Fix unused argument diagnostic emission for baremetal targets

Author: Il-Capitano

clang/lib/Driver/ToolChain.cpp

@@ -210,7 +210,9 @@ static void getAArch64MultilibFlags(const Driver &D,
                                           const llvm::opt::ArgList &Args,
                                           Multilib::flags_list &Result) {
   std::vector<StringRef> Features;
-  tools::aarch64::getAArch64TargetFeatures(D, Triple, Args, Features, false);
+  tools::aarch64::getAArch64TargetFeatures(D, Triple, Args, Features,
+                                           /*ForAS=*/false,
+                                           /*ForMultilib=*/true);
   const auto UnifiedFeatures = tools::unifyTargetFeatures(Features);
   llvm::DenseSet<StringRef> FeatureSet(UnifiedFeatures.begin(),
                                        UnifiedFeatures.end());

clang/lib/Driver/ToolChains/Arch/AArch64.cpp

@@ -196,7 +196,7 @@ void aarch64::getAArch64TargetFeatures(const Driver &D,
                                        const llvm::Triple &Triple,
                                        const ArgList &Args,
                                        std::vector<StringRef> &Features,
-                                       bool ForAS) {
+                                       bool ForAS, bool ForMultilib) {
   Arg *A;
   bool success = true;
   llvm::StringRef WaMArch;
@@ -334,7 +334,9 @@ void aarch64::getAArch64TargetFeatures(const Driver &D,
 
   // Generate execute-only output (no data access to code sections).
   // This only makes sense for the compiler, not for the assembler.
-  if (!ForAS) {
+  // It's not needed for multilib selection and may hide an unused
+  // argument diagnostic if the code is always run.
+  if (!ForAS && !ForMultilib) {
     if (Arg *A = Args.getLastArg(options::OPT_mexecute_only,
                                  options::OPT_mno_execute_only)) {
       if (A->getOption().matches(options::OPT_mexecute_only)) {

clang/lib/Driver/ToolChains/Arch/AArch64.h

@@ -23,7 +23,7 @@ namespace aarch64 {
 void getAArch64TargetFeatures(const Driver &D, const llvm::Triple &Triple,
                               const llvm::opt::ArgList &Args,
                               std::vector<llvm::StringRef> &Features,
-                              bool ForAS);
+                              bool ForAS, bool ForMultilib = false);
 
 std::string getAArch64TargetCPU(const llvm::opt::ArgList &Args,
                                 const llvm::Triple &Triple, llvm::opt::Arg *&A);

clang/test/Driver/aarch64-execute-only.c

@@ -3,4 +3,7 @@
 
 // RUN: %clang -### --target=aarch64-unknown-linux-gnu -x assembler -mexecute-only %s -c -### 2>&1 \
 // RUN:    | FileCheck %s --check-prefix=CHECK-NO-EXECUTE-ONLY-ASM
+// RUN: %clang -### --multi-lib-config=%S/Inputs/multilib/empty.yaml --sysroot= \
+// RUN:     --target=aarch64-none-elf -x assembler -mexecute-only %s -c -### 2>&1 \
+// RUN:    | FileCheck %s --check-prefix=CHECK-NO-EXECUTE-ONLY-ASM
 // CHECK-NO-EXECUTE-ONLY-ASM: warning: argument unused during compilation: '-mexecute-only'