsage, OneSpec, SpecFailWarnings)   -- Rule and binding, warnings if any

-- spec_one creates a specialised copy of the function, together
-- with a rule for using it.  I'm very proud of how short this
-- function is, considering what it does :-).

{-
  Example

     In-scope: a, x::a
     f = /\b \y::[(a,b)] -> ....f (b,c) ((:) (a,(b,c)) (x,v) (h w))...
          [c::*, v::(b,c) are presumably bound by the (...) part]
  ==>
     f_spec = /\ b c \ v::(b,c) hw::[(a,(b,c))] ->
                  (...entire body of f...) [b -> (b,c),
                                            y -> ((:) (a,(b,c)) (x,v) hw)]

     RULE:  forall b::* c::*,           -- Note, *not* forall a, x
                   v::(b,c),
                   hw::[(a,(b,c))] .

            f (b,c) ((:) (a,(b,c)) (x,v) hw) = f_spec b c v hw
-}

spec_one :: ScEnv
-> Id
-> [Id]
-> Expr Id
-> (CallPat, Int)
-> UniqSM (ScUsage, OneSpec, [SpecFailWarning])
spec_one ScEnv
env Id
fn [Id]
arg_bndrs Expr Id
body (CallPat
call_pat, Int
rule_number)
  | CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qvars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
pats, cp_strict_args :: CallPat -> [Id]
cp_strict_args = [Id]
cbv_args } <- CallPat
call_pat
  = do  { -- pprTraceM "spec_one {" (ppr fn <+> ppr pats)

        ; spec_uniq <- UniqSM Unique
forall (m :: * -> *). MonadUnique m => m Unique
getUniqueM
        ; let env1 = ScEnv -> [(Id, Expr Id)] -> ScEnv
extendScSubstList (ScEnv -> [Id] -> ScEnv
extendScInScope ScEnv
env [Id]
qvars)
                                       ([Id]
arg_bndrs [Id] -> [Expr Id] -> [(Id, Expr Id)]
forall a b. [a] -> [b] -> [(a, b)]
`zip` [Expr Id]
pats)
              (body_env, extra_bndrs) = extendBndrs env1 (dropList pats arg_bndrs)
              -- Remember, there may be fewer pats than arg_bndrs
              -- See Note [SpecConstr call patterns]
              -- extra_bndrs will then be arguments in the specialized version
              -- which are *not* applied to arguments immediately at the call sites.
              -- e.g. let f x y = ... in map (f True) xs
              -- will result in y becoming an extra_bndr

              fn_name  = Id -> Name
idName Id
fn
              fn_loc   = Name -> SrcSpan
nameSrcSpan Name
fn_name
              fn_occ   = Name -> OccName
nameOccName Name
fn_name
              spec_occ = OccName -> OccName
mkSpecOcc OccName
fn_occ
              -- We use fn_occ rather than fn in the rule_name string
              -- as we don't want the uniq to end up in the rule, and
              -- hence in the ABI, as that can cause spurious ABI
              -- changes (#4012).
              rule_name  = String -> FastString
mkFastString (String
"SC:" String -> String -> String
forall a. [a] -> [a] -> [a]
++ OccName -> String
occNameString OccName
fn_occ String -> String -> String
forall a. [a] -> [a] -> [a]
++ Int -> String
forall a. Show a => a -> String
show Int
rule_number)
              spec_name  = Unique -> OccName -> SrcSpan -> Name
mkInternalName Unique
spec_uniq OccName
spec_occ SrcSpan
fn_loc

        -- Specialise the body
        -- ; pprTraceM "body_subst_for" $ ppr (spec_occ) $$ ppr (sc_subst body_env)
        ; (spec_usg, spec_body, body_warnings) <- scExpr body_env body

                -- And build the results
        ; (qvars', pats') <- generaliseDictPats qvars pats
        ; let spec_body_ty = HasDebugCallStack => Expr Id -> InType
Expr Id -> InType
exprType Expr Id
spec_body
              (spec_lam_args, spec_call_args, spec_sig)
                  = calcSpecInfo fn arg_bndrs call_pat extra_bndrs

              spec_arity = (Id -> Bool) -> [Id] -> Int
forall a. (a -> Bool) -> [a] -> Int
count Id -> Bool
isId [Id]
spec_lam_args
              spec_join_arity | Id -> Bool
isJoinId Id
fn = Int -> JoinPointHood
JoinPoint ([Id] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Id]
spec_call_args)
                              | Bool
otherwise   = JoinPointHood
NotJoinPoint
              spec_id    = Id -> Id
asWorkerLikeId (Id -> Id) -> Id -> Id
forall a b. (a -> b) -> a -> b
$
                           HasDebugCallStack => Name -> InType -> InType -> Id
Name -> InType -> InType -> Id
mkLocalId Name
spec_name InType
ManyTy
                                     ([Id] -> InType -> InType
mkLamTypes [Id]
spec_lam_args InType
spec_body_ty)
                             -- See Note [Transfer strictness]
                             Id -> DmdSig -> Id
`setIdDmdSig`    DmdSig
spec_sig
                             Id -> CprSig -> Id
`setIdCprSig`    CprSig
topCprSig
                             Id -> Int -> Id
`setIdArity`     Int
spec_arity
                             Id -> JoinPointHood -> Id
`asJoinId_maybe` JoinPointHood
spec_join_arity

        -- Conditionally use result of new worker-wrapper transform
        -- mkSeqs: see Note [SpecConstr and strict fields]
              spec_rhs = [Id] -> Expr Id -> Expr Id
forall b. [b] -> Expr b -> Expr b
mkLams [Id]
spec_lam_args ([Id] -> InType -> Expr Id -> Expr Id
mkSeqs [Id]
cbv_args InType
spec_body_ty Expr Id
spec_body)
              rule_rhs = Expr Id -> [Id] -> Expr Id
forall b. Expr b -> [Id] -> Expr b
mkVarApps (Id -> Expr Id
forall b. Id -> Expr b
Var Id
spec_id) [Id]
spec_call_args
              inline_act = Id -> Activation
idInlineActivation Id
fn
              this_mod   = SpecConstrOpts -> Module
sc_module (SpecConstrOpts -> Module) -> SpecConstrOpts -> Module
forall a b. (a -> b) -> a -> b
$ ScEnv -> SpecConstrOpts
sc_opts ScEnv
env
              rule       = Module
-> Bool
-> Bool
-> FastString
-> Activation
-> Name
-> [Id]
-> [Expr Id]
-> Expr Id
-> CoreRule
mkRule Module
this_mod Bool
True {- Auto -} Bool
True {- Local -}
                                  FastString
rule_name Activation
inline_act
                                  Name
fn_name [Id]
qvars' [Expr Id]
pats' Expr Id
rule_rhs
                           -- See Note [Transfer activation]

--        ; pprTraceM "spec_one end }" $
--          vcat [ text "function:" <+> ppr fn <+> braces (ppr (idUnique fn))
--               , text "pats:" <+> ppr pats
--               , text "call_pat:" <+> ppr call_pat
--               , text "-->" <+> ppr spec_name
--               , text "bndrs" <+> ppr arg_bndrs
--               , text "extra_bndrs" <+> ppr extra_bndrs
--               , text "cbv_args" <+> ppr cbv_args
--               , text "spec_lam_args" <+> ppr spec_lam_args
--               , text "spec_call_args" <+> ppr spec_call_args
--               , text "rule_rhs" <+> ppr rule_rhs
--               , text "adds_void_worker_arg" <+> ppr add_void_arg
----               , text "body" <+> ppr body
----               , text "spec_rhs" <+> ppr spec_rhs
----               , text "how_bound" <+> ppr (sc_how_bound env) ]
--               ]
        ; return (spec_usg, OS { os_pat = call_pat, os_rule = rule
                               , os_id = spec_id
                               , os_rhs = spec_rhs }, body_warnings) }

generaliseDictPats :: [Var] -> [CoreExpr]  -- Quantified vars and pats
                   -> UniqSM ([Var], [CoreExpr]) -- New quantified vars and pats
-- See Note [generaliseDictPats]
generaliseDictPats :: [Id] -> [Expr Id] -> UniqSM ([Id], [Expr Id])
generaliseDictPats [Id]
qvars [Expr Id]
pats
  = do { (extra_qvars, pats') <- ([Id] -> Expr Id -> UniqSM ([Id], Expr Id))
-> [Id] -> [Expr Id] -> UniqSM ([Id], [Expr Id])
forall (m :: * -> *) (t :: * -> *) acc x y.
(Monad m, Traversable t) =>
(acc -> x -> m (acc, y)) -> acc -> t x -> m (acc, t y)
mapAccumLM [Id] -> Expr Id -> UniqSM ([Id], Expr Id)
go [] [Expr Id]
pats
       ; case extra_qvars of
             [] -> ([Id], [Expr Id]) -> UniqSM ([Id], [Expr Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return ([Id]
qvars,                [Expr Id]
pats)
             [Id]
_  -> ([Id], [Expr Id]) -> UniqSM ([Id], [Expr Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return ([Id]
qvars [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id]
extra_qvars, [Expr Id]
pats') }
  where
    qvar_set :: VarSet
qvar_set = [Id] -> VarSet
mkVarSet [Id]
qvars
    go :: [Id] -> CoreExpr -> UniqSM ([Id], CoreExpr)
    go :: [Id] -> Expr Id -> UniqSM ([Id], Expr Id)
go [Id]
extra_qvs Expr Id
pat
       | Bool -> Bool
not (Expr Id -> Bool
forall b. Expr b -> Bool
isTyCoArg Expr Id
pat)
       , let pat_ty :: InType
pat_ty = HasDebugCallStack => Expr Id -> InType
Expr Id -> InType
exprType Expr Id
pat
       , InType -> Bool
typeDeterminesValue InType
pat_ty
       , Expr Id -> VarSet
exprFreeVars Expr Id
pat VarSet -> VarSet -> Bool
`disjointVarSet` VarSet
qvar_set
       = do { id <- FastString -> InType -> InType -> UniqSM Id
forall (m :: * -> *).
MonadUnique m =>
FastString -> InType -> InType -> m Id
mkSysLocalOrCoVarM (String -> FastString
fsLit String
"dict") InType
ManyTy InType
pat_ty
            ; return (id:extra_qvs, Var id) }
       | Bool
otherwise
       = ([Id], Expr Id) -> UniqSM ([Id], Expr Id)
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return ([Id]
extra_qvs, Expr Id
pat)

