Merge branch 'master' of http://darcs.haskell.org/ghc

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

diff --git a/compiler/simplCore/CoreMonad.lhs b/compiler/simplCore/CoreMonad.lhs
index bb598c6..6ddcff2 100644 (file)
--- a/compiler/simplCore/CoreMonad.lhs
+++ b/compiler/simplCore/CoreMonad.lhs
@@ -370,13 +370,21 @@ getCoreToDo dflags
 
     simpl_phase phase names iter
       = CoreDoPasses
-          [ maybe_strictness_before phase
+      $   [ maybe_strictness_before phase
           , CoreDoSimplify iter
                 (base_mode { sm_phase = Phase phase
                            , sm_names = names })
 
-          , maybe_rule_check (Phase phase)
-          ]
+          , maybe_rule_check (Phase phase) ]
+
+          -- Vectorisation can introduce a fair few common sub expressions involving 
+          --  DPH primitives. For example, see the Reverse test from dph-examples.
+          --  We need to eliminate these common sub expressions before their definitions
+          --  are inlined in phase 2. The CSE introduces lots of  v1 = v2 bindings, 
+          --  so we also run simpl_gently to inline them.
+      ++  (if dopt Opt_Vectorise dflags && phase == 3
+           then [CoreCSE, simpl_gently]
+           else [])
 
     vectorisation
       = runWhen (dopt Opt_Vectorise dflags) $
@@ -401,7 +409,7 @@ getCoreToDo dflags
     simpl_gently = CoreDoSimplify max_iter
                        (base_mode { sm_phase = InitialPhase
                                   , sm_names = ["Gentle"]
-                                  , sm_rules = True     -- Note [RULEs enabled in SimplGently]
+                                  , sm_rules = rules_on   -- Note [RULEs enabled in SimplGently]
                                   , sm_inline = False
                                   , sm_case_case = False })
                           -- Don't do case-of-case transformations.
@@ -568,9 +576,6 @@ RULES are enabled when doing "gentle" simplification.  Two reasons:
 But watch out: list fusion can prevent floating.  So use phase control
 to switch off those rules until after floating.
 
-Currently (Oct10) I think that sm_rules is always True, so we
-could remove it.
-
 
 %************************************************************************
 %*                                                                     *