R600/SI: Check for empty stack in SIAnnotateControlFlow::isTopOfStack

Fixes assertion failure in newly added lit test. Might just be a bandaid that
needs to be revisited.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175139 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/R600/SIAnnotateControlFlow.cpp b/lib/Target/R600/SIAnnotateControlFlow.cpp
index f58037741861251f487f47bffaf8de7f51318d7c..2477e2a9dcc33b5435b884c887e395d2006304a4 100644 (file)
--- a/lib/Target/R600/SIAnnotateControlFlow.cpp
+++ b/lib/Target/R600/SIAnnotateControlFlow.cpp
@@ -147,7 +147,7 @@ bool SIAnnotateControlFlow::doInitialization(Module &M) {
 
 /// \brief Is BB the last block saved on the stack ?
 bool SIAnnotateControlFlow::isTopOfStack(BasicBlock *BB) {
-  return Stack.back().first == BB;
+  return !Stack.empty() && Stack.back().first == BB;
 }
 
 /// \brief Pop the last saved value from the control flow stack