[PPC] Undefine __ppc64__ to match GCC

[MaskRay]

Summary

GCC only defines __ppc64__ for darwin while the darwin support has been
removed from llvm-project. The existence of __ppc64__ makes some software
think we are compiling for big-endian PowerPC Mac; also it lures users to write
code which is not portable to GCC.

It is straightforward if a distro wants to keep the macro: add
-D__ppc64__=1 to a Clang configuration file.

[q66]

The __ppc__ macro should get the same treatment. That said, I believe there are instances of both macros being used across the LLVM codebase, and those cases are valid, so that should also be updated (one instance i know of is the limits header of libcxx, there are likely more)

[thesamesam]

This needs to go in Breaking Changes in the release notes, not least so we can link to it when updating upstreams.

What do you mean by "while the darwin support has been removed from llvm-project."? I don't think that's the case, if you mean that LLVM.org's LLVM lacks support for Darwin.

[MaskRay]

In D137511#3911052, @thesamesam wrote:

This needs to go in Breaking Changes in the release notes, not least so we can link to it when updating upstreams.

What do you mean by "while the darwin support has been removed from llvm-project."? I don't think that's the case, if you mean that LLVM.org's LLVM lacks support for Darwin.

Clarified it to "The darwin ppc support has been removed from llvm-project."

In D137511#3910880, @q66 wrote:

The __ppc__ macro should get the same treatment. That said, I believe there are instances of both macros being used across the LLVM codebase, and those cases are valid, so that should also be updated (one instance i know of is the limits header of libcxx, there are likely more)

__ppc__ is defined for FreeBSD in GCC, so perhaps we can make a separate change making __ppc__ only defined for FreeBSD (@dim @Bdragon28 @jhibbits).

[MaskRay]

update releasenote

[nemanjai]

As mentioned by @q66 above, this can't go in until usage of this macro in the Clang/LLVM codebase is fixed. Looks like the uses in clang/lib/Headers/ppc_wrappers and some of the uses in libcxx and libunwind must be fixed while others should probably also be fixed to avoid confusion.

[nemanjai]

I am going to block this since the uses of the macros in clang/lib/Headers/ppc_wrappers will likely cause build bot failures.

[MaskRay]

In D137511#3911149, @nemanjai wrote:

I am going to block this since the uses of the macros in clang/lib/Headers/ppc_wrappers will likely cause build bot failures.

clang/lib/Headers/ppc_wrappers was fixed yesterday. The only dependency is D137513 :)

[MaskRay]

Hi @nemanjai , I think there is no relevant __ppc64__ in llvm-project now. (The libc++ change has landed and third_party/benchmark has a non-interesting use as that code has defined(__powerpc64__) as well).

[nemanjai]

LGTM.
Thanks so much for fixing up the existing code.

clang/docs/ReleaseNotes.rst

void h() {
       g(42);
     }
 
 - Clang's resource dir used to include the full clang version. It will now
   include only the major version. The new resource directory is
   ``$prefix/lib/clang/$CLANG_MAJOR_VERSION`` and can be queried using
   ``clang -print-resource-dir``, just like before.
 
+- To match GCC, ``__ppc64__`` is no longer defined on PowerPC64 targets. Use
+  ``__powerpc64__`` instead.
+
 What's New in Clang |release|?
 ==============================
 Some of the major new features and improvements to Clang are listed
 here. Generic improvements to Clang as a whole or to its underlying
 infrastructure are described first, followed by language-specific
 sections with improvements to Clang's support for those languages.
 
 Major New Features

clang/lib/Basic/Targets/PPC.cpp

void PPCTargetInfo::getTargetDefines(const LangOptions &Opts,
   Builder.defineMacro("__ppc__");
   Builder.defineMacro("__PPC__");
   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__");
   } else if (getTriple().isOSAIX()) {
     // The XL compilers on AIX define _ARCH_PPC64 for both 32 and 64-bit modes.
     Builder.defineMacro("_ARCH_PPC64");
   }
   if (getTriple().isOSAIX()) {
     Builder.defineMacro("__THW_PPC__");
     // Define __PPC and __powerpc for AIX XL C/C++ compatibility

