LoopRotate: When reconstructing loop simplify form don't split edges from indirectbrs.

Yet another chapter in the endless story. While this looks like we leave
the loop in a non-canonical state this replicates the logic in
LoopSimplify so it doesn't diverge from the canonical form in any way.

PR21968

llvm-svn: 230058

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopRotation.cpp b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
index 2606805400f..4d123490537 100644
--- a/llvm/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopRotation.cpp
@@ -535,6 +535,8 @@ bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
       Loop *PredLoop = LI->getLoopFor(*PI);
       if (!PredLoop || PredLoop->contains(Exit))
         continue;
+      if (isa<IndirectBrInst>((*PI)->getTerminator()))
+        continue;
       SplitLatchEdge |= L->getLoopLatch() == *PI;
       BasicBlock *ExitSplit = SplitCriticalEdge(
           *PI, Exit, CriticalEdgeSplittingOptions(DT, LI).setPreserveLCSSA());