mkSeqs :: [Var] -> Type -> CoreExpr -> CoreExpr
-- See Note [SpecConstr and strict fields]
mkSeqs :: [Id] -> InType -> Expr Id -> Expr Id
mkSeqs [Id]
seqees InType
res_ty Expr Id
rhs =
  (Id -> Expr Id -> Expr Id) -> Expr Id -> [Id] -> Expr Id
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Id -> Expr Id -> Expr Id
addEval Expr Id
rhs [Id]
seqees
    where
      addEval :: Var -> CoreExpr -> CoreExpr
      addEval :: Id -> Expr Id -> Expr Id
addEval Id
arg_id Expr Id
rhs
        -- Argument representing strict field and it's worth passing via cbv
        | Id -> Bool
shouldStrictifyIdForCbv Id
arg_id
        = Expr Id -> Id -> InType -> [Alt Id] -> Expr Id
forall b. Expr b -> b -> InType -> [Alt b] -> Expr b
Case (Id -> Expr Id
forall b. Id -> Expr b
Var Id
arg_id)
               (Id -> Id
localiseId Id
arg_id)  -- See (SCF1) in Note [SpecConstr and strict fields]
               InType
res_ty
               ([AltCon -> [Id] -> Expr Id -> Alt Id
forall b. AltCon -> [b] -> Expr b -> Alt b
Alt AltCon
DEFAULT [] Expr Id
rhs])

        | Bool
otherwise
        = Expr Id
rhs


{- Note [SpecConstr void argument insertion]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider a function
    f :: Bool -> forall t. blah
    f start @t = e
We want to specialize for a partially applied call `f True`.
See also Note [SpecConstr call patterns], second Wrinkle.
Naively we would expect to get
    $sf :: forall t. blah
    $sf @t = $se
    RULE: f True = $sf
The specialized function only takes a single type argument so we add a
void argument to prevent it from turning into a thunk. See Note
[Protecting the last value argument] for details why. Normally we
would add the void argument after the type argument giving us:

    $sf :: forall t. Void# -> bla
    $sf @t void = $se
    RULE: f True = $sf void# (wrong)

But if you look closely this wouldn't typecheck!  If we substitute `f
True` with `$sf void#` we expect the type argument to be applied first
but we apply void# first.  The easiest fix seems to be just to add the
void argument to the front of the arguments.  Now we get:

    $sf :: Void# -> forall t. bla
    $sf void @t = $se
    RULE: f True = $sf void#

And now we can substitute `f True` with `$sf void#` with everything working out nicely!

More precisely, in `calcSpecInfo`
(i)  we need the void arg to /precede/ the `extra_bndrs`, but
(ii) it must still /follow/ `qvar_bndrs`.

Example to illustrate (ii):
  f :: forall r (a :: TYPE r). Bool -> a
  f = /\r. /\(a::TYPE r). \b. body

  {- Specialise for f _ _ True -}

  $sf :: forall r (a :: TYPE r). Void# -> a
  $sf = /\r. /\(a::TYPE r). \v. body[True/b]
  RULE: forall r (a :: TYPE r). f @r @a True = $sf @r @a void#

The void argument must follow the foralls, lest the forall be
ill-kinded.  See Note [Worker/wrapper needs to add void arg last] in
GHC.Core.Opt.WorkWrap.Utils.

Note [generaliseDictPats]
~~~~~~~~~~~~~~~~~~~~~~~~~
Consider these two rules (#21831, item 2):
  RULE "SPEC:foo"  forall d1 d2. foo @Int @Integer d1 d2 = $sfoo1
  RULE "SC:foo"    forall a. foo @Int @a $fNumInteger = $sfoo2 @a
The former comes from the type class specialiser, the latter from SpecConstr.
Note that $fNumInteger is a top-level binding for Num Integer.

The trouble is that neither is more general than the other.  In a call
   (foo @Int @Integer $fNumInteger d)
it isn't clear which rule to fire.

The trouble is that the SpecConstr rule fires on a /specific/ dict, $fNumInteger,
but actually /could/ fire regardless.  That is, it could be
  RULE "SC:foo"    forall a d. foo @Int @a d = $sfoo2 @a

Now, it is clear that SPEC:foo is more specific.  But GHC can't tell
that, because SpecConstr doesn't know that dictionary arguments are
singleton types!  So generaliseDictPats teaches it this fact.  It
spots such patterns (using typeDeterminesValue), and quantifies over
the dictionary.  Now we get

  RULE "SC:foo"    forall a d. foo @Int @a d = $sfoo2 @a

And /now/ "SPEC:foo" is clearly more specific: we can instantiate the new
"SC:foo" to match the (prefix of) "SPEC:foo".
-}

calcSpecInfo :: Id           -- The original function
             -> [InVar]      -- Lambda binders of original RHS
             -> CallPat      -- Call pattern
             -> [Var]        -- Extra bndrs
             -> ( [Var]           -- Demand-decorated lambda binders
                                  --   for RHS of specialised function
                , [Var]           -- Args for call site
                , DmdSig )        -- Strictness of specialised thing
-- Calculate bits of IdInfo for the specialised function
-- See Note [Transfer strictness]
-- See Note [Strictness information in worker binders]
calcSpecInfo :: Id -> [Id] -> CallPat -> [Id] -> ([Id], [Id], DmdSig)
calcSpecInfo Id
fn [Id]
arg_bndrs (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qvars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
pats }) [Id]
extra_bndrs
  = ( [Id]
spec_lam_bndrs_w_dmds
    , [Id]
spec_call_args
    , DmdSig -> DmdSig
zapDmdEnvSig (DmdType -> DmdSig
DmdSig (DmdType
dt{dt_args = spec_fn_dmds})) )
  where
    DmdSig dt :: DmdType
dt@DmdType{dt_args :: DmdType -> [Demand]
dt_args=[Demand]
fn_dmds} = Id -> DmdSig
idDmdSig Id
fn
    spec_fn_dmds :: [Demand]
spec_fn_dmds = [Id -> Demand
idDemandInfo Id
b | Id
b <- [Id]
spec_lam_bndrs_w_dmds, Id -> Bool
isId Id
b]

    val_pats :: [Expr Id]
val_pats   = (Expr Id -> Bool) -> [Expr Id] -> [Expr Id]
forall a. (a -> Bool) -> [a] -> [a]
filterOut Expr Id -> Bool
forall b. Expr b -> Bool
isTypeArg [Expr Id]
pats
                 -- Value args at call sites, used to determine how many demands to drop
                 -- from the original functions demand and for setting up arg_dmd_env.
    arg_dmd_env :: VarEnv Demand
arg_dmd_env = VarEnv Demand -> [Demand] -> [Expr Id] -> VarEnv Demand
go VarEnv Demand
forall a. VarEnv a
emptyVarEnv [Demand]
fn_dmds [Expr Id]
val_pats
    qvar_dmds :: [Demand]
qvar_dmds  = [ VarEnv Demand -> Id -> Maybe Demand
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv VarEnv Demand
arg_dmd_env Id
qv Maybe Demand -> Demand -> Demand
forall a. Maybe a -> a -> a
`orElse` Demand
topDmd | Id
qv <- [Id]
qvars, Id -> Bool
isId Id
qv ]
    extra_dmds :: [Demand]
extra_dmds = [Expr Id] -> [Demand] -> [Demand]
forall b a. [b] -> [a] -> [a]
dropList [Expr Id]
val_pats [Demand]
fn_dmds

    -- Annotate the variables with the strictness information from
    -- the function (see Note [Strictness information in worker binders])
    qvars_w_dmds :: [Id]
qvars_w_dmds          = [Id] -> [Demand] -> [Id]
set_dmds [Id]
qvars       [Demand]
qvar_dmds
    extras_w_dmds :: [Id]
extras_w_dmds         = [Id] -> [Demand] -> [Id]
set_dmds [Id]
extra_bndrs [Demand]
extra_dmds
    spec_lam_bndrs_w_dmds :: [Id]
spec_lam_bndrs_w_dmds = [Id]
final_qvars_w_dmds [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id]
extras_w_dmds

    ([Id]
final_qvars_w_dmds, [Id]
spec_call_args)
       | Id -> [Id] -> [Id] -> Bool
needsVoidWorkerArg Id
fn [Id]
arg_bndrs ([Id]
qvars [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id]
extra_bndrs)
         -- Usual w/w hack to avoid generating
         -- a spec_rhs of unlifted or ill-kinded type and no args.
         -- See Note [SpecConstr void argument insertion]
       = ( [Id]
qvars_w_dmds [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id
voidArgId], [Id]
qvars [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ [Id
voidPrimId] )
       | Bool
otherwise
       = ( [Id]
qvars_w_dmds,                [Id]
qvars )

    set_dmds :: [Var] -> [Demand] -> [Var]
    set_dmds :: [Id] -> [Demand] -> [Id]
set_dmds [] [Demand]
_   = []
    set_dmds [Id]
vs  [] = [Id]
vs  -- Run out of demands
    set_dmds (Id
v:[Id]
vs) ds :: [Demand]
ds@(Demand
d:[Demand]
ds') | Id -> Bool
isTyVar Id
v = Id
v                   Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
: [Id] -> [Demand] -> [Id]
set_dmds [Id]
vs [Demand]
ds
                               | Bool
otherwise = Id -> Demand -> Id
setIdDemandInfo Id
v Demand
d Id -> [Id] -> [Id]
forall a. a -> [a] -> [a]
: [Id] -> [Demand] -> [Id]
set_dmds [Id]
vs [Demand]
ds'

    go :: VarEnv Demand -> [Demand] -> [CoreExpr] -> VarEnv Demand
    -- We've filtered out all the type patterns already
    go :: VarEnv Demand -> [Demand] -> [Expr Id] -> VarEnv Demand
go VarEnv Demand
env (Demand
d:[Demand]
ds) (Expr Id
pat : [Expr Id]
pats)     = VarEnv Demand -> [Demand] -> [Expr Id] -> VarEnv Demand
go (VarEnv Demand -> Demand -> Expr Id -> VarEnv Demand
go_one VarEnv Demand
env Demand
d Expr Id
pat) [Demand]
ds [Expr Id]
pats
    go VarEnv Demand
env [Demand]
_      [Expr Id]
_                = VarEnv Demand
env

    go_one :: VarEnv Demand -> Demand -> CoreExpr -> VarEnv Demand
    go_one :: VarEnv Demand -> Demand -> Expr Id -> VarEnv Demand
go_one VarEnv Demand
env Demand
d          (Var Id
v) = (Demand -> Demand -> Demand)
-> VarEnv Demand -> Id -> Demand -> VarEnv Demand
forall a. (a -> a -> a) -> VarEnv a -> Id -> a -> VarEnv a
extendVarEnv_C Demand -> Demand -> Demand
plusDmd VarEnv Demand
env Id
v Demand
d
    go_one VarEnv Demand
env (Card
_n :* SubDemand
cd) Expr Id
e -- NB: _n does not have to be strict
      | (Var Id
_, [Expr Id]
args) <- Expr Id -> (Expr Id, [Expr Id])
forall b. Expr b -> (Expr b, [Expr b])
collectArgs Expr Id
e
      , Just (Boxity
_b, [Demand]
ds) <- Int -> SubDemand -> Maybe (Boxity, [Demand])
viewProd ([Expr Id] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [Expr Id]
args) SubDemand
cd -- TODO: We may want to look at boxity _b, though...
      = VarEnv Demand -> [Demand] -> [Expr Id] -> VarEnv Demand
go VarEnv Demand
env [Demand]
ds [Expr Id]
args
    go_one VarEnv Demand
env Demand
_  Expr Id
_ = VarEnv Demand
env

{-
Note [spec_usg includes rhs_usg]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In calls to 'specialise', the returned ScUsage must include the rhs_usg in
the passed-in SpecInfo in si_mb_unspec, unless there are no calls at all to
the function.

The caller can, indeed must, assume this.  They should not combine in rhs_usg
themselves, or they'll get rhs_usg twice -- and that can lead to an exponential
blowup of duplicates in the CallEnv.  This is what gave rise to the massive
performance loss in #8852.

Note [Specialise original body]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The RhsInfo for a binding keeps the *original* body of the binding.  We
must specialise that, *not* the result of applying specExpr to the RHS
(which is also kept in RhsInfo). Otherwise we end up specialising a
specialised RHS, and that can lead directly to exponential behaviour.

Note [Transfer activation]
~~~~~~~~~~~~~~~~~~~~~~~~~~
  This note is for SpecConstr, but exactly the same thing
  happens in the overloading specialiser; see
  Note [Auto-specialisation and RULES] in GHC.Core.Opt.Specialise.

