{- (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 \section[PrimOp]{Primitive operations (machine-level)} -} {-# LANGUAGE CPP #-} {-# LANGUAGE LambdaCase #-} module GHC.Builtin.PrimOps ( PrimOp(..), PrimOpVecCat(..), allThePrimOps, primOpType, primOpSig, primOpResultType, primOpTag, maxPrimOpTag, primOpOcc, primOpWrapperId, pprPrimOp, tagToEnumKey, primOpOutOfLine, primOpCodeSize, primOpOkForSpeculation, primOpOkForSideEffects, primOpIsCheap, primOpFixity, primOpDocs, primOpIsDiv, primOpIsReallyInline, getPrimOpResultInfo, isComparisonPrimOp, PrimOpResultInfo(..), PrimCall(..) ) where import GHC.Prelude import GHC.Builtin.Types.Prim import GHC.Builtin.Types import GHC.Builtin.Uniques (mkPrimOpIdUnique, mkPrimOpWrapperUnique ) import GHC.Builtin.Names ( gHC_PRIMOPWRAPPERS ) import GHC.Core.TyCon ( TyCon, isPrimTyCon, PrimRep(..) ) import GHC.Core.Type import GHC.Cmm.Type import GHC.Types.Demand import GHC.Types.Id import GHC.Types.Id.Info import GHC.Types.Name import GHC.Types.RepType ( tyConPrimRep1 ) import GHC.Types.Basic import GHC.Types.Fixity ( Fixity(..), FixityDirection(..) ) import GHC.Types.SrcLoc ( wiredInSrcSpan ) import GHC.Types.ForeignCall ( CLabelString ) import GHC.Types.SourceText ( SourceText(..) ) import GHC.Types.Unique ( Unique) import GHC.Unit.Types ( Unit ) import GHC.Utils.Outputable import GHC.Data.FastString {- ************************************************************************ * * \subsection[PrimOp-datatype]{Datatype for @PrimOp@ (an enumeration)} * * ************************************************************************ These are in \tr{state-interface.verb} order. -} -- supplies: -- data PrimOp = ... #include "primop-data-decl.hs-incl" -- supplies -- primOpTag :: PrimOp -> Int #include "primop-tag.hs-incl" primOpTag PrimOp _ = String -> Int forall a. HasCallStack => String -> a error String "primOpTag: unknown primop" instance Eq PrimOp where PrimOp op1 == :: PrimOp -> PrimOp -> Bool == PrimOp op2 = PrimOp -> Int primOpTag PrimOp op1 Int -> Int -> Bool forall a. Eq a => a -> a -> Bool == PrimOp -> Int primOpTag PrimOp op2 instance Ord PrimOp where PrimOp op1 < :: PrimOp -> PrimOp -> Bool < PrimOp op2 = PrimOp -> Int primOpTag PrimOp op1 Int -> Int -> Bool forall a. Ord a => a -> a -> Bool < PrimOp -> Int primOpTag PrimOp op2 PrimOp op1 <= :: PrimOp -> PrimOp -> Bool <= PrimOp op2 = PrimOp -> Int primOpTag PrimOp op1 Int -> Int -> Bool forall a. Ord a => a -> a -> Bool <= PrimOp -> Int primOpTag PrimOp op2 PrimOp op1 >= :: PrimOp -> PrimOp -> Bool >= PrimOp op2 = PrimOp -> Int primOpTag PrimOp op1 Int -> Int -> Bool forall a. Ord a => a -> a -> Bool >= PrimOp -> Int primOpTag PrimOp op2 PrimOp op1 > :: PrimOp -> PrimOp -> Bool > PrimOp op2 = PrimOp -> Int primOpTag PrimOp op1 Int -> Int -> Bool forall a. Ord a => a -> a -> Bool > PrimOp -> Int primOpTag PrimOp op2 PrimOp op1 compare :: PrimOp -> PrimOp -> Ordering `compare` PrimOp op2 | PrimOp op1 PrimOp -> PrimOp -> Bool forall a. Ord a => a -> a -> Bool < PrimOp op2 = Ordering LT | PrimOp op1 PrimOp -> PrimOp -> Bool forall a. Eq a => a -> a -> Bool == PrimOp op2 = Ordering EQ | Bool otherwise = Ordering GT instance Outputable PrimOp where ppr :: PrimOp -> SDoc ppr PrimOp op = PrimOp -> SDoc forall doc. IsLine doc => PrimOp -> doc pprPrimOp PrimOp op data PrimOpVecCat = IntVec | WordVec | FloatVec -- An @Enum@-derived list would be better; meanwhile... (ToDo) allThePrimOps :: [PrimOp] [PrimOp] allThePrimOps = #include "primop-list.hs-incl" tagToEnumKey :: Unique tagToEnumKey :: Unique tagToEnumKey = Int -> Unique mkPrimOpIdUnique (PrimOp -> Int primOpTag PrimOp TagToEnumOp) {- ************************************************************************ * * \subsection[PrimOp-info]{The essential info about each @PrimOp@} * * ************************************************************************ -} data PrimOpInfo = Compare OccName -- string :: T -> T -> Int# Type | GenPrimOp