// Copyright (c) 2012 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.
//
// LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears.
#ifndef BASE_ATOMICOPS_INTERNALS_MIPS_GCC_H_
#define BASE_ATOMICOPS_INTERNALS_MIPS_GCC_H_
namespace base {
namespace subtle {
// Atomically execute:
// result = *ptr;
// if (*ptr == old_value)
// *ptr = new_value;
// return result;
//
// I.e., replace "*ptr" with "new_value" if "*ptr" used to be "old_value".
// Always return the old value of "*ptr"
//
// This routine implies no memory barriers.
inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
Atomic32 prev, tmp;
__asm__ __volatile__(".set push\n"
".set noreorder\n"
"1:\n"
"ll %0, %5\n" // prev = *ptr
"bne %0, %3, 2f\n" // if (prev != old_value) goto 2
"move %2, %4\n" // tmp = new_value
"sc %2, %1\n" // *ptr = tmp (with atomic check)
"beqz %2, 1b\n" // start again on atomic error
"nop\n" // delay slot nop
"2:\n"
".set pop\n"
: "=&r" (prev), "=m" (*ptr), "=&r" (tmp)
: "Ir" (old_value), "r" (new_value), "m" (*ptr)
: "memory");
return prev;
}
// Atomically store new_value into *ptr, returning the previous value held in
// *ptr. This routine implies no memory barriers.
inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
Atomic32 new_value) {
Atomic32 temp, old;
__asm__ __volatile__(".set push\n"
".set noreorder\n"
"1:\n"
"ll %1, %2\n" // old = *ptr
"move %0, %3\n" // temp = new_value
"sc %0, %2\n" // *ptr = temp (with atomic check)
"beqz %0, 1b\n" // start again on atomic error
"nop\n" // delay slot nop
".set pop\n"
: "=&r" (temp), "=&r" (old), "=m" (*ptr)
: "r" (new_value), "m" (*ptr)
: "memory");
return old;
}
// Atomically increment *ptr by "increment". Returns the new value of
// *ptr with the increment applied. This routine implies no memory barriers.
inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
Atomic32 increment) {
Atomic32 temp, temp2;
__asm__ __volatile__(".set push\n"
".set noreorder\n"
"1:\n"
"ll %0, %2\n" // temp = *ptr
"addu %1, %0, %3\n" // temp2 = temp + increment
"sc %1, %2\n" // *ptr = temp2 (with atomic check)
"beqz %1, 1b\n" // start again on atomic error
"addu %1, %0, %3\n" // temp2 = temp + increment
".set pop\n"
: "=&r" (temp), "=&r" (temp2), "=m" (*ptr)
: "Ir" (increment), "m" (*ptr)
: "memory");
// temp2 now holds the final value.
return temp2;
}
inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
Atomic32 increment) {
MemoryBarrier();
Atomic32 res = NoBarrier_AtomicIncrement(ptr, increment);
MemoryBarrier();
return res;
}
// "Acquire" operations
// ensure that no later memory access can be reordered ahead of the operation.
// "Release" operations ensure that no previous memory access can be reordered
// after the operation. "Barrier" operations have both "Acquire" and "Release"
// semantics. A MemoryBarrier() has "Barrier" semantics, but does no memory
// access.
inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
Atomic32 res = NoBarrier_CompareAndSwap(ptr, old_value, new_value);
MemoryBarrier();
return res;
}
inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
Atomic32 old_value,
Atomic32 new_value) {
MemoryBarrier();
return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
}
inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
*ptr = value;
}
inline void MemoryBarrier() {
__asm__ __volatile__("sync" : : : "memory");
}
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;
}
} // namespace base::subtle
} // namespace base
#endif // BASE_ATOMICOPS_INTERNALS_MIPS_GCC_H_