In which phase should the specialise-constructor rules be active?
Originally I made them always-active, but Manuel found that this
defeated some clever user-written rules.  Then I made them active only
in FinalPhase; after all, currently, the specConstr transformation is
only run after the simplifier has reached FinalPhase, but that meant
that specialisations didn't fire inside wrappers; see test
simplCore/should_compile/spec-inline.

So now I just use the inline-activation of the parent Id, as the
activation for the specialisation RULE, just like the main specialiser;

This in turn means there is no point in specialising NOINLINE things,
so we test for that.

Note [Transfer strictness]
~~~~~~~~~~~~~~~~~~~~~~~~~~
We must transfer strictness information from the original function to
the specialised one.  Suppose, for example

  f has strictness     SSx
        and a RULE     f (a:as) b = f_spec a as b

Now we want f_spec to have strictness  LLSx, otherwise we'll use call-by-need
when calling f_spec instead of call-by-value.  And that can result in
unbounded worsening in space (cf the classic foldl vs foldl')

See #3437 for a good example.

The function calcSpecStrictness performs the calculation.

Note [Strictness information in worker binders]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
After having calculated the strictness annotation for the worker (see Note
[Transfer strictness] above), we also want to have this information attached to
the worker’s arguments, for the benefit of later passes. The function
handOutStrictnessInformation decomposes the strictness annotation calculated by
calcSpecStrictness and attaches them to the variables.


************************************************************************
*                                                                      *
\subsection{Argument analysis}
*                                                                      *
************************************************************************

This code deals with analysing call-site arguments to see whether
they are constructor applications.

Note [Free type variables of the qvar types]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In a call (f @a x True), that we want to specialise, what variables should
we quantify over.  Clearly over 'a' and 'x', but what about any type variables
free in x's type?  In fact we don't need to worry about them because (f @a)
can only be a well-typed application if its type is compatible with x, so any
variables free in x's type must be free in (f @a), and hence either be gathered
via 'a' itself, or be in scope at f's defn.  Hence we just take
  (exprsFreeVars pats).

BUT phantom type synonyms can mess this reasoning up,
  eg   x::T b   with  type T b = Int
So we apply expandTypeSynonyms to the bound Ids.
See # 5458.  Yuk.

Note [SpecConstr call patterns]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
A "call patterns" that we collect is going to become the LHS of a RULE.

Wrinkles:

* The list of argument patterns, cp_args, is no longer than the
  visible lambdas of the binding, ri_arg_occs.  This is done via
  the zipWithM in callToPat.

* The list of argument patterns can certainly be shorter than the
  lambdas in the function definition (under-saturated).  For example
      f x y = case x of { True -> e1; False -> e2 }
      ....map (f True) e...
  We want to specialise `f` for `f True`.

* In fact we deliberately shrink the list of argument patterns,
  cp_args, by trimming off all the boring ones at the end (see
  `dropWhileEnd is_boring` in callToPat).  Since the RULE only
  applies when it is saturated, this shrinking makes the RULE more
  applicable.  But it does mean that the argument patterns do not
  necessarily saturate the lambdas of the function.

* It's important that the pattern arguments do not look like
     e |> Refl
  or
    e |> g1 |> g2
  because both of these will be optimised by Simplify.simplRule. In the
  former case such optimisation benign, because the rule will match more
  terms; but in the latter we may lose a binding of 'g1' or 'g2', and
  end up with a rule LHS that doesn't bind the template variables
  (#10602).

  The simplifier eliminates such things, but SpecConstr itself constructs
  new terms by substituting.  So the 'mkCast' in the Cast case of scExpr
  is very important!

Note [Choosing patterns]
~~~~~~~~~~~~~~~~~~~~~~~~
If we get lots of patterns we may not want to make a specialisation
for each of them (code bloat), so we choose as follows, implemented
by trim_pats.

* The flag -fspec-constr-count-N sets the sc_count field
  of the ScEnv to (Just n).  This limits the total number
  of specialisations for a given function to N.

* -fno-spec-constr-count sets the sc_count field to Nothing,
  which switches of the limit.

* The ghastly ForceSpecConstr trick also switches of the limit
  for a particular function

* Otherwise we sort the patterns to choose the most general
  ones first; more general => more widely applicable.

Note [SpecConstr and casts]
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider (#14270) a call like

    let f = e
    in ... f (K @(a |> cv)) ...

where 'cv' is a coercion variable not in scope at f's definition site.
If we aren't careful we'll get

    let $sf a cv = e (K @(a |> cv))
        RULE "SC:f" forall a cv.  f (K @(a |> cv)) = $sf a co
        f = e
    in ...

But alas, when we match the call we may fail to bind 'co', because the rule
matcher in GHC.Core.Rules cannot reliably bind coercion variables that appear
in casts (see Note [Casts in the template] in GHC.Core.Rules).

This seems intractable (see #23209). So:

* Key point: we /never/ quantify over coercion variables in a SpecConstr rule.
  If we would need to quantify over a coercion variable, we just discard the
  call pattern. See the test for `bad_covars` in callToPat.

