[clang] [TBAA] Add bail-out to skip tbaa generation to getTBAAStructInfo. (PR #84386)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

Author: Florian Hahn (fhahn)

<details>
<summary>Changes</summary>

Without this bail out, we may generate fields with null nodes as tags are generated by using getTypeInfo which has the same bail out.

---
Full diff: https://github.com/llvm/llvm-project/pull/84386.diff


2 Files Affected:

- (modified) clang/lib/CodeGen/CodeGenTBAA.cpp (+3) 
- (modified) clang/test/CodeGen/tbaa-struct-relaxed-aliasing-with-tsan.cpp (-2) 


``````````diff
diff --git a/clang/lib/CodeGen/CodeGenTBAA.cpp b/clang/lib/CodeGen/CodeGenTBAA.cpp
index 8a081612193978..1f07205a5af225 100644
--- a/clang/lib/CodeGen/CodeGenTBAA.cpp
+++ b/clang/lib/CodeGen/CodeGenTBAA.cpp
@@ -343,6 +343,9 @@ CodeGenTBAA::CollectFields(uint64_t BaseOffset,
 
 llvm::MDNode *
 CodeGenTBAA::getTBAAStructInfo(QualType QTy) {
+  if (CodeGenOpts.OptimizationLevel == 0 || CodeGenOpts.RelaxedAliasing)
+    return nullptr;
+
   const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
 
   if (llvm::MDNode *N = StructMetadataCache[Ty])
diff --git a/clang/test/CodeGen/tbaa-struct-relaxed-aliasing-with-tsan.cpp b/clang/test/CodeGen/tbaa-struct-relaxed-aliasing-with-tsan.cpp
index 931ff2476cd1bb..ce613b9d6b23f8 100644
--- a/clang/test/CodeGen/tbaa-struct-relaxed-aliasing-with-tsan.cpp
+++ b/clang/test/CodeGen/tbaa-struct-relaxed-aliasing-with-tsan.cpp
@@ -5,9 +5,7 @@
 // RUN:     FileCheck %s
 //
 // Check that we do not create tbaa for instructions generated for copies.
-// FIXME: !tbaa.struct is generated with null node as tag.
 
-// CHECK: !tbaa.struct
 // CHECK-NOT: !tbaa
 
 struct A {

``````````

</details>


https://github.com/llvm/llvm-project/pull/84386