Teach llc about -Oz and -Os

[paquette]

Summary

This is the second patch necessary for turning the MachineOutliner on by default under -Oz for AArch64. This teaches llc about -Oz and -Os that it can run passes that are added by default in -Oz and -Os to its pass pipeline.

Since this is a part of a series of patches, the intent here is that the MachineOutliner test that will be added in the final patch will test the behaviour of llc.

[paquette]

Added context to diff.

[paquette]

We decided it'd be better to just use function attributes for the outliner, so I'm abandoning this.

tools/llc/llc.cpp

 static cl::opt<bool>
     PreserveComments("preserve-as-comments", cl::Hidden,
                      cl::desc("Preserve Comments in outputted assembly"),
                      cl::init(true));
 
 // Determine optimization level.
 static cl::opt<char>
 OptLevel("O",
-         cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
+         cl::desc("Optimization level. [-O0, -O1, -O2, -O3, -Oz, or -Os] "
                   "(default = '-O2')"),
          cl::Prefix,
          cl::ZeroOrMore,
          cl::init(' '));
 
 static cl::opt<std::string>
 TargetTriple("mtriple", cl::desc("Override target triple for module"));
 
static int compileModule(char **argv, LLVMContext &Context) {
   if (!TheTarget) {
     errs() << argv[0] << ": " << Error;
     return 1;
   }
 
   std::string CPUStr = getCPUStr(), FeaturesStr = getFeaturesStr();
 
   CodeGenOpt::Level OLvl = CodeGenOpt::Default;
+  CodeGenSizeOpt::Level SLvl = CodeGenSizeOpt::None;
   switch (OptLevel) {
   default:
     errs() << argv[0] << ": invalid optimization level.\n";
     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;
+  case 's': SLvl = CodeGenSizeOpt::OptSize; break;
+  case 'z': SLvl = CodeGenSizeOpt::MinSize; break;
   }
 
   TargetOptions Options = 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;
 
   std::unique_ptr<TargetMachine> Target(TheTarget->createTargetMachine(
       TheTriple.getTriple(), CPUStr, FeaturesStr, Options, getRelocModel(),
-      getCodeModel(), OLvl));
+      getCodeModel(), OLvl, SLvl));
 
   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.
   if (SkipModule)
     return 0;