[AIX] Define __HOS_AIX__ macro only for AIX target

[Jake-Egan]

Summary

This patch defines the macro __HOS_AIX__ when the target is AIX and without any dependency on the host. The macro indicates that the host is AIX. Defining the macro will help minimize porting pain for existing code compiled with xlc/xlC. xlC never shipped cross-compiling support, so the difference is not observable anyway.

This is a follow up to the discussion in https://reviews.llvm.org/D107242.

[joerg]

LGTM. Maybe include a small hint in the commit message that xlC never shipped cross-compiling support and the difference is therefore not observable anyway.

clang/lib/Basic/Targets/OSTargets.h

void getOSDefines(const LangOptions &Opts, const llvm::Triple &Triple,
                     MacroBuilder &Builder) const override {
     DefineStd(Builder, "unix", Opts);
     Builder.defineMacro("_IBMR2");
     Builder.defineMacro("_POWER");
     Builder.defineMacro("__THW_BIG_ENDIAN__");
 
     Builder.defineMacro("_AIX");
     Builder.defineMacro("__TOS_AIX__");
+    Builder.defineMacro("__HOS_AIX__");
 
     if (Opts.C11) {
       Builder.defineMacro("__STDC_NO_ATOMICS__");
       Builder.defineMacro("__STDC_NO_THREADS__");
     }
 
     if (Opts.EnableAIXExtendedAltivecABI)
       Builder.defineMacro("__EXTABI__");

clang/lib/Basic/Targets/PPC.cpp

 //===--- PPC.cpp - Implement PPC target feature support -------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements PPC TargetInfo objects.
 //
 //===----------------------------------------------------------------------===//
 
 #include "PPC.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/MacroBuilder.h"
 #include "clang/Basic/TargetBuiltins.h"
-#include "llvm/Support/Host.h"
 
 using namespace clang;
 using namespace clang::targets;
 
 const Builtin::Info PPCTargetInfo::BuiltinInfo[] = {
 #define BUILTIN(ID, TYPE, ATTRS)                                               \
   {#ID, TYPE, ATTRS, nullptr, ALL_LANGUAGES, nullptr},
 #define LIBBUILTIN(ID, TYPE, ATTRS, HEADER)                                    \
else
       Builder.defineMacro("__LONG_DOUBLE_IBM128__");
   }
 
   if (getTriple().isOSAIX() && Opts.LongDoubleSize == 64) {
     assert(LongDoubleWidth == 64);
     Builder.defineMacro("__LONGDOUBLE64");
   }
 
-  if (llvm::Triple(llvm::sys::getProcessTriple()).isOSAIX() &&
-      getTriple().isOSAIX()) {
-    Builder.defineMacro("__HOS_AIX__");
-  }
-
   // Define this for elfv2 (64-bit only) or 64-bit darwin.
   if (ABI == "elfv2" ||
       (getTriple().getOS() == llvm::Triple::Darwin && PointerWidth == 64))
     Builder.defineMacro("__STRUCT_PARM_ALIGN__", "16");
 
   if (ArchDefs & ArchDefineName)
     Builder.defineMacro(Twine("_ARCH_", StringRef(CPU).upper()));
   if (ArchDefs & ArchDefinePpcgr)

clang/test/Preprocessor/host-aix.c

-// REQUIRES: system-aix
-// 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:#define __HOS_AIX__ 1

clang/test/Preprocessor/init-ppc.c

 // PPC-AIX:#define __FLT_MANT_DIG__ 24
 // PPC-AIX:#define __FLT_MAX_10_EXP__ 38
 // PPC-AIX:#define __FLT_MAX_EXP__ 128
 // PPC-AIX:#define __FLT_MAX__ 3.40282347e+38F
 // PPC-AIX:#define __FLT_MIN_10_EXP__ (-37)
 // PPC-AIX:#define __FLT_MIN_EXP__ (-125)
 // PPC-AIX:#define __FLT_MIN__ 1.17549435e-38F
 // PPC-AIX:#define __FLT_RADIX__ 2
+// PPC-AIX:#define __HOS_AIX__ 1
 // PPC-AIX:#define __INT16_C_SUFFIX__
 // PPC-AIX:#define __INT16_FMTd__ "hd"
 // PPC-AIX:#define __INT16_FMTi__ "hi"
 // PPC-AIX:#define __INT16_MAX__ 32767
 // PPC-AIX:#define __INT16_TYPE__ short
 // PPC-AIX:#define __INT32_C_SUFFIX__
 // PPC-AIX:#define __INT32_FMTd__ "d"
 // PPC-AIX:#define __INT32_FMTi__ "i"

clang/test/Preprocessor/not-host-aix.c

-// UNSUPPORTED: system-aix
-// 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 __HOS_AIX__ 1