[NewGVN] Skip uses in unreachable blocks.

Otherwise we ask for a domtree node that's not there, and we crash.

Differential Revision:  https://reviews.llvm.org/D29145

llvm-svn: 293122

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
index fe5a43872f5..747c913278f 100644
--- a/llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -1936,6 +1936,12 @@ void NewGVN::convertDenseToDFSOrdered(
           IBlock = I->getParent();
           VD.LocalNum = InstrDFS.lookup(I);
         }
+
+        // Skip uses in unreachable blocks, as we're going
+        // to delete them.
+        if (ReachableBlocks.count(IBlock) == 0)
+          continue;
+
         DomTreeNode *DomNode = DT->getNode(IBlock);
         VD.DFSIn = DomNode->getDFSNumIn();
         VD.DFSOut = DomNode->getDFSNumOut();