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[ghc-hetmet.git] / compiler / simplCore / Simplify.lhs

diff --git a/compiler/simplCore/Simplify.lhs b/compiler/simplCore/Simplify.lhs
index 28193eb..c3fb34d 100644 (file)
--- a/compiler/simplCore/Simplify.lhs
+++ b/compiler/simplCore/Simplify.lhs
@@ -410,7 +410,7 @@ becomes
 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 coersions]
+prepareRhs env (Cast rhs co)   -- Note [Float coercions]
   = do { (env', rhs') <- makeTrivial env rhs
        ; return (env', Cast rhs' co) }
 
@@ -630,12 +630,12 @@ simplExprF env e cont
   = -- pprTrace "simplExprF" (ppr e $$ ppr cont $$ ppr (seTvSubst env) $$ ppr (seIdSubst env) {- $$ ppr (seFloats env) -} ) $
     simplExprF' env e cont
                                     
-simplExprF' env (Var v)              cont = simplVar env v cont
+simplExprF' env (Var v)               cont = simplVar env v cont
 simplExprF' env (Lit lit)      cont = rebuild env (Lit lit) cont
 simplExprF' env (Note n expr)  cont = simplNote env n expr cont
 simplExprF' env (Cast body co) cont = simplCast env body co cont
 simplExprF' env (App fun arg)  cont = simplExprF env fun $
-                                    ApplyTo NoDup arg env cont
+                                     ApplyTo NoDup arg env cont
 
 simplExprF' env expr@(Lam _ _) cont 
   = simplLam env (map zap bndrs) body cont
@@ -733,12 +733,12 @@ simplCast env body co cont
   = do { co' <- simplType env co
        ; simplExprF env body (addCoerce co' cont) }
   where
-       addCoerce co cont 
-         | (s1, k1) <- coercionKind co
-         , s1 `coreEqType` k1 = cont
-       addCoerce co1 (CoerceIt co2 cont)
-         | (s1, k1) <- coercionKind co1
-         , (l1, t1) <- coercionKind co2
+       addCoerce co cont = add_coerce co (coercionKind co) cont
+
+       add_coerce co (s1, k1) cont 
+         | s1 `coreEqType` k1 = cont
+       add_coerce co1 (s1, k2) (CoerceIt co2 cont)
+         | (l1, t1) <- coercionKind co2
                 --     coerce T1 S1 (coerce S1 K1 e)
                -- ==>
                --      e,                      if T1=K1
@@ -751,11 +751,10 @@ simplCast env body co cont
          , s1 `coreEqType` t1  = cont           -- The coerces cancel out  
          | otherwise           = CoerceIt (mkTransCoercion co1 co2) cont
     
-       addCoerce co (ApplyTo dup arg arg_se cont)
-         | not (isTypeArg arg)    -- This whole case only works for value args
+       add_coerce co (s1s2, t1t2) (ApplyTo dup arg arg_se cont)
+         | not (isTypeArg arg)  -- This whole case only works for value args
                                -- Could upgrade to have equiv thing for type apps too  
-         , Just (s1s2, t1t2) <- splitCoercionKind_maybe co
-         , isFunTy s1s2
+         , isFunTy s1s2          -- t1t2 must be a function type, becuase it's applied
                 -- co : s1s2 :=: t1t2
                --      (coerce (T1->T2) (S1->S2) F) E
                -- ===> 
@@ -768,6 +767,8 @@ simplCast env body co cont
                -- with the InExpr in the argument, so we simply substitute
                -- to make it all consistent.  It's a bit messy.
                -- But it isn't a common case.
+               --
+               -- Example of use: Trac #995
          = ApplyTo dup new_arg (zapSubstEnv env) (addCoerce co2 cont)
          where
            -- we split coercion t1->t2 :=: s1->s2 into t1 :=: s1 and 
@@ -777,7 +778,7 @@ simplCast env body co cont
            new_arg    = mkCoerce (mkSymCoercion co1) arg'
           arg'       = substExpr arg_se arg
 
-       addCoerce co cont = CoerceIt co cont
+       add_coerce co _ cont = CoerceIt co cont
 \end{code}
 
 
@@ -875,16 +876,8 @@ simplNote env InlineMe e cont
   = simplExprF env e cont
 
 simplNote env (CoreNote s) e cont
-  = do { e' <- simplExpr env e
-       ; rebuild env (Note (CoreNote s) e') cont }
-
-simplNote env note@(TickBox {}) e cont
-  = do { e' <- simplExpr env e
-       ; rebuild env (Note note e') cont }
-
-simplNote env note@(BinaryTickBox {}) e cont
-  = do { e' <- simplExpr env e
-       ; rebuild env (Note note e') cont }
+  = simplExpr env e    `thenSmpl` \ e' ->
+    rebuild env (Note (CoreNote s) e') cont
 \end{code}
 
 
@@ -1130,18 +1123,10 @@ in action in spectral/cichelli/Prog.hs:
         [(m,n) | m <- [1..max], n <- [1..max]]
 Hence the check for NoCaseOfCase.
 
-Note [Case of cast]
-~~~~~~~~~~~~~~~~~~~
-Consider       case (v `cast` co) of x { I# ->
-               ... (case (v `cast` co) of {...}) ...
-We'd like to eliminate the inner case.  We can get this neatly by 
-arranging that inside the outer case we add the unfolding
-       v |-> x `cast` (sym co)
-to v.  Then we should inline v at the inner case, cancel the casts, and away we go
-       
-Note 2
-~~~~~~
-There is another situation when we don't want to do it.  If we have
+Note [Suppressing the case binder-swap]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+There is another situation when it might make sense to suppress the
+case-expression binde-swap. If we have
 
     case x of w1 { DEFAULT -> case x of w2 { A -> e1; B -> e2 }
                   ...other cases .... }
@@ -1203,6 +1188,15 @@ The point is that we bring into the envt a binding
 after the outer case, and that makes (a,b) alive.  At least we do unless
 the case binder is guaranteed dead.
 
+Note [Case of cast]
+~~~~~~~~~~~~~~~~~~~
+Consider       case (v `cast` co) of x { I# ->
+               ... (case (v `cast` co) of {...}) ...
+We'd like to eliminate the inner case.  We can get this neatly by 
+arranging that inside the outer case we add the unfolding
+       v |-> x `cast` (sym co)
+to v.  Then we should inline v at the inner case, cancel the casts, and away we go
+       
 \begin{code}
 simplCaseBinder :: SimplEnv -> OutExpr -> InId -> SimplM (SimplEnv, OutId)
 simplCaseBinder env scrut case_bndr