NCG: Reverse SCCs after each round in the graph allocator

diff --git a/compiler/nativeGen/RegAlloc/Liveness.hs b/compiler/nativeGen/RegAlloc/Liveness.hs
index 61e800f..cc1bf12 100644 (file)
--- a/compiler/nativeGen/RegAlloc/Liveness.hs
+++ b/compiler/nativeGen/RegAlloc/Liveness.hs
@@ -27,6 +27,7 @@ module RegAlloc.Liveness (
        eraseDeltasLive,
        patchEraseLive,
        patchRegsLiveInstr,
+       reverseBlocksInTops,
        regLiveness,
        natCmmTopToLive
   ) where
@@ -670,9 +671,6 @@ regLiveness (CmmProc info lbl params sccs)
                           lbl params ann_sccs
 
 
-
-
-
 -- -----------------------------------------------------------------------------
 -- | Check ordering of Blocks
 --     The computeLiveness function requires SCCs to be in reverse dependent order.
@@ -711,8 +709,17 @@ checkIsReverseDependent sccs'
                = unionManyUniqSets
                $ map (mkUniqSet . jumpDestsOfInstr) 
                        [ i | LiveInstr i _ <- instrs]
-       
 
+
+-- | If we've compute liveness info for this code already we have to reverse
+--   the SCCs in each top to get them back to the right order so we can do it again.
+reverseBlocksInTops :: LiveCmmTop instr -> LiveCmmTop instr
+reverseBlocksInTops top
+ = case top of
+       CmmData{}                       -> top
+       CmmProc info lbl params sccs    -> CmmProc info lbl params (reverse sccs)
+
+       
 -- | Computing liveness
 --     
 --  On entry, the SCCs must be in "reverse" order: later blocks may transfer