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1 /* | 1 /* |
2 * Copyright 2014 Google Inc. | 2 * Copyright 2014 Google Inc. |
3 * | 3 * |
4 * Use of this source code is governed by a BSD-style license that can be | 4 * Use of this source code is governed by a BSD-style license that can be |
5 * found in the LICENSE file. | 5 * found in the LICENSE file. |
6 */ | 6 */ |
7 | 7 |
8 #ifndef SkBarriers_arm_DEFINED | 8 #ifndef SkBarriers_arm_DEFINED |
9 #define SkBarriers_arm_DEFINED | 9 #define SkBarriers_arm_DEFINED |
10 | 10 |
11 static inline void sk_compiler_barrier() { asm volatile("" : : : "memory"); } | 11 static inline void sk_compiler_barrier() { asm volatile("" : : : "memory"); } |
12 | 12 |
13 template <typename T> | 13 template <typename T> |
14 T sk_acquire_load(T* ptr) { | 14 T sk_acquire_load(T* ptr) { |
15 T val = *ptr; | 15 T val = *ptr; |
16 __sync_synchronize(); // Issue a full barrier, which is an overkill acquire
barrier. | 16 __sync_synchronize(); // Issue a full barrier, which is an overkill acquire
barrier. |
17 return val; | 17 return val; |
18 } | 18 } |
19 | 19 |
20 template <typename T> | 20 template <typename T> |
| 21 T sk_consume_load(T* ptr) { |
| 22 T val = *ptr; |
| 23 // Unlike acquire, consume loads (data-dependent loads) are guaranteed not t
o reorder on ARM. |
| 24 // No memory barrier is needed, so we just use a compiler barrier. |
| 25 // C.f. http://preshing.com/20140709/the-purpose-of-memory_order_consume-in-
cpp11/ |
| 26 sk_compiler_barrier(); |
| 27 return val; |
| 28 } |
| 29 |
| 30 template <typename T> |
21 void sk_release_store(T* ptr, T val) { | 31 void sk_release_store(T* ptr, T val) { |
22 __sync_synchronize(); // Issue a full barrier, which is an overkill release
barrier. | 32 __sync_synchronize(); // Issue a full barrier, which is an overkill release
barrier. |
23 *ptr = val; | 33 *ptr = val; |
24 } | 34 } |
25 | 35 |
26 #endif//SkBarriers_x86_DEFINED | 36 #endif//SkBarriers_x86_DEFINED |
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