* However (#14936) we /do/ still allow casts in call patterns. For example
     f ((e1,e2) |> sym co)
  where, say,
     f  :: Foo -> blah   -- Foo is a newtype
     f = f_rhs
     co :: Foo ~R (Int,Int)
  We want to specialise on that pair!

So for our function f, we might generate
  RULE forall x y.  f ((x,y) |> co) = $sf x y
  $sf x y = f_rhs ((x,y) |> co)

This works provided the free vars of `co` are either in-scope at the
definition of `f`, or quantified. For the latter, suppose `f` was polymorphic:

     f2  :: Foo2 a -> blah   -- Foo is a newtype
     f2 = f2_rhs
     co2 :: Foo a ~R (a,a)

Then it's fine for `co2` to mention `a`.  We'll get
  RULE forall a (x::a) (y::a).  f2 @a ((x,y) |> co2) = $sf2 a x y
  $sf2 @a x y = f2_rhs ((x,y) |> co2)
-}

data CallPat = CP { CallPat -> [Id]
cp_qvars :: [Var]           -- Quantified variables
                  , CallPat -> [Expr Id]
cp_args  :: [CoreExpr]      -- Arguments
                  , CallPat -> [Id]
cp_strict_args :: [Var] }   -- Arguments we want to pass unlifted even if they are boxed
                                                -- See Note [SpecConstr and strict fields]

     -- See Note [SpecConstr call patterns]

instance Outputable CallPat where
  ppr :: CallPat -> SDoc
ppr (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qvars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
args, cp_strict_args :: CallPat -> [Id]
cp_strict_args =  [Id]
strict })
    = String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"CP" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc
braces ([SDoc] -> SDoc
forall doc. IsLine doc => [doc] -> doc
sep [ String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"cp_qvars =" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> [Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
qvars SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> SDoc
forall doc. IsLine doc => doc
comma
                               , String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"cp_args =" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> [Expr Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Expr Id]
args
                               , String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"cp_strict_args = " SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> [Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Id]
strict ])

newtype SpecFailWarning = SpecFailForcedArgCount { SpecFailWarning -> Name
spec_failed_fun_name :: Name }

type SpecFailWarnings = [SpecFailWarning]

instance Outputable SpecFailWarning where
  ppr :: SpecFailWarning -> SDoc
ppr (SpecFailForcedArgCount Name
name) = Name -> SDoc
forall a. Outputable a => a -> SDoc
ppr Name
name SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> Name -> SDoc
pprDefinedAt Name
name

combineSpecWarning :: SpecFailWarnings -> SpecFailWarnings -> SpecFailWarnings
combineSpecWarning :: [SpecFailWarning] -> [SpecFailWarning] -> [SpecFailWarning]
combineSpecWarning = [SpecFailWarning] -> [SpecFailWarning] -> [SpecFailWarning]
forall a. [a] -> [a] -> [a]
(++)

data ArgCountResult = WorkerSmallEnough | WorkerTooLarge | WorkerTooLargeForced Name

callsToNewPats :: ScEnv -> Id
               -> SpecInfo
               -> [ArgOcc] -> [Call]
               -> UniqSM ( Bool        -- At least one boring call
                         , Bool        -- Patterns were discarded
                         , [CallPat]   -- Patterns to specialise
                         , [SpecFailWarning] -- Things that didn't specialise we want to warn the user about)
                         )
-- Result has no duplicate patterns,
-- nor ones mentioned in si_specs (hence "new" patterns)
-- Bool indicates that there was at least one boring pattern
-- The "New" in the name means "patterns that are not already covered
-- by an existing specialisation"
callsToNewPats :: ScEnv
-> Id
-> SpecInfo
-> [ArgOcc]
-> [Call]
-> UniqSM (Bool, Bool, [CallPat], [SpecFailWarning])
callsToNewPats ScEnv
env Id
fn spec_info :: SpecInfo
spec_info@(SI { si_specs :: SpecInfo -> [OneSpec]
si_specs = [OneSpec]
done_specs }) [ArgOcc]
bndr_occs [Call]
calls
  = do  { mb_pats <- (Call -> UniqSM (Maybe CallPat))
-> [Call] -> UniqSM [Maybe CallPat]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe CallPat)
callToPat ScEnv
env [ArgOcc]
bndr_occs) [Call]
calls

        ; let have_boring_call = (Maybe CallPat -> Bool) -> [Maybe CallPat] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any Maybe CallPat -> Bool
forall a. Maybe a -> Bool
isNothing [Maybe CallPat]
mb_pats

              good_pats :: [CallPat]
              good_pats = [Maybe CallPat] -> [CallPat]
forall a. [Maybe a] -> [a]
catMaybes [Maybe CallPat]
mb_pats

              in_scope = Subst -> InScopeSet
getSubstInScope (ScEnv -> Subst
sc_subst ScEnv
env)

              -- Remove patterns we have already done
              new_pats = (CallPat -> Bool) -> [CallPat] -> [CallPat]
forall a. (a -> Bool) -> [a] -> [a]
filterOut CallPat -> Bool
is_done [CallPat]
good_pats
              is_done CallPat
p = (OneSpec -> Bool) -> [OneSpec] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any OneSpec -> Bool
is_better [OneSpec]
done_specs
                 where
                   is_better :: OneSpec -> Bool
is_better OneSpec
done = InScopeSet -> CallPat -> CallPat -> Bool
betterPat InScopeSet
in_scope (OneSpec -> CallPat
os_pat OneSpec
done) CallPat
p

              -- Remove duplicates
              non_dups = InScopeSet -> [CallPat] -> [CallPat]
subsumePats InScopeSet
in_scope [CallPat]
new_pats

              -- Remove ones that have too many worker variables
              (small_pats, arg_count_warnings) = partitionByWorkerSize too_many_worker_args non_dups

              -- too_many_worker_args :: CallPat -> Either SpecFailWarning Bool
              too_many_worker_args (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
vars, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
args })
                | ScEnv -> Bool
sc_force ScEnv
env
                -- See (FS5) of Note [Forcing specialisation]
                = if (Int -> Int -> [Id] -> Bool
isWorkerSmallEnough (SpecConstrOpts -> Int
sc_max_forced_args (SpecConstrOpts -> Int) -> SpecConstrOpts -> Int
forall a b. (a -> b) -> a -> b
$ ScEnv -> SpecConstrOpts
sc_opts ScEnv
env) ([Expr Id] -> Int
forall b. [Arg b] -> Int
valArgCount [Expr Id]
args) [Id]
vars)
                    then ArgCountResult
WorkerSmallEnough
                    else Name -> ArgCountResult
WorkerTooLargeForced (Id -> Name
idName Id
fn)
                | (Int -> Int -> [Id] -> Bool
isWorkerSmallEnough (SpecConstrOpts -> Int
sc_max_args (SpecConstrOpts -> Int) -> SpecConstrOpts -> Int
forall a b. (a -> b) -> a -> b
$ ScEnv -> SpecConstrOpts
sc_opts ScEnv
env) ([Expr Id] -> Int
forall b. [Arg b] -> Int
valArgCount [Expr Id]
args) [Id]
vars)
                = ArgCountResult
WorkerSmallEnough
                | Bool
otherwise = ArgCountResult
WorkerTooLarge
                  -- We are about to construct w/w pair in 'spec_one'.
                  -- Omit specialisation leading to high arity workers.
                  -- See Note [Limit w/w arity] in GHC.Core.Opt.WorkWrap.Utils

                -- Discard specialisations if there are too many of them
              (pats_were_discarded, trimmed_pats) = trim_pats env fn spec_info small_pats

--        ; pprTraceM "callsToPats" (vcat [ text "calls to" <+> ppr fn <> colon <+> ppr calls
--                                        , text "good_pats:" <+> ppr good_pats
--                                        , text "new_pats:" <+> ppr new_pats
--                                        , text "non_dups:" <+> ppr non_dups
--                                        , text "small_pats:" <+> ppr small_pats
--                                        , text "done_specs:" <+> ppr (map os_pat done_specs)
--                                        , text "trimmed_pats:" <+> ppr trimmed_pats ])

