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atomicops_internals_arm_gcc.h
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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.
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 
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 
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 
79  Atomic32 increment) {
80  return Barrier_AtomicIncrement(ptr, increment);
81 }
82 
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 
99  Atomic32 old_value,
100  Atomic32 new_value) {
101  return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
102 }
103 
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_
void Acquire_Store(volatile Atomic32 *ptr, Atomic32 value)
void(* LinuxKernelMemoryBarrierFunc)(void)
Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32 *ptr, Atomic32 old_value, Atomic32 new_value)
Atomic32 Release_CompareAndSwap(volatile Atomic32 *ptr, Atomic32 old_value, Atomic32 new_value)
LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak))
Atomic32(* LinuxKernelCmpxchgFunc)(Atomic32 old_value, Atomic32 new_value, volatile Atomic32 *ptr)
void NoBarrier_Store(volatile Atomic32 *ptr, Atomic32 value)
Atomic32 NoBarrier_AtomicExchange(volatile Atomic32 *ptr, Atomic32 new_value)
Atomic32 Release_Load(volatile const Atomic32 *ptr)
Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32 *ptr, Atomic32 increment)
void Release_Store(volatile Atomic32 *ptr, Atomic32 value)
Atomic32 Barrier_AtomicIncrement(volatile Atomic32 *ptr, Atomic32 increment)
Atomic32 NoBarrier_Load(volatile const Atomic32 *ptr)
Atomic32 Acquire_Load(volatile const Atomic32 *ptr)
int32_t Atomic32
Definition: atomicops.h:57
Atomic32 Acquire_CompareAndSwap(volatile Atomic32 *ptr, Atomic32 old_value, Atomic32 new_value)