OccName -- string :: \/a1..an . T1 -> .. -> Tk -> T [TyVarBinder] [Type] Type mkCompare :: FastString -> Type -> PrimOpInfo mkCompare :: FastString -> Type -> PrimOpInfo mkCompare FastString str Type ty = OccName -> Type -> PrimOpInfo Compare (FastString -> OccName mkVarOccFS FastString str) Type ty mkGenPrimOp :: FastString -> [TyVarBinder] -> [Type] -> Type -> PrimOpInfo mkGenPrimOp :: FastString -> [TyVarBinder] -> [Type] -> Type -> PrimOpInfo mkGenPrimOp FastString str [TyVarBinder] tvs [Type] tys Type ty = OccName -> [TyVarBinder] -> [Type] -> Type -> PrimOpInfo GenPrimOp (FastString -> OccName mkVarOccFS FastString str) [TyVarBinder] tvs [Type] tys Type ty {- ************************************************************************ * * \subsubsection{Strictness} * * ************************************************************************ Not all primops are strict! -} primOpStrictness :: PrimOp -> Arity -> DmdSig -- See Demand.DmdSig for discussion of what the results -- The arity should be the arity of the primop; that's why -- this function isn't exported. #include "primop-strictness.hs-incl" {- ************************************************************************ * * \subsubsection{Fixity} * * ************************************************************************ -} primOpFixity :: PrimOp -> Maybe Fixity #include "primop-fixity.hs-incl" {- ************************************************************************ * * \subsubsection{Docs} * * ************************************************************************ See Note [GHC.Prim Docs] -} primOpDocs :: [(String, String)] #include "primop-docs.hs-incl" {- ************************************************************************ * * \subsubsection[PrimOp-comparison]{PrimOpInfo basic comparison ops} * * ************************************************************************ @primOpInfo@ gives all essential information (from which everything else, notably a type, can be constructed) for each @PrimOp@. -} primOpInfo :: PrimOp -> PrimOpInfo #include "primop-primop-info.hs-incl" primOpInfo PrimOp _ = String -> PrimOpInfo forall a. HasCallStack => String -> a error String "primOpInfo: unknown primop" {- Here are a load of comments from the old primOp info: A @Word#@ is an unsigned @Int#@. @decodeFloat#@ is given w/ Integer-stuff (it's similar). @decodeDouble#@ is given w/ Integer-stuff (it's similar). Decoding of floating-point numbers is sorta Integer-related. Encoding is done with plain ccalls now (see PrelNumExtra.hs). A @Weak@ Pointer is created by the @mkWeak#@ primitive: mkWeak# :: k -> v -> f -> State# RealWorld -> (# State# RealWorld, Weak# v #) In practice, you'll use the higher-level data Weak v = Weak# v mkWeak :: k -> v -> IO () -> IO (Weak v) The following operation dereferences a weak pointer. The weak pointer may have been finalized, so the operation returns a result code which must be inspected before looking at the dereferenced value. deRefWeak# :: Weak# v -> State# RealWorld -> (# State# RealWorld, v, Int# #) Only look at v if the Int# returned is /= 0 !! The higher-level op is deRefWeak :: Weak v -> IO (Maybe v) Weak pointers can be finalized early by using the finalize# operation: finalizeWeak# :: Weak# v -> State# RealWorld -> (# State# RealWorld, Int#, IO () #) The Int# returned is either 0 if the weak pointer has already been finalized, or it has no finalizer (the third component is then invalid). 