[AIX] Define __THW_PPC__ macro

[Jake-Egan]

Summary

This patch defines the macro __THW_PPC__ for AIX.

Tested with SPEC.

[cebowleratibm]

LGTM. THW_PPC is a macro historically defined by xlc on AIX and defining it may help users port to clang.

clang/lib/Basic/Targets/PPC.cpp

void PPCTargetInfo::getTargetDefines(const LangOptions &Opts,
   Builder.defineMacro("__powerpc__");
   Builder.defineMacro("__POWERPC__");
   if (PointerWidth == 64) {
     Builder.defineMacro("_ARCH_PPC64");
     Builder.defineMacro("__powerpc64__");
     Builder.defineMacro("__ppc64__");
     Builder.defineMacro("__PPC64__");
   }
+  if (getTriple().isOSAIX()) {
+    Builder.defineMacro("__THW_PPC__");
+  }
 
   // Target properties.
   if (getTriple().getArch() == llvm::Triple::ppc64le ||
       getTriple().getArch() == llvm::Triple::ppcle) {
     Builder.defineMacro("_LITTLE_ENDIAN");
   } else {
     if (!getTriple().isOSNetBSD() &&
         !getTriple().isOSOpenBSD())

clang/test/Preprocessor/init-ppc.c

 // PPC-AIX:#define __SIZEOF_PTRDIFF_T__ 4
 // PPC-AIX:#define __SIZEOF_SHORT__ 2
 // PPC-AIX:#define __SIZEOF_SIZE_T__ 4
 // PPC-AIX:#define __SIZEOF_WCHAR_T__ 2
 // PPC-AIX:#define __SIZEOF_WINT_T__ 4
 // PPC-AIX:#define __SIZE_MAX__ 4294967295UL
 // PPC-AIX:#define __SIZE_TYPE__ long unsigned int
 // PPC-AIX:#define __SIZE_WIDTH__ 32
+// PPC-AIX:#define __THW_PPC__ 1
 // PPC-AIX:#define __TOS_AIX__ 1
 // PPC-AIX:#define __UINT16_C_SUFFIX__
 // PPC-AIX:#define __UINT16_MAX__ 65535
 // PPC-AIX:#define __UINT16_TYPE__ unsigned short
 // PPC-AIX:#define __UINT32_C_SUFFIX__ U
 // PPC-AIX:#define __UINT32_MAX__ 4294967295U
 // PPC-AIX:#define __UINT32_TYPE__ unsigned int
 // PPC-AIX:#define __UINT64_C_SUFFIX__ ULL