[libc++abi] Remove unnecessary atomic_support.h header from libc++abi

[ldionne]

Summary

The file was a duplicate of atomic_support.h in libc++. Since we now
require the libc++ sources in order to build libc++abi, it's OK to
remove this duplication.

Thanks to @chandlerc for noticing this.

[chandlerc]

LGTM.

As mentioned in chat, there are other includes of uncopied files: https://github.com/llvm/llvm-project/blob/main/libcxxabi/src/stdlib_stdexcept.cpp#L17

[ldionne]

Make comment consistent

[ldionne]

I'll ship this once CI passes.

[ldionne]

Try to fix libc++abi tests.

[ldionne]

Fix the single-threaded build and the modules build.

@chandlerc I am standardizing around using #include "include/FILE.h" // from libc++ instead of
#include "src/include/FILE.h" because having libc++'s root in the header search path breaks
modular builds (due to conflicting modulemaps in the generated <build>/include/c++/v1 and <src>/include).

libcxxabi/src/cxa_default_handlers.cpp

 
 #include <exception>
 #include <stdlib.h>
 #include "abort_message.h"
 #include "cxxabi.h"
 #include "cxa_handlers.h"
 #include "cxa_exception.h"
 #include "private_typeinfo.h"
-#include "include/atomic_support.h"
+#include "src/include/atomic_support.h" // from libc++
 
 #if !defined(LIBCXXABI_SILENT_TERMINATE)
 
 _LIBCPP_SAFE_STATIC
 static const char* cause = "uncaught";
 
 __attribute__((noreturn))
 static void demangling_terminate_handler()

libcxxabi/src/cxa_exception.cpp

 
 #include "cxxabi.h"
 
 #include <exception>        // for std::terminate
 #include <string.h>         // for memset
 #include "cxa_exception.h"
 #include "cxa_handlers.h"
 #include "fallback_malloc.h"
-#include "include/atomic_support.h"
+#include "src/include/atomic_support.h" // from libc++
 
 #if __has_feature(address_sanitizer)
 #include <sanitizer/asan_interface.h>
 #endif
 
 // +---------------------------+-----------------------------+---------------+
 // | __cxa_exception           | _Unwind_Exception CLNGC++\0 | thrown object |
 // +---------------------------+-----------------------------+---------------+

libcxxabi/src/cxa_guard_impl.h

  *
  *  Overall Design:
  *    The implementation was designed to allow each implementation to be tested
  *    independent of the C++ runtime or platform support.
  *
  */
 
 #include "__cxxabi_config.h"
-#include "include/atomic_support.h"
+#include "src/include/atomic_support.h" // from libc++
 #include <unistd.h>
 #if defined(__has_include)
 #  if __has_include(<sys/syscall.h>)
 #    include <sys/syscall.h>
 #  endif
 #endif
 
 #include <stdlib.h>

libcxxabi/src/cxa_handlers.cpp

 #include <stdexcept>
 #include <new>
 #include <exception>
 #include "abort_message.h"
 #include "cxxabi.h"
 #include "cxa_handlers.h"
 #include "cxa_exception.h"
 #include "private_typeinfo.h"
-#include "include/atomic_support.h"
+#include "src/include/atomic_support.h" // from libc++
 
 namespace std
 {
 
 unexpected_handler
 get_unexpected() noexcept
 {
     return __libcpp_atomic_load(&__cxa_unexpected_handler, _AO_Acquire);

