LoopSimplify does not update domfrontier correctly.

This fixes PR7649.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108513 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 22 insertions, 2 deletions

diff --git a/lib/VMCore/Dominators.cpp b/lib/VMCore/Dominators.cpp
index ef83033..58ce05c 100644
--- a/lib/VMCore/Dominators.cpp
+++ b/lib/VMCore/Dominators.cpp
@@ -148,11 +148,11 @@ void DominanceFrontier::splitBlock(BasicBlock *NewBB) {
   }
 
   // If NewBB dominates NewBBSucc, then DF(NewBB) is now going to be the
-  // DF(PredBlocks[0]) without the stuff that the new block does not dominate
+  // DF(NewBBSucc) without the stuff that the new block does not dominate
   // a predecessor of.
   DominatorTree &DT = getAnalysis<DominatorTree>();
   if (DT.dominates(NewBB, NewBBSucc)) {
-    DominanceFrontier::iterator DFI = find(PredBlocks[0]);
+    DominanceFrontier::iterator DFI = find(NewBBSucc);
     if (DFI != end()) {
       DominanceFrontier::DomSetType Set = DFI->second;
       // Filter out stuff in Set that we do not dominate a predecessor of.
diff --git a/test/Transforms/LoopSimplify/2010-07-15-IncorrectDomFrontierUpdate.ll b/test/Transforms/LoopSimplify/2010-07-15-IncorrectDomFrontierUpdate.ll
new file mode 100644
index 0000000..2a1ee7d
--- /dev/null
+++ b/test/Transforms/LoopSimplify/2010-07-15-IncorrectDomFrontierUpdate.ll
@@ -0,0 +1,20 @@
+; RUN: opt < %s -domfrontier -loopsimplify -domfrontier -verify-dom-info -analyze 
+
+
+define void @a() nounwind {
+entry:
+  br i1 undef, label %bb37, label %bb1.i
+
+bb1.i:                                            ; preds = %bb1.i, %bb
+  %indvar = phi i64 [ %indvar.next, %bb1.i ], [ 0, %entry ] ; <i64> [#uses=1]
+  %indvar.next = add i64 %indvar, 1               ; <i64> [#uses=2]
+  %exitcond = icmp eq i64 %indvar.next, 576       ; <i1> [#uses=1]
+  br i1 %exitcond, label %bb37, label %bb1.i
+
+bb37:                                             ; preds = %bb1.i, %bb
+  br label %return
+
+
+return:                                           ; preds = %bb39
+  ret void
+}