File: AtomicOperations-mips-shared.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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 */

// NOTE, MIPS32 unlike MIPS64 doesn't provide hardware support for lock-free
// 64-bit atomics. We lie down below about 8-byte atomics being always lock-
// free in order to support wasm jit. The 64-bit atomic for MIPS32 do not use
// __atomic intrinsic and therefore do not relay on -latomic.
// Access to a aspecific 64-bit variable in memory is protected by an
// AddressLock whose instance is shared between jit and AtomicOperations.

#ifndef jit_mips_shared_AtomicOperations_mips_shared_h
#define jit_mips_shared_AtomicOperations_mips_shared_h

#include "mozilla/Assertions.h"
#include "mozilla/Types.h"

#include "builtin/AtomicsObject.h"
#include "vm/ArrayBufferObject.h"

#if !defined(__clang__) && !defined(__GNUC__)
#error "This file only for gcc-compatible compilers"
#endif

#if defined(JS_SIMULATOR_MIPS32) && !defined(__i386__)
#error "The MIPS32 simulator atomics assume x86"
#endif

namespace js {
namespace jit {

#if !defined(JS_64BIT)

struct AddressLock {
 public:
  void acquire();
  void release();

 private:
  uint32_t spinlock;
};

static_assert(sizeof(AddressLock) == sizeof(uint32_t),
              "AddressLock must be 4 bytes for it to be consumed by jit");

// For now use a single global AddressLock.
static AddressLock gAtomic64Lock;

struct MOZ_RAII AddressGuard {
  explicit AddressGuard(void* addr) { gAtomic64Lock.acquire(); }

  ~AddressGuard() { gAtomic64Lock.release(); }
};

#endif
}
}  // namespace js

inline bool js::jit::AtomicOperations::hasAtomic8() { return true; }

inline bool js::jit::AtomicOperations::isLockfree8() {
  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));
#if defined(JS_64BIT)
  MOZ_ASSERT(__atomic_always_lock_free(sizeof(int64_t), 0));
#endif
  return true;
}

inline void js::jit::AtomicOperations::fenceSeqCst() {
  __atomic_thread_fence(__ATOMIC_SEQ_CST);
}

template <typename T>
inline T js::jit::AtomicOperations::loadSeqCst(T* addr) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  T v;
  __atomic_load(addr, &v, __ATOMIC_SEQ_CST);
  return v;
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::loadSeqCst(int64_t* addr) {
  AddressGuard guard(addr);
  return *addr;
}

template <>
inline uint64_t js::jit::AtomicOperations::loadSeqCst(uint64_t* addr) {
  AddressGuard guard(addr);
  return *addr;
}

#endif
}
}  // namespace js

template <typename T>
inline void js::jit::AtomicOperations::storeSeqCst(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  __atomic_store(addr, &val, __ATOMIC_SEQ_CST);
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline void js::jit::AtomicOperations::storeSeqCst(int64_t* addr, int64_t val) {
  AddressGuard guard(addr);
  *addr = val;
}

template <>
inline void js::jit::AtomicOperations::storeSeqCst(uint64_t* addr,
                                                   uint64_t val) {
  AddressGuard guard(addr);
  *addr = val;
}

#endif
}
}  // namespace js

template <typename T>
inline T js::jit::AtomicOperations::compareExchangeSeqCst(T* addr, T oldval,
                                                          T newval) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  __atomic_compare_exchange(addr, &oldval, &newval, false, __ATOMIC_SEQ_CST,
                            __ATOMIC_SEQ_CST);
  return oldval;
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::compareExchangeSeqCst(
    int64_t* addr, int64_t oldval, int64_t newval) {
  AddressGuard guard(addr);
  int64_t val = *addr;
  if (val == oldval) *addr = newval;
  return val;
}

template <>
inline uint64_t js::jit::AtomicOperations::compareExchangeSeqCst(
    uint64_t* addr, uint64_t oldval, uint64_t newval) {
  AddressGuard guard(addr);
  uint64_t val = *addr;
  if (val == oldval) *addr = newval;
  return val;
}

#endif
}
}  // namespace js

template <typename T>
inline T js::jit::AtomicOperations::fetchAddSeqCst(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  return __atomic_fetch_add(addr, val, __ATOMIC_SEQ_CST);
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::fetchAddSeqCst(int64_t* addr,
                                                         int64_t val) {
  AddressGuard guard(addr);
  int64_t old = *addr;
  *addr = old + val;
  return old;
}

template <>
inline uint64_t js::jit::AtomicOperations::fetchAddSeqCst(uint64_t* addr,
                                                          uint64_t val) {
  AddressGuard guard(addr);
  uint64_t old = *addr;
  *addr = old + val;
  return old;
}

#endif
}
}  // namespace js

template <typename T>
inline T js::jit::AtomicOperations::fetchSubSeqCst(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  return __atomic_fetch_sub(addr, val, __ATOMIC_SEQ_CST);
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::fetchSubSeqCst(int64_t* addr,
                                                         int64_t val) {
  AddressGuard guard(addr);
  int64_t old = *addr;
  *addr = old - val;
  return old;
}

template <>
inline uint64_t js::jit::AtomicOperations::fetchSubSeqCst(uint64_t* addr,
                                                          uint64_t val) {
  AddressGuard guard(addr);
  uint64_t old = *addr;
  *addr = old - val;
  return old;
}

#endif
}
}  // namespace js

template <typename T>
inline T js::jit::AtomicOperations::fetchAndSeqCst(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  return __atomic_fetch_and(addr, val, __ATOMIC_SEQ_CST);
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::fetchAndSeqCst(int64_t* addr,
                                                         int64_t val) {
  AddressGuard guard(addr);
  int64_t old = *addr;
  *addr = old & val;
  return old;
}

template <>
inline uint64_t js::jit::AtomicOperations::fetchAndSeqCst(uint64_t* addr,
                                                          uint64_t val) {
  AddressGuard guard(addr);
  uint64_t old = *addr;
  *addr = old & val;
  return old;
}

