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

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

Author: DanielKristofKiss

clang/lib/CodeGen/CGCall.cpp

@@ -2030,6 +2030,9 @@ static void getTrivialDefaultFunctionAttributes(
     std::tie(Var, Value) = Attr.split('=');
     FuncAttrs.addAttribute(Var, Value);
   }
+
+  TargetInfo::BranchProtectionInfo BPI(LangOpts);
+  TargetCodeGenInfo::setBranchProtectionFnAttributes(BPI, FuncAttrs);
 }
 
 /// Merges `target-features` from \TargetOpts and \F, and sets the result in

clang/test/CodeGenCXX/arm64-generated-fn-attr.cpp

@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -triple aarch64 -mbranch-target-enforce -msign-return-address=all -fcxx-exceptions -fexceptions -emit-llvm %s -o - | FileCheck %s
+
+// 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" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"
+// CHECK: attributes [[ATTR2]] = { {{.*}}"branch-target-enforcement" {{.*}}"sign-return-address"="all" "sign-return-address-key"="a_key"