code: purgatorio

ref: f4624471579e0cfb531ffc733cdbe007ecdfed9d
dir: /lib9/lock-Irix-mips.s/

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#include <sys/regdef.h>
#include <sys/asm.h>

/*
 * lock from r4000 book
 */
LEAF(canlock)
	.set 	noreorder
1:
	ll	t0,0(a0)		/* a0 is argument */
	or	t1, t0, 1
	sc	t1,0(a0)
	beq	t1,zero,1b	
	nop
	j	$31			/* lock held */
	xor	v0, t0, 1

	.set 	reorder
	END(canlock)