NCG: Remember to keep the entry block first when erasing liveness info

diff --git a/compiler/nativeGen/RegAlloc/Liveness.hs b/compiler/nativeGen/RegAlloc/Liveness.hs
index 69ec7ae..18dd01a 100644 (file)
--- a/compiler/nativeGen/RegAlloc/Liveness.hs
+++ b/compiler/nativeGen/RegAlloc/Liveness.hs
@@ -457,10 +457,21 @@ stripLive live
        = stripCmm live
 
  where stripCmm (CmmData sec ds)       = CmmData sec ds
-       stripCmm (CmmProc (LiveInfo info _ _) label params sccs)
-               = CmmProc info label params
-                          (ListGraph $ map stripLiveBlock $ flattenSCCs sccs)
-       
+
+       stripCmm (CmmProc (LiveInfo info (Just first_id) _) label params sccs)
+        = let  final_blocks    = flattenSCCs sccs
+               
+               -- make sure the block that was first in the input list
+               --      stays at the front of the output. This is the entry point
+               --      of the proc, and it needs to come first.
+               ((first':_), rest')
+                               = partition ((== first_id) . blockId) final_blocks
+
+          in   CmmProc info label params
+                          (ListGraph $ map stripLiveBlock $ first' : rest')
+
+       stripCmm _
+                = panic "RegAlloc.Liveness.stripLive: no first_id on proc"     
 
 -- | Strip away liveness information from a basic block,
 --     and make real spill instructions out of SPILL, RELOAD pseudos along the way.