1 if the weak pointer is still alive, with the finalizer returned as the third component. A {\em stable name/pointer} is an index into a table of stable name entries. Since the garbage collector is told about stable pointers, it is safe to pass a stable pointer to external systems such as C routines. \begin{verbatim} makeStablePtr# :: a -> State# RealWorld -> (# State# RealWorld, StablePtr# a #) freeStablePtr :: StablePtr# a -> State# RealWorld -> State# RealWorld deRefStablePtr# :: StablePtr# a -> State# RealWorld -> (# State# RealWorld, a #) eqStablePtr# :: StablePtr# a -> StablePtr# a -> Int# \end{verbatim} It may seem a bit surprising that @makeStablePtr#@ is a @IO@ operation since it doesn't (directly) involve IO operations. The reason is that if some optimisation pass decided to duplicate calls to @makeStablePtr#@ and we only pass one of the stable pointers over, a massive space leak can result. Putting it into the IO monad prevents this. (Another reason for putting them in a monad is to ensure correct sequencing wrt the side-effecting @freeStablePtr@ operation.) An important property of stable pointers is that if you call makeStablePtr# twice on the same object you get the same stable pointer back. Note that we can implement @freeStablePtr#@ using @_ccall_@ (and, besides, it's not likely to be used from Haskell) so it's not a primop. Question: Why @RealWorld@ - won't any instance of @_ST@ do the job? [ADR] Stable Names ~~~~~~~~~~~~ A stable name is like a stable pointer, but with three important differences: (a) You can't deRef one to get back to the original object. (b) You can convert one to an Int. (c) You don't need to 'freeStableName' The existence of a stable name doesn't guarantee to keep the object it points to alive (unlike a stable pointer), hence (a). Invariants: (a) makeStableName always returns the same value for a given object (same as stable pointers). (b) if two stable names are equal, it implies that the objects from which they were created were the same. (c) stableNameToInt always returns the same Int for a given stable name. These primops are pretty weird. tagToEnum# :: Int -> a (result type must be an enumerated type) The constraints aren't currently checked by the front end, but the code generator will fall over if they aren't satisfied. ************************************************************************ * * Which PrimOps are out-of-line * * ************************************************************************ Some PrimOps need to be called out-of-line because they either need to perform a heap check or they block. -} primOpOutOfLine :: PrimOp -> Bool #include "primop-out-of-line.hs-incl" {- ************************************************************************ * * Failure and side effects * * ************************************************************************ Note [Checking versus non-checking primops] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ In GHC primops break down into two classes: a. Checking primops behave, for instance, like division. In this case the primop may throw an exception (e.g. division-by-zero) and is consequently is marked with the can_fail flag described below. The ability to fail comes at the expense of precluding some optimizations. b. Non-checking primops behavior, for instance, like addition. While addition can overflow it does not produce an exception. So can_fail is set to False, and we get more optimisation opportunities. But we must never throw an exception, so we cannot rewrite to a call to error. It is important that a non-checking primop never be transformed in a way that would cause it to bottom. Doing so would violate Core's let-can-float invariant (see Note [Core let-can-float invariant] in GHC.Core) which is critical to the simplifier's ability to float without fear of changing program meaning. Note [PrimOp can_fail and has_side_effects] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Both can_fail and has_side_effects mean that the primop has some effect that is not captured entirely by its result value. ---------- has_side_effects --------------------- A primop "has_side_effects" if it has some side effect, visible elsewhere, apart from the result it returns - reading or writing to the world (I/O) - reading or writing to a mutable data structure (writeIORef) - throwing a synchronous Haskell exception Often such primops have a type like State -> input -> (State, output) so the state token guarantees ordering. In general we rely on data dependencies of the state token to enforce write-effect ordering, but as the notes below make clear, the matter is a bit more complicated than that. * NB1: if you inline unsafePerformIO, you may end up with side-effecting ops whose 'state' output is discarded. And programmers may do that by hand; see #9390. That is why we (conservatively) do not discard write-effecting primops even if both their state and result is discarded. * NB2: We consider primops, such as raiseIO#, that can raise a (Haskell) synchronous exception to "have_side_effects" but not "can_fail". We must be careful about not discarding such things; see the paper "A semantics for imprecise exceptions". * NB3: *Read* effects on *mutable* cells (like reading an IORef or a MutableArray#) /are/ included. You may find this surprising because it doesn't matter if we don't do them, or do them more than once. *Sequencing* is maintained by the data dependency of the state token. But see "Duplication" below under Note [Transformations affected by can_fail and has_side_effects] Note that read operations on *immutable* values (like indexArray#) do not have has_side_effects. (They might be marked can_fail, however, because you might index out of bounds.) Using has_side_effects in this way is a bit of a blunt instrument. We could be more refined by splitting read and write effects (see comments with #3207 and #20195) ---------- can_fail ---------------------------- A primop "can_fail" if it can fail with an *unchecked* exception on some elements of its input domain. Main examples: division (fails on zero denominator) array indexing (fails if the index is out of bounds) An "unchecked exception" is one that is an outright error, (not turned into a Haskell exception,) such as seg-fault or divide-by-zero error. Such can_fail primops are ALWAYS surrounded with a test that checks for the bad cases, but we need to be very careful about code motion that might move it out of the scope of the test. Note [Transformations affected by can_fail and has_side_effects] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The can_fail and has_side_effects properties have the following effect on program transformations. Summary table is followed by details. can_fail has_side_effects Discard YES NO Float in YES YES Float out NO NO Duplicate YES NO * Discarding. case (a `op` b) of _ -> rhs ===> rhs You should not discard a has_side_effects primop; e.g. case (writeIntArray# a i v s of (# _, _ #) -> True Arguably you should be able to discard this, since the returned stat token is not used, but that relies on NEVER inlining unsafePerformIO, and programmers sometimes write this kind of stuff by hand (#9390). So we (conservatively) never discard a has_side_effects primop. However, it's fine to discard a can_fail primop. For example case (indexIntArray# a i) of _ -> True We can discard indexIntArray#; it has can_fail, but not has_side_effects; see #5658 which was all about this. Notice that indexIntArray# is (in a more general handling of effects) read effect, but we don't care about that here, and treat read effects as *not* has_side_effects. Similarly (a `/#` b) can be discarded. It can seg-fault or cause a hardware exception, but not a synchronous Haskell exception. Synchronous Haskell exceptions, e.g. from raiseIO#, are treated as has_side_effects and hence are not discarded. * Float in. You can float a can_fail or has_side_effects primop *inwards*, but not inside a lambda (see Duplication below). * Float out. You must not float a can_fail primop *outwards* lest you escape the dynamic scope of the test. Example: case d ># 0# of True -> case x /# d of r -> r +# 1 False -> 0 Here we must not float the case outwards to give case x/# d of r -> case d ># 0# of True -> r +# 1 False -> 0 Nor can you float out a has_side_effects primop. For example: if