libcxxabi/src/include/atomic_support.h

-//===----------------------------------------------------------------------===////
-//
-// 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
-//
-//===----------------------------------------------------------------------===////
-
-// FIXME: This file is copied from libcxx/src/include/atomic_support.h. Instead
-// of duplicating the file in libc++abi we should require that the libc++
-// sources are available when building libc++abi.
-
-#ifndef ATOMIC_SUPPORT_H
-#define ATOMIC_SUPPORT_H
-
-#include "__config"
-#include "memory" // for __libcpp_relaxed_load
-
-#if defined(__clang__) && __has_builtin(__atomic_load_n)             \
-                       && __has_builtin(__atomic_store_n)            \
-                       && __has_builtin(__atomic_add_fetch)          \
-                       && __has_builtin(__atomic_exchange_n)         \
-                       && __has_builtin(__atomic_compare_exchange_n) \
-                       && defined(__ATOMIC_RELAXED)                  \
-                       && defined(__ATOMIC_CONSUME)                  \
-                       && defined(__ATOMIC_ACQUIRE)                  \
-                       && defined(__ATOMIC_RELEASE)                  \
-                       && defined(__ATOMIC_ACQ_REL)                  \
-                       && defined(__ATOMIC_SEQ_CST)
-#   define _LIBCXXABI_HAS_ATOMIC_BUILTINS
-#elif defined(_LIBCPP_COMPILER_GCC)
-#   define _LIBCXXABI_HAS_ATOMIC_BUILTINS
-#endif
-
-#if !defined(_LIBCXXABI_HAS_ATOMIC_BUILTINS) && !defined(_LIBCXXABI_HAS_NO_THREADS)
-# if defined(_LIBCPP_WARNING)
-    _LIBCPP_WARNING("Building libc++ without __atomic builtins is unsupported")
-# else
-#   warning Building libc++ without __atomic builtins is unsupported
-# endif
-#endif
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-namespace {
-
-#if defined(_LIBCXXABI_HAS_ATOMIC_BUILTINS) && !defined(_LIBCXXABI_HAS_NO_THREADS)
-
-enum __libcpp_atomic_order {
-    _AO_Relaxed = __ATOMIC_RELAXED,
-    _AO_Consume = __ATOMIC_CONSUME,
-    _AO_Acquire = __ATOMIC_ACQUIRE,
-    _AO_Release = __ATOMIC_RELEASE,
-    _AO_Acq_Rel = __ATOMIC_ACQ_REL,
-    _AO_Seq     = __ATOMIC_SEQ_CST
-};
-
-template <class _ValueType, class _FromType>
-inline _LIBCPP_INLINE_VISIBILITY
-void __libcpp_atomic_store(_ValueType* __dest, _FromType __val,
-                           int __order = _AO_Seq)
-{
-    __atomic_store_n(__dest, __val, __order);
-}
-
-template <class _ValueType, class _FromType>
-inline _LIBCPP_INLINE_VISIBILITY
-void __libcpp_relaxed_store(_ValueType* __dest, _FromType __val)
-{
-    __atomic_store_n(__dest, __val, _AO_Relaxed);
-}
-
-template <class _ValueType>
-inline _LIBCPP_INLINE_VISIBILITY
-_ValueType __libcpp_atomic_load(_ValueType const* __val,
-                                int __order = _AO_Seq)
-{
-    return __atomic_load_n(__val, __order);
-}
-
-template <class _ValueType, class _AddType>
-inline _LIBCPP_INLINE_VISIBILITY
-_ValueType __libcpp_atomic_add(_ValueType* __val, _AddType __a,
-                               int __order = _AO_Seq)
-{
-    return __atomic_add_fetch(__val, __a, __order);
-}
-
-template <class _ValueType>
-inline _LIBCPP_INLINE_VISIBILITY
-_ValueType __libcpp_atomic_exchange(_ValueType* __target,
-                                    _ValueType __value, int __order = _AO_Seq)
-{
-    return __atomic_exchange_n(__target, __value, __order);
-}
-
-template <class _ValueType>
-inline _LIBCPP_INLINE_VISIBILITY
-bool __libcpp_atomic_compare_exchange(_ValueType* __val,
-    _ValueType* __expected, _ValueType __after,
-    int __success_order = _AO_Seq,
-    int __fail_order = _AO_Seq)
-{
-    return __atomic_compare_exchange_n(__val, __expected, __after, true,
-                                       __success_order, __fail_order);
-}
-
-#else // _LIBCPP_HAS_NO_THREADS
-
-enum __libcpp_atomic_order {
-    _AO_Relaxed,
-    _AO_Consume,
-    _AO_Acquire,
-    _AO_Release,
-    _AO_Acq_Rel,
-    _AO_Seq
-};
-
-template <class _ValueType, class _FromType>
-inline _LIBCPP_INLINE_VISIBILITY
-void __libcpp_atomic_store(_ValueType* __dest, _FromType __val,
-                           int = 0)
-{
-    *__dest = __val;
-}
-
-template <class _ValueType, class _FromType>
-inline _LIBCPP_INLINE_VISIBILITY
-void __libcpp_relaxed_store(_ValueType* __dest, _FromType __val)
-{
-    *__dest = __val;
-}
-
-template <class _ValueType>
-inline _LIBCPP_INLINE_VISIBILITY
-_ValueType __libcpp_atomic_load(_ValueType const* __val,
-                                int = 0)
-{
-    return *__val;
-}
-
-template <class _ValueType, class _AddType>
-inline _LIBCPP_INLINE_VISIBILITY
-_ValueType __libcpp_atomic_add(_ValueType* __val, _AddType __a,
-                               int = 0)
-{
-    return *__val += __a;
-}
-
-template <class _ValueType>
-inline _LIBCPP_INLINE_VISIBILITY
-_ValueType __libcpp_atomic_exchange(_ValueType* __target,
-                                    _ValueType __value, int  = _AO_Seq)
-{
-    _ValueType old = *__target;
-    *__target = __value;
-    return old;
-}
-
-template <class _ValueType>
-inline _LIBCPP_INLINE_VISIBILITY
-bool __libcpp_atomic_compare_exchange(_ValueType* __val,
-    _ValueType* __expected, _ValueType __after,
-    int = 0, int = 0)
-{
-    if (*__val == *__expected) {
-        *__val = __after;
-        return true;
-    }
-    *__expected = *__val;
-    return false;
-}
-
-#endif // _LIBCPP_HAS_NO_THREADS
-
-} // end namespace
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // ATOMIC_SUPPORT_H