X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FsimplCore%2FSimplify.lhs;h=d05e4a11e49b4ed805511170c4c8b369477c144b;hb=4f56b4074079380d4b115a05d5aa71004f716710;hp=97ad75c9e6536e567e8c8d3aebd82f5d37b32f36;hpb=ad94d40948668032189ad22a0ad741ac1f645f50;p=ghc-hetmet.git

diff --git a/compiler/simplCore/Simplify.lhs b/compiler/simplCore/Simplify.lhs
index 97ad75c..d05e4a1 100644
--- a/compiler/simplCore/Simplify.lhs
+++ b/compiler/simplCore/Simplify.lhs
@@ -8,7 +8,7 @@
 -- The above warning supression flag is a temporary kludge.
 -- While working on this module you are encouraged to remove it and fix
 -- any warnings in the module. See
---     http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module Simplify ( simplTopBinds, simplExpr ) where
@@ -422,6 +422,8 @@ That's what the 'go' loop in prepareRhs does
 prepareRhs :: SimplEnv -> OutExpr -> SimplM (SimplEnv, OutExpr)
 -- Adds new floats to the env iff that allows us to return a good RHS
 prepareRhs env (Cast rhs co)	-- Note [Float coercions]
+  | (ty1, ty2) <- coercionKind co	-- Do *not* do this if rhs has an unlifted type
+  , not (isUnLiftedType ty1)		-- see Note [Float coercions (unlifted)]
   = do	{ (env', rhs') <- makeTrivial env rhs
 	; return (env', Cast rhs' co) }
 
@@ -474,6 +476,22 @@ and lead to further optimisation.  Example:
           go n = case x of { T m -> go (n-m) }
 		-- This case should optimise
 
+Note [Float coercions (unlifted)]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+BUT don't do [Float coercions] if 'e' has an unlifted type. 
+This *can* happen:
+
+     foo :: Int = (error (# Int,Int #) "urk") 
+		  `cast` CoUnsafe (# Int,Int #) Int
+
+If do the makeTrivial thing to the error call, we'll get
+    foo = case error (# Int,Int #) "urk" of v -> v `cast` ...
+But 'v' isn't in scope!  
+
+These strange casts can happen as a result of case-of-case
+	bar = case (case x of { T -> (# 2,3 #); F -> error "urk" }) of
+		(# p,q #) -> p+q
+
 
 \begin{code}
 makeTrivial :: SimplEnv -> OutExpr -> SimplM (SimplEnv, OutExpr)
@@ -1662,25 +1680,27 @@ knownAlt env scrut args bndr (DataAlt dc, bs, rhs) cont
 	; env <- simplNonRecX env bndr bndr_rhs
 	; -- pprTrace "knownCon2" (ppr bs $$ ppr rhs $$ ppr (seIdSubst env)) $
 	  simplExprF env rhs cont }
-
--- Ugh!
-bind_args env dead_bndr [] _  = return env
-
-bind_args env dead_bndr (b:bs) (Type ty : args)
-  = ASSERT( isTyVar b )
-    bind_args (extendTvSubst env b ty) dead_bndr bs args
-    
-bind_args env dead_bndr (b:bs) (arg : args)
-  = ASSERT( isId b )
-    do	{ let b' = if dead_bndr then b else zapOccInfo b
-		-- Note that the binder might be "dead", because it doesn't occur 
-		-- in the RHS; and simplNonRecX may therefore discard it via postInlineUnconditionally
-		-- Nevertheless we must keep it if the case-binder is alive, because it may
-		-- be used in the con_app.  See Note [zapOccInfo]
-	; env <- simplNonRecX env b' arg
-	; bind_args env dead_bndr bs args }
-
-bind_args _ _ _ _ = panic "bind_args"
+  where
+    -- Ugh!
+    bind_args env dead_bndr [] _  = return env
+
+    bind_args env dead_bndr (b:bs) (Type ty : args)
+      = ASSERT( isTyVar b )
+        bind_args (extendTvSubst env b ty) dead_bndr bs args
+
+    bind_args env dead_bndr (b:bs) (arg : args)
+      = ASSERT( isId b )
+        do	{ let b' = if dead_bndr then b else zapOccInfo b
+                    -- Note that the binder might be "dead", because it doesn't occur 
+                    -- in the RHS; and simplNonRecX may therefore discard it via postInlineUnconditionally
+                    -- Nevertheless we must keep it if the case-binder is alive, because it may
+                    -- be used in the con_app.  See Note [zapOccInfo]
+            ; env <- simplNonRecX env b' arg
+            ; bind_args env dead_bndr bs args }
+
+    bind_args _ _ _ _ = 
+      pprPanic "bind_args" $ ppr dc $$ ppr bs $$ ppr args $$ 
+                             text "scrut:" <+> ppr scrut
 \end{code}