If the preheader of the loop was the entry block of the function, make sure

that the exit block of the loop becomes the new entry block of the function.

This was causing a verifier assertion on 252.eon.

llvm-svn: 13039

1 files changed, 7 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopUnroll.cpp b/llvm/lib/Transforms/Scalar/LoopUnroll.cpp
index 266afbbe9b3..90de9e946da 100644
--- a/llvm/lib/Transforms/Scalar/LoopUnroll.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopUnroll.cpp
@@ -300,10 +300,15 @@ bool LoopUnroll::visitLoop(Loop *L) {
     ChangeExitBlocksFromTo(LI->begin(), LI->end(),
                            Preheader, LoopExit);
 
+  // If the preheader was the entry block of this function, move the exit block
+  // to be the new entry of the loop.
+  Function *F = LoopExit->getParent();
+  if (Preheader == &F->front())
+    F->getBasicBlockList().splice(F->begin(), F->getBasicBlockList(), LoopExit);
 
   // Actually delete the blocks now.
-  LoopExit->getParent()->getBasicBlockList().erase(Preheader);
-  LoopExit->getParent()->getBasicBlockList().erase(BB);
+  F->getBasicBlockList().erase(Preheader);
+  F->getBasicBlockList().erase(BB);
 
   ++NumUnrolled;
   return true;