X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FsimplCore%2FFloatOut.lhs;h=2af48bde13c172814d0cba2abcb65d47857a61a5;hp=c97bbce28e32a721b90669d0d0b600e010bf7830;hb=7fc749a43b4b6b85d234fa95d4928648259584f4;hpb=2f41dd510a893312dfaa0d652f448cc3a045eb88

diff --git a/compiler/simplCore/FloatOut.lhs b/compiler/simplCore/FloatOut.lhs
index c97bbce..2af48bd 100644
--- a/compiler/simplCore/FloatOut.lhs
+++ b/compiler/simplCore/FloatOut.lhs
@@ -6,12 +6,19 @@
 ``Long-distance'' floating of bindings towards the top level.
 
 \begin{code}
+{-# OPTIONS -w #-}
+-- 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/Commentary/CodingStyle#Warnings
+-- for details
+
 module FloatOut ( floatOutwards ) where
 
 #include "HsVersions.h"
 
 import CoreSyn
-import CoreUtils	( mkSCC, exprIsHNF, exprIsTrivial )
+import CoreUtils
 
 import DynFlags	( DynFlags, DynFlag(..), FloatOutSwitches(..) )
 import ErrUtils		( dumpIfSet_dyn )
@@ -224,7 +231,7 @@ floatCaseAlt lvl arg	-- Used rec rhss, and case-alternative rhss
 floatRhs lvl arg	-- Used for nested non-rec rhss, and fn args
 			-- See Note [Floating out of RHS]
   = case (floatExpr lvl arg) of { (fsa, floats, arg') ->
-    if exprIsHNF arg' || exprIsTrivial arg' then
+    if exprIsCheap arg' then	
 	(fsa, floats, arg')
     else
     case (partitionByMajorLevel lvl floats) of { (floats', heres) ->
@@ -250,6 +257,9 @@ floatRhs lvl arg	-- Used for nested non-rec rhss, and fn args
 --	bindings just after the '='.  And some of them might (correctly)
 --	be strict even though the 'let f' is lazy, because f, being a value,
 --	gets its demand-info zapped by the simplifier.
+--
+-- We use exprIsCheap because that is also what's used by the simplifier
+-- to decide whether to float a let out of a let
 
 floatExpr _ (Var v)   = (zeroStats, [], Var v)
 floatExpr _ (Type ty) = (zeroStats, [], Type ty)
@@ -323,8 +333,9 @@ floatExpr lvl (Cast expr co)
 
 floatExpr lvl (Let (NonRec (TB bndr bndr_lvl) rhs) body)
   | isUnLiftedType (idType bndr)	-- Treat unlifted lets just like a case
-  = case floatExpr lvl rhs	of { (fs, rhs_floats, rhs') ->
-    case floatRhs bndr_lvl body of { (fs, body_floats, body') ->
+				-- I.e. floatExpr for rhs, floatCaseAlt for body
+  = case floatExpr lvl rhs	    of { (fs, rhs_floats, rhs') ->
+    case floatCaseAlt bndr_lvl body of { (fs, body_floats, body') ->
     (fs, rhs_floats ++ body_floats, Let (NonRec bndr rhs') body') }}
 
 floatExpr lvl (Let bind body)