fix PR5640 by tracking whether a block is the header of a loop more
precisely, which prevents us from infinitely peeling the loop.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90211 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 5864113..1b93f34 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -158,12 +158,18 @@
if (BBI->isTerminator()) {
// Since TryToSimplifyUncondBranchFromEmptyBlock may delete the
// block, we have to make sure it isn't in the LoopHeaders set. We
- // reinsert afterward in the rare case when the block isn't deleted.
+ // reinsert afterward if needed.
bool ErasedFromLoopHeaders = LoopHeaders.erase(BB);
+ BasicBlock *Succ = BI->getSuccessor(0);
- if (TryToSimplifyUncondBranchFromEmptyBlock(BB))
+ if (TryToSimplifyUncondBranchFromEmptyBlock(BB)) {
Changed = true;
- else if (ErasedFromLoopHeaders)
+ // If we deleted BB and BB was the header of a loop, then the
+ // successor is now the header of the loop.
+ BB = Succ;
+ }
+
+ if (ErasedFromLoopHeaders)
LoopHeaders.insert(BB);
}
}