[HLSL] emit-obj when set output.

[python3kgae]

Summary

When not set output, set default output to stdout.
When set output with -Fo and no -fcgl, set -emit-obj to generate dx container.

[beanz]

LGTM

clang/lib/Driver/Driver.cpp

if (AtTopLevel && !CCGenDiagnostics && HasPreprocessOutput(JA)) {
     return "-";
   }
 
   if (JA.getType() == types::TY_ModuleFile &&
       C.getArgs().getLastArg(options::OPT_module_file_info)) {
     return "-";
   }
 
+  if (IsDXCMode() && !C.getArgs().hasArg(options::OPT_o))
+    return "-";
+
   // Is this the assembly listing for /FA?
   if (JA.getType() == types::TY_PP_Asm &&
       (C.getArgs().hasArg(options::OPT__SLASH_FA) ||
        C.getArgs().hasArg(options::OPT__SLASH_Fa))) {
     // Use /Fa and the input filename to determine the asm file name.
     StringRef BaseName = llvm::sys::path::filename(BaseInput);
     StringRef FaValue = C.getArgs().getLastArgValue(options::OPT__SLASH_Fa);
     return C.addResultFile(

clang/lib/Driver/ToolChains/Clang.cpp

 
 static void RenderHLSLOptions(const ArgList &Args, ArgStringList &CmdArgs,
                               types::ID InputType) {
   const unsigned ForwardedArguments[] = {options::OPT_dxil_validator_version,
                                          options::OPT_D,
                                          options::OPT_I,
                                          options::OPT_S,
                                          options::OPT_emit_llvm,
+                                         options::OPT_emit_obj,
                                          options::OPT_disable_llvm_passes,
                                          options::OPT_fnative_half_type,
                                          options::OPT_hlsl_entrypoint};
 
   for (const auto &Arg : ForwardedArguments)
     if (const auto *A = Args.getLastArg(Arg))
       A->renderAsInput(Args, CmdArgs);
   // Add the default headers if dxc_no_stdinc is not set.

clang/lib/Driver/ToolChains/HLSL.cpp

if (A->getOption().getID() == options::OPT_emit_pristine_llvm) {
       DAL->AddFlagArg(nullptr, Opts.getOption(options::OPT_emit_llvm));
       DAL->AddFlagArg(nullptr,
                       Opts.getOption(options::OPT_disable_llvm_passes));
       A->claim();
       continue;
     }
     DAL->append(A);
   }
+
+  if (DAL->hasArg(options::OPT_o)) {
+    // When run the whole pipeline.
+    if (!DAL->hasArg(options::OPT_emit_llvm))
+      // Emit obj if write to file.
+      DAL->AddFlagArg(nullptr, Opts.getOption(options::OPT_emit_obj));
+  } else
+    DAL->AddSeparateArg(nullptr, Opts.getOption(options::OPT_o), "-");
+
   // Add default validator version if not set.
   // TODO: remove this once read validator version from validator.
   if (!DAL->hasArg(options::OPT_dxil_validator_version)) {
     const StringRef DefaultValidatorVer = "1.7";
     DAL->AddSeparateArg(nullptr,
                         Opts.getOption(options::OPT_dxil_validator_version),
                         DefaultValidatorVer);
   }
   // FIXME: add validation for enable_16bit_types should be after HLSL 2018 and
   // shader model 6.2.
   return DAL;
 }

clang/test/Driver/dxc_Fo.hlsl

+// RUN: %clang_dxc -T lib_6_7 foo.hlsl -### %s 2>&1 | FileCheck %s --check-prefix=DEFAULT
+// RUN: %clang_dxc -fcgl -T lib_6_7 foo.hlsl -### %s 2>&1 | FileCheck %s --check-prefix=FCGL
+// RUN: %clang_dxc  -T lib_6_7 foo.hlsl -Fo foo.dxc -### %s 2>&1 | FileCheck %s --check-prefix=EMITOBJ
+
+
+// Make sure default use "-" as output and not emit obj.
+// DEFAULT-NOT:"-emit-obj"
+// DEFAULT:"-o" "-"
+
+// Make sure -fcgl without -Fo use "-" as output.
+// FCGL:"-o" "-"
+
+
+// Make sure emit-obj when set -Fo.
+// EMITOBJ:"-emit-obj"