blah then case writeMutVar# v True s0 of (# s1 #) -> s1 else s0 Notice that s0 is mentioned in both branches of the 'if', but only one of these two will actually be consumed. But if we float out to case writeMutVar# v True s0 of (# s1 #) -> if blah then s1 else s0 the writeMutVar will be performed in both branches, which is utterly wrong. * Duplication. You cannot duplicate a has_side_effect primop. You might wonder how this can occur given the state token threading, but just look at Control.Monad.ST.Lazy.Imp.strictToLazy! We get something like this p = case readMutVar# s v of (# s', r #) -> (State# s', r) s' = case p of (s', r) -> s' r = case p of (s', r) -> r (All these bindings are boxed.) If we inline p at its two call sites, we get a catastrophe: because the read is performed once when s' is demanded, and once when 'r' is demanded, which may be much later. Utterly wrong. #3207 is real example of this happening. However, it's fine to duplicate a can_fail primop. That is really the only difference between can_fail and has_side_effects. Note [Implementation: how can_fail/has_side_effects affect transformations] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ How do we ensure that floating/duplication/discarding are done right in the simplifier? Two main predicates on primops test these flags: primOpOkForSideEffects <=> not has_side_effects primOpOkForSpeculation <=> not (has_side_effects || can_fail) * The "no-float-out" thing is achieved by ensuring that we never let-bind a can_fail or has_side_effects primop. The RHS of a let-binding (which can float in and out freely) satisfies exprOkForSpeculation; this is the let-can-float invariant. And exprOkForSpeculation is false of can_fail and has_side_effects. * So can_fail and has_side_effects primops will appear only as the scrutinees of cases, and that's why the FloatIn pass is capable of floating case bindings inwards. * The no-duplicate thing is done via primOpIsCheap, by making has_side_effects things (very very very) not-cheap! -} primOpHasSideEffects :: PrimOp -> Bool #include "primop-has-side-effects.hs-incl" primOpCanFail :: PrimOp -> Bool #include "primop-can-fail.hs-incl" primOpOkForSpeculation :: PrimOp -> Bool -- See Note [PrimOp can_fail and has_side_effects] -- See comments with GHC.Core.Utils.exprOkForSpeculation -- primOpOkForSpeculation => primOpOkForSideEffects primOpOkForSpeculation :: PrimOp -> Bool primOpOkForSpeculation PrimOp op = PrimOp -> Bool primOpOkForSideEffects PrimOp op Bool -> Bool -> Bool && Bool -> Bool not (PrimOp -> Bool primOpOutOfLine PrimOp op Bool -> Bool -> Bool || PrimOp -> Bool primOpCanFail PrimOp op) -- I think the "out of line" test is because out of line things can -- be expensive (eg sine, cosine), and so we may not want to speculate them primOpOkForSideEffects :: PrimOp -> Bool primOpOkForSideEffects :: PrimOp -> Bool primOpOkForSideEffects PrimOp op = Bool -> Bool not (PrimOp -> Bool primOpHasSideEffects PrimOp op) {- Note [primOpIsCheap] ~~~~~~~~~~~~~~~~~~~~ @primOpIsCheap@, as used in GHC.Core.Opt.Simplify.Utils. For now (HACK WARNING), we just borrow some other predicates for a what-should-be-good-enough test. "Cheap" means willing to call it more than once, and/or push it inside a lambda. The latter could change the behaviour of 'seq' for primops that can fail, so we don't treat them as cheap. -} primOpIsCheap :: PrimOp -> Bool -- See Note [PrimOp can_fail and has_side_effects] primOpIsCheap :: PrimOp -> Bool primOpIsCheap PrimOp op = PrimOp -> Bool primOpOkForSpeculation PrimOp op -- In March 2001, we changed this to -- primOpIsCheap op = False -- thereby making *no* primops seem cheap. But this killed eta -- expansion on case (x ==# y) of True -> \s -> ... -- which is bad. In particular a loop like -- doLoop n = loop 0 -- where -- loop i | i == n = return () -- | otherwise = bar i >> loop (i+1) -- allocated a closure every time round because it doesn't eta