diff options
| -rw-r--r-- | compiler/basicTypes/MkId.hs | 9 | ||||
| -rw-r--r-- | libraries/base/Control/Monad/ST/Lazy/Imp.hs | 3 | ||||
| -rw-r--r-- | libraries/ghc-prim/GHC/Magic.hs | 24 |
3 files changed, 23 insertions, 13 deletions
diff --git a/compiler/basicTypes/MkId.hs b/compiler/basicTypes/MkId.hs index 417a6c7869..65860d9045 100644 --- a/compiler/basicTypes/MkId.hs +++ b/compiler/basicTypes/MkId.hs @@ -1236,12 +1236,11 @@ runRWId = pcMiscPrelId runRWName ty info -- State# RealWorld stateRW = mkTyConApp statePrimTyCon [realWorldTy] - -- (# State# RealWorld, o #) - ret_ty = mkTupleTy Unboxed [stateRW, openAlphaTy] - -- State# RealWorld -> (# State# RealWorld, o #) + -- o + ret_ty = openAlphaTy + -- State# RealWorld -> o arg_ty = stateRW `mkFunTy` ret_ty - -- (State# RealWorld -> (# State# RealWorld, o #)) - -- -> (# State# RealWorld, o #) + -- (State# RealWorld -> o) -> o ty = mkSpecForAllTys [runtimeRep1TyVar, openAlphaTyVar] $ arg_ty `mkFunTy` ret_ty diff --git a/libraries/base/Control/Monad/ST/Lazy/Imp.hs b/libraries/base/Control/Monad/ST/Lazy/Imp.hs index 45d2219dce..414c06c8c3 100644 --- a/libraries/base/Control/Monad/ST/Lazy/Imp.hs +++ b/libraries/base/Control/Monad/ST/Lazy/Imp.hs @@ -89,12 +89,11 @@ instance Monad (ST s) where in k_a new_s -{-# NOINLINE runST #-} -- | Return the value computed by a state transformer computation. -- The @forall@ ensures that the internal state used by the 'ST' -- computation is inaccessible to the rest of the program. runST :: (forall s. ST s a) -> a -runST st = case st of ST the_st -> let (r,_) = the_st (S# realWorld#) in r +runST (ST st) = runRW# (\s -> case st (S# s) of (r, _) -> r) -- | Allow the result of a state transformer computation to be used (lazily) -- inside the computation. diff --git a/libraries/ghc-prim/GHC/Magic.hs b/libraries/ghc-prim/GHC/Magic.hs index 96f1742dea..ecdffc5600 100644 --- a/libraries/ghc-prim/GHC/Magic.hs +++ b/libraries/ghc-prim/GHC/Magic.hs @@ -3,6 +3,8 @@ {-# LANGUAGE NoImplicitPrelude #-} {-# LANGUAGE MagicHash #-} {-# LANGUAGE UnboxedTuples #-} +{-# LANGUAGE TypeInType #-} +{-# LANGUAGE ScopedTypeVariables #-} ----------------------------------------------------------------------------- -- | @@ -25,6 +27,7 @@ module GHC.Magic ( inline, noinline, lazy, oneShot, runRW# ) where import GHC.Prim import GHC.CString () +import GHC.Types (RuntimeRep, TYPE) -- | The call @inline f@ arranges that 'f' is inlined, regardless of -- its size. More precisely, the call @inline f@ rewrites to the @@ -88,16 +91,25 @@ lazy x = x -- that would otherwise be shared are re-evaluated every time they are used. Otherwise, -- the use of `oneShot` is safe. -- --- 'oneShot' is open kinded, i.e. the type variables can refer to unlifted --- types as well. -oneShot :: (a -> b) -> (a -> b) +-- 'oneShot' is representation polymorphic: the type variables may refer to lifted +-- or unlifted types. +oneShot :: forall (q :: RuntimeRep) (r :: RuntimeRep) + (a :: TYPE q) (b :: TYPE r). + (a -> b) -> a -> b oneShot f = f -- Implementation note: This is wired in in MkId.lhs, so the code here is -- mostly there to have a place for the documentation. --- | Apply a function to a 'RealWorld' token. -runRW# :: (State# RealWorld -> (# State# RealWorld, o #)) - -> (# State# RealWorld, o #) +-- | Apply a function to a 'State# RealWorld' token. When manually applying +-- a function to `realWorld#`, it is necessary to use `NOINLINE` to prevent +-- semantically undesirable floating. `runRW#` is inlined, but only very late +-- in compilation after all floating is complete. + +-- 'runRW#' is representation polymorphic: the result may have a lifted or +-- unlifted type. + +runRW# :: forall (r :: RuntimeRep) (o :: TYPE r). + (State# RealWorld -> o) -> o -- See Note [runRW magic] in MkId #if !defined(__HADDOCK_VERSION__) runRW# m = m realWorld# |