[AIX] Define _ARCH_PPC64 macro for 32-bit

[Jake-Egan]

Summary

The macro _ARCH_PPC64 is already defined for 64-bit, but this patch defines it for 32-bit on AIX to follow xlc. See: https://www.ibm.com/docs/en/xl-c-and-cpp-aix/13.1.0?topic=features-macros-related-architecture-settings

Note: This change creates a discrepancy between GCC, which defines _ARCH_PPC64 only for 64-bit mode.

Tested with SPEC.

[cebowleratibm]

The divergence with GCC is regrettable. Unfortunately defining _ARCH_PPC64 in 32-bit has been a long-standing discrepancy between xlc and gcc and one I don't expect gcc to change. This patch is preferable in order to retain preprocessing behaviour on AIX for customers porting 32-bit AIX xlc applications to clang.

My request for change is simply to add a brief explanation in the code, otherwise, it looks like a coding error.

clang/lib/Basic/Targets/PPC.cpp

260

A comment is warranted here to explain that __ARCH_PPC64 is only defined in 32-bit on AIX.

[hubert.reinterpretcast]

clang/lib/Basic/Targets/PPC.cpp

260

s/only/also/; ?

[Jake-Egan]

Added the comment. clang-format suggests a second indent, but I think this is correct because the comment is addressing the else clause.

[hubert.reinterpretcast]

clang/lib/Basic/Targets/PPC.cpp

259

Merge else with single if-statement as the sole contents of the block into else if. Comment can be placed at the top of the block controlled by the else if (and, in that position, should be indented).

[Jake-Egan]

Merge else and if.

[cebowleratibm]

clang/lib/Basic/Targets/PPC.cpp

260

Suggest:

// The XL compilers on AIX define _ARCH_PPC64 for both 32 and 64-bit modes.

[Jake-Egan]

Updated the comment.

[cebowleratibm]

LGTM.

clang/lib/Basic/Targets/PPC.cpp

void PPCTargetInfo::getTargetDefines(const LangOptions &Opts,
   Builder.defineMacro("_ARCH_PPC");
   Builder.defineMacro("__powerpc__");
   Builder.defineMacro("__POWERPC__");
   if (PointerWidth == 64) {
     Builder.defineMacro("_ARCH_PPC64");
     Builder.defineMacro("__powerpc64__");
     Builder.defineMacro("__ppc64__");
     Builder.defineMacro("__PPC64__");
+  // Also define _ARCH_PPC64 for 32-bit on AIX.
+  } else {
+    if (getTriple().isOSAIX())
+      Builder.defineMacro("_ARCH_PPC64");
   }
 
   // Target properties.
   if (getTriple().getArch() == llvm::Triple::ppc64le ||
       getTriple().getArch() == llvm::Triple::ppcle) {
     Builder.defineMacro("_LITTLE_ENDIAN");
   } else {
     if (!getTriple().isOSNetBSD() &&

clang/test/Preprocessor/init-ppc.c

 // PPC:#define __WINT_WIDTH__ 32
 // PPC:#define __ppc__ 1
 
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc-ibm-aix7.1.0.0 -fno-signed-char < /dev/null | FileCheck -match-full-lines -check-prefix PPC-AIX %s
 //
 // PPC-AIX-NOT:#define __64BIT__ 1
 // PPC-AIX:#define _AIX 1
 // PPC-AIX:#define _ARCH_PPC 1
+// PPC-AIX:#define _ARCH_PPC64 1
 // PPC-AIX:#define _BIG_ENDIAN 1
 // PPC-AIX:#define _IBMR2 1
 // PPC-AIX:#define _LONG_LONG 1
 // PPC-AIX-NOT:#define _LP64 1
 // PPC-AIX:#define _POWER 1
 // PPC-AIX:#define __BIGGEST_ALIGNMENT__ 16
 // PPC-AIX:#define __BIG_ENDIAN__ 1
 // PPC-AIX:#define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__