From 890090f7f58e780f1b81f553cc933f3f4e36013a Mon Sep 17 00:00:00 2001
From: Alina Sbirlea <asbirlea@google.com>
Date: Tue, 1 Oct 2019 19:09:50 +0000
Subject: [MemorySSA] Check for unreachable blocks when getting last
 definition.

If a single predecessor is found, still check if the block is
unreachable. The test that found this had a self loop unreachable block.
Resolves PR43493.

llvm-svn: 373383
---
 llvm/lib/Analysis/MemorySSAUpdater.cpp | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'llvm/lib/Analysis')

diff --git a/llvm/lib/Analysis/MemorySSAUpdater.cpp b/llvm/lib/Analysis/MemorySSAUpdater.cpp
index 315037bcc04..e0b27f1d501 100644
--- a/llvm/lib/Analysis/MemorySSAUpdater.cpp
+++ b/llvm/lib/Analysis/MemorySSAUpdater.cpp
@@ -839,6 +839,9 @@ void MemorySSAUpdater::applyInsertUpdates(ArrayRef<CFGUpdate> Updates,
       } else {
         // Single predecessor, BB cannot be dead. GetLastDef of Pred.
         assert(Count == 1 && Pred && "Single predecessor expected.");
+        // BB can be unreachable though, return LoE if that is the case.
+        if (!DT.getNode(BB))
+          return MSSA->getLiveOnEntryDef();
         BB = Pred;
       }
     };
-- 
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