clang/test/Preprocessor/init-ppc64.c

 // PPC64:#define __UINT_LEAST8_MAX__ 255
 // PPC64:#define __UINT_LEAST8_TYPE__ unsigned char
 // PPC64:#define __USER_LABEL_PREFIX__
 // PPC64:#define __WCHAR_MAX__ 2147483647
 // PPC64:#define __WCHAR_TYPE__ int
 // PPC64:#define __WCHAR_WIDTH__ 32
 // PPC64:#define __WINT_TYPE__ int
 // PPC64:#define __WINT_WIDTH__ 32
-// PPC64:#define __ppc64__ 1
 // PPC64:#define __ppc__ 1
 //
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64le-none-none -target-cpu pwr7 -fno-signed-char < /dev/null | FileCheck -match-full-lines -check-prefix PPC64LE %s
 //
 // PPC64LE:#define _ARCH_PPC 1
 // PPC64LE:#define _ARCH_PPC64 1
 // PPC64LE:#define _ARCH_PPCGR 1
 // PPC64LE:#define _ARCH_PPCSQ 1

 // PPC64LE:#define __UINT_LEAST8_MAX__ 255
 // PPC64LE:#define __UINT_LEAST8_TYPE__ unsigned char
 // PPC64LE:#define __USER_LABEL_PREFIX__
 // PPC64LE:#define __WCHAR_MAX__ 2147483647
 // PPC64LE:#define __WCHAR_TYPE__ int
 // PPC64LE:#define __WCHAR_WIDTH__ 32
 // PPC64LE:#define __WINT_TYPE__ int
 // PPC64LE:#define __WINT_WIDTH__ 32
-// PPC64LE:#define __ppc64__ 1
 // PPC64LE:#define __ppc__ 1
 //
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-none-none -target-cpu 630 -fno-signed-char < /dev/null | FileCheck -match-full-lines -check-prefix PPC630 %s
 //
 // PPC630:#define _ARCH_630 1
 // PPC630:#define _ARCH_PPC 1
 // PPC630:#define _ARCH_PPC64 1
 // PPC630:#define _ARCH_PPCGR 1

 // PPC64-AIX:#define __USER_LABEL_PREFIX__
 // PPC64-AIX:#define __WCHAR_MAX__ 4294967295U
 // PPC64-AIX:#define __WCHAR_TYPE__ unsigned int
 // PPC64-AIX:#define __WCHAR_WIDTH__ 32
 // PPC64-AIX:#define __WINT_TYPE__ int
 // PPC64-AIX:#define __WINT_WIDTH__ 32
 // PPC64-AIX:#define __powerpc64__ 1
 // PPC64-AIX:#define __powerpc__ 1
-// PPC64-AIX:#define __ppc64__ 1
 // PPC64-AIX:#define __ppc__ 1
 //
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-unknown-linux-gnu -fno-signed-char < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-LINUX %s
 //
 // PPC64-LINUX:#define _ARCH_PPC 1
 // PPC64-LINUX:#define _ARCH_PPC64 1
 // PPC64-LINUX:#define _BIG_ENDIAN 1
 // PPC64-LINUX:#define _CALL_LINUX 1

 // PPC64-LINUX:#define __WCHAR_MAX__ 2147483647
 // PPC64-LINUX:#define __WCHAR_TYPE__ int
 // PPC64-LINUX:#define __WCHAR_WIDTH__ 32
 // PPC64-LINUX:#define __WINT_TYPE__ unsigned int
 // PPC64-LINUX:#define __WINT_UNSIGNED__ 1
 // PPC64-LINUX:#define __WINT_WIDTH__ 32
 // PPC64-LINUX:#define __powerpc64__ 1
 // PPC64-LINUX:#define __powerpc__ 1
-// PPC64-LINUX:#define __ppc64__ 1
 // PPC64-LINUX:#define __ppc__ 1
 
 // RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64-unknown-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64-unknown-linux-gnu -target-abi elfv1 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64-unknown-linux-gnu -target-abi elfv2 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64le-unknown-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64le-unknown-linux-gnu -target-abi elfv1 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
 // RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64le-unknown-linux-gnu -target-abi elfv2 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s