1 98014aa5 2003-10-03 devnull #include "u.h"
 2 98014aa5 2003-10-03 devnull #include "libc.h"
 3 98014aa5 2003-10-03 devnull 
 4 98014aa5 2003-10-03 devnull /*
 5 98014aa5 2003-10-03 devnull  * first argument (l) is in r3 at entry.
 6 98014aa5 2003-10-03 devnull  * r3 contains return value upon return.
 7 98014aa5 2003-10-03 devnull  */
 8 98014aa5 2003-10-03 devnull int
 9 912fba95 2003-11-24 devnull _tas(int *x)
10 98014aa5 2003-10-03 devnull {
11 98014aa5 2003-10-03 devnull 	int     v;
12 98014aa5 2003-10-03 devnull 	/*
13 98014aa5 2003-10-03 devnull 	 * this __asm__ works with gcc 2.95.2 (mac os x 10.1).
14 98014aa5 2003-10-03 devnull 	 * this assembly language destroys r0 (0), some other register (v),
15 98014aa5 2003-10-03 devnull 	 * r4 (x) and r5 (temp).
16 98014aa5 2003-10-03 devnull 	 */
17 98014aa5 2003-10-03 devnull 	__asm__("\n	sync\n"
18 98014aa5 2003-10-03 devnull 	"	li	r0,0\n"
19 98014aa5 2003-10-03 devnull 	"	mr	r4,%1		/* &l->val */\n"
20 98014aa5 2003-10-03 devnull 	"	lis	r5,0xdead	/* assemble constant 0xdeaddead */\n"
21 98014aa5 2003-10-03 devnull 	"	ori	r5,r5,0xdead	/* \" */\n"
22 98014aa5 2003-10-03 devnull 	"tas1:\n"
23 98014aa5 2003-10-03 devnull 	"	dcbf	r4,r0	/* cache flush; \"fix for 603x bug\" */\n"
24 98014aa5 2003-10-03 devnull 	"	lwarx	%0,r4,r0	/* v = l->val with reservation */\n"
25 98014aa5 2003-10-03 devnull 	"	cmp	cr0,0,%0,r0	/* v == 0 */\n"
26 98014aa5 2003-10-03 devnull 	"	bne	tas0\n"
27 98014aa5 2003-10-03 devnull 	"	stwcx.	r5,r4,r0   /* if (l->val same) l->val = 0xdeaddead */\n"
28 98014aa5 2003-10-03 devnull 	"	bne	tas1\n"
29 98014aa5 2003-10-03 devnull 	"tas0:\n"
30 98014aa5 2003-10-03 devnull 	"	sync\n"
31 98014aa5 2003-10-03 devnull 	"	isync\n"
32 98014aa5 2003-10-03 devnull 	: "=r" (v)
33 98014aa5 2003-10-03 devnull 	: "r"  (x)
34 98014aa5 2003-10-03 devnull 	: "cc", "memory", "r0", "r4", "r5"
35 98014aa5 2003-10-03 devnull 	);
36 98014aa5 2003-10-03 devnull 	switch(v) {
37 98014aa5 2003-10-03 devnull 	case 0:		return 0;
38 98014aa5 2003-10-03 devnull 	case 0xdeaddead: return 1;
39 912fba95 2003-11-24 devnull 	default:	fprint(2, "tas: corrupted 0x%lux\n", v);
40 98014aa5 2003-10-03 devnull 	}
41 98014aa5 2003-10-03 devnull 	return 0;
42 98014aa5 2003-10-03 devnull }