        ; return (have_boring_call, pats_were_discarded, trimmed_pats, arg_count_warnings) }
          -- If any of the calls does not give rise to a specialisation, either
          -- because it is boring, or because there are too many specialisations,
          -- return a flag to say so, so that we know to keep the original function.
  where
    partitionByWorkerSize :: (a -> ArgCountResult) -> [a] -> ([a], [SpecFailWarning])
partitionByWorkerSize a -> ArgCountResult
worker_size [a]
pats = [a] -> [a] -> [SpecFailWarning] -> ([a], [SpecFailWarning])
go [a]
pats [] []
      where
        go :: [a] -> [a] -> [SpecFailWarning] -> ([a], [SpecFailWarning])
go [] [a]
small [SpecFailWarning]
warnings = ([a]
small, [SpecFailWarning]
warnings)
        go (a
p:[a]
ps) [a]
small [SpecFailWarning]
warnings =
          case a -> ArgCountResult
worker_size a
p of
            ArgCountResult
WorkerSmallEnough -> [a] -> [a] -> [SpecFailWarning] -> ([a], [SpecFailWarning])
go [a]
ps (a
pa -> [a] -> [a]
forall a. a -> [a] -> [a]
:[a]
small) [SpecFailWarning]
warnings
            ArgCountResult
WorkerTooLarge -> [a] -> [a] -> [SpecFailWarning] -> ([a], [SpecFailWarning])
go [a]
ps [a]
small [SpecFailWarning]
warnings
            WorkerTooLargeForced Name
name -> [a] -> [a] -> [SpecFailWarning] -> ([a], [SpecFailWarning])
go [a]
ps [a]
small (Name -> SpecFailWarning
SpecFailForcedArgCount Name
name SpecFailWarning -> [SpecFailWarning] -> [SpecFailWarning]
forall a. a -> [a] -> [a]
: [SpecFailWarning]
warnings)


trim_pats :: ScEnv -> Id -> SpecInfo -> [CallPat] -> (Bool, [CallPat])
-- True <=> some patterns were discarded
-- See Note [Choosing patterns]
trim_pats :: ScEnv -> Id -> SpecInfo -> [CallPat] -> (Bool, [CallPat])
trim_pats ScEnv
env Id
fn (SI { si_n_specs :: SpecInfo -> Int
si_n_specs = Int
done_spec_count }) [CallPat]
pats
  | ScEnv -> Bool
sc_force ScEnv
env
    Bool -> Bool -> Bool
|| Maybe Int -> Bool
forall a. Maybe a -> Bool
isNothing Maybe Int
mb_scc
    Bool -> Bool -> Bool
|| Int
n_remaining Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
>= Int
n_pats
  = -- pprTrace "trim_pats: no-trim" (ppr (sc_force env) $$ ppr mb_scc $$ ppr n_remaining $$ ppr n_pats)
    (Bool
False, [CallPat]
pats)          -- No need to trim

  | Bool
otherwise
  = (Bool, [CallPat]) -> (Bool, [CallPat])
emit_trace ((Bool, [CallPat]) -> (Bool, [CallPat]))
-> (Bool, [CallPat]) -> (Bool, [CallPat])
forall a b. (a -> b) -> a -> b
$  -- Need to trim, so keep the best ones
    (Bool
True, Int -> [CallPat] -> [CallPat]
forall a. Int -> [a] -> [a]
take Int
n_remaining [CallPat]
sorted_pats)

  where
    n_pats :: Int
n_pats         = [CallPat] -> Int
forall a. [a] -> Int
forall (t :: * -> *) a. Foldable t => t a -> Int
length [CallPat]
pats
    spec_count' :: Int
spec_count'    = Int
n_pats Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
done_spec_count
    n_remaining :: Int
n_remaining    = Int
max_specs Int -> Int -> Int
forall a. Num a => a -> a -> a
- Int
done_spec_count
    mb_scc :: Maybe Int
mb_scc         = SpecConstrOpts -> Maybe Int
sc_count (SpecConstrOpts -> Maybe Int) -> SpecConstrOpts -> Maybe Int
forall a b. (a -> b) -> a -> b
$ ScEnv -> SpecConstrOpts
sc_opts ScEnv
env
    Just Int
max_specs = Maybe Int
mb_scc

    sorted_pats :: [CallPat]
sorted_pats = ((CallPat, Int) -> CallPat) -> [(CallPat, Int)] -> [CallPat]
forall a b. (a -> b) -> [a] -> [b]
map (CallPat, Int) -> CallPat
forall a b. (a, b) -> a
fst ([(CallPat, Int)] -> [CallPat]) -> [(CallPat, Int)] -> [CallPat]
forall a b. (a -> b) -> a -> b
$
                  ((CallPat, Int) -> (CallPat, Int) -> Ordering)
-> [(CallPat, Int)] -> [(CallPat, Int)]
forall a. (a -> a -> Ordering) -> [a] -> [a]
sortBy (((CallPat, Int) -> Int)
-> (CallPat, Int) -> (CallPat, Int) -> Ordering
forall a b. Ord a => (b -> a) -> b -> b -> Ordering
comparing (CallPat, Int) -> Int
forall a b. (a, b) -> b
snd) ([(CallPat, Int)] -> [(CallPat, Int)])
-> [(CallPat, Int)] -> [(CallPat, Int)]
forall a b. (a -> b) -> a -> b
$
                  [(CallPat
pat, CallPat -> Int
pat_cons CallPat
pat) | CallPat
pat <- [CallPat]
pats]
     -- Sort in order of increasing number of constructors
     -- (i.e. decreasing generality) and pick the initial
     -- segment of this list

    pat_cons :: CallPat -> Int
    -- How many data constructors of literals are in
    -- the pattern.  More data-cons => less general
    pat_cons :: CallPat -> Int
pat_cons (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
qs, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
ps })
       = (Expr Id -> Int -> Int) -> Int -> [Expr Id] -> Int
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr (Int -> Int -> Int
forall a. Num a => a -> a -> a
(+) (Int -> Int -> Int) -> (Expr Id -> Int) -> Expr Id -> Int -> Int
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Expr Id -> Int
n_cons) Int
0 [Expr Id]
ps
       where
          q_set :: VarSet
q_set = [Id] -> VarSet
mkVarSet [Id]
qs
          n_cons :: Expr Id -> Int
n_cons (Var Id
v) | Id
v Id -> VarSet -> Bool
`elemVarSet` VarSet
q_set = Int
0
                         | Bool
otherwise            = Int
1
          n_cons (Cast Expr Id
e Coercion
_)  = Expr Id -> Int
n_cons Expr Id
e
          n_cons (App Expr Id
e1 Expr Id
e2) = Expr Id -> Int
n_cons Expr Id
e1 Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Expr Id -> Int
n_cons Expr Id
e2
          n_cons (Lit {})    = Int
1
          n_cons Expr Id
_           = Int
0

    emit_trace :: (Bool, [CallPat]) -> (Bool, [CallPat])
emit_trace (Bool, [CallPat])
result
       | Bool
debugIsOn Bool -> Bool -> Bool
|| SpecConstrOpts -> Bool
sc_debug (ScEnv -> SpecConstrOpts
sc_opts ScEnv
env)
         -- Suppress this scary message for ordinary users!  #5125
       = String -> SDoc -> (Bool, [CallPat]) -> (Bool, [CallPat])
forall a. String -> SDoc -> a -> a
pprTrace String
"SpecConstr" SDoc
msg (Bool, [CallPat])
result
       | Bool
otherwise
       = (Bool, [CallPat])
result
    msg :: SDoc
msg = [SDoc] -> SDoc
forall doc. IsDoc doc => [doc] -> doc
vcat [ [SDoc] -> SDoc
forall doc. IsLine doc => [doc] -> doc
sep [ String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"Function" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> SDoc -> SDoc
quotes (Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Id
fn)
                     , Int -> SDoc -> SDoc
nest Int
2 (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"has" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+>
                               Int -> SDoc -> SDoc
speakNOf Int
spec_count' (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"call pattern") SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> SDoc
forall doc. IsLine doc => doc
comma SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+>
                               String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"but the limit is" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> Int -> SDoc
forall doc. IsLine doc => Int -> doc
int Int
max_specs) ]
               , String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"Use -fspec-constr-count=n to set the bound"
               , String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"done_spec_count =" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> Int -> SDoc
forall doc. IsLine doc => Int -> doc
int Int
done_spec_count
               , String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"Keeping " SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> Int -> SDoc
forall doc. IsLine doc => Int -> doc
int Int
n_remaining SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> String -> SDoc
forall doc. IsLine doc => String -> doc
text String
", out of" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> Int -> SDoc
forall doc. IsLine doc => Int -> doc
int Int
n_pats
               , String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"Discarding:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<+> [CallPat] -> SDoc
forall a. Outputable a => a -> SDoc
ppr (Int -> [CallPat] -> [CallPat]
forall a. Int -> [a] -> [a]
drop Int
n_remaining [CallPat]
sorted_pats) ]


callToPat :: ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe CallPat)
        -- The [Var] is the variables to quantify over in the rule
        --      Type variables come first, since they may scope
        --      over the following term variables
        -- The [CoreExpr] are the argument patterns for the rule
callToPat :: ScEnv -> [ArgOcc] -> Call -> UniqSM (Maybe CallPat)
callToPat ScEnv
env [ArgOcc]
bndr_occs call :: Call
call@(Call Id
fn [Expr Id]
args ValueEnv
con_env)
  = do  { let in_scope :: InScopeSet
in_scope = Subst -> InScopeSet
getSubstInScope (ScEnv -> Subst
sc_subst ScEnv
env)

        ; arg_triples <- (Expr Id
 -> ArgOcc -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id]))
-> [Expr Id]
-> [ArgOcc]
-> [StrictnessMark]
-> UniqSM [(Bool, Expr Id, [Id])]
forall (m :: * -> *) a b c d.
Monad m =>
(a -> b -> c -> m d) -> [a] -> [b] -> [c] -> m [d]
zipWith3M (ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
con_env) [Expr Id]
args [ArgOcc]
bndr_occs ((Expr Id -> StrictnessMark) -> [Expr Id] -> [StrictnessMark]
forall a b. (a -> b) -> [a] -> [b]
map (StrictnessMark -> Expr Id -> StrictnessMark
forall a b. a -> b -> a
const StrictnessMark
NotMarkedStrict) [Expr Id]
args)
                   -- This zip trims the args to be no longer than
                   -- the lambdas in the function definition (bndr_occs)

