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#include <stdint.h>
#include <pthread.h>
static int32_t *low_32_bits(int64_t *ptr)
{
int32_t *low= (int32_t*)ptr;
// Test if the machine is big endian - constant propagation at compile time
// should eliminate this completely.
int one = 1;
if (*(char*)&one != 1)
{
low++;
}
return low;
}
extern "C" int __cxa_guard_acquire(int64_t *guard_object)
{
char first_byte = (*guard_object) >> 56;
if (1 == first_byte) { return 0; }
int32_t *lock = low_32_bits(guard_object);
while (!__sync_bool_compare_and_swap_4(lock, 0, 1))
{
// TODO: Use some of the remaining 24 bits to define a mutex to sleep
// on. Whether this is actually worth bothering with depends on
// whether there is likely to be any contention.
sched_yield();
}
return 1;
}
extern "C" void __cxa_guard_abort(int64_t *guard_object)
{
int32_t *lock = low_32_bits(guard_object);
*lock = 0;
}
extern "C" void __cxa_guard_release(int64_t *guard_object)
{
// Set the first byte to 1
*guard_object |= ((int64_t)1) << 57;
__cxa_guard_abort(guard_object);
}
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