[llvm] Reapply [AA] Improve precision for monotonic atomic load/stor… (PR #195015)

[Jin Huang via llvm-commits]

https://github.com/jinhuang1102 updated https://github.com/llvm/llvm-project/pull/195015

>From 26ba751686fdf64ad96206f2cb3439fd52cc0bad Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Sun, 24 May 2026 13:51:22 -0700
Subject: [PATCH] [Clang][Driver] Reenable test on UBSan/HWAsan (#199448)

It passes locally, presumably due to
15488a7f78ce7b9ae3c06b031134e5cb339b335c fixing the behavior here.
---
 llvm/lib/Analysis/AliasAnalysis.cpp           |  6 ++---
 .../DeadStoreElimination/atomic-todo.ll       | 23 -------------------
 2 files changed, 2 insertions(+), 27 deletions(-)
 delete mode 100644 llvm/test/Transforms/DeadStoreElimination/atomic-todo.ll

diff --git a/llvm/lib/Analysis/AliasAnalysis.cpp b/llvm/lib/Analysis/AliasAnalysis.cpp
index a1e4a18718b52..c7984c35e87ae 100644
--- a/llvm/lib/Analysis/AliasAnalysis.cpp
+++ b/llvm/lib/Analysis/AliasAnalysis.cpp
@@ -493,8 +493,7 @@ ModRefInfo AAResults::getModRefInfo(const LoadInst *L,
     AliasResult AR = alias(MemoryLocation::get(L), Loc, AAQI, L);
     if (AR == AliasResult::NoAlias) {
       // Synchronization effects may affect locations that do not alias.
-      // FIXME: Should be isStrongerThanMonotonic().
-      if (isStrongerThanUnordered(L->getOrdering()))
+      if (isStrongerThanMonotonic(L->getOrdering()))
         return getSyncEffects(this, Loc, AAQI);
       return ModRefInfo::NoModRef;
     }
@@ -517,8 +516,7 @@ ModRefInfo AAResults::getModRefInfo(const StoreInst *S,
     // specified memory cannot be modified by the store.
     if (AR == AliasResult::NoAlias) {
       // Synchronization effects may affect locations that do not alias.
-      // FIXME: Should be isStrongerThanMonotonic().
-      if (isStrongerThanUnordered(S->getOrdering()))
+      if (isStrongerThanMonotonic(S->getOrdering()))
         return getSyncEffects(this, Loc, AAQI);
       return ModRefInfo::NoModRef;
     }
diff --git a/llvm/test/Transforms/DeadStoreElimination/atomic-todo.ll b/llvm/test/Transforms/DeadStoreElimination/atomic-todo.ll
deleted file mode 100644
index 1c160442f8579..0000000000000
--- a/llvm/test/Transforms/DeadStoreElimination/atomic-todo.ll
+++ /dev/null
@@ -1,23 +0,0 @@
-; XFAIL: *
-; RUN: opt -passes=dse -S < %s | FileCheck %s
-
-target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
-target triple = "x86_64-apple-macosx10.7.0"
-
-; Basic correctness tests for atomic stores.
-; Note that it turns out essentially every transformation DSE does is legal on
-; atomic ops, just some transformations are not allowed across release-acquire pairs.
-
- at x = common global i32 0, align 4
- at y = common global i32 0, align 4
-
-; DSE across monotonic load (allowed as long as the eliminated store isUnordered)
-define i32 @test9() {
-; CHECK-LABEL: test9
-; CHECK-NOT: store i32 0
-; CHECK: store i32 1
-  store i32 0, ptr @x
-  %x = load atomic i32, ptr @y monotonic, align 4
-  store i32 1, ptr @x
-  ret i32 %x
-}