[SafeStack] Handle unreachable code with safe stack coloring.

Instead of asserting that the function doesn't have any unreachable
code, just ignore it for the purpose of computing liveness.

Differential Revision: https://reviews.llvm.org/D51070

llvm-svn: 340456

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SafeStackColoring.cpp b/llvm/lib/CodeGen/SafeStackColoring.cpp
index 329458778a9..b1914b5d380 100644
--- a/llvm/lib/CodeGen/SafeStackColoring.cpp
+++ b/llvm/lib/CodeGen/SafeStackColoring.cpp
@@ -172,7 +172,9 @@ void StackColoring::calculateLocalLiveness() {
       BitVector LocalLiveIn;
       for (auto *PredBB : predecessors(BB)) {
         LivenessMap::const_iterator I = BlockLiveness.find(PredBB);
-        assert(I != BlockLiveness.end() && "Predecessor not found");
+        // If a predecessor is unreachable, ignore it.
+        if (I == BlockLiveness.end())
+          continue;
         LocalLiveIn |= I->second.LiveOut;
       }