          -- Drop boring patterns from the end
          -- See Note [SpecConstr call patterns]
        ; let arg_triples' | Id -> Bool
isJoinId Id
fn     = [(Bool, Expr Id, [Id])]
arg_triples
                           | Bool
otherwise       = ((Bool, Expr Id, [Id]) -> Bool)
-> [(Bool, Expr Id, [Id])] -> [(Bool, Expr Id, [Id])]
forall a. (a -> Bool) -> [a] -> [a]
dropWhileEnd (Bool, Expr Id, [Id]) -> Bool
forall {b} {c}. (Bool, b, c) -> Bool
is_boring [(Bool, Expr Id, [Id])]
arg_triples
              is_boring (Bool
interesting, b
_,c
_)   = Bool -> Bool
not Bool
interesting
              (interesting_s, pats, cbv_ids) = unzip3 arg_triples'
              interesting                    = [Bool] -> Bool
forall (t :: * -> *). Foldable t => t Bool -> Bool
or [Bool]
interesting_s

        ; let pat_fvs = [Expr Id] -> [Id]
exprsFreeVarsList [Expr Id]
pats
                -- To get determinism we need the list of free variables in
                -- deterministic order. Otherwise we end up creating
                -- lambdas with different argument orders. See
                -- determinism/simplCore/should_compile/spec-inline-determ.hs
                -- for an example. For explanation of determinism
                -- considerations See Note [Unique Determinism] in GHC.Types.Unique.

              in_scope_vars = InScopeSet -> VarSet
getInScopeVars InScopeSet
in_scope
              is_in_scope Id
v = Id
v Id -> VarSet -> Bool
`elemVarSet` VarSet
in_scope_vars
              qvars         = (Id -> Bool) -> [Id] -> [Id]
forall a. (a -> Bool) -> [a] -> [a]
filterOut Id -> Bool
is_in_scope [Id]
pat_fvs
                -- Quantify over variables that are not in scope
                -- at the call site
                -- See Note [Free type variables of the qvar types]
                -- See Note [Shadowing in SpecConstr] at the top

              (qktvs, qids) = partition isTyVar qvars
              qvars'        = [Id] -> [Id]
scopedSort [Id]
qktvs [Id] -> [Id] -> [Id]
forall a. [a] -> [a] -> [a]
++ (Id -> Id) -> [Id] -> [Id]
forall a b. (a -> b) -> [a] -> [b]
map Id -> Id
sanitise [Id]
qids
                -- Order into kind variables, type variables, term variables
                -- The kind of a type variable may mention a kind variable
                -- and the type of a term variable may mention a type variable

              sanitise Id
id = (InType -> InType) -> Id -> Id
updateIdTypeAndMult InType -> InType
expandTypeSynonyms Id
id
                -- See Note [Free type variables of the qvar types]

        -- Check for bad coercion variables: see Note [SpecConstr and casts]
        ; let bad_covars = (Id -> Bool) -> [Id] -> [Id]
forall a. (a -> Bool) -> [a] -> [a]
filter Id -> Bool
isCoVar [Id]
qids
        ; warnPprTrace (not (null bad_covars))
              "SpecConstr: bad covars"
              (ppr bad_covars $$ ppr call) $

          if interesting && null bad_covars
          then do { let cp_res = CP { cp_qvars :: [Id]
cp_qvars = [Id]
qvars', cp_args :: [Expr Id]
cp_args = [Expr Id]
pats
                                    , cp_strict_args :: [Id]
cp_strict_args = [[Id]] -> [Id]
forall (t :: * -> *) a. Foldable t => t [a] -> [a]
concat [[Id]]
cbv_ids }
--                  ; pprTraceM "callToPatOut" $
--                    vcat [ text "fn:" <+> ppr fn
--                         , text "args:" <+> ppr args
--                         , text "bndr_occs:" <+> ppr bndr_occs
--                         , text "pat_fvs:" <+> ppr pat_fvs
--                         , text "cp_res:" <+> ppr cp_res ]
                  ; return (Just cp_res) }
          else return Nothing }

    -- argToPat takes an actual argument, and returns an abstracted
    -- version, consisting of just the "constructor skeleton" of the
    -- argument, with non-constructor sub-expression replaced by new
    -- placeholder variables.  For example:
    --    C a (D (f x) (g y))  ==>  C p1 (D p2 p3)

argToPat :: ScEnv
         -> InScopeSet                  -- What's in scope at the fn defn site
         -> ValueEnv                    -- ValueEnv at the call site
         -> CoreArg                     -- A call arg (or component thereof)
         -> ArgOcc
         -> StrictnessMark              -- Tells us if this argument is a strict field of a data constructor
                                        -- See Note [SpecConstr and strict fields]
         -> UniqSM (Bool, CoreArg, [Id])

-- Returns (interesting, pat),
-- where pat is the pattern derived from the argument
--            interesting=True if the pattern is non-trivial (not a variable or type)
-- E.g.         x:xs         --> (True, x:xs)
--              f xs         --> (False, w)        where w is a fresh wildcard
--              (f xs, 'c')  --> (True, (w, 'c'))  where w is a fresh wildcard
--              \x. x+y      --> (True, \x. x+y)
--              lvl7         --> (True, lvl7)      if lvl7 is bound
--                                                 somewhere further out

argToPat :: ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
  = do
    -- pprTraceM "argToPatIn" (ppr arg)
    !res <- ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
    -- pprTraceM "argToPatOut" (ppr res)
    return res

argToPat1 :: ScEnv
  -> InScopeSet
  -> ValueEnv
  -> Expr CoreBndr
  -> ArgOcc
  -> StrictnessMark
  -> UniqSM (Bool, Expr CoreBndr, [Id])
argToPat1 :: ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat1 ScEnv
_env InScopeSet
_in_scope ValueEnv
_val_env arg :: Expr Id
arg@(Type {}) ArgOcc
_arg_occ StrictnessMark
_arg_str
  = (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
False, Expr Id
arg, [])

argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Tick CoreTickish
_ Expr Id
arg) ArgOcc
arg_occ StrictnessMark
arg_str
  = ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
        -- Note [Tick annotations in call patterns]
        -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        -- Ignore Notes.  In particular, we want to ignore any InlineMe notes
        -- Perhaps we should not ignore profiling notes, but I'm going to
        -- ride roughshod over them all for now.
        --- See Note [Tick annotations in RULE matching] in GHC.Core.Rules

argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Let OutBind
_ Expr Id
arg) ArgOcc
arg_occ StrictnessMark
arg_str
  = ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
        -- See Note [Matching lets] in "GHC.Core.Rules"
        -- Look through let expressions
        -- e.g.         f (let v = rhs in (v,w))
        -- Here we can specialise for f (v,w)
        -- because the rule-matcher will look through the let.

   -- Casts: see Note [SpecConstr and casts]
argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Cast Expr Id
arg Coercion
co) ArgOcc
arg_occ StrictnessMark
arg_str
  | Bool -> Bool
not (ScEnv -> InType -> Bool
ignoreType ScEnv
env InType
ty2)
  = do  { (interesting, arg', strict_args) <- ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
arg_str
        ; if not interesting then
                wildCardPat ty2 arg_str
          else
                return (interesting, Cast arg' co, strict_args) }
  where
    ty2 :: InType
ty2 = HasDebugCallStack => Coercion -> InType
Coercion -> InType
coercionRKind Coercion
co

