DivergenceAnalysis: Fix crash with no return blocks

The post dominator tree does not have a root node in this case.

llvm-svn: 268933

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/DivergenceAnalysis.cpp b/llvm/lib/Analysis/DivergenceAnalysis.cpp
index d38725ff0ac..1b36569f7a0 100644
--- a/llvm/lib/Analysis/DivergenceAnalysis.cpp
+++ b/llvm/lib/Analysis/DivergenceAnalysis.cpp
@@ -143,7 +143,13 @@ void DivergencePropagator::exploreSyncDependency(TerminatorInst *TI) {
   if (!DT.isReachableFromEntry(ThisBB))
     return;
 
-  BasicBlock *IPostDom = PDT.getNode(ThisBB)->getIDom()->getBlock();
+  // If the function has no exit blocks or doesn't reach any exit blocks, the
+  // post dominator may be null.
+  DomTreeNode *ThisNode = PDT.getNode(ThisBB);
+  if (!ThisNode)
+    return;
+
+  BasicBlock *IPostDom = ThisNode->getIDom()->getBlock();
   if (IPostDom == nullptr)
     return;