[llc] Initialize TargetOptions after Triple is available

[MaskRay]

Summary

Some targets have different defaults. This patch defers initialization of TargetOptions so that a future patch can pass TargetOptions to InitTargetOptionsFromCodeGenFlags

[jasonliu]

llvm/tools/llc/llc.cpp

429

Thanks for the patch.
An ideal solution would be actually pass the Triple as argument to the codegen::InitTargetOptionsFromCodeGenFlags. So that InitTargetOptionsFromCodeGenFlags could always initialize the correct default value depending on the target triple if an explicit setting is not present.
And we would do something similar to this:
Options.DataSections = codegen::getExplicitDataSections.getValueOr(Triple.hasDefaultDataSections());

Doing it after codegen::InitTargetOptionsFromCodeGenFlags gets called looks like an aftermath, and there could be tools other than llc called codegen::InitTargetOptionsFromCodeGenFlags and they should do this dance, but they do not.

[MaskRay]

llvm/tools/llc/llc.cpp

429

Mentioned in the description: "This patch defers initialization of TargetOptions so that a future patch can pass TargetOptions to InitTargetOptionsFromCodeGenFlags"

The InitTargetOptionsFromCodeGenFlags change will be yours:)

---

I'll change Triple &TheTriple to const Triple &TheTriple.

[jasonliu]

llvm/tools/llc/llc.cpp

429

Sounds good. Let me give it a try in that direction.

llvm/tools/llc/llc.cpp

default:
     return 1;
   case ' ': break;
   case '0': OLvl = CodeGenOpt::None; break;
   case '1': OLvl = CodeGenOpt::Less; break;
   case '2': OLvl = CodeGenOpt::Default; break;
   case '3': OLvl = CodeGenOpt::Aggressive; break;
   }
 
-  TargetOptions Options = codegen::InitTargetOptionsFromCodeGenFlags();
+  TargetOptions Options;
+  auto InitializeOptions = [&](Triple &TheTriple) {
+    Options = codegen::InitTargetOptionsFromCodeGenFlags();
     Options.DisableIntegratedAS = NoIntegratedAssembler;
     Options.MCOptions.ShowMCEncoding = ShowMCEncoding;
     Options.MCOptions.MCUseDwarfDirectory = EnableDwarfDirectory;
     Options.MCOptions.AsmVerbose = AsmVerbose;
     Options.MCOptions.PreserveAsmComments = PreserveComments;
     Options.MCOptions.IASSearchPaths = IncludeDirs;
     Options.MCOptions.SplitDwarfFile = SplitDwarfFile;
+  };
 
   Optional<Reloc::Model> RM = codegen::getExplicitRelocModel();
 
   const Target *TheTarget = nullptr;
   std::unique_ptr<TargetMachine> Target;
 
   // If user just wants to list available options, skip module loading
   if (!SkipModule) {
auto SetDataLayout =
       // On AIX, setting the relocation model to anything other than PIC is
       // considered a user error.
       if (TheTriple.isOSAIX() && RM.hasValue() && *RM != Reloc::PIC_) {
         WithColor::error(errs(), argv[0])
             << "invalid relocation model, AIX only supports PIC.\n";
         exit(1);
       }
 
+      InitializeOptions(TheTriple);
       Target = std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine(
           TheTriple.getTriple(), CPUStr, FeaturesStr, Options, RM,
           codegen::getExplicitCodeModel(), OLvl));
       assert(Target && "Could not allocate target machine!");
 
       return Target->createDataLayout().getStringRepresentation();
     };
     if (InputLanguage == "mir" ||
if (!SkipModule) {
     // On AIX, setting the relocation model to anything other than PIC is
     // considered a user error.
     if (TheTriple.isOSAIX() && RM.hasValue() && *RM != Reloc::PIC_) {
       WithColor::error(errs(), argv[0])
           << "invalid relocation model, AIX only supports PIC.\n";
       return 1;
     }
 
+    InitializeOptions(TheTriple);
     Target = std::unique_ptr<TargetMachine>(TheTarget->createTargetMachine(
         TheTriple.getTriple(), CPUStr, FeaturesStr, Options, RM,
         codegen::getExplicitCodeModel(), OLvl));
     assert(Target && "Could not allocate target machine!");
 
     // If we don't have a module then just exit now. We do this down
     // here since the CPU/Feature help is underneath the target machine
     // creation.