Add Arm64 atomicops to base.

base/atomicops_internals_arm64_gcc.h

+// Copyright 2014 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_ARM64_GCC_H_
+#define BASE_ATOMICOPS_INTERNALS_ARM64_GCC_H_
+
+#if defined(OS_QNX)
+#include <sys/cpuinline.h>
+#endif
+
+namespace base {
+namespace subtle {
+
+inline void MemoryBarrier() {
+  __asm__ __volatile__ (  // NOLINT
+    "dmb ish                                  \n\t"  // Data memory barrier.
+    ::: "memory"
+  );  // NOLINT
+}
+
+
+inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
+                                         Atomic32 old_value,
+                                         Atomic32 new_value) {
+  Atomic32 prev;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %w[prev], [%[ptr]]               \n\t"  // Load the previous value.
+    "cmp %w[prev], %w[old_value]           \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %w[new_value], [%[ptr]]\n\t"  // Try to store the new value.
+    "cbnz %w[temp], 0b                     \n\t"  // Retry if it did not work.
+    "1:                                    \n\t"
+    "clrex                                 \n\t"  // In case we didn't swap.
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),

[JF, 2014/03/20 21:55:50]

Shouldn't ptr always be "m"?

[rmcilroy, 2014/03/21 15:27:20]

I'm not entirely sure on this (I'm not very knowledgeable on gcc asm semantics).
 It doesn't seem to be "m" on atomicops_internal_arm_gcc.h from what I can tell
(there does seem to be an "+m"(*ptr), but that seems unused to me).

This is what is currently in V8.  Rodolph: do you have any advice on "r" vs "m"
here?

[JF, 2014/03/21 17:57:38]

I looked into this and checked with Roland McGrath, "+m" would be correct if an
immediate displacement were allowed, but for these instructions it isn't so "+Q"
is actually the right choice.

It should therefore be:

"ldxr %w[prev], %[ptr]" // Note the brackets are gone.
...
: // ...
: [ptr]"+Q" (*ptr), // Note the dereference.
...

[rmcilroy, 2014/03/24 15:19:25]

Done.

