[llc] Use CPUStr instead of calling codegen::getMCPU(). NFC

[SixWeining]

Summary

getCPUStr() fallsback to getMCPU().

The only difference between getCPUStr() and getMCPU() is that
getCPUStr() handles -mcpu=native. That doesn't matter for this case.

This is just a simplification of the original code and it does not
change the functionality. So no new tests added.

[serge-sans-paille]

getCPUStr() fallsback to getMCPU so this looks good to me.

[MaskRay]

Test?

[craig.topper]

In D132849#3756675, @MaskRay wrote:

Test?

The only difference between getCPUStr() and getMCPU() is that getCPUStr() handles -mcpu=native. That doesn't matter for this case. I believe this is NFC as the title says.

[SixWeining]

In D132849#3756719, @craig.topper wrote:

In D132849#3756675, @MaskRay wrote:

Test?

The only difference between getCPUStr() and getMCPU() is that getCPUStr() handles -mcpu=native. That doesn't matter for this case. I believe this is NFC as the title says.

Yes. This is just a simplification of the original code and it does not change the functionality.

Maybe there is only one difference that if sys::getHostCPUName() returns help. But I believe no targets will do like this.

573 std::string codegen::getCPUStr() {
574   // If user asked for the 'native' CPU, autodetect here. If autodection fails,
575   // this will set the CPU to an empty string which tells the target to
576   // pick a basic default.
577   if (getMCPU() == "native")
578     return std::string(sys::getHostCPUName());
579 
580   return getMCPU();
581 }

[MaskRay]

In D132849#3756719, @craig.topper wrote:

In D132849#3756675, @MaskRay wrote:

Test?

The only difference between getCPUStr() and getMCPU() is that getCPUStr() handles -mcpu=native. That doesn't matter for this case. I believe this is NFC as the title says.

This is fine. The motivation should be mentioned in the summary.

[MaskRay]

LGTM.

llvm/tools/llc/llc.cpp

std::string CPUStr = codegen::getCPUStr(),
               FeaturesStr = codegen::getFeaturesStr();
 
   // Set attributes on functions as loaded from MIR from command line arguments.
   auto setMIRFunctionAttributes = [&CPUStr, &FeaturesStr](Function &F) {
     codegen::setFunctionAttributes(CPUStr, FeaturesStr, F);
   };
 
   auto MAttrs = codegen::getMAttrs();
-  bool SkipModule = codegen::getMCPU() == "help" ||
-                    (!MAttrs.empty() && MAttrs.front() == "help");
+  bool SkipModule =
+      CPUStr == "help" || (!MAttrs.empty() && MAttrs.front() == "help");
 
   CodeGenOpt::Level OLvl = CodeGenOpt::Default;
   switch (OptLevel) {
   default:
     WithColor::error(errs(), argv[0]) << "invalid optimization level.\n";
     return 1;
   case ' ': break;
   case '0': OLvl = CodeGenOpt::None; break;