[project @ 2001-03-01 14:27:22 by simonmar]

don't needlessly duplicate a binder.

diff --git a/ghc/compiler/stgSyn/CoreToStg.lhs b/ghc/compiler/stgSyn/CoreToStg.lhs
index a5e0e85..b59411d 100644 (file)
--- a/ghc/compiler/stgSyn/CoreToStg.lhs
+++ b/ghc/compiler/stgSyn/CoreToStg.lhs
@@ -295,9 +295,11 @@ coreToStgExpr (Case scrut bndr alts)
     lookupLiveVarsForSet alts_fvs              `thenLne` \ alts_lvs ->
     let
        -- determine whether the default binder is dead or not
-       bndr' = bndr `setIdOccInfo` occ_info
-       occ_info | bndr `elementOfFVInfo` alts_fvs = NoOccInfo
-                | otherwise                       = IAmDead
+       -- This helps the code generator to avoid generating an assignment
+       -- for the case binder (is extremely rare cases) ToDo: remove.
+       bndr'= if (bndr `elementOfFVInfo` alts_fvs) 
+                 then bndr
+                 else bndr `setIdOccInfo` IAmDead
 
         -- for a _ccall_GC_, some of the *arguments* need to live across the
         -- call (see findLiveArgs comments.), so we annotate them as being live