expand. -- -- The problem that originally gave rise to the change was -- let x = a +# b *# c in x +# x -- were we don't want to inline x. But primopIsCheap doesn't control -- that (it's exprIsDupable that does) so the problem doesn't occur -- even if primOpIsCheap sometimes says 'True'. -- | True of dyadic operators that can fail only if the second arg is zero! -- -- This function probably belongs in an automagically generated file.. but it's -- such a special case I thought I'd leave it here for now. primOpIsDiv :: PrimOp -> Bool primOpIsDiv :: PrimOp -> Bool primOpIsDiv PrimOp op = case PrimOp op of PrimOp IntQuotOp -> Bool True PrimOp Int8QuotOp -> Bool True PrimOp Int16QuotOp -> Bool True PrimOp Int32QuotOp -> Bool True PrimOp Int64QuotOp -> Bool True PrimOp IntRemOp -> Bool True PrimOp Int8RemOp -> Bool True PrimOp Int16RemOp -> Bool True PrimOp Int32RemOp -> Bool True PrimOp Int64RemOp -> Bool True PrimOp IntQuotRemOp -> Bool True PrimOp Int8QuotRemOp -> Bool True PrimOp Int16QuotRemOp -> Bool True PrimOp Int32QuotRemOp -> Bool True -- Int64QuotRemOp doesn't exist (yet) PrimOp WordQuotOp -> Bool True PrimOp Word8QuotOp -> Bool True PrimOp Word16QuotOp -> Bool True PrimOp Word32QuotOp -> Bool True PrimOp Word64QuotOp -> Bool True PrimOp WordRemOp -> Bool True PrimOp Word8RemOp -> Bool True PrimOp Word16RemOp -> Bool True PrimOp Word32RemOp -> Bool True PrimOp Word64RemOp -> Bool True PrimOp WordQuotRemOp -> Bool True PrimOp Word8QuotRemOp -> Bool True PrimOp Word16QuotRemOp -> Bool True PrimOp Word32QuotRemOp -> Bool True -- Word64QuotRemOp doesn't exist (yet) PrimOp WordQuotRem2Op -> Bool True PrimOp FloatDivOp -> Bool True PrimOp DoubleDivOp -> Bool True PrimOp _ -> Bool False {- ************************************************************************ * * PrimOp code size * * ************************************************************************ primOpCodeSize ~~~~~~~~~~~~~~ Gives an indication of the code size of a primop, for the purposes of calculating unfolding sizes; see GHC.Core.Unfold.sizeExpr. -} primOpCodeSize :: PrimOp -> Int #include "primop-code-size.hs-incl" primOpCodeSizeDefault :: Int primOpCodeSizeDefault :: Int primOpCodeSizeDefault = Int 1 -- GHC.Core.Unfold.primOpSize already takes into account primOpOutOfLine -- and adds some further costs for the args in that case. primOpCodeSizeForeignCall :: Int primOpCodeSizeForeignCall :: Int primOpCodeSizeForeignCall = Int 4 {- ************************************************************************ * * PrimOp types * * ************************************************************************ -} primOpType :: PrimOp -> Type -- you may want to use primOpSig instead primOpType :: PrimOp -> Type primOpType PrimOp op = case PrimOp -> PrimOpInfo primOpInfo PrimOp op of Compare OccName _occ Type ty -> Type -> Type compare_fun_ty Type ty GenPrimOp OccName _occ [TyVarBinder] tyvars [Type] arg_tys Type res_ty -> [TyVarBinder] -> Type -> Type mkForAllTys [TyVarBinder] tyvars ([Type] -> Type -> Type mkVisFunTysMany [Type] arg_tys Type res_ty) primOpResultType :: PrimOp -> Type primOpResultType :: PrimOp -> Type primOpResultType PrimOp op = case PrimOp -> PrimOpInfo primOpInfo PrimOp op of Compare OccName _occ Type _ty -> Type intPrimTy GenPrimOp OccName _occ [TyVarBinder] _tyvars [Type] _arg_tys Type res_ty -> Type res_ty primOpOcc :: PrimOp -> OccName primOpOcc :: PrimOp -> OccName primOpOcc PrimOp op = case PrimOp -> PrimOpInfo primOpInfo PrimOp op of Compare OccName occ Type _ -> OccName occ GenPrimOp OccName occ [TyVarBinder] _ [Type] _ Type _ -> OccName occ {- Note [Primop wrappers] ~~~~~~~~~~~~~~~~~~~~~~~~~ To support (limited) use of primops in GHCi genprimopcode generates the GHC.PrimopWrappers module. This module contains a "primop wrapper" binding for each primop. These are standard Haskell functions mirroring the types of the primops they wrap. For instance, in the case of plusInt# we would