[PowerPC] Do not special case Darwin on PowerPC in target cpu handling

[stevewan]

Summary

This patch removes the special handling for Darwin on PowerPC in the default target cpu handling, because Darwin is no longer supported on the PowerPC platform.

[hubert.reinterpretcast]

Calling it the "Darwin factor" gives it a certain je ne sais quoi. :)

clang/lib/Driver/ToolChains/CommonArgs.cpp

296–297

I think we can reduce the nesting while keeping the NRVO and reorder the checks to prefer the more likely (for non-AIX) case of ppc64le:

if (!TargetCPUName.empty())
  return TargetCPUName;

if (T.isOSAIX())
  TargetCPUName = "pwr4";
else if (T.getArch() == llvm::Triple::ppc64le)
  TargetCPUName = "ppc64le";
else if (T.getArch() == llvm::Triple::ppc64)
  TargetCPUName = "ppc64";
else
  TargetCPUName = "ppc";

return TargetCPUName;

[stevewan]

Reduce the nested 'if' and reorder it to prefer the more likely case.

[hubert.reinterpretcast]

LGTM; thanks.

[stevewan]

The unit test failure (instrprof-gcov-multithread_fork.test) in pre merge checks is caused by another commit. See http://lab.llvm.org:8011/builders/llvm-avr-linux/builds/2205.

clang/lib/Driver/ToolChains/CommonArgs.cpp

if (const Arg *A = Args.getLastArg(options::OPT_march_EQ))
       return A->getValue();
     return "";
 
   case llvm::Triple::ppc:
   case llvm::Triple::ppc64:
   case llvm::Triple::ppc64le: {
     std::string TargetCPUName = ppc::getPPCTargetCPU(Args);
     // LLVM may default to generating code for the native CPU,
     // but, like gcc, we default to a more generic option for
-    // each architecture. (except on AIX or Darwin)
-    if (TargetCPUName.empty()) {
-      if (T.isOSAIX())
-        TargetCPUName = "pwr4";
-      else if (!T.isOSDarwin()) {
-        if (T.getArch() == llvm::Triple::ppc64)
-          TargetCPUName = "ppc64";
-        else if (T.getArch() == llvm::Triple::ppc64le)
-          TargetCPUName = "ppc64le";
-        else
-          TargetCPUName = "ppc";
-      }
-    }
+    // each architecture. (except on AIX)
+    if (!TargetCPUName.empty())
+      return TargetCPUName;
+
+    else if (T.getArch() == llvm::Triple::ppc64)
+      TargetCPUName = "ppc64";
+
     return TargetCPUName;
   }
 
   case llvm::Triple::bpfel:
   case llvm::Triple::bpfeb:
   case llvm::Triple::sparc:
   case llvm::Triple::sparcel:
   case llvm::Triple::sparcv9: