X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FnativeGen%2FX86%2FRegInfo.hs;fp=compiler%2FnativeGen%2FX86%2FRegInfo.hs;h=39ff4063b02a7227e62d2db445101a0d211b0dee;hb=31a9d04804d9cacda35695c5397590516b964964;hp=a3bf8e4655e0a196a50b1ac28217f4c4d7f3cba8;hpb=6d38e24ea3da7ca9b435e9b1e59b2de8fcd91da4;p=ghc-hetmet.git

diff --git a/compiler/nativeGen/X86/RegInfo.hs b/compiler/nativeGen/X86/RegInfo.hs
index a3bf8e4..39ff406 100644
--- a/compiler/nativeGen/X86/RegInfo.hs
+++ b/compiler/nativeGen/X86/RegInfo.hs
@@ -51,14 +51,17 @@ canShortcut (JMP (OpImm imm)) 	= Just (DestImm imm)
 canShortcut _ 			= Nothing
 
 
+-- The helper ensures that we don't follow cycles.
 shortcutJump :: (BlockId -> Maybe JumpDest) -> Instr -> Instr
-shortcutJump fn insn@(JXX cc id) = 
-  case fn id of
-    Nothing                -> insn
-    Just (DestBlockId id') -> shortcutJump fn (JXX cc id')
-    Just (DestImm imm)     -> shortcutJump fn (JXX_GBL cc imm)
-
-shortcutJump _ other = other
+shortcutJump fn insn = shortcutJump' fn emptyBlockSet insn
+  where shortcutJump' fn seen insn@(JXX cc id) =
+          if elemBlockSet id seen then insn
+          else case fn id of
+                 Nothing                -> insn
+                 Just (DestBlockId id') -> shortcutJump' fn seen' (JXX cc id')
+                 Just (DestImm imm)     -> shortcutJump' fn seen' (JXX_GBL cc imm)
+               where seen' = extendBlockSet seen id
+        shortcutJump' _ _ other = other
 
 
 -- Here because it knows about JumpDest