1 files changed, 14 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/StructurizeCFG.cpp b/lib/Transforms/Scalar/StructurizeCFG.cpp
index 0124dfdbeb..5045ff8fdf 100644
--- a/lib/Transforms/Scalar/StructurizeCFG.cpp
+++ b/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -779,6 +779,20 @@ void StructurizeCFG::handleLoops(bool ExitUseAllowed,
     handleLoops(false, LoopEnd);
   }
 
+  // If the start of the loop is the entry block, we can't branch to it so
+  // insert a new dummy entry block.
+  Function *LoopFunc = LoopStart->getParent();
+  if (LoopStart == &LoopFunc->getEntryBlock()) {
+    LoopStart->setName("entry.orig");
+
+    BasicBlock *NewEntry =
+      BasicBlock::Create(LoopStart->getContext(),
+                         "entry",
+                         LoopFunc,
+                         LoopStart);
+    BranchInst::Create(LoopStart, NewEntry);
+  }
+
   // Create an extra loop end node
   LoopEnd = needPrefix(false);
   BasicBlock *Next = needPostfix(LoopEnd, ExitUseAllowed);