/*
 * @(#)sparc.gcc	11.4 (Sleepycat) 9/14/99
 *
 * The ldstub instruction takes the location specified by its first argument
 * (a register containing a memory address) and loads its contents into its
 * second argument (a register) and atomically sets the contents the location
 * specified by its first argument to a byte of 1s.  (The value in the second
 * argument is never read, but only overwritten.)
 *
 * The stbar is needed for v8, and is implemented as membar #sync on v9,
 + so is functional there as well.  For v7, stbar may generate an illegal
 + instruction and we have no way to tell what we're running on.  Some
 + operating systems notice and skip this instruction in the fault handler.
 *
 * For gcc/sparc, 0 is clear, 1 is set.
 */
#define	MUTEX_SET(tsl) ({						\
	register tsl_t *__l = (tsl);					\
	register tsl_t __r;						\
	__asm__ volatile						\
	    ("ldstub [%1],%0; stbar"					\
	    : "=r"( __r) : "r" (__l));					\
	!__r;								\
})

#define	MUTEX_UNSET(tsl)	(*(tsl) = 0)
#define	MUTEX_INIT(tsl)		MUTEX_UNSET(tsl)