[llvm-branch-commits] [llvm] release/20.x: [GlobalOpt] Do not promote malloc if there are atomic loads/stores (#137158) (PR #137179)

[via llvm-branch-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: None (llvmbot)

<details>
<summary>Changes</summary>

Backport 57530c23a53b5e003d389437637f61c5b9814e22

Requested by: @<!-- -->nikic

---
Full diff: https://github.com/llvm/llvm-project/pull/137179.diff


2 Files Affected:

- (modified) llvm/lib/Transforms/IPO/GlobalOpt.cpp (+4) 
- (added) llvm/test/Transforms/GlobalOpt/malloc-promote-atomic.ll (+28) 


``````````diff
diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 9586fc97a39f7..236a531317678 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -719,10 +719,14 @@ static bool allUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
     const Value *P = Worklist.pop_back_val();
     for (const auto *U : P->users()) {
       if (auto *LI = dyn_cast<LoadInst>(U)) {
+        if (!LI->isSimple())
+          return false;
         SmallPtrSet<const PHINode *, 8> PHIs;
         if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
           return false;
       } else if (auto *SI = dyn_cast<StoreInst>(U)) {
+        if (!SI->isSimple())
+          return false;
         // Ignore stores to the global.
         if (SI->getPointerOperand() != P)
           return false;
diff --git a/llvm/test/Transforms/GlobalOpt/malloc-promote-atomic.ll b/llvm/test/Transforms/GlobalOpt/malloc-promote-atomic.ll
new file mode 100644
index 0000000000000..0ecdf095efdd8
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/malloc-promote-atomic.ll
@@ -0,0 +1,28 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=globalopt -S < %s | FileCheck %s
+
+ at g = internal global ptr null, align 8
+
+define void @init() {
+; CHECK-LABEL: define void @init() local_unnamed_addr {
+; CHECK-NEXT:    [[ALLOC:%.*]] = call ptr @malloc(i64 48)
+; CHECK-NEXT:    store atomic ptr [[ALLOC]], ptr @g seq_cst, align 8
+; CHECK-NEXT:    ret void
+;
+  %alloc = call ptr @malloc(i64 48)
+  store atomic ptr %alloc, ptr @g seq_cst, align 8
+  ret void
+}
+
+define i1 @check() {
+; CHECK-LABEL: define i1 @check() local_unnamed_addr {
+; CHECK-NEXT:    [[VAL:%.*]] = load atomic ptr, ptr @g seq_cst, align 8
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq ptr [[VAL]], null
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
+  %val = load atomic ptr, ptr @g seq_cst, align 8
+  %cmp = icmp eq ptr %val, null
+  ret i1 %cmp
+}
+
+declare ptr @malloc(i64) allockind("alloc,uninitialized") allocsize(0)

``````````

</details>


https://github.com/llvm/llvm-project/pull/137179