Avoid spliting loops where two split condition branches are not independent.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41148 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 980990e..9b4319d 100644
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -711,12 +711,22 @@
|| Latch == SplitTerminator->getSuccessor(1)))
return false;
-
+ // If one of the split condition branch is post dominating other then loop
+ // index split is not appropriate.
BasicBlock *Succ0 = SplitTerminator->getSuccessor(0);
BasicBlock *Succ1 = SplitTerminator->getSuccessor(1);
if (DT->dominates(Succ0, Latch) || DT->dominates(Succ1, Latch))
return false;
+ // If one of the split condition branch is a predecessor of the other
+ // split condition branch head then do not split loop on this condition.
+ for(pred_iterator PI = pred_begin(Succ0), PE = pred_end(Succ0); PI != PE; ++PI)
+ if (Succ1 == *PI)
+ return false;
+ for(pred_iterator PI = pred_begin(Succ1), PE = pred_end(Succ1); PI != PE; ++PI)
+ if (Succ0 == *PI)
+ return false;
+
// True loop is original loop. False loop is cloned loop.
bool SignedPredicate = ExitCondition->isSignedPredicate();