Update implementation of atomics with latest Chromium version but use compiler builtin atomics

src/base/atomicops_internals_mips_gcc.h

-// Copyright 2010 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// This file is an internal atomic implementation, use atomicops.h instead.
-
-#ifndef V8_BASE_ATOMICOPS_INTERNALS_MIPS_GCC_H_
-#define V8_BASE_ATOMICOPS_INTERNALS_MIPS_GCC_H_
-
-namespace v8 {
-namespace base {
-
-// Atomically execute:
-//      result = *ptr;
-//      if (*ptr == old_value)
-//        *ptr = new_value;
-//      return result;
-//
-// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value".
-// Always return the old value of "*ptr"
-//
-// This routine implies no memory barriers.
-inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
-                                         Atomic32 old_value,
-                                         Atomic32 new_value) {
-  Atomic32 prev, tmp;
-  __asm__ __volatile__(".set push\n"
-                       ".set noreorder\n"
-                       "1:\n"
-                       "ll %0, 0(%4)\n"  // prev = *ptr
-                       "bne %0, %2, 2f\n"  // if (prev != old_value) goto 2
-                       "move %1, %3\n"  // tmp = new_value
-                       "sc %1, 0(%4)\n"  // *ptr = tmp (with atomic check)
-                       "beqz %1, 1b\n"  // start again on atomic error
-                       "nop\n"  // delay slot nop
-                       "2:\n"
-                       ".set pop\n"
-                       : "=&r" (prev), "=&r" (tmp)
-                       : "r" (old_value), "r" (new_value), "r" (ptr)
-                       : "memory");
-  return prev;
-}
-
-// Atomically store new_value into *ptr, returning the previous value held in
-// *ptr.  This routine implies no memory barriers.
-inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
-                                         Atomic32 new_value) {
-  Atomic32 temp, old;
-  __asm__ __volatile__(".set push\n"
-                       ".set noreorder\n"
-                       ".set at\n"
-                       "1:\n"
-                       "ll %1, 0(%3)\n"  // old = *ptr
-                       "move %0, %2\n"  // temp = new_value
-                       "sc %0, 0(%3)\n"  // *ptr = temp (with atomic check)
-                       "beqz %0, 1b\n"  // start again on atomic error
-                       "nop\n"  // delay slot nop
-                       ".set pop\n"
-                       : "=&r" (temp), "=&r" (old)
-                       : "r" (new_value), "r" (ptr)
-                       : "memory");
-
-  return old;
-}
-
-// Atomically increment *ptr by "increment".  Returns the new value of
-// *ptr with the increment applied.  This routine implies no memory barriers.
-inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
-                                          Atomic32 increment) {
-  Atomic32 temp, temp2;
-
-  __asm__ __volatile__(".set push\n"
-                       ".set noreorder\n"
-                       "1:\n"
-                       "ll %0, 0(%3)\n"  // temp = *ptr
-                       "addu %1, %0, %2\n"  // temp2 = temp + increment
-                       "sc %1, 0(%3)\n"  // *ptr = temp2 (with atomic check)
-                       "beqz %1, 1b\n"  // start again on atomic error
-                       "addu %1, %0, %2\n"  // temp2 = temp + increment
-                       ".set pop\n"
-                       : "=&r" (temp), "=&r" (temp2)
-                       : "Ir" (increment), "r" (ptr)
-                       : "memory");
-  // temp2 now holds the final value.
-  return temp2;
-}
-
-inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
-                                        Atomic32 increment) {
-  MemoryBarrier();
-  Atomic32 res = NoBarrier_AtomicIncrement(ptr, increment);
-  MemoryBarrier();
-  return res;
-}
-
-// "Acquire" operations
-// ensure that no later memory access can be reordered ahead of the operation.
-// "Release" operations ensure that no previous memory access can be reordered
-// after the operation.  "Barrier" operations have both "Acquire" and "Release"
-// semantics.   A MemoryBarrier() has "Barrier" semantics, but does no memory
-// access.
-inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
-                                       Atomic32 old_value,
-                                       Atomic32 new_value) {
-  Atomic32 res = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
-  MemoryBarrier();
-  return res;
-}
-
-inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
-                                       Atomic32 old_value,
-                                       Atomic32 new_value) {
-  MemoryBarrier();
-  return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
-}
-
-inline void NoBarrier_Store(volatile Atomic8* ptr, Atomic8 value) {
-  *ptr = value;
-}
-
-inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
-  *ptr = value;
-}
-
-inline void MemoryBarrier() {
-  __asm__ __volatile__("sync" : : : "memory");
-}
-
-inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
-  *ptr = value;
-  MemoryBarrier();
-}
-
-inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
-  MemoryBarrier();
-  *ptr = value;
-}
-
-inline Atomic8 NoBarrier_Load(volatile const Atomic8* ptr) {
-  return *ptr;
-}
-
-inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
-  return *ptr;
-}
-
-inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
-  Atomic32 value = *ptr;
-  MemoryBarrier();
-  return value;
-}
-
-inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
-  MemoryBarrier();
-  return *ptr;
-}
-
-}  // namespace base
-}  // namespace v8
-
-#endif  // V8_BASE_ATOMICOPS_INTERNALS_MIPS_GCC_H_