1 // Copyright 2010 the V8 project authors. All rights reserved.
2 // Redistribution and use in source and binary forms, with or without
3 // modification, are permitted provided that the following conditions are
4 // met:
5 //
6 // * Redistributions of source code must retain the above copyright
7 // notice, this list of conditions and the following disclaimer.
8 // * Redistributions in binary form must reproduce the above
9 // copyright notice, this list of conditions and the following
10 // disclaimer in the documentation and/or other materials provided
11 // with the distribution.
12 // * Neither the name of Google Inc. nor the names of its
13 // contributors may be used to endorse or promote products derived
14 // from this software without specific prior written permission.
15 //
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
28 // This file is an internal atomic implementation, use atomicops.h instead.
29 //
30 // LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears.
31
32 #ifndef V8_ATOMICOPS_INTERNALS_ARM_GCC_H_
33 #define V8_ATOMICOPS_INTERNALS_ARM_GCC_H_
34
35 namespace v8 {
36 namespace internal {
37
38 // 0xffff0fc0 is the hard coded address of a function provided by
39 // the kernel which implements an atomic compare-exchange. On older
40 // ARM architecture revisions (pre-v6) this may be implemented using
41 // a syscall. This address is stable, and in active use (hard coded)
42 // by at least glibc-2.7 and the Android C library.
43 typedef Atomic32 (*LinuxKernelCmpxchgFunc)(Atomic32 old_value,
44 Atomic32 new_value,
45 volatile Atomic32* ptr);
46 LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak)) =
47 (LinuxKernelCmpxchgFunc) 0xffff0fc0;
48
49 typedef void (*LinuxKernelMemoryBarrierFunc)(void);
50 LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
51 (LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
52
53
NoBarrier_CompareAndSwap(volatile Atomic32 * ptr,Atomic32 old_value,Atomic32 new_value)54 inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
55 Atomic32 old_value,
56 Atomic32 new_value) {
57 Atomic32 prev_value = *ptr;
58 do {
59 if (!pLinuxKernelCmpxchg(old_value, new_value,
60 const_cast<Atomic32*>(ptr))) {
61 return old_value;
62 }
63 prev_value = *ptr;
64 } while (prev_value == old_value);
65 return prev_value;
66 }
67
NoBarrier_AtomicExchange(volatile Atomic32 * ptr,Atomic32 new_value)68 inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
69 Atomic32 new_value) {
70 Atomic32 old_value;
71 do {
72 old_value = *ptr;
73 } while (pLinuxKernelCmpxchg(old_value, new_value,
74 const_cast<Atomic32*>(ptr)));
75 return old_value;
76 }
77
NoBarrier_AtomicIncrement(volatile Atomic32 * ptr,Atomic32 increment)78 inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
79 Atomic32 increment) {
80 return Barrier_AtomicIncrement(ptr, increment);
81 }
82
Barrier_AtomicIncrement(volatile Atomic32 * ptr,Atomic32 increment)83 inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
84 Atomic32 increment) {
85 for (;;) {
86 // Atomic exchange the old value with an incremented one.
87 Atomic32 old_value = *ptr;
88 Atomic32 new_value = old_value + increment;
89 if (pLinuxKernelCmpxchg(old_value, new_value,
90 const_cast<Atomic32*>(ptr)) == 0) {
91 // The exchange took place as expected.
92 return new_value;
93 }
94 // Otherwise, *ptr changed mid-loop and we need to retry.
95 }
96 }
97
Acquire_CompareAndSwap(volatile Atomic32 * ptr,Atomic32 old_value,Atomic32 new_value)98 inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
99 Atomic32 old_value,
100 Atomic32 new_value) {
101 return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
102 }
103
Release_CompareAndSwap(volatile Atomic32 * ptr,Atomic32 old_value,Atomic32 new_value)104 inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
105 Atomic32 old_value,
106 Atomic32 new_value) {
107 return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
108 }
109
NoBarrier_Store(volatile Atomic32 * ptr,Atomic32 value)110 inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
111 *ptr = value;
112 }
113
MemoryBarrier()114 inline void MemoryBarrier() {
115 pLinuxKernelMemoryBarrier();
116 }
117
Acquire_Store(volatile Atomic32 * ptr,Atomic32 value)118 inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
119 *ptr = value;
120 MemoryBarrier();
121 }
122
Release_Store(volatile Atomic32 * ptr,Atomic32 value)123 inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
124 MemoryBarrier();
125 *ptr = value;
126 }
127
NoBarrier_Load(volatile const Atomic32 * ptr)128 inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
129 return *ptr;
130 }
131
Acquire_Load(volatile const Atomic32 * ptr)132 inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
133 Atomic32 value = *ptr;
134 MemoryBarrier();
135 return value;
136 }
137
Release_Load(volatile const Atomic32 * ptr)138 inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
139 MemoryBarrier();
140 return *ptr;
141 }
142
143 } } // namespace v8::internal
144
145 #endif // V8_ATOMICOPS_INTERNALS_ARM_GCC_H_
146