[libc++abi] Replace __sync_* functions with __libcpp_atomic_* functions.

[efriedma]

Summary

This is basically part 2 of r313694.

It's a little unfortunate that I had to copy-paste atomic_support.h, but I don't really see any alternative.

The refstring.h changes are the same as the libcxx changes in r313694.

[efriedma]

Ping.

[compnerd]

I definitely like the clean up. Not sure I understand the motivation for the __libcpp_relaxed_store, but I suppose thats because its a copy from libc++ where it may be more useful.

[efriedma]

https://reviews.llvm.org/rL330162

src/cxa_default_handlers.cpp

 #include <new>
 #include <exception>
 #include <cstdlib>
 #include "abort_message.h"
 #include "cxxabi.h"
 #include "cxa_handlers.hpp"
 #include "cxa_exception.hpp"
 #include "private_typeinfo.h"
+#include "include/atomic_support.h"
 
 #if !defined(LIBCXXABI_SILENT_TERMINATE)
 static const char* cause = "uncaught";
 
 __attribute__((noreturn))
 static void demangling_terminate_handler()
 {
     // If there might be an uncaught exception

 // Global variables that hold the pointers to the current handler
 //
 _LIBCXXABI_DATA_VIS
 std::terminate_handler __cxa_terminate_handler = default_terminate_handler;
 
 _LIBCXXABI_DATA_VIS
 std::unexpected_handler __cxa_unexpected_handler = default_unexpected_handler;
 
-// In the future these will become:
-// std::atomic<std::terminate_handler>  __cxa_terminate_handler(default_terminate_handler);
-// std::atomic<std::unexpected_handler> __cxa_unexpected_handler(default_unexpected_handler);
-
 namespace std
 {
 
 unexpected_handler
 set_unexpected(unexpected_handler func) _NOEXCEPT
 {
     if (func == 0)
         func = default_unexpected_handler;
-    return __atomic_exchange_n(&__cxa_unexpected_handler, func,
-                               __ATOMIC_ACQ_REL);
-//  Using of C++11 atomics this should be rewritten
-//  return __cxa_unexpected_handler.exchange(func, memory_order_acq_rel);
+    return __libcpp_atomic_exchange(&__cxa_unexpected_handler, func,
+                                    _AO_Acq_Rel);
 }
 
 terminate_handler
 set_terminate(terminate_handler func) _NOEXCEPT
 {
     if (func == 0)
         func = default_terminate_handler;
-    return __atomic_exchange_n(&__cxa_terminate_handler, func,
-                               __ATOMIC_ACQ_REL);
-//  Using of C++11 atomics this should be rewritten
-//  return __cxa_terminate_handler.exchange(func, memory_order_acq_rel);
+    return __libcpp_atomic_exchange(&__cxa_terminate_handler, func,
+                                    _AO_Acq_Rel);
 }
 
 }

src/cxa_exception.cpp

 
 #include "cxxabi.h"
 
 #include <exception>        // for std::terminate
 #include <cstring>          // for memset
 #include "cxa_exception.hpp"
 #include "cxa_handlers.hpp"
 #include "fallback_malloc.h"
+#include "include/atomic_support.h"
 
 #if __has_feature(address_sanitizer)
 extern "C" void __asan_handle_no_return(void);
 #endif
 
 // +---------------------------+-----------------------------+---------------+
 // | __cxa_exception           | _Unwind_Exception CLNGC++\0 | thrown object |
 // +---------------------------+-----------------------------+---------------+
/*
 
     Requires:  If thrown_object is not NULL, it is a native exception.
 */
 void
 __cxa_increment_exception_refcount(void *thrown_object) throw() {
     if (thrown_object != NULL )
     {
         __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
-        __sync_add_and_fetch(&exception_header->referenceCount, 1);
+        std::__libcpp_atomic_add(&exception_header->referenceCount, size_t(1));
     }
 }
 
 /*
     If thrown_object is not null, atomically decrement the referenceCount field
     of the __cxa_exception header associated with the thrown object referred to
     by thrown_object.  If the referenceCount drops to zero, destroy and
     deallocate the exception.
 
     Requires:  If thrown_object is not NULL, it is a native exception.
 */
 void
 __cxa_decrement_exception_refcount(void *thrown_object) throw() {
     if (thrown_object != NULL )
     {
         __cxa_exception* exception_header = cxa_exception_from_thrown_object(thrown_object);
-        if (__sync_sub_and_fetch(&exception_header->referenceCount, size_t(1)) == 0)
+        if (std::__libcpp_atomic_add(&exception_header->referenceCount, size_t(-1)) == 0)
         {
             if (NULL != exception_header->exceptionDestructor)
                 exception_header->exceptionDestructor(thrown_object);
             __cxa_free_exception(thrown_object);
         }
     }
 }
 

