From a3335b259b71cf95eaacb59f0852f092bc597de5 Mon Sep 17 00:00:00 2001
From: Davide Italiano <davide@freebsd.org>
Date: Mon, 15 May 2017 18:50:53 +0000
Subject: [PATCH] [NewGVN] Fix verification of MemoryPhis in
 verifyMemoryCongruency().

verifyMemoryCongruency() filters out trivially dead MemoryDef(s),
as we find them immediately dead, before moving from TOP to a new
congruence class.
This fixes the same problem for PHI(s) skipping MemoryPhis if all
the operands are dead.

Differential Revision:  https://reviews.llvm.org/D33044

llvm-svn: 303100
---
 lib/Transforms/Scalar/NewGVN.cpp           | 13 ++++++++++
 test/Transforms/NewGVN/verify-memoryphi.ll | 29 ++++++++++++++++++++++
 2 files changed, 42 insertions(+)
 create mode 100644 test/Transforms/NewGVN/verify-memoryphi.ll

diff --git a/lib/Transforms/Scalar/NewGVN.cpp b/lib/Transforms/Scalar/NewGVN.cpp
index a8f399d49cc..c70c08dfecd 100644
--- a/lib/Transforms/Scalar/NewGVN.cpp
+++ b/lib/Transforms/Scalar/NewGVN.cpp
@@ -2549,6 +2549,19 @@ void NewGVN::verifyMemoryCongruency() const {
           return false;
         if (auto *MemDef = dyn_cast<MemoryDef>(Pair.first))
           return !isInstructionTriviallyDead(MemDef->getMemoryInst());
+
+        // We could have phi nodes which operands are all trivially dead,
+        // so we don't process them.
+        if (auto *MemPHI = dyn_cast<MemoryPhi>(Pair.first)) {
+          for (auto &U : MemPHI->incoming_values()) {
+            if (Instruction *I = dyn_cast<Instruction>(U.get())) {
+              if (!isInstructionTriviallyDead(I))
+                return true;
+            }
+          }
+          return false;
+        }
+
         return true;
       };
 
diff --git a/test/Transforms/NewGVN/verify-memoryphi.ll b/test/Transforms/NewGVN/verify-memoryphi.ll
new file mode 100644
index 00000000000..57dbd18986d
--- /dev/null
+++ b/test/Transforms/NewGVN/verify-memoryphi.ll
@@ -0,0 +1,29 @@
+; Skip dead MemoryPhis when performing memory congruency verification
+; in NewGVN.
+; RUN: opt -S -newgvn %s | FileCheck %s
+; REQUIRES: asserts
+
+; CHECK: define void @tinkywinky() {
+; CHECK-NEXT: entry:
+; CHECK-NEXT:   br i1 false, label %body, label %end
+; CHECK:      body:
+; CHECK-NEXT:   store i8 undef, i8* null
+; CHECK-NEXT:   br label %end
+; CHECK:      end:
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
+
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
+
+define void @tinkywinky() {
+entry:
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* undef)
+  br i1 false, label %body, label %end
+
+body:
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* undef)
+  br label %end
+
+end:
+  ret void
+}