Remove the (very) old strictness analyser

[ghc-hetmet.git] / compiler / prelude / PrimOp.lhs

diff --git a/compiler/prelude/PrimOp.lhs b/compiler/prelude/PrimOp.lhs
index 7c30d9e..4ac1577 100644 (file)
--- a/compiler/prelude/PrimOp.lhs
+++ b/compiler/prelude/PrimOp.lhs
@@ -21,7 +21,9 @@ module PrimOp (
        primOpOutOfLine, primOpNeedsWrapper, 
        primOpOkForSpeculation, primOpIsCheap, primOpIsDupable,
 
        primOpOutOfLine, primOpNeedsWrapper, 
        primOpOkForSpeculation, primOpIsCheap, primOpIsDupable,
 

-       getPrimOpResultInfo,  PrimOpResultInfo(..)
+       getPrimOpResultInfo,  PrimOpResultInfo(..),
+
+        PrimCall(..)

     ) where
 
 #include "HsVersions.h"
     ) where
 
 #include "HsVersions.h"

@@ -29,13 +31,14 @@ module PrimOp (
 import TysPrim
 import TysWiredIn
 
 import TysPrim
 import TysWiredIn
 

-import NewDemand
+import Demand

 import Var             ( TyVar )
 import OccName         ( OccName, pprOccName, mkVarOccFS )
 import TyCon           ( TyCon, isPrimTyCon, tyConPrimRep, PrimRep(..) )
 import Type            ( Type, mkForAllTys, mkFunTy, mkFunTys, tyConAppTyCon,
                          typePrimRep )
 import BasicTypes      ( Arity, Boxity(..) )
 import Var             ( TyVar )
 import OccName         ( OccName, pprOccName, mkVarOccFS )
 import TyCon           ( TyCon, isPrimTyCon, tyConPrimRep, PrimRep(..) )
 import Type            ( Type, mkForAllTys, mkFunTy, mkFunTys, tyConAppTyCon,
                          typePrimRep )
 import BasicTypes      ( Arity, Boxity(..) )

+import ForeignCall     ( CLabelString )

 import Unique          ( Unique, mkPrimOpIdUnique )
 import Outputable
 import FastTypes
 import Unique          ( Unique, mkPrimOpIdUnique )
 import Outputable
 import FastTypes

@@ -286,12 +289,6 @@ These primops are pretty wierd.
 The constraints aren't currently checked by the front end, but the
 code generator will fall over if they aren't satisfied.
 
 The constraints aren't currently checked by the front end, but the
 code generator will fall over if they aren't satisfied.
 

-\begin{code}
-#ifdef DEBUG
-primOpInfo op = pprPanic "primOpInfo:" (ppr op)
-#endif
-\end{code}
-

 %************************************************************************
 %*                                                                     *
 \subsubsection[PrimOp-ool]{Which PrimOps are out-of-line}
 %************************************************************************
 %*                                                                     *
 \subsubsection[PrimOp-ool]{Which PrimOps are out-of-line}

@@ -386,6 +383,38 @@ primOpCanFail :: PrimOp -> Bool
 And some primops have side-effects and so, for example, must not be
 duplicated.
 
 And some primops have side-effects and so, for example, must not be
 duplicated.
 

+This predicate means a little more than just "modifies the state of
+the world".  What it really means is "it cosumes the state on its
+input".  To see what this means, consider
+
+ let
+     t = case readMutVar# v s0 of (# s1, x #) -> (S# s1, x)
+     y = case t of (s,x) -> x
+ in
+     ... y ... y ...
+
+Now, this is part of an ST or IO thread, so we are guaranteed by
+construction that the program uses the state in a single-threaded way.
+Whenever the state resulting from the readMutVar# is demanded, the
+readMutVar# will be performed, and it will be ordered correctly with
+respect to other operations in the monad.
+
+But there's another way this could go wrong: GHC can inline t into y,
+and inline y.  Then although the original readMutVar# will still be
+correctly ordered with respect to the other operations, there will be
+one or more extra readMutVar#s performed later, possibly out-of-order.
+This really happened; see #3207.
+
+The property we need to capture about readMutVar# is that it consumes
+the State# value on its input.  We must retain the linearity of the
+State#.
+
+Our fix for this is to declare any primop that must be used linearly
+as having side-effects.  When primOpHasSideEffects is True,
+primOpOkForSpeculation will be False, and hence primOpIsCheap will
+also be False, and applications of the primop will never be
+duplicated.
+

 \begin{code}
 primOpHasSideEffects :: PrimOp -> Bool
 #include "primop-has-side-effects.hs-incl"
 \begin{code}
 primOpHasSideEffects :: PrimOp -> Bool
 #include "primop-has-side-effects.hs-incl"

@@ -480,3 +509,17 @@ pprPrimOp  :: PrimOp -> SDoc
 pprPrimOp other_op = pprOccName (primOpOcc other_op)
 \end{code}
 
 pprPrimOp other_op = pprOccName (primOpOcc other_op)
 \end{code}
 

+
+%************************************************************************
+%*                                                                     *
+\subsubsection[PrimCall]{User-imported primitive calls}
+%*                                                                     *
+%************************************************************************
+
+\begin{code}
+newtype PrimCall = PrimCall CLabelString
+
+instance Outputable PrimCall where
+  ppr (PrimCall lbl) = ppr lbl
+
+\end{code}