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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* For documentation, see jit/AtomicOperations.h */
#ifndef jit_arm_AtomicOperations_arm_h
#define jit_arm_AtomicOperations_arm_h
#include "jit/arm/Architecture-arm.h"
#if defined(__clang__) || defined(__GNUC__)
// The default implementation tactic for gcc/clang is to use the newer
// __atomic intrinsics added for use in C++11 <atomic>. Where that
// isn't available, we use GCC's older __sync functions instead.
//
// ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS is kept as a backward
// compatible option for older compilers: enable this to use GCC's old
// __sync functions instead of the newer __atomic functions. This
// will be required for GCC 4.6.x and earlier, and probably for Clang
// 3.1, should we need to use those versions.
//#define ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
inline bool
js::jit::AtomicOperations::isLockfree8()
{
// The JIT and the C++ compiler must agree on whether to use atomics
// for 64-bit accesses. There are two ways to do this: either the
// JIT defers to the C++ compiler (so if the C++ code is compiled
// for ARMv6, say, and __atomic_always_lock_free(8) is false, then the
// JIT ignores the fact that the program is running on ARMv7 or newer);
// or the C++ code in this file calls out to run-time generated code
// to do whatever the JIT does.
//
// For now, make the JIT defer to the C++ compiler when we know what
// the C++ compiler will do, otherwise assume a lock is needed.
# ifndef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
MOZ_ASSERT(__atomic_always_lock_free(sizeof(int8_t), 0));
MOZ_ASSERT(__atomic_always_lock_free(sizeof(int16_t), 0));
MOZ_ASSERT(__atomic_always_lock_free(sizeof(int32_t), 0));
return HasLDSTREXBHD() && __atomic_always_lock_free(sizeof(int64_t), 0);
# else
return false;
# endif
}
inline void
js::jit::AtomicOperations::fenceSeqCst()
{
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
__sync_synchronize();
# else
__atomic_thread_fence(__ATOMIC_SEQ_CST);
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::loadSeqCst(T* addr)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
__sync_synchronize();
T v = *addr;
__sync_synchronize();
# else
T v;
__atomic_load(addr, &v, __ATOMIC_SEQ_CST);
# endif
return v;
}
template<typename T>
inline void
js::jit::AtomicOperations::storeSeqCst(T* addr, T val)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
__sync_synchronize();
*addr = val;
__sync_synchronize();
# else
__atomic_store(addr, &val, __ATOMIC_SEQ_CST);
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::exchangeSeqCst(T* addr, T val)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
T v;
__sync_synchronize();
do {
v = *addr;
} while (__sync_val_compare_and_swap(addr, v, val) != v);
return v;
# else
T v;
__atomic_exchange(addr, &val, &v, __ATOMIC_SEQ_CST);
return v;
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::compareExchangeSeqCst(T* addr, T oldval, T newval)
{
MOZ_ASSERT(sizeof(T) < 8 || isLockfree8());
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
return __sync_val_compare_and_swap(addr, oldval, newval);
# else
__atomic_compare_exchange(addr, &oldval, &newval, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
return oldval;
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::fetchAddSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
return __sync_fetch_and_add(addr, val);
# else
return __atomic_fetch_add(addr, val, __ATOMIC_SEQ_CST);
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::fetchSubSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
return __sync_fetch_and_sub(addr, val);
# else
return __atomic_fetch_sub(addr, val, __ATOMIC_SEQ_CST);
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::fetchAndSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
return __sync_fetch_and_and(addr, val);
# else
return __atomic_fetch_and(addr, val, __ATOMIC_SEQ_CST);
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::fetchOrSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
return __sync_fetch_and_or(addr, val);
# else
return __atomic_fetch_or(addr, val, __ATOMIC_SEQ_CST);
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::fetchXorSeqCst(T* addr, T val)
{
static_assert(sizeof(T) <= 4, "not available for 8-byte values yet");
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
return __sync_fetch_and_xor(addr, val);
# else
return __atomic_fetch_xor(addr, val, __ATOMIC_SEQ_CST);
# endif
}
template<typename T>
inline T
js::jit::AtomicOperations::loadSafeWhenRacy(T* addr)
{
return *addr; // FIXME (1208663): not yet safe
}
template<typename T>
inline void
js::jit::AtomicOperations::storeSafeWhenRacy(T* addr, T val)
{
*addr = val; // FIXME (1208663): not yet safe
}
inline void
js::jit::AtomicOperations::memcpySafeWhenRacy(void* dest, const void* src, size_t nbytes)
{
memcpy(dest, src, nbytes); // FIXME (1208663): not yet safe
}
inline void
js::jit::AtomicOperations::memmoveSafeWhenRacy(void* dest, const void* src, size_t nbytes)
{
memmove(dest, src, nbytes); // FIXME (1208663): not yet safe
}
template<size_t nbytes>
inline void
js::jit::RegionLock::acquire(void* addr)
{
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
while (!__sync_bool_compare_and_swap(&spinlock, 0, 1))
;
# else
uint32_t zero = 0;
uint32_t one = 1;
while (!__atomic_compare_exchange(&spinlock, &zero, &one, false, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE)) {
zero = 0;
continue;
}
# endif
}
template<size_t nbytes>
inline void
js::jit::RegionLock::release(void* addr)
{
MOZ_ASSERT(AtomicOperations::loadSeqCst(&spinlock) == 1, "releasing unlocked region lock");
# ifdef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
__sync_sub_and_fetch(&spinlock, 1);
# else
uint32_t zero = 0;
__atomic_store(&spinlock, &zero, __ATOMIC_SEQ_CST);
# endif
}
# undef ATOMICS_IMPLEMENTED_WITH_SYNC_INTRINSICS
#elif defined(ENABLE_SHARED_ARRAY_BUFFER)
# error "Either disable JS shared memory at compile time, use GCC or Clang, or add code here"
#endif
#endif // jit_arm_AtomicOperations_arm_h
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