[commit: ghc] supercompiler: Make impossible-alternative-finding code more reusable (4fc8355)

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : supercompiler

http://hackage.haskell.org/trac/ghc/changeset/4fc83553450e55131dfcd3593f0d2f619555d3a3

>---------------------------------------------------------------

commit 4fc83553450e55131dfcd3593f0d2f619555d3a3
Author: Max Bolingbroke <[email protected]>
Date:   Fri Jan 6 09:36:05 2012 +0000

    Make impossible-alternative-finding code more reusable
    
    Makes the following changes:
     1. Generalises the type signatures of some functions relating to alternatives
        so that the type of "variables" and "expression" is not specified
     2. Puts the bulk of the alternative-filtering code into a new function filterAlts
        (in CoreUtils) that can be used outside of the SimplM monad
     3. Allows prepareAlts to return a null alternatives list if none are applicable -
        it turns out that this case was already handled by the caller (in the simplifier).
        This should result in a modest optimisation improvement in some cases.

>---------------------------------------------------------------

 compiler/simplCore/SimplUtils.lhs |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/compiler/simplCore/SimplUtils.lhs b/compiler/simplCore/SimplUtils.lhs
index 87aefba..e669551 100644
--- a/compiler/simplCore/SimplUtils.lhs
+++ b/compiler/simplCore/SimplUtils.lhs
@@ -13,7 +13,7 @@
 
 module SimplUtils (
 	-- Rebuilding
-	mkLam, mkCase, prepareAlts, tryEtaExpand,
+	mkLam, mkCase, prepareAlts, filterAlts, tryEtaExpand,
 
 	-- Inlining,
 	preInlineUnconditionally, postInlineUnconditionally,