[clang] [Clang][ARM][AArch64] Add branch protection attributes to the defaults. (PR #83277)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-codegen

Author: Dani (DanielKristofKiss)

<details>
<summary>Changes</summary>

These attributes are no longer inherited from the module flags, therefore need to be added for synthetic functions.

---
Full diff: https://github.com/llvm/llvm-project/pull/83277.diff


2 Files Affected:

- (modified) clang/lib/CodeGen/CGCall.cpp (+16) 
- (added) clang/test/CodeGenCXX/arm64-generated-fn-attr.cpp (+30) 


``````````diff
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index d05cf1c6e1814e..d677a2e64be77e 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -2022,6 +2022,22 @@ static void getTrivialDefaultFunctionAttributes(
     std::tie(Var, Value) = Attr.split('=');
     FuncAttrs.addAttribute(Var, Value);
   }
+
+  TargetInfo::BranchProtectionInfo BPI(LangOpts);
+
+  if (BPI.SignReturnAddr != LangOptions::SignReturnAddressScopeKind::None) {
+    FuncAttrs.addAttribute("sign-return-address", BPI.getSignReturnAddrStr());
+    FuncAttrs.addAttribute(
+        "sign-return-address-key",
+        BPI.SignKey == LangOptions::SignReturnAddressKeyKind::AKey ? "a_key"
+                                                                   : "b_key");
+  }
+  if (BPI.BranchTargetEnforcement)
+    FuncAttrs.addAttribute("branch-target-enforcement", "true");
+  if (BPI.BranchProtectionPAuthLR)
+    FuncAttrs.addAttribute("branch-protection-pauth-lr", "true");
+  if (BPI.GuardedControlStack)
+    FuncAttrs.addAttribute("guarded-control-stack", "true");
 }
 
 /// Merges `target-features` from \TargetOpts and \F, and sets the result in
diff --git a/clang/test/CodeGenCXX/arm64-generated-fn-attr.cpp b/clang/test/CodeGenCXX/arm64-generated-fn-attr.cpp
new file mode 100644
index 00000000000000..8daf44abd4f91c
--- /dev/null
+++ b/clang/test/CodeGenCXX/arm64-generated-fn-attr.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -triple aarch64-none-none -mbranch-target-enforce -msign-return-address=all -fcxx-exceptions -fexceptions -emit-llvm %s -o - | FileCheck %s --check-prefixes=CHECK
+
+// Check that functions generated by clang have the correct attributes
+
+class Example {
+public:
+  Example();
+  int fn();
+};
+
+// Initialization of var1 causes __cxx_global_var_init and __tls_init to be generated
+thread_local Example var1;
+extern thread_local Example var2;
+extern void fn();
+
+int testfn() noexcept {
+  // Calling fn in a noexcept function causes __clang_call_terminate to be generated
+  fn();
+  // Use of var1 and var2 causes TLS wrapper functions to be generated
+  return var1.fn() + var2.fn();
+}
+
+// CHECK: define {{.*}} @__cxx_global_var_init() [[ATTR1:#[0-9]+]]
+// CHECK: define {{.*}} @__clang_call_terminate({{.*}}) [[ATTR2:#[0-9]+]]
+// CHECK: define {{.*}} @_ZTW4var1() [[ATTR1]]
+// CHECK: define {{.*}} @_ZTW4var2() [[ATTR1]]
+// CHECK: define {{.*}} @__tls_init() [[ATTR1]]
+
+// CHECK: attributes [[ATTR1]] = { {{.*}}"branch-target-enforcement"="true"{{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"
+// CHECK: attributes [[ATTR2]] = { {{.*}}"branch-target-enforcement"="true"{{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"

``````````

</details>


https://github.com/llvm/llvm-project/pull/83277