kasperl@chromium.org | a555126 | 2010-12-07 12:49:48 +0000 | [diff] [blame] | 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 | |
| 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 | |
| 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 | |
| 78 | inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr, |
| 79 | Atomic32 increment) { |
| 80 | return Barrier_AtomicIncrement(ptr, increment); |
| 81 | } |
| 82 | |
| 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 | |
| 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 | |
| 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 | |
| 110 | inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) { |
| 111 | *ptr = value; |
| 112 | } |
| 113 | |
| 114 | inline void MemoryBarrier() { |
| 115 | pLinuxKernelMemoryBarrier(); |
| 116 | } |
| 117 | |
| 118 | inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) { |
| 119 | *ptr = value; |
| 120 | MemoryBarrier(); |
| 121 | } |
| 122 | |
| 123 | inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) { |
| 124 | MemoryBarrier(); |
| 125 | *ptr = value; |
| 126 | } |
| 127 | |
| 128 | inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) { |
| 129 | return *ptr; |
| 130 | } |
| 131 | |
| 132 | inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) { |
| 133 | Atomic32 value = *ptr; |
| 134 | MemoryBarrier(); |
| 135 | return value; |
| 136 | } |
| 137 | |
| 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_ |