module GHC.StgToCmm.Types ( CmmCgInfos (..) , LambdaFormInfo (..) , ModuleLFInfos , StandardFormInfo (..) , DoSCCProfiling , DoExtDynRefs ) where import GHC.Prelude import GHC.Core.DataCon import GHC.Runtime.Heap.Layout import GHC.Types.Basic import GHC.Types.ForeignStubs import GHC.Types.Name.Env import GHC.Types.Name.Set import GHC.Utils.Outputable {- Note [Conveying CAF-info and LFInfo between modules] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Some information about an Id is generated in the code generator, and is not available earlier. Namely: * CAF info. Code motion in Cmm or earlier phases may move references around so we compute information about which bits of code refer to which CAF late in the Cmm pipeline. * LambdaFormInfo. This records the details of a closure representation, including - the final arity (for functions) - whether it is a data constructor, and if so its tag Collectively we call this CgInfo (see GHC.StgToCmm.Types). It's very useful for importing modules to have this information. We can always make a conservative assumption, but that is bad: e.g. * For CAF info, if we know nothing we have to assume it is a CAF which bloats the SRTs of the importing module. Conservative assumption here is made when creating new Ids. * For data constructors, we really like having well-tagged pointers. See #14677, #16559, #15155, and wiki: commentary/rts/haskell-execution/pointer-tagging Conservative assumption here is made when we import an Id without a LambdaFormInfo in the interface, in GHC.StgToCmm.Closure.importedIdLFInfo. So we arrange to always serialise this information into the interface file. The moving parts are: * We record the CgInfo in the IdInfo of the Id. * GHC.Driver.Pipeline: the call to updateModDetailsIdInfos augments the ModDetails constructed at the end of the Core pipeline, with CgInfo gleaned from the back end. The hard work is done in GHC.Iface.UpdateIdInfos. * For ModIface we generate the final ModIface with CgInfo in GHC.Iface.Make.mkFullIface. * We don't absolutely guarantee to serialise the CgInfo: we won't if you have -fomit-interface-pragmas or -fno-code; and we won't read it in if you have -fignore-interface-pragmas. (We could revisit this decision.) Note [Imported unlifted nullary datacon wrappers must have correct LFInfo] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ As described in `Note [Conveying CAF-info and LFInfo between modules]`, imported unlifted nullary datacons must have their LambdaFormInfo set to reflect the fact that they are evaluated. This is necessary as otherwise references to them may be passed untagged to code that expects tagged references because of the unlifted nature of the argument. For example, in type T :: UnliftedType data T = T1 | T2 f :: T -> Int f x = case x of T1 -> 1; T2 -> 2 `f` expects `x` to be evaluated and properly tagged due to its unliftedness. We can guarantee all occurrences of `T1` and `T2` are considered evaluated and are properly tagged by giving them the `LFCon` LambdaFormInfo which indicates they are fully saturated constructor applications. (The LambdaFormInfo is used to tag the pointer with the tag of the constructor, in `litIdInfo`) What may be less obvious is that this must be done for not only datacon workers but also *wrappers*. The reason is found in this program from #23146: module B where type NP :: [UnliftedType] -> UnliftedType data NP xs where UNil :: NP '[] module A where import B fieldsSam :: NP xs -> NP xs -> Bool fieldsSam UNil UNil = True x = fieldsSam UNil UNil Due to its GADT nature, `B.UNil` produces a trivial wrapper $WUNil :: NP '[] $WUNil = UNil @'[] @~(<co:1>) which is referenced in the RHS of `A.x`. If we fail to give `$WUNil` the correct `LFCon 0` `LambdaFormInfo` then we will end up passing an untagged pointer to `fieldsSam`. This is problematic as `fieldsSam` may take advantage of the unlifted nature of its arguments by omitting handling of the zero tag when scrutinising them. The fix is straightforward: ensure