Revert of Remove old/unused atomicops code

base/atomicops_internals_x86_gcc.h

+// Copyright (c) 2011 The Chromium 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 base/atomicops.h instead.
+
+#ifndef BASE_ATOMICOPS_INTERNALS_X86_GCC_H_
+#define BASE_ATOMICOPS_INTERNALS_X86_GCC_H_
+
+#define ATOMICOPS_COMPILER_BARRIER() __asm__ __volatile__("" : : : "memory")
+
+namespace base {
+namespace subtle {
+
+// 32-bit low-level operations on any platform.
+
+inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
+                                         Atomic32 old_value,
+                                         Atomic32 new_value) {
+  Atomic32 prev;
+  __asm__ __volatile__("lock; cmpxchgl %1,%2"
+                       : "=a" (prev)
+                       : "q" (new_value), "m" (*ptr), "0" (old_value)
+                       : "memory");
+  return prev;
+}
+
+inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
+                                         Atomic32 new_value) {
+  __asm__ __volatile__("xchgl %1,%0"  // The lock prefix is implicit for xchg.
+                       : "=r" (new_value)
+                       : "m" (*ptr), "0" (new_value)
+                       : "memory");
+  return new_value;  // Now it's the previous value.
+}
+
+inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
+                                          Atomic32 increment) {
+  Atomic32 temp = increment;
+  __asm__ __volatile__("lock; xaddl %0,%1"
+                       : "+r" (temp), "+m" (*ptr)
+                       : : "memory");
+  // temp now holds the old value of *ptr
+  return temp + increment;
+}
+
+inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
+                                        Atomic32 increment) {
+  Atomic32 temp = increment;
+  __asm__ __volatile__("lock; xaddl %0,%1"
+                       : "+r" (temp), "+m" (*ptr)
+                       : : "memory");
+  // temp now holds the old value of *ptr
+  if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
+    __asm__ __volatile__("lfence" : : : "memory");
+  }
+  return temp + increment;
+}
+
+inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
+                                       Atomic32 old_value,
+                                       Atomic32 new_value) {
+  Atomic32 x = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+  if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
+    __asm__ __volatile__("lfence" : : : "memory");
+  }
+  return x;
+}
+
+inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
+                                       Atomic32 old_value,
+                                       Atomic32 new_value) {
+  return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+}
+
+inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
+  *ptr = value;
+}
+
+inline void MemoryBarrier() {
+  __asm__ __volatile__("mfence" : : : "memory");
+}
+
+inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
+  *ptr = value;
+  MemoryBarrier();
+}
+
+inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
+  ATOMICOPS_COMPILER_BARRIER();
+  *ptr = value; // An x86 store acts as a release barrier.
+  // See comments in Atomic64 version of Release_Store(), below.
+}
+
+inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
+  return *ptr;
+}
+
+inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
+  Atomic32 value = *ptr; // An x86 load acts as a acquire barrier.
+  // See comments in Atomic64 version of Release_Store(), below.
+  ATOMICOPS_COMPILER_BARRIER();
+  return value;
+}
+
+inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
+  MemoryBarrier();
+  return *ptr;
+}
+
+#if defined(__x86_64__)
+
+// 64-bit low-level operations on 64-bit platform.
+
+inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
+                                         Atomic64 old_value,
+                                         Atomic64 new_value) {
+  Atomic64 prev;
+  __asm__ __volatile__("lock; cmpxchgq %1,%2"
+                       : "=a" (prev)
+                       : "q" (new_value), "m" (*ptr), "0" (old_value)
+                       : "memory");
+  return prev;
+}
+
+inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
+                                         Atomic64 new_value) {
+  __asm__ __volatile__("xchgq %1,%0"  // The lock prefix is implicit for xchg.
+                       : "=r" (new_value)
+                       : "m" (*ptr), "0" (new_value)
+                       : "memory");
+  return new_value;  // Now it's the previous value.
+}
+
+inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
+                                          Atomic64 increment) {
+  Atomic64 temp = increment;
+  __asm__ __volatile__("lock; xaddq %0,%1"
+                       : "+r" (temp), "+m" (*ptr)
+                       : : "memory");
+  // temp now contains the previous value of *ptr
+  return temp + increment;
+}
+
+inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
+                                        Atomic64 increment) {
+  Atomic64 temp = increment;
+  __asm__ __volatile__("lock; xaddq %0,%1"
+                       : "+r" (temp), "+m" (*ptr)
+                       : : "memory");
+  // temp now contains the previous value of *ptr
+  if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
+    __asm__ __volatile__("lfence" : : : "memory");
+  }
+  return temp + increment;
+}
+
+inline void NoBarrier_Store(volatile Atomic64* ptr, Atomic64 value) {
+  *ptr = value;
+}
+
+inline void Acquire_Store(volatile Atomic64* ptr, Atomic64 value) {
+  *ptr = value;
+  MemoryBarrier();
+}
+
+inline void Release_Store(volatile Atomic64* ptr, Atomic64 value) {
+  ATOMICOPS_COMPILER_BARRIER();
+
+  *ptr = value; // An x86 store acts as a release barrier
+                // for current AMD/Intel chips as of Jan 2008.
+                // See also Acquire_Load(), below.
+
+  // When new chips come out, check:
+  //  IA-32 Intel Architecture Software Developer's Manual, Volume 3:
+  //  System Programming Guide, Chatper 7: Multiple-processor management,
+  //  Section 7.2, Memory Ordering.
+  // Last seen at:
+  //   http://developer.intel.com/design/pentium4/manuals/index_new.htm
+  //
+  // x86 stores/loads fail to act as barriers for a few instructions (clflush
+  // maskmovdqu maskmovq movntdq movnti movntpd movntps movntq) but these are
+  // not generated by the compiler, and are rare.  Users of these instructions
+  // need to know about cache behaviour in any case since all of these involve
+  // either flushing cache lines or non-temporal cache hints.
+}
+
+inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
+  return *ptr;
+}
+
+inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
+  Atomic64 value = *ptr; // An x86 load acts as a acquire barrier,
+                         // for current AMD/Intel chips as of Jan 2008.
+                         // See also Release_Store(), above.
+  ATOMICOPS_COMPILER_BARRIER();
+  return value;
+}
+
+inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
+  MemoryBarrier();
+  return *ptr;
+}
+
+inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
+                                       Atomic64 old_value,
+                                       Atomic64 new_value) {
+  Atomic64 x = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+  if (AtomicOps_Internalx86CPUFeatures.has_amd_lock_mb_bug) {
+    __asm__ __volatile__("lfence" : : : "memory");
+  }
+  return x;
+}
+
+inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
+                                       Atomic64 old_value,
+                                       Atomic64 new_value) {
+  return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
+}
+
+#endif  // defined(__x86_64__)
+
+}  // namespace subtle
+}  // namespace base
+
+#undef ATOMICOPS_COMPILER_BARRIER
+
+#endif  // BASE_ATOMICOPS_INTERNALS_X86_GCC_H_