+      [old_value]"r" (old_value),
+      [new_value]"r" (new_value)
+    : "memory", "cc"
+  );  // NOLINT
+
+  return prev;
+}
+
+inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
+                                         Atomic32 new_value) {
+  Atomic32 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %w[result], [%[ptr]]             \n\t"  // Load the previous value.
+    "stxr %w[temp], %w[new_value], [%[ptr]]\n\t"  // Try to store the new value.
+    "cbnz %w[temp], 0b                     \n\t"  // Retry if it did not work.
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [new_value]"r" (new_value)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
+                                          Atomic32 increment) {
+  Atomic32 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                       \n\t"
+    "ldxr %w[result], [%[ptr]]                \n\t"  // Load the previous value.
+    "add %w[result], %w[result], %w[increment]\n\t"
+    "stxr %w[temp], %w[result], [%[ptr]]      \n\t"  // Try to store the result.
+    "cbnz %w[temp], 0b                        \n\t"  // Retry on failure.
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [increment]"r" (increment)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
+                                        Atomic32 increment) {
+  MemoryBarrier();
+  Atomic32 result = NoBarrier_AtomicIncrement(ptr, increment);
+  MemoryBarrier();
+
+  return result;
+}
+
+inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
+                                       Atomic32 old_value,
+                                       Atomic32 new_value) {
+  Atomic32 prev;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %w[prev], [%[ptr]]               \n\t"  // Load the previous value.
+    "cmp %w[prev], %w[old_value]           \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %w[new_value], [%[ptr]]\n\t"  // Try to store the new value.
+    "cbnz %w[temp], 0b                     \n\t"  // Retry if it did not work.
+    "dmb ish                               \n\t"  // Data memory barrier.
+    "1:                                    \n\t"
+    // If the compare failed the 'dmb' is unnecessary, but we still need a
+    // 'clrex'.
+    "clrex                                 \n\t"
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [old_value]"r" (old_value),
+      [new_value]"r" (new_value)
+    : "memory", "cc"
+  );  // NOLINT
+
+  return prev;
+}
+
+inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
+                                       Atomic32 old_value,
+                                       Atomic32 new_value) {
+  Atomic32 prev;
+  int32_t temp;
+
+  MemoryBarrier();
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %w[prev], [%[ptr]]               \n\t"  // Load the previous value.
+    "cmp %w[prev], %w[old_value]           \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %w[new_value], [%[ptr]]\n\t"  // Try to store the new value.
+    "cbnz %w[temp], 0b                     \n\t"  // Retry if it did not work.
+    "1:                                    \n\t"
+    // If the compare failed the we still need a 'clrex'.
+    "clrex                                 \n\t"
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [old_value]"r" (old_value),
+      [new_value]"r" (new_value)
+    : "memory", "cc"
+  );  // NOLINT
+
+  return prev;
+}
+
+inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
+  *ptr = value;
+}
+
+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 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;
+}
+
+// 64-bit versions of the operations.
+// See the 32-bit versions for comments.
+
+inline Atomic64 NoBarrier_CompareAndSwap(volatile Atomic64* ptr,
+                                         Atomic64 old_value,
+                                         Atomic64 new_value) {
+  Atomic64 prev;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %[prev], [%[ptr]]                \n\t"
+    "cmp %[prev], %[old_value]             \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %[new_value], [%[ptr]] \n\t"
+    "cbnz %w[temp], 0b                     \n\t"
+    "1:                                    \n\t"
+    "clrex                                 \n\t"
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [old_value]"r" (old_value),
+      [new_value]"r" (new_value)
+    : "memory", "cc"
+  );  // NOLINT
+
+  return prev;
+}
+
+inline Atomic64 NoBarrier_AtomicExchange(volatile Atomic64* ptr,
+                                         Atomic64 new_value) {
+  Atomic64 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %[result], [%[ptr]]              \n\t"
+    "stxr %w[temp], %[new_value], [%[ptr]] \n\t"
+    "cbnz %w[temp], 0b                     \n\t"
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [new_value]"r" (new_value)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic64 NoBarrier_AtomicIncrement(volatile Atomic64* ptr,
+                                          Atomic64 increment) {
+  Atomic64 result;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                     \n\t"
+    "ldxr %[result], [%[ptr]]               \n\t"
+    "add %[result], %[result], %[increment] \n\t"
+    "stxr %w[temp], %[result], [%[ptr]]     \n\t"
+    "cbnz %w[temp], 0b                      \n\t"
+    : [result]"=&r" (result),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [increment]"r" (increment)
+    : "memory"
+  );  // NOLINT
+
+  return result;
+}
+
+inline Atomic64 Barrier_AtomicIncrement(volatile Atomic64* ptr,
+                                        Atomic64 increment) {
+  MemoryBarrier();
+  Atomic64 result = NoBarrier_AtomicIncrement(ptr, increment);
+  MemoryBarrier();
+
+  return result;
+}
+
+inline Atomic64 Acquire_CompareAndSwap(volatile Atomic64* ptr,
+                                       Atomic64 old_value,
+                                       Atomic64 new_value) {
+  Atomic64 prev;
+  int32_t temp;
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %[prev], [%[ptr]]                \n\t"
+    "cmp %[prev], %[old_value]             \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %[new_value], [%[ptr]] \n\t"
+    "cbnz %w[temp], 0b                     \n\t"
+    "dmb ish                               \n\t"
+    "1:                                    \n\t"
+    "clrex                                 \n\t"
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [old_value]"r" (old_value),
+      [new_value]"r" (new_value)
+    : "memory", "cc"
+  );  // NOLINT
+
+  return prev;
+}
+
+inline Atomic64 Release_CompareAndSwap(volatile Atomic64* ptr,
+                                       Atomic64 old_value,
+                                       Atomic64 new_value) {
+  Atomic64 prev;
+  int32_t temp;
+
+  MemoryBarrier();
+
+  __asm__ __volatile__ (  // NOLINT
+    "0:                                    \n\t"
+    "ldxr %[prev], [%[ptr]]                \n\t"
+    "cmp %[prev], %[old_value]             \n\t"
+    "bne 1f                                \n\t"
+    "stxr %w[temp], %[new_value], [%[ptr]] \n\t"
+    "cbnz %w[temp], 0b                     \n\t"
+    "1:                                    \n\t"
+    "clrex                                 \n\t"
+    : [prev]"=&r" (prev),
+      [temp]"=&r" (temp)
+    : [ptr]"r" (ptr),
+      [old_value]"r" (old_value),
+      [new_value]"r" (new_value)
+    : "memory", "cc"
+  );  // NOLINT
+
+  return prev;
+}
+
+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) {
+  MemoryBarrier();
+  *ptr = value;
+}
+
+inline Atomic64 NoBarrier_Load(volatile const Atomic64* ptr) {
+  return *ptr;
+}
+
+inline Atomic64 Acquire_Load(volatile const Atomic64* ptr) {
+  Atomic64 value = *ptr;
+  MemoryBarrier();
+  return value;
+}
+
+inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
+  MemoryBarrier();
+  return *ptr;
+}
+
+}  // namespace base::subtle
+}  // namespace base
+
+#endif  // BASE_ATOMICOPS_INTERNALS_ARM64_GCC_H_