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

llvm-svn: 330162
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Eli Friedman committed Apr 16, 2018
1 parent aca6d00 commit 17a47b9
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Showing 5 changed files with 199 additions and 35 deletions.
17 changes: 5 additions & 12 deletions libcxxabi/src/cxa_default_handlers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
#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";
Expand Down Expand Up @@ -101,10 +102,6 @@ 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
{

Expand All @@ -113,21 +110,17 @@ 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);
}

}
5 changes: 3 additions & 2 deletions libcxxabi/src/cxa_exception.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#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);
Expand Down Expand Up @@ -618,7 +619,7 @@ __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));
}
}

Expand All @@ -635,7 +636,7 @@ 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);
Expand Down
22 changes: 5 additions & 17 deletions libcxxabi/src/cxa_handlers.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -18,17 +18,15 @@
#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
Expand All @@ -49,10 +47,7 @@ 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
Expand Down Expand Up @@ -99,27 +94,20 @@ terminate() _NOEXCEPT
__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
181 changes: 181 additions & 0 deletions libcxxabi/src/include/atomic_support.h
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Original file line number Diff line number Diff line change
@@ -0,0 +1,181 @@
//===----------------------------------------------------------------------===////
//
// 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
9 changes: 5 additions & 4 deletions libcxxabi/src/include/refstring.h
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@
#include <dlfcn.h>
#include <mach-o/dyld.h>
#endif
#include "atomic_support.h"

_LIBCPP_BEGIN_NAMESPACE_STD

Expand Down Expand Up @@ -87,7 +88,7 @@ __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
Expand All @@ -96,10 +97,10 @@ __libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) _
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);
}
Expand All @@ -111,7 +112,7 @@ 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);
}
}
Expand Down

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