Improve fix to handle irreducible CFGs.

src/Compiler/Hoopl/Passes/Dominator.hs

@@ -48,8 +48,10 @@ domLattice = addPoints "dominators" extend
 extend :: JoinFun DPath
 extend _ (OldFact (DPath l)) (NewFact (DPath l')) =
                                 (changeIf (l `lengthDiffers` j), DPath j)
-    where j = filter (\elem -> Set.member elem common) l
+    where lx = filter (\elem -> Set.member elem common) l
+          rx = filter (\elem -> Set.member elem common) l'
           common = Set.intersection (Set.fromList l) (Set.fromList l')
+          j = [x | (x, y) <- zip lx rx, x == y]
 
           lengthDiffers [] [] = False
           lengthDiffers (_:xs) (_:ys) = lengthDiffers xs ys