locks.h

gcc的组建

// locks.h - Thread synchronization primitives. Sparc implementation.

/* Copyright (C) 2002  Free Software Foundation

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */

#ifndef __SYSDEP_LOCKS_H__
#define __SYSDEP_LOCKS_H__

typedef size_t obj_addr_t;	/* Integer type big enough for object	*/
				/* address.				*/

#ifdef __arch64__
/* Sparc64 implementation, use cas instruction.  */
inline static bool
compare_and_swap(volatile obj_addr_t *addr,
		 obj_addr_t old,
		 obj_addr_t new_val)
{
  __asm__ __volatile__("casx [%2], %3, %0\n\t"
		       "membar #StoreLoad | #StoreStore"
		       : "=&r" (new_val)
		       : "0" (new_val), "r" (addr), "r" (old)
		       : "memory");

  return (new_val == old) ? true : false;
}

inline static void
release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
{
  __asm__ __volatile__("membar #StoreStore | #LoadStore" : : : "memory");
  *(addr) = new_val;
}

inline static bool
compare_and_swap_release(volatile obj_addr_t *addr,
		  				     obj_addr_t old,
						     obj_addr_t new_val)
{
  return compare_and_swap(addr, old, new_val);
}
#else
/* Sparc32 implementation, use a spinlock.  */
static unsigned char __cas_lock = 0;

inline static void
__cas_start_atomic(void)
{
  unsigned int tmp;
  __asm__ __volatile__(
"1:	ldstub	[%1], %0\n"
"	orcc	%0, 0x0, %%g0\n"
"	be	3f\n"
"	 nop\n"
"2:	ldub	[%1], %0\n"
"	orcc	%0, 0x0, %%g0\n"
"	bne	2b\n"
"	 nop\n"
"3:"	: "=&r" (tmp)
	: "r" (&__cas_lock)
	: "memory", "cc");
}

inline static void
__cas_end_atomic(void)
{
  __asm__ __volatile__(
  "stb %%g0, [%0]"
  : /* no outputs */
  : "r" (&__cas_lock)
  : "memory");
}

inline static bool
compare_and_swap(volatile obj_addr_t *addr,
		 obj_addr_t old,
		 obj_addr_t new_val)
{
  bool ret;

  __cas_start_atomic ();
  if (*addr != old)
    {
      ret = false;
    }
  else
    {
      *addr = new_val;
      ret = true;
    }
  __cas_end_atomic ();

  return ret;
}

inline static void
release_set(volatile obj_addr_t *addr, obj_addr_t new_val)
{
  /* Technically stbar would be needed here but no sparc32
     system actually requires it.  Also the stbar would mean
     this code would not work on sparcv7 chips.  */
  __asm__ __volatile__("" : : : "memory");
  *(addr) = new_val;
}

inline static bool
compare_and_swap_release(volatile obj_addr_t *addr,
		  				     obj_addr_t old,
						     obj_addr_t new_val)
{
  return compare_and_swap(addr, old, new_val);
}
#endif /* __arch64__ */

#endif /* ! __SYSDEP_LOCKS_H__ */