  -- Check for a constructor application
  -- NB: this *precedes* the Var case, so that we catch nullary constrs
argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env Expr Id
arg ArgOcc
arg_occ StrictnessMark
_arg_str
  | Just (ConVal Bool
_wf (DataAlt DataCon
dc) [Expr Id]
args) <- ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
val_env Expr Id
arg
    -- Ignore `_wf` here; see Note [ConVal work-free-ness] (2)
  , Bool -> Bool
not (ScEnv -> DataCon -> Bool
ignoreDataCon ScEnv
env DataCon
dc)        -- See Note [NoSpecConstr]
  , Just [ArgOcc]
arg_occs <- DataCon -> Maybe [ArgOcc]
mb_scrut DataCon
dc
  = do { let ([Expr Id]
ty_args, [Expr Id]
rest_args) = [Id] -> [Expr Id] -> ([Expr Id], [Expr Id])
forall b a. [b] -> [a] -> ([a], [a])
splitAtList (DataCon -> [Id]
dataConUnivTyVars DataCon
dc) [Expr Id]
args
             con_str, matched_str :: [StrictnessMark]
             -- con_str corresponds 1-1 with the /value/ arguments
             -- matched_str corresponds 1-1 with /all/ arguments
             con_str :: [StrictnessMark]
con_str = DataCon -> [StrictnessMark]
dataConRepStrictness DataCon
dc
             matched_str :: [StrictnessMark]
matched_str = [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
con_str [Expr Id]
rest_args
      --  ; pprTraceM "bangs" (ppr (length rest_args == length con_str) $$
      --       ppr dc $$
      --       ppr con_str $$
      --       ppr rest_args $$
      --       ppr (map isTypeArg rest_args))
       ; prs <- (Expr Id
 -> ArgOcc -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id]))
-> [Expr Id]
-> [ArgOcc]
-> [StrictnessMark]
-> UniqSM [(Bool, Expr Id, [Id])]
forall (m :: * -> *) a b c d.
Monad m =>
(a -> b -> c -> m d) -> [a] -> [b] -> [c] -> m [d]
zipWith3M (ScEnv
-> InScopeSet
-> ValueEnv
-> Expr Id
-> ArgOcc
-> StrictnessMark
-> UniqSM (Bool, Expr Id, [Id])
argToPat ScEnv
env InScopeSet
in_scope ValueEnv
val_env) [Expr Id]
rest_args [ArgOcc]
arg_occs [StrictnessMark]
matched_str
       ; let args' = ((Bool, Expr Id, [Id]) -> Expr Id)
-> [(Bool, Expr Id, [Id])] -> [Expr Id]
forall a b. (a -> b) -> [a] -> [b]
map (Bool, Expr Id, [Id]) -> Expr Id
forall a b c. (a, b, c) -> b
sndOf3 [(Bool, Expr Id, [Id])]
prs :: [CoreArg]
       ; assertPpr (length con_str == length (filter isRuntimeArg rest_args))
            ( ppr con_str $$ ppr rest_args $$
              ppr (length con_str) $$ ppr (length rest_args)
            ) $ return ()
       ; return (True, mkConApp dc (ty_args ++ args'), concat (map thdOf3 prs)) }
  where
    mb_scrut :: DataCon -> Maybe [ArgOcc]
mb_scrut DataCon
dc = case ArgOcc
arg_occ of
                ScrutOcc DataConEnv [ArgOcc]
bs | Just [ArgOcc]
occs <- DataConEnv [ArgOcc] -> DataCon -> Maybe [ArgOcc]
forall key elt. Uniquable key => UniqFM key elt -> key -> Maybe elt
lookupUFM DataConEnv [ArgOcc]
bs DataCon
dc
                            -> [ArgOcc] -> Maybe [ArgOcc]
forall a. a -> Maybe a
Just ([ArgOcc]
occs)  -- See Note [Reboxing]
                ArgOcc
_other      | ScEnv -> Bool
sc_force ScEnv
env Bool -> Bool -> Bool
|| SpecConstrOpts -> Bool
sc_keen (ScEnv -> SpecConstrOpts
sc_opts ScEnv
env)
                            -> [ArgOcc] -> Maybe [ArgOcc]
forall a. a -> Maybe a
Just (ArgOcc -> [ArgOcc]
forall a. a -> [a]
repeat ArgOcc
UnkOcc)
                            | Bool
otherwise
                            -> Maybe [ArgOcc]
forall a. Maybe a
Nothing
    match_vals :: [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
bangs (Expr Id
arg:[Expr Id]
args)
      | Expr Id -> Bool
forall b. Expr b -> Bool
isTypeArg Expr Id
arg
      = StrictnessMark
NotMarkedStrict StrictnessMark -> [StrictnessMark] -> [StrictnessMark]
forall a. a -> [a] -> [a]
: [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
bangs [Expr Id]
args
      | (StrictnessMark
b:[StrictnessMark]
bs) <- [StrictnessMark]
bangs
      = StrictnessMark
b StrictnessMark -> [StrictnessMark] -> [StrictnessMark]
forall a. a -> [a] -> [a]
: [StrictnessMark] -> [Expr Id] -> [StrictnessMark]
match_vals [StrictnessMark]
bs [Expr Id]
args
    match_vals [] [] = []
    match_vals [StrictnessMark]
as [Expr Id]
bs =
        String -> SDoc -> [StrictnessMark]
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"spec-constr:argToPat - Bangs don't match value arguments"
            (String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"arg:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> Expr Id -> SDoc
forall a. Outputable a => a -> SDoc
ppr Expr Id
arg SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$
             String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"remaining args:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> [StrictnessMark] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [StrictnessMark]
as SDoc -> SDoc -> SDoc
forall doc. IsDoc doc => doc -> doc -> doc
$$
             String -> SDoc
forall doc. IsLine doc => String -> doc
text String
"remaining bangs:" SDoc -> SDoc -> SDoc
forall doc. IsLine doc => doc -> doc -> doc
<> [Expr Id] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Expr Id]
bs)

  -- Check if the argument is a variable that
  --    (a) is used in an interesting way in the function body
  ---       i.e. ScrutOcc. UnkOcc and NoOcc are not interesting
  --        (NoOcc means we could drop the argument, but that's the
  --         business of absence analysis, not SpecConstr.)
  --    (b) we know what its value is
  -- In that case it counts as "interesting"
argToPat1 ScEnv
env InScopeSet
in_scope ValueEnv
val_env (Var Id
v) ArgOcc
arg_occ StrictnessMark
arg_str
  | ScEnv -> Bool
sc_force ScEnv
env Bool -> Bool -> Bool
|| ArgOcc -> Bool
specialisableArgOcc ArgOcc
arg_occ  -- (a)
    -- See Note [Forcing specialisation], point (FS3)
  , Bool
is_value                                     -- (b)
       -- Ignoring sc_keen here to avoid gratuitously incurring Note [Reboxing]
       -- So sc_keen focused just on f (I# x), where we have freshly-allocated
       -- box that we can eliminate in the caller
  , Bool -> Bool
not (ScEnv -> InType -> Bool
ignoreType ScEnv
env (Id -> InType
varType Id
v))
  -- See Note [SpecConstr and strict fields]
  = (Bool, Expr Id, [Id]) -> UniqSM (Bool, Expr Id, [Id])
forall a. a -> UniqSM a
forall (m :: * -> *) a. Monad m => a -> m a
return (Bool
True, Id -> Expr Id
forall b. Id -> Expr b
Var Id
v, if StrictnessMark -> Bool
isMarkedStrict StrictnessMark
arg_str then [Id
v] else [Id]
forall a. Monoid a => a
mempty)
  where
    is_value :: Bool
is_value
        | Id -> Bool
isLocalId Id
v = Id
v Id -> InScopeSet -> Bool
`elemInScopeSet` InScopeSet
in_scope
                        Bool -> Bool -> Bool
&& Maybe Value -> Bool
forall a. Maybe a -> Bool
isJust (ValueEnv -> Id -> Maybe Value
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv ValueEnv
val_env Id
v)
                -- Local variables have values in val_env
        | Bool
otherwise   = Unfolding -> Bool
isValueUnfolding (IdUnfoldingFun
idUnfolding Id
v)
                -- Imports have unfoldings

--      I'm really not sure what this comment means
--      And by not wild-carding we tend to get forall'd
--      variables that are in scope, which in turn can
--      expose the weakness in let-matching
--      See Note [Matching lets] in GHC.Core.Rules

  -- Check for a variable bound inside the function.
  -- Don't make a wild-card, because we may usefully share
  --    e.g.  f a = let x = ... in f (x,x)
  -- NB: this case follows the lambda and con-app cases!!
-- argToPat _in_scope _val_env (Var v) _arg_occ
--   = return (False, Var v)
        -- SLPJ : disabling this to avoid proliferation of versions
        -- also works badly when thinking about seeding the loop
        -- from the body of the let
        --       f x y = letrec g z = ... in g (x,y)
        -- We don't want to specialise for that *particular* x,y


{- Disabled; see Note [Matching cases] in "GHC.Core.Rules"
argToPat env in_scope val_env (Case scrut _ _ [(_, _, rhs)]) arg_occ
  | exprOkForSpeculation scrut  -- See Note [Matching cases] in "GHC.Core.Rules"
  = argToPat env in_scope val_env rhs arg_occ
-}

{-      Disabling lambda specialisation for now
        It's fragile, and the spec_loop can be infinite
argToPat in_scope val_env arg arg_occ
  | is_value_lam arg
  = return (True, arg)
  where
    is_value_lam (Lam v e)         -- Spot a value lambda, even if
        | isId v       = True      -- it is inside a type lambda
        | otherwise    = is_value_lam e
    is_value_lam other = False
-}

  -- The default case: make a wild-card
  -- We use this for coercions too
argToPat1 ScEnv
_env InScopeSet
_in_scope ValueEnv
_val_env Expr Id
arg ArgOcc
_arg_occ StrictnessMark
arg_str
  = InType -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id])
wildCardPat (HasDebugCallStack => Expr Id -> InType
Expr Id -> InType
exprType Expr Id
arg) StrictnessMark
arg_str

-- | wildCardPats are always boring
wildCardPat :: Type -> StrictnessMark -> UniqSM (Bool, CoreArg, [Id])
wildCardPat :: InType -> StrictnessMark -> UniqSM (Bool, Expr Id, [Id])
wildCardPat InType
ty StrictnessMark
str
  = do { id <- FastString -> InType -> InType -> UniqSM Id
forall (m :: * -> *).
MonadUnique m =>
FastString -> InType -> InType -> m Id
mkSysLocalOrCoVarM (String -> FastString
fsLit String
"sc") InType
ManyTy InType
ty
       -- ; pprTraceM "wildCardPat" (ppr id' <+> ppr (idUnfolding id'))
       ; return (False, varToCoreExpr id, if isMarkedStrict str then [id] else []) }

isValue :: ValueEnv -> CoreExpr -> Maybe Value
isValue :: ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
_env (Lit Literal
lit)
  | Literal -> Bool
litIsLifted Literal
lit = Maybe Value
forall a. Maybe a
Nothing
  | Bool
otherwise       = Value -> Maybe Value
forall a. a -> Maybe a
Just (Bool -> AltCon -> [Expr Id] -> Value
ConVal Bool
True (Literal -> AltCon
LitAlt Literal
lit) [])

isValue ValueEnv
env (Var Id
v)
  | Just Value
cval <- ValueEnv -> Id -> Maybe Value
forall a. VarEnv a -> Id -> Maybe a
lookupVarEnv ValueEnv
env Id
v
  = Value -> Maybe Value
forall a. a -> Maybe a
Just Value
cval  -- You might think we could look in the idUnfolding here
               -- but that doesn't take account of which branch of a
               -- case we are in, which is the whole point

  | Bool -> Bool
not (Id -> Bool
isLocalId Id
v)
  , Unfolding -> Bool
isCheapUnfolding Unfolding
unf
  , Just Expr Id
rhs <- Unfolding -> Maybe (Expr Id)
maybeUnfoldingTemplate Unfolding
unf  -- Succeds if isCheapUnfolding does
  = ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
env Expr Id
rhs   -- Can't use isEvaldUnfolding because
                      -- we want to consult the `env`
  where
    unf :: Unfolding
unf = IdUnfoldingFun
idUnfolding Id
v
        -- However we do want to consult the unfolding
        -- as well, for let-bound constructors!

