defensive patch: if CGP is merging a block with the entry block, make sure
it ends up being the entry block.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60180 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index caf60c8..9bf3991 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -204,8 +204,15 @@
// If the destination block has a single pred, then this is a trivial edge,
// just collapse it.
- if (DestBB->getSinglePredecessor()) {
+ if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
+ // Remember if SinglePred was the entry block of the function. If so, we
+ // will need to move BB back to the entry position.
+ bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
MergeBasicBlockIntoOnlyPred(DestBB);
+
+ if (isEntry && BB != &BB->getParent()->getEntryBlock())
+ BB->moveBefore(&BB->getParent()->getEntryBlock());
+
DOUT << "AFTER:\n" << *DestBB << "\n\n\n";
return;
}