we always construct a /correct/ LFInfo for datacon workers and wrappers, and populate the `lfInfo` with it. See Note [LFInfo of DataCon workers and wrappers]. This fixed #23146. See also Note [The LFInfo of Imported Ids] -} -- | Codegen-generated Id infos, to be passed to downstream via interfaces. -- -- This stuff is for optimization purposes only, they're not compulsory. -- -- * When CafInfo of an imported Id is not known it's safe to treat it as CAFFY. -- * When LambdaFormInfo of an imported Id is not known it's safe to treat it as -- `LFUnknown True` (which just says "it could be anything" and we do slow -- entry). -- -- See also Note [Conveying CAF-info and LFInfo between modules] above. -- data CmmCgInfos = CmmCgInfos { CmmCgInfos -> NonCaffySet cgNonCafs :: !NonCaffySet -- ^ Exported Non-CAFFY closures in the current module. Everything else is -- either not exported of CAFFY. , CmmCgInfos -> ModuleLFInfos cgLFInfos :: !ModuleLFInfos -- ^ LambdaFormInfos of exported closures in the current module. , CmmCgInfos -> CStub cgIPEStub :: !CStub -- ^ The C stub which is used for IPE information } -------------------------------------------------------------------------------- -- LambdaFormInfo -------------------------------------------------------------------------------- -- | Maps names in the current module to their LambdaFormInfos type ModuleLFInfos = NameEnv LambdaFormInfo -- | Information about an identifier, from the code generator's point of view. -- Every identifier is bound to a LambdaFormInfo in the environment, which gives -- the code generator enough info to be able to tail call or return that -- identifier. data LambdaFormInfo = LFReEntrant -- Reentrant closure (a function) !TopLevelFlag -- True if top level !RepArity -- Arity. Invariant: always > 0 !Bool -- True <=> no fvs !ArgDescr -- Argument descriptor (should really be in ClosureInfo) | LFThunk -- Thunk (zero arity) !TopLevelFlag !Bool -- True <=> no free vars !Bool -- True <=> updatable (i.e., *not* single-entry) !StandardFormInfo !Bool -- True <=> *might* be a function type | LFCon -- A saturated data constructor application !DataCon -- The constructor | LFUnknown -- Used for function arguments and imported things. -- We know nothing about this closure. -- Treat like updatable "LFThunk"... -- Imported things which we *do* know something about use -- one of the other LF constructors (eg LFReEntrant for -- known functions) !Bool -- True <=> *might* be a function type -- The False case is good when we want to enter it, -- because then we know the entry code will do -- For a function, the entry code is the fast entry point | LFUnlifted -- A value of unboxed type; -- always a value, needs evaluation | LFLetNoEscape -- See LetNoEscape module for precise description instance Outputable LambdaFormInfo where ppr :: LambdaFormInfo -> SDoc ppr (LFReEntrant TopLevelFlag top RepArity rep Bool fvs ArgDescr argdesc) = String -> SDoc forall doc. IsLine doc => String -> doc text String "LFReEntrant" SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <> SDoc -> SDoc forall doc. IsLine doc => doc -> doc brackets (TopLevelFlag -> SDoc forall a. Outputable a => a -> SDoc ppr TopLevelFlag top SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> RepArity -> SDoc forall a. Outputable a => a -> SDoc ppr RepArity rep SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> Bool -> SDoc pprFvs Bool fvs SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> ArgDescr -> SDoc forall a. Outputable a => a -> SDoc ppr ArgDescr argdesc) ppr (LFThunk TopLevelFlag top Bool hasfv Bool updateable StandardFormInfo sfi Bool m_function) = String -> SDoc forall doc. IsLine doc => String -> doc text String "LFThunk" SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <> SDoc -> SDoc forall doc. IsLine doc => doc -> doc brackets (TopLevelFlag -> SDoc forall a. Outputable a => a -> SDoc ppr TopLevelFlag top SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> Bool -> SDoc pprFvs Bool hasfv SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> Bool -> SDoc pprUpdateable Bool updateable SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> StandardFormInfo -> SDoc forall a. Outputable a => a -> SDoc ppr StandardFormInfo sfi SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> Bool -> SDoc pprFuncFlag Bool m_function) ppr (LFCon DataCon con) = String -> SDoc forall doc. IsLine doc => String -> doc text String "LFCon" SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <> SDoc -> SDoc forall doc. IsLine doc => doc -> doc brackets (DataCon -> SDoc forall a. Outputable a => a -> SDoc ppr DataCon con) ppr (LFUnknown Bool m_func) = String -> SDoc forall doc. IsLine doc => String -> doc text String "LFUnknown" SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <> SDoc -> SDoc forall doc. IsLine doc => doc -> doc brackets (Bool -> SDoc pprFuncFlag Bool m_func) ppr LambdaFormInfo LFUnlifted = String -> SDoc forall doc. IsLine doc => String -> doc text String "LFUnlifted" ppr LambdaFormInfo LFLetNoEscape = String -> SDoc forall doc. IsLine doc => String -> doc text String "LFLetNoEscape" pprFvs :: Bool -> SDoc pprFvs :: Bool -> SDoc pprFvs Bool True = String -> SDoc forall doc. IsLine doc => String -> doc text String "no-fvs" pprFvs Bool False = String -> SDoc forall doc. IsLine doc => String -> doc text String "fvs" pprFuncFlag :: Bool -> SDoc pprFuncFlag :: Bool -> SDoc pprFuncFlag Bool True = String -> SDoc forall doc. IsLine doc => String -> doc text String "mFunc" pprFuncFlag Bool False = String -> SDoc forall doc. IsLine doc => String -> doc text String "value" pprUpdateable :: Bool -> SDoc pprUpdateable :: Bool -> SDoc pprUpdateable Bool True = String -> SDoc forall doc. IsLine doc => String -> doc text String "updateable" pprUpdateable Bool False = String -> SDoc forall doc. IsLine doc => String -> doc text String "oneshot" -------------------------------------------------------------------------------- -- | StandardFormInfo tells whether this thunk has one of a small number of -- standard forms data StandardFormInfo = NonStandardThunk -- The usual case: not of the standard forms | SelectorThunk -- A SelectorThunk is of form -- case x of -- con a1,..,an -> ak -- and the constructor is from a single-constr type. !WordOff -- 0-origin offset of ak within the "goods" of -- constructor (Recall that the a1,...,an may be laid -- out in the heap in a non-obvious order.) | ApThunk -- An ApThunk is of form -- x1 ... xn -- The code for the thunk just pushes x2..xn on the stack and enters x1. -- There are a few of these (for 1 <= n <= MAX_SPEC_AP_SIZE) pre-compiled -- in the RTS to save space. !RepArity -- Arity, n deriving (StandardFormInfo -> StandardFormInfo -> Bool (StandardFormInfo -> StandardFormInfo -> Bool) -> (StandardFormInfo -> StandardFormInfo -> Bool) -> Eq StandardFormInfo forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a $c== :: StandardFormInfo -> StandardFormInfo -> Bool == :: StandardFormInfo -> StandardFormInfo -> Bool $c/= :: StandardFormInfo -> StandardFormInfo -> Bool /= :: StandardFormInfo -> StandardFormInfo -> Bool Eq) instance Outputable StandardFormInfo where ppr :: StandardFormInfo -> SDoc ppr StandardFormInfo NonStandardThunk = String -> SDoc forall doc. IsLine doc => String -> doc text String "RegThunk" ppr (SelectorThunk RepArity w) = String -> SDoc forall doc. IsLine doc => String -> doc text String "SelThunk:" SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <> RepArity -> SDoc forall a. Outputable a => a -> SDoc ppr RepArity w ppr (ApThunk RepArity n) = String -> SDoc forall doc. IsLine doc => String -> doc text String "ApThunk:" SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <> RepArity -> SDoc forall a. Outputable a => a -> SDoc ppr RepArity n -------------------------------------------------------------------------------- -- Gaining sight in a sea of blindness -------------------------------------------------------------------------------- type DoSCCProfiling = Bool type DoExtDynRefs = Bool