[LOOPGUARD] Remove asserts in getLoopGuardBranch

Summary: The assertion in getLoopGuardBranch can be a 'return nullptr'
under if condition.
Authored By: DTharun
Reviewer: Whitney, fhahn
Reviewed By: Whitney, fhahn
Subscribers: fhahn, llvm-commits
Tag: LLVM
Differential Revision: https://reviews.llvm.org/D66084

llvm-svn: 373857

1 files changed, 9 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/LoopInfo.cpp b/llvm/lib/Analysis/LoopInfo.cpp
index 1dc63a3c333..dbab5db7dbc 100644
--- a/llvm/lib/Analysis/LoopInfo.cpp
+++ b/llvm/lib/Analysis/LoopInfo.cpp
@@ -360,11 +360,17 @@ bool Loop::isAuxiliaryInductionVariable(PHINode &AuxIndVar,
 }
 
 BranchInst *Loop::getLoopGuardBranch() const {
-  assert(isLoopSimplifyForm() && "Only valid for loop in simplify form");
+  if (!isLoopSimplifyForm())
+    return nullptr;
+
   BasicBlock *Preheader = getLoopPreheader();
-  assert(Preheader && getLoopLatch() &&
+  BasicBlock *Latch = getLoopLatch();
+  assert(Preheader && Latch &&
          "Expecting a loop with valid preheader and latch");
-  assert(isLoopExiting(getLoopLatch()) && "Only valid for rotated loop");
+
+  // Loop should be in rotate form.
+  if (!isLoopExiting(Latch))
+    return nullptr;
 
   // Disallow loops with more than one unique exit block, as we do not verify
   // that GuardOtherSucc post dominates all exit blocks.