have: module GHC.PrimopWrappers where import GHC.Prim as P plusInt# :: Int# -> Int# -> Int# plusInt# a b = P.plusInt# a b The Id for the wrapper of a primop can be found using 'GHC.Builtin.PrimOps.primOpWrapperId'. However, GHCi does not use this mechanism to link primops; it rather does a rather hacky symbol lookup (see GHC.ByteCode.Linker.primopToCLabel). TODO: Perhaps this should be changed? Note that these wrappers aren't *quite* as expressive as their unwrapped brethren, in that they may exhibit less representation polymorphism. For instance, consider the case of mkWeakNoFinalizer#, which has type: mkWeakNoFinalizer# :: forall (r :: RuntimeRep) (k :: TYPE r) (v :: Type). k -> v -> State# RealWorld -> (# State# RealWorld, Weak# v #) Naively we could generate a wrapper of the form, mkWeakNoFinalizer# k v s = GHC.Prim.mkWeakNoFinalizer# k v s However, this would require that 'k' bind the representation-polymorphic key, which is disallowed by our representation polymorphism validity checks (see Note [Representation polymorphism invariants] in GHC.Core). Consequently, we give the wrapper the simpler, less polymorphic type mkWeakNoFinalizer# :: forall (k :: Type) (v :: Type). k -> v -> State# RealWorld -> (# State# RealWorld, Weak# v #) This simplification tends to be good enough for GHCi uses given that there are few representation-polymorphic primops, and we do little simplification on interpreted code anyways. TODO: This behavior is actually wrong; a program becomes ill-typed upon replacing a real primop occurrence with one of its wrapper due to the fact that the former has an additional type binder. Hmmm.... Note [Eta expanding primops] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ STG requires that primop applications be saturated. This makes code generation significantly simpler since otherwise we would need to define a calling convention for curried applications that can accommodate representation polymorphism. To ensure saturation, CorePrep eta expands all primop applications as described in Note [Eta expansion of hasNoBinding things in CorePrep] in GHC.Core.Prep. Historical Note: For a short period around GHC 8.8 we rewrote unsaturated primop applications to rather use the primop's wrapper (see Note [Primop wrappers] in GHC.Builtin.PrimOps) instead of eta expansion. This was because at the time CoreTidy would try to predict the CAFfyness of bindings that would be produced by CorePrep for inclusion in interface files. Eta expanding during CorePrep proved to be very difficult to predict, leading to nasty inconsistencies in CAFfyness determinations (see #16846). Thankfully, we now no longer try to predict CAFfyness but rather compute it on GHC STG (see Note [SRTs] in GHC.Cmm.Info.Build) and inject it into the interface file after code generation (see TODO: Refer to whatever falls out of #18096). This is much simpler and avoids the potential for inconsistency, allowing us to return to the somewhat simpler eta expansion approach for unsaturated primops. See #18079. -} -- | Returns the 'Id' of the wrapper associated with the given 'PrimOp'. -- See Note [Primop wrappers]. primOpWrapperId :: PrimOp -> Id primOpWrapperId :: PrimOp -> Id primOpWrapperId PrimOp op = Name -> Type -> IdInfo -> Id mkVanillaGlobalWithInfo Name name Type ty IdInfo info where info :: IdInfo info = IdInfo -> CafInfo -> IdInfo setCafInfo IdInfo vanillaIdInfo CafInfo NoCafRefs name :: Name name = Unique -> Module -> OccName -> SrcSpan -> Name mkExternalName Unique uniq Module gHC_PRIMOPWRAPPERS (PrimOp -> OccName primOpOcc PrimOp op) SrcSpan wiredInSrcSpan uniq :: Unique uniq = Int -> Unique mkPrimOpWrapperUnique (PrimOp -> Int primOpTag PrimOp op) ty :: Type ty = PrimOp -> Type primOpType PrimOp op isComparisonPrimOp :: PrimOp -> Bool isComparisonPrimOp :: PrimOp -> Bool isComparisonPrimOp PrimOp op = case PrimOp -> PrimOpInfo primOpInfo PrimOp op of Compare {} -> Bool True GenPrimOp {} -> Bool False -- primOpSig is like primOpType but gives the result split apart: -- (type variables, argument types, result type) -- It also gives arity, strictness info primOpSig :: PrimOp -> ([TyVarBinder], [Type], Type, Arity, DmdSig) primOpSig :: PrimOp -> ([TyVarBinder], [Type], Type, Int, DmdSig) primOpSig PrimOp op = ([TyVarBinder] tyvars, [Type] arg_tys, Type res_ty, Int arity, PrimOp -> Int -> DmdSig primOpStrictness PrimOp op Int arity) where arity :: Int arity = [Type] -> Int forall a. [a] -> Int forall (t :: * -> *) a. Foldable t => t a -> Int length [Type] arg_tys ([TyVarBinder] tyvars, [Type] arg_tys, Type res_ty) = case (PrimOp -> PrimOpInfo primOpInfo PrimOp op) of Compare OccName _occ Type ty -> ([], [Type ty,Type ty], Type intPrimTy) GenPrimOp OccName _occ [TyVarBinder] tyvars [Type] arg_tys Type res_ty -> ([TyVarBinder] tyvars, [Type] arg_tys, Type res_ty ) data PrimOpResultInfo = ReturnsPrim PrimRep | ReturnsAlg TyCon -- Some PrimOps need not return a manifest primitive or algebraic value -- (i.e. they might return a polymorphic value). These PrimOps *must* -- be out of line, or the code generator won't work. getPrimOpResultInfo :: PrimOp -> PrimOpResultInfo getPrimOpResultInfo :: PrimOp -> PrimOpResultInfo getPrimOpResultInfo PrimOp op = case (PrimOp -> PrimOpInfo primOpInfo PrimOp op) of Compare OccName _ Type _ -> PrimRep -> PrimOpResultInfo ReturnsPrim (HasDebugCallStack => TyCon -> PrimRep TyCon -> PrimRep tyConPrimRep1 TyCon intPrimTyCon) GenPrimOp OccName _ [TyVarBinder] _ [Type] _ Type ty | TyCon -> Bool isPrimTyCon TyCon tc -> PrimRep -> PrimOpResultInfo ReturnsPrim (HasDebugCallStack => TyCon -> PrimRep TyCon -> PrimRep tyConPrimRep1 TyCon tc) | Bool otherwise -> TyCon -> PrimOpResultInfo ReturnsAlg TyCon tc where tc :: TyCon tc = HasDebugCallStack => Type -> TyCon Type -> TyCon tyConAppTyCon Type ty -- All primops return a tycon-app result -- The tycon can be an unboxed tuple or sum, though, -- which gives rise to a ReturnAlg {- We do not currently make use of whether primops are commutable. We used to try to move constants to the right hand side for strength reduction. -} {- commutableOp :: PrimOp -> Bool #include "primop-commutable.hs-incl" -} -- Utils: compare_fun_ty :: Type -> Type compare_fun_ty :: Type -> Type compare_fun_ty Type ty = [Type] -> Type -> Type mkVisFunTysMany [Type ty, Type ty] Type intPrimTy -- Output stuff: pprPrimOp :: IsLine doc => PrimOp -> doc pprPrimOp :: forall doc. IsLine doc => PrimOp -> doc pprPrimOp PrimOp other_op = OccName -> doc forall doc. IsLine doc => OccName -> doc pprOccName (PrimOp -> OccName primOpOcc PrimOp other_op) {-# SPECIALIZE pprPrimOp :: PrimOp -> SDoc #-} {-# SPECIALIZE pprPrimOp :: PrimOp -> HLine #-} -- see Note [SPECIALIZE to HDoc] in GHC.Utils.Outputable {- ************************************************************************ * * \subsubsection[PrimCall]{User-imported primitive calls} * * ************************************************************************ -} data PrimCall = PrimCall CLabelString Unit instance Outputable PrimCall where ppr :: PrimCall -> SDoc ppr (PrimCall FastString lbl Unit pkgId) = String -> SDoc forall doc. IsLine doc => String -> doc text String "__primcall" SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> Unit -> SDoc forall a. Outputable a => a -> SDoc ppr Unit pkgId SDoc -> SDoc -> SDoc forall doc. IsLine doc => doc -> doc -> doc <+> FastString -> SDoc forall a. Outputable a => a -> SDoc ppr FastString lbl -- | Indicate if a primop is really inline: that is, it isn't out-of-line and it -- isn't SeqOp/DataToTagOp which are two primops that evaluate their argument -- hence induce thread/stack/heap changes. primOpIsReallyInline :: PrimOp -> Bool primOpIsReallyInline :: PrimOp -> Bool primOpIsReallyInline = \case PrimOp SeqOp -> Bool False PrimOp DataToTagOp -> Bool False PrimOp p -> Bool -> Bool not (PrimOp -> Bool primOpOutOfLine PrimOp p)