Support -masm= flag for x86 assembly targets

[ygao]

Summary

For assembly files without .intel_syntax or .att_syntax directives, allow the
-masm= flag to supply a default assembly dialect. For example,

C:\TMP> type intel.s
.text
mov al,0

C:\TMP> clang -masm=intel -c intel.s

Without this patch, one would need to pass an -mllvm -x86-asm-syntax= flag directly to the backend.
C:\TMP> clang -mllvm --x86-asm-syntax=intel -c intel.s

Does it seem acceptable to expose -masm= flag as a way to configure the input assembly syntax?

[bruno]

LGTM with one small fix, see below.

lib/Driver/Tools.cpp

6379

Fix the param indentation.

[ygao]

lib/Driver/Tools.cpp

6379

Good catch! Thanks.

[ygao]

Closed by rL275877.

lib/Driver/Tools.h

       : Tool("clang::as", "clang integrated assembler", TC, RF_Full) {}
   void AddMIPSTargetArgs(const llvm::opt::ArgList &Args,
                          llvm::opt::ArgStringList &CmdArgs) const;
+  void AddX86TargetArgs(const llvm::opt::ArgList &Args,
+                        llvm::opt::ArgStringList &CmdArgs) const;
   bool hasGoodDiagnostics() const override { return true; }
   bool hasIntegratedAssembler() const override { return false; }
   bool hasIntegratedCPP() const override { return false; }

lib/Driver/Tools.cpp

   CmdArgs.push_back(ABIName.data());
 }
 
+void ClangAs::AddX86TargetArgs(const ArgList &Args,
+                                ArgStringList &CmdArgs) const {
+  if (Arg *A = Args.getLastArg(options::OPT_masm_EQ)) {
+    StringRef Value = A->getValue();
+    if (Value == "intel" || Value == "att") {
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back(Args.MakeArgString("-x86-asm-syntax=" + Value));
+    } else {
+      getToolChain().getDriver().Diag(diag::err_drv_unsupported_option_argument)
+          << A->getOption().getName() << Value;
+    }
+  }
+}
+
 void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
                            const InputInfo &Output, const InputInfoList &Inputs,
                            const ArgList &Args,

   case llvm::Triple::mips64el:
     AddMIPSTargetArgs(Args, CmdArgs);
     break;
+    
+  case llvm::Triple::x86:
+  case llvm::Triple::x86_64:
+    AddX86TargetArgs(Args, CmdArgs);
+    break;
   }
 
   // Consume all the warning flags. Usually this would be handled more

test/Driver/masm.s

+// RUN: %clang -target i386-unknown-linux -masm=intel -c %s -### 2>&1 | FileCheck --check-prefix=CHECK-INTEL %s
+// RUN: %clang -target i386-unknown-linux -masm=att -c %s -### 2>&1 | FileCheck --check-prefix=CHECK-ATT %s
+// RUN: %clang -target i386-unknown-linux -c -masm=somerequired %s -### 2>&1 | FileCheck --check-prefix=CHECK-SOMEREQUIRED %s
+// RUN: %clang -target arm-unknown-eabi -c -masm=intel %s -### 2>&1 | FileCheck --check-prefix=CHECK-ARM %s
+
+// CHECK-INTEL: -x86-asm-syntax=intel
+// CHECK-ATT: -x86-asm-syntax=att
+// CHECK-SOMEREQUIRED: error: unsupported argument 'somerequired' to option 'masm='
+// CHECK-ARM: warning: argument unused during compilation: '-masm=intel'
+.text
+mov    al, 0