#endif
}
}  // namespace js

template <typename T>
inline T js::jit::AtomicOperations::fetchOrSeqCst(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  return __atomic_fetch_or(addr, val, __ATOMIC_SEQ_CST);
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::fetchOrSeqCst(int64_t* addr,
                                                        int64_t val) {
  AddressGuard guard(addr);
  int64_t old = *addr;
  *addr = old | val;
  return old;
}

template <>
inline uint64_t js::jit::AtomicOperations::fetchOrSeqCst(uint64_t* addr,
                                                         uint64_t val) {
  AddressGuard guard(addr);
  uint64_t old = *addr;
  *addr = old | val;
  return old;
}

#endif
}
}  // namespace js

template <typename T>
inline T js::jit::AtomicOperations::fetchXorSeqCst(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  return __atomic_fetch_xor(addr, val, __ATOMIC_SEQ_CST);
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::fetchXorSeqCst(int64_t* addr,
                                                         int64_t val) {
  AddressGuard guard(addr);
  int64_t old = *addr;
  *addr = old ^ val;
  return old;
}

template <>
inline uint64_t js::jit::AtomicOperations::fetchXorSeqCst(uint64_t* addr,
                                                          uint64_t val) {
  AddressGuard guard(addr);
  uint64_t old = *addr;
  *addr = old ^ val;
  return old;
}

#endif
}
}  // namespace js

template <typename T>
inline T js::jit::AtomicOperations::loadSafeWhenRacy(T* addr) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  T v;
  __atomic_load(addr, &v, __ATOMIC_RELAXED);
  return v;
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::loadSafeWhenRacy(int64_t* addr) {
  return *addr;
}

template <>
inline uint64_t js::jit::AtomicOperations::loadSafeWhenRacy(uint64_t* addr) {
  return *addr;
}

#endif

template <>
inline uint8_clamped js::jit::AtomicOperations::loadSafeWhenRacy(
    uint8_clamped* addr) {
  uint8_t v;
  __atomic_load(&addr->val, &v, __ATOMIC_RELAXED);
  return uint8_clamped(v);
}

template <>
inline float js::jit::AtomicOperations::loadSafeWhenRacy(float* addr) {
  return *addr;
}

template <>
inline double js::jit::AtomicOperations::loadSafeWhenRacy(double* addr) {
  return *addr;
}
}
}  // namespace js

template <typename T>
inline void js::jit::AtomicOperations::storeSafeWhenRacy(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  __atomic_store(addr, &val, __ATOMIC_RELAXED);
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline void js::jit::AtomicOperations::storeSafeWhenRacy(int64_t* addr,
                                                         int64_t val) {
  *addr = val;
}

template <>
inline void js::jit::AtomicOperations::storeSafeWhenRacy(uint64_t* addr,
                                                         uint64_t val) {
  *addr = val;
}

#endif

template <>
inline void js::jit::AtomicOperations::storeSafeWhenRacy(uint8_clamped* addr,
                                                         uint8_clamped val) {
  __atomic_store(&addr->val, &val.val, __ATOMIC_RELAXED);
}

template <>
inline void js::jit::AtomicOperations::storeSafeWhenRacy(float* addr,
                                                         float val) {
  *addr = val;
}

template <>
inline void js::jit::AtomicOperations::storeSafeWhenRacy(double* addr,
                                                         double val) {
  *addr = val;
}
}
}  // namespace js

inline void js::jit::AtomicOperations::memcpySafeWhenRacy(void* dest,
                                                          const void* src,
                                                          size_t nbytes) {
  MOZ_ASSERT(!((char*)dest <= (char*)src && (char*)src < (char*)dest + nbytes));
  MOZ_ASSERT(!((char*)src <= (char*)dest && (char*)dest < (char*)src + nbytes));
  ::memcpy(dest, src, nbytes);
}

inline void js::jit::AtomicOperations::memmoveSafeWhenRacy(void* dest,
                                                           const void* src,
                                                           size_t nbytes) {
  ::memmove(dest, src, nbytes);
}

template <typename T>
inline T js::jit::AtomicOperations::exchangeSeqCst(T* addr, T val) {
  static_assert(sizeof(T) <= sizeof(void*),
                "atomics supported up to pointer size only");
  T v;
  __atomic_exchange(addr, &val, &v, __ATOMIC_SEQ_CST);
  return v;
}

namespace js {
namespace jit {

#if !defined(JS_64BIT)

template <>
inline int64_t js::jit::AtomicOperations::exchangeSeqCst(int64_t* addr,
                                                         int64_t val) {
  AddressGuard guard(addr);
  int64_t old = *addr;
  *addr = val;
  return old;
}

template <>
inline uint64_t js::jit::AtomicOperations::exchangeSeqCst(uint64_t* addr,
                                                          uint64_t val) {
  AddressGuard guard(addr);
  uint64_t old = *addr;
  *addr = val;
  return old;
}

#endif
}
}  // namespace js

#if !defined(JS_64BIT)

inline void js::jit::AddressLock::acquire() {
  uint32_t zero = 0;
  uint32_t one = 1;
  while (!__atomic_compare_exchange(&spinlock, &zero, &one, true,
                                    __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
    zero = 0;
  }
}

inline void js::jit::AddressLock::release() {
  uint32_t zero = 0;
  __atomic_store(&spinlock, &zero, __ATOMIC_SEQ_CST);
}

#endif

#endif  // jit_mips_shared_AtomicOperations_mips_shared_h