vendor/llvm/llvm-trunk-r306325

1 files changed, 7 insertions, 2 deletions

diff --git a/include/llvm/Analysis/LoopInfoImpl.h b/include/llvm/Analysis/LoopInfoImpl.h
index 6ff4335f1ad5..372fc8b21745 100644
--- a/include/llvm/Analysis/LoopInfoImpl.h
+++ b/include/llvm/Analysis/LoopInfoImpl.h
@@ -91,8 +91,9 @@ getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const {
 
 /// getLoopPreheader - If there is a preheader for this loop, return it.  A
 /// loop has a preheader if there is only one edge to the header of the loop
-/// from outside of the loop.  If this is the case, the block branching to the
-/// header of the loop is the preheader node.
+/// from outside of the loop and it is legal to hoist instructions into the
+/// predecessor. If this is the case, the block branching to the header of the
+/// loop is the preheader node.
 ///
 /// This method returns null if there is no preheader for the loop.
 ///
@@ -102,6 +103,10 @@ BlockT *LoopBase<BlockT, LoopT>::getLoopPreheader() const {
   BlockT *Out = getLoopPredecessor();
   if (!Out) return nullptr;
 
+  // Make sure we are allowed to hoist instructions into the predecessor.
+  if (!Out->isLegalToHoistInto())
+    return nullptr;
+
   // Make sure there is only one exit out of the preheader.
   typedef GraphTraits<BlockT*> BlockTraits;
   typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);