isValue ValueEnv
env (Lam Id
b Expr Id
e)
  | Id -> Bool
isTyVar Id
b = case ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
env Expr Id
e of
                  Just Value
_  -> Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal
                  Maybe Value
Nothing -> Maybe Value
forall a. Maybe a
Nothing
  | Bool
otherwise = Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal

isValue ValueEnv
env (Tick CoreTickish
t Expr Id
e)
  | Bool -> Bool
not (CoreTickish -> Bool
forall (pass :: TickishPass). GenTickish pass -> Bool
tickishIsCode CoreTickish
t)
  = ValueEnv -> Expr Id -> Maybe Value
isValue ValueEnv
env Expr Id
e

isValue ValueEnv
_env Expr Id
expr       -- Maybe it's a constructor application
  | (Var Id
fun, [Expr Id]
args, [CoreTickish]
_) <- (CoreTickish -> Bool)
-> Expr Id -> (Expr Id, [Expr Id], [CoreTickish])
forall b.
(CoreTickish -> Bool)
-> Expr b -> (Expr b, [Expr b], [CoreTickish])
collectArgsTicks (Bool -> Bool
not (Bool -> Bool) -> (CoreTickish -> Bool) -> CoreTickish -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CoreTickish -> Bool
forall (pass :: TickishPass). GenTickish pass -> Bool
tickishIsCode) Expr Id
expr
  = case Id -> IdDetails
idDetails Id
fun of
        DataConWorkId DataCon
con | [Expr Id]
args [Expr Id] -> Int -> Bool
forall a. [a] -> Int -> Bool
`lengthAtLeast` DataCon -> Int
dataConRepArity DataCon
con
                -- Check saturated; might be > because the
                --                  arity excludes type args
                -> Value -> Maybe Value
forall a. a -> Maybe a
Just (Bool -> AltCon -> [Expr Id] -> Value
ConVal ((Expr Id -> Bool) -> [Expr Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all Expr Id -> Bool
exprIsWorkFree [Expr Id]
args) (DataCon -> AltCon
DataAlt DataCon
con) [Expr Id]
args)

        DFunId {} -> Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal
        -- DFunId: see Note [Specialising on dictionaries]

        IdDetails
_other | [Expr Id] -> Int
forall b. [Arg b] -> Int
valArgCount [Expr Id]
args Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
< Id -> Int
idArity Id
fun
                -- Under-applied function
               -> Value -> Maybe Value
forall a. a -> Maybe a
Just Value
LambdaVal        -- Partial application

        IdDetails
_other -> Maybe Value
forall a. Maybe a
Nothing

isValue ValueEnv
_env Expr Id
_expr = Maybe Value
forall a. Maybe a
Nothing

betterPat :: InScopeSet -> CallPat -> CallPat -> Bool
-- pat1    f @a   (Just @a   (x::a))
--      is better than
-- pat2    f @Int (Just @Int (x::Int))
-- That is, we can instantiate pat1 to get pat2, using only type instantiate
-- See Note [Pattern duplicate elimination]
betterPat :: InScopeSet -> CallPat -> CallPat -> Bool
betterPat InScopeSet
is (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
vs1, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
as1 })
             (CP { cp_qvars :: CallPat -> [Id]
cp_qvars = [Id]
vs2, cp_args :: CallPat -> [Expr Id]
cp_args = [Expr Id]
as2 })
  | [Expr Id] -> [Expr Id] -> Bool
forall a b. [a] -> [b] -> Bool
equalLength [Expr Id]
as1 [Expr Id]
as2
  = case InScopeEnv
-> [Id]
-> [Expr Id]
-> [Expr Id]
-> Maybe (Expr Id -> Expr Id, [Expr Id])
matchExprs InScopeEnv
ise [Id]
vs1 [Expr Id]
as1 [Expr Id]
as2 of
      Just (Expr Id -> Expr Id
_, [Expr Id]
ms) -> (Expr Id -> Bool) -> [Expr Id] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all Expr Id -> Bool
exprIsTrivial [Expr Id]
ms
      Maybe (Expr Id -> Expr Id, [Expr Id])
Nothing      -> Bool
False

  | Bool
otherwise -- We must handle patterns of unequal length separately (#24282)
  = Bool
False  -- For the pattern with more args, the last arg is "interesting"
           -- but the corresponding one on the other is "not interesting";
           -- So we can't get from one to the other with only exprIsTrivial
           -- instantiation.  Example nofib/spectral/ansi, function `loop`:
           --    P1: loop (I# x) (a : b)
           --    P2: loop (I# y)           -- Pattern eta-reduced
           -- Neither is better than the other, in the sense of betterPat
  where
    ise :: InScopeEnv
ise = InScopeSet -> IdUnfoldingFun -> InScopeEnv
ISE (InScopeSet
is InScopeSet -> [Id] -> InScopeSet
`extendInScopeSetList` [Id]
vs2) (Unfolding -> IdUnfoldingFun
forall a b. a -> b -> a
const Unfolding
noUnfolding)

subsumePats :: InScopeSet -> [CallPat] -> [CallPat]
-- Remove any patterns subsumed by others
-- See Note [Pattern duplicate elimination]
-- Other than deleting subsumed patterns, this operation is a no-op;
-- in particular it does not reverse the input.  It should not matter
-- but in #24282 it did; doing it this way keeps the existing behaviour.
subsumePats :: InScopeSet -> [CallPat] -> [CallPat]
subsumePats InScopeSet
is [CallPat]
pats = ([CallPat] -> CallPat -> [CallPat])
-> [CallPat] -> [CallPat] -> [CallPat]
forall b a. (b -> a -> b) -> b -> [a] -> b
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl [CallPat] -> CallPat -> [CallPat]
add [] [CallPat]
pats
  where
    add :: [CallPat] -> CallPat -> [CallPat]
    add :: [CallPat] -> CallPat -> [CallPat]
add []        CallPat
ci                         = [CallPat
ci]
    add (CallPat
ci1:[CallPat]
cis) CallPat
ci2 | InScopeSet -> CallPat -> CallPat -> Bool
betterPat InScopeSet
is CallPat
ci1 CallPat
ci2 = CallPat
ci1 CallPat -> [CallPat] -> [CallPat]
forall a. a -> [a] -> [a]
: [CallPat]
cis
                      | InScopeSet -> CallPat -> CallPat -> Bool
betterPat InScopeSet
is CallPat
ci2 CallPat
ci1 = CallPat
ci2 CallPat -> [CallPat] -> [CallPat]
forall a. a -> [a] -> [a]
: [CallPat]
cis
                      | Bool
otherwise            = CallPat
ci1 CallPat -> [CallPat] -> [CallPat]
forall a. a -> [a] -> [a]
: [CallPat] -> CallPat -> [CallPat]
add [CallPat]
cis CallPat
ci2

{-
Note [Pattern duplicate elimination]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider f :: (a,a) -> blah, and two calls
   f @Int  (x,y)
   f @Bool (p,q)

The danger is that we'll generate two *essentially identical* specialisations,
both for pairs, but with different types instantiating `a` (see #24229).

But we'll only make a `CallPat` for an argument (a,b) if `foo` scrutinises
that argument.  So SpecConstr should never need to specialise f's polymorphic
type arguments.  Even with only one of these calls we should be able to
generalise to the `CallPat`

  cp_qvars = [a, r::a, s::a], cp_args = [@a (r,s)]

Doing so isn't trivial, though.

For now we content ourselves with a simpler plan: eliminate a call pattern
if another pattern subsumes it; this is done by `subsumePats`.
For example here are two patterns

  cp_qvars = [a, r::a, s::a],  cp_args = [@a (r,s)]
  cp_qvars = [x::Int, y::Int], cp_args = [@Int (x,y)]

The first can be instantiated to the second, /by instantiating types only/.
This subsumption relationship is checked by `betterPat`.  Note that if
we have

  cp_qvars = [a, r::a, s::a], cp_args = [@a (r,s)]
  cp_qvars = [],              cp_args = [@Bool (True,False)]

the first does *not* subsume the second; the second is more specific.

In our initial example with `f @Int` and `f @Bool` neither subsumes the other,
so we will get two essentially-identical specialisations. Boo.  We rely on our
crude throttling mechanisms to stop this getting out of control -- with
polymorphic recursion we can generate an infinite number of specialisations.
Example is Data.Sequence.adjustTree, I think.
-}