Float constants to top-level even in first full laziness pass

[ghc-hetmet.git] / compiler / main / DynFlags.hs

diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
index e3fd426..47cc3fe 100644 (file)
--- a/compiler/main/DynFlags.hs
+++ b/compiler/main/DynFlags.hs
@@ -1000,8 +1000,8 @@ pprFloatOutSwitches sw = pp_not (floatOutLambdas sw) <+> text "lambdas" <> comma
     pp_not False = text "not"
 
 -- | Switches that specify the minimum amount of floating out
-gentleFloatOutSwitches :: FloatOutSwitches
-gentleFloatOutSwitches = FloatOutSwitches False False
+-- gentleFloatOutSwitches :: FloatOutSwitches
+-- gentleFloatOutSwitches = FloatOutSwitches False False
 
 -- | Switches that do not specify floating out of lambdas, just of constants
 constantsOnlyFloatOutSwitches :: FloatOutSwitches
@@ -1103,7 +1103,14 @@ getCoreToDo dflags
         -- so that overloaded functions have all their dictionary lambdas manifest
         CoreDoSpecialising,
 
-        runWhen full_laziness (CoreDoFloatOutwards gentleFloatOutSwitches),
+        runWhen full_laziness (CoreDoFloatOutwards constantsOnlyFloatOutSwitches),
+               -- Was: gentleFloatOutSwitches  
+               -- I have no idea why, but not floating constants to top level is
+               -- very bad in some cases. 
+               -- Notably: p_ident in spectral/rewrite
+               --          Changing from "gentle" to "constantsOnly" improved
+               --          rewrite's allocation by 19%, and made  0.0% difference
+               --          to any other nofib benchmark
 
         CoreDoFloatInwards,