[NewGVN] Check that call has an access.

Check that a call has an attached MemoryAccess before calling
getClobbering on the instruction.
If no access is attached, the instruction does not access memory.

Resolves PR43441.

llvm-svn: 374920

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
index f62a5e553f1..b213264de55 100644
--- a/llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -1639,8 +1639,11 @@ const Expression *NewGVN::performSymbolicCallEvaluation(Instruction *I) const {
   if (AA->doesNotAccessMemory(CI)) {
     return createCallExpression(CI, TOPClass->getMemoryLeader());
   } else if (AA->onlyReadsMemory(CI)) {
-    MemoryAccess *DefiningAccess = MSSAWalker->getClobberingMemoryAccess(CI);
-    return createCallExpression(CI, DefiningAccess);
+    if (auto *MA = MSSA->getMemoryAccess(CI)) {
+      auto *DefiningAccess = MSSAWalker->getClobberingMemoryAccess(MA);
+      return createCallExpression(CI, DefiningAccess);
+    } else // MSSA determined that CI does not access memory.
+      return createCallExpression(CI, TOPClass->getMemoryLeader());
   }
   return nullptr;
 }