[clang] [clang] Drop `sign-return-address-buildattr` module flag emission (PR #211021)

[via cfe-commits]

llvmorg-github-actions[bot] wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-codegen

Author: Daniil Kovalev (kovdan01)

<details>
<summary>Changes</summary>

1. The flag emission was gated by `ptrauth` target feature which does not actually exist: see `AArch64TargetInfo::computeFeatureLookup()` and `ARMTargetInfo::hasFeature(StringRef Feature)`. So, it was never emitted.

2. The flag is never exercised elsewhere by existing tests or code across the whole LLVM source tree.

Note: the flag was previously introduced in https://reviews.llvm.org/D112421

---
Full diff: https://github.com/llvm/llvm-project/pull/211021.diff


1 Files Affected:

- (modified) clang/lib/CodeGen/CodeGenModule.cpp (+3-9) 


``````````diff
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 5f5fc4401bb4e..c1cd7a0d5b597 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1496,20 +1496,14 @@ void CodeGenModule::Release() {
   if (CodeGenOpts.IndirectBranchCSPrefix)
     getModule().addModuleFlag(llvm::Module::Override, "indirect_branch_cs_prefix", 1);
 
-  // Add module metadata for return address signing (ignoring
-  // non-leaf/all) and stack tagging. These are actually turned on by function
-  // attributes, but we use module metadata to emit build attributes. This is
-  // needed for LTO, where the function attributes are inside bitcode
+  // Add module metadata for stack tagging. This is actually turned on by
+  // function attributes, but we use module metadata to emit build attributes.
+  // This is needed for LTO, where the function attributes are inside bitcode
   // serialised into a global variable by the time build attributes are
   // emitted, so we can't access them. LTO objects could be compiled with
   // different flags therefore module flags are set to "Min" behavior to achieve
   // the same end result of the normal build where e.g BTI is off if any object
   // doesn't support it.
-  if (Context.getTargetInfo().hasFeature("ptrauth") &&
-      LangOpts.getSignReturnAddressScope() !=
-          LangOptions::SignReturnAddressScopeKind::None)
-    getModule().addModuleFlag(llvm::Module::Override,
-                              "sign-return-address-buildattr", 1);
   if (LangOpts.Sanitize.has(SanitizerKind::MemtagStack))
     getModule().addModuleFlag(llvm::Module::Override,
                               "tag-stack-memory-buildattr", 1);

``````````

</details>


https://github.com/llvm/llvm-project/pull/211021