src/cxa_handlers.cpp

 #include <stdexcept>
 #include <new>
 #include <exception>
 #include "abort_message.h"
 #include "cxxabi.h"
 #include "cxa_handlers.hpp"
 #include "cxa_exception.hpp"
 #include "private_typeinfo.h"
+#include "include/atomic_support.h"
 
 namespace std
 {
 
 unexpected_handler
 get_unexpected() _NOEXCEPT
 {
-    return __sync_fetch_and_add(&__cxa_unexpected_handler, (unexpected_handler)0);
-//  The above is safe but overkill on x86
-//  Using of C++11 atomics this should be rewritten
-//  return __cxa_unexpected_handler.load(memory_order_acq);
+    return __libcpp_atomic_load(&__cxa_unexpected_handler, _AO_Acquire);
 }
 
 void
 __unexpected(unexpected_handler func)
 {
     func();
     // unexpected handler should not return
     abort_message("unexpected_handler unexpectedly returned");
 }
 
 __attribute__((noreturn))
 void
 unexpected()
 {
     __unexpected(get_unexpected());
 }
 
 terminate_handler
 get_terminate() _NOEXCEPT
 {
-    return __sync_fetch_and_add(&__cxa_terminate_handler, (terminate_handler)0);
-//  The above is safe but overkill on x86
-//  Using of C++11 atomics this should be rewritten
-//  return __cxa_terminate_handler.load(memory_order_acq);
+    return __libcpp_atomic_load(&__cxa_terminate_handler, _AO_Acquire);
 }
 
 void
 __terminate(terminate_handler func) _NOEXCEPT
 {
 #ifndef _LIBCXXABI_NO_EXCEPTIONS
     try
     {
if (globals)
                                (kOurExceptionClass & get_vendor_and_language);
             if (native_exception)
                 __terminate(exception_header->terminateHandler);
         }
     }
     __terminate(get_terminate());
 }
 
-// In the future this will become:
-// std::atomic<std::new_handler>  __cxa_new_handler(0);
 extern "C" {
 new_handler __cxa_new_handler = 0;
 }
 
 new_handler
 set_new_handler(new_handler handler) _NOEXCEPT
 {
-    return __atomic_exchange_n(&__cxa_new_handler, handler, __ATOMIC_ACQ_REL);
-//  Using of C++11 atomics this should be rewritten
-//  return __cxa_new_handler.exchange(handler, memory_order_acq_rel);
+    return __libcpp_atomic_exchange(&__cxa_new_handler, handler, _AO_Acq_Rel);
 }
 
 new_handler
 get_new_handler() _NOEXCEPT
 {
-    return __sync_fetch_and_add(&__cxa_new_handler, (new_handler)0);
-//  The above is safe but overkill on x86
-//  Using of C++11 atomics this should be rewritten
-//  return __cxa_new_handler.load(memory_order_acq);
+    return __libcpp_atomic_load(&__cxa_new_handler, _AO_Acquire);
 }
 
 }  // std

src/include/atomic_support.h

+//===----------------------------------------------------------------------===////
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===////
+
+// 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(__clang__) && defined(_GNUC_VER) && _GNUC_VER >= 407
+#   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 __order = _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

src/include/refstring.h

 #include <__config>
 #include <stdexcept>
 #include <cstddef>
 #include <cstring>
 #ifdef __APPLE__
 #include <dlfcn.h>
 #include <mach-o/dyld.h>
 #endif
+#include "atomic_support.h"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace __refstring_imp { namespace {
 typedef int count_t;
 
 struct _Rep_base {
     std::size_t len;
__libcpp_refstring::__libcpp_refstring(const char* msg) {
     __imp_ = data;
 }
 
 inline
 __libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) _NOEXCEPT
     : __imp_(s.__imp_)
 {
     if (__uses_refcount())
-        __sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
+        __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
 }
 
 inline
 __libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) _NOEXCEPT {
     bool adjust_old_count = __uses_refcount();
     struct _Rep_base *old_rep = rep_from_data(__imp_);
     __imp_ = s.__imp_;
     if (__uses_refcount())
-        __sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
+        __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
     if (adjust_old_count)
     {
-        if (__sync_add_and_fetch(&old_rep->count, count_t(-1)) < 0)
+        if (__libcpp_atomic_add(&old_rep->count, count_t(-1)) < 0)
         {
             ::operator delete(old_rep);
         }
     }
     return *this;
 }
 
 inline
 __libcpp_refstring::~__libcpp_refstring() {
     if (__uses_refcount()) {
         _Rep_base* rep = rep_from_data(__imp_);
-        if (__sync_add_and_fetch(&rep->count, count_t(-1)) < 0) {
+        if (__libcpp_atomic_add(&rep->count, count_t(-1)) < 0) {
             ::operator delete(rep);
         }
     }
 }
 
 inline
 bool __libcpp_refstring::__uses_refcount() const {
 #ifdef __APPLE__