[BasicBlockUtils] Check for nullptr before updating LoopInfo.

LoopInfo::getLoopFor returns nullptr if a BB is not in a loop and only
then can the loop be updated to contain the newly created BBs. Add the
missing nullptr check to SplitBlockAndInsertIfThen.

Within LLVM, the only user of this function that also passes a LoopInfo
to be updated is InnerLoopVectorizer::predicateInstructions().
As the method's name implies, the BB operataten on will always be within
a loop, but out-of-tree users may also use it differently (here: Polly).

All other uses of LoopInfo::getLoopFor in the file properly check its
return value for nullptr.

llvm-svn: 297016

1 files changed, 4 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
index 6a237c4d1e1..22af21d55c0 100644
--- a/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -646,9 +646,10 @@ llvm::SplitBlockAndInsertIfThen(Value *Cond, Instruction *SplitBefore,
   }
 
   if (LI) {
-    Loop *L = LI->getLoopFor(Head);
-    L->addBasicBlockToLoop(ThenBlock, *LI);
-    L->addBasicBlockToLoop(Tail, *LI);
+    if (Loop *L = LI->getLoopFor(Head)) {
+      L->addBasicBlockToLoop(ThenBlock, *LI);
+      L->addBasicBlockToLoop(Tail, *LI);
+    }
   }
 
   return CheckTerm;