[clang] [clang][dataflow] Fix bug in `Value` comparison. (PR #76746)

[Yitzhak Mandelbaum via cfe-commits]

https://github.com/ymand created https://github.com/llvm/llvm-project/pull/76746

Makes value equivalence require that the values have no properties, except in
the case of equivalence by pointer equality (if the pointers are equal, nothing
else is checked).

Fixes issue #76459.


>From 87cc967ebb2bcf9db90bab367400eb6348a4b98b Mon Sep 17 00:00:00 2001
From: Yitzhak Mandelbaum <yitzhakm at google.com>
Date: Tue, 2 Jan 2024 19:27:21 +0000
Subject: [PATCH] [clang][dataflow] Fix bug in `Value` comparison.

Makes value equivalence require that the values have no properties, except in
the case of equivalence by pointer equality (if the pointers are equal, nothing
else is checked).

Fixes issue #76459.
---
 clang/lib/Analysis/FlowSensitive/Value.cpp           | 10 +++++++---
 clang/unittests/Analysis/FlowSensitive/ValueTest.cpp |  4 ++--
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/clang/lib/Analysis/FlowSensitive/Value.cpp b/clang/lib/Analysis/FlowSensitive/Value.cpp
index 349f873f1e6c4d..50475ef5553036 100644
--- a/clang/lib/Analysis/FlowSensitive/Value.cpp
+++ b/clang/lib/Analysis/FlowSensitive/Value.cpp
@@ -27,9 +27,13 @@ static bool areEquivalentIndirectionValues(const Value &Val1,
 }
 
 bool areEquivalentValues(const Value &Val1, const Value &Val2) {
-  return &Val1 == &Val2 || (Val1.getKind() == Val2.getKind() &&
-                            (isa<TopBoolValue>(&Val1) ||
-                             areEquivalentIndirectionValues(Val1, Val2)));
+  // If values are distinct and have properties, we don't consider them equal,
+  // leaving equality up to the user model.
+  return &Val1 == &Val2 ||
+         (Val1.getKind() == Val2.getKind() &&
+          // (Val1.properties().empty() && Val2.properties().empty()) &&
+          (isa<TopBoolValue>(&Val1) ||
+           areEquivalentIndirectionValues(Val1, Val2)));
 }
 
 raw_ostream &operator<<(raw_ostream &OS, const Value &Val) {
diff --git a/clang/unittests/Analysis/FlowSensitive/ValueTest.cpp b/clang/unittests/Analysis/FlowSensitive/ValueTest.cpp
index c5d18ba74c3ed6..2060b7eb264f74 100644
--- a/clang/unittests/Analysis/FlowSensitive/ValueTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/ValueTest.cpp
@@ -53,8 +53,8 @@ TEST(ValueTest, EquivalentValuesWithDifferentPropsEquivalent) {
   TopBoolValue V2(A.makeAtomRef(Atom(3)));
   V1.setProperty("foo", Prop1);
   V2.setProperty("bar", Prop2);
-  EXPECT_TRUE(areEquivalentValues(V1, V2));
-  EXPECT_TRUE(areEquivalentValues(V2, V1));
+  EXPECT_FALSE(areEquivalentValues(V1, V2));
+  EXPECT_FALSE(areEquivalentValues(V2, V1));
 }
 
 TEST(ValueTest, DifferentKindsNotEquivalent) {