xref: /plan9/sys/src/cmd/unix/drawterm/posix-power/tas.c (revision 8ccd4a6360d974db7bd7bbd4f37e7018419ea908)
1*8ccd4a63SDavid du Colombier #include "u.h"
2*8ccd4a63SDavid du Colombier #include "libc.h"
3*8ccd4a63SDavid du Colombier 
4*8ccd4a63SDavid du Colombier /*
5*8ccd4a63SDavid du Colombier  * first argument (l) is in r3 at entry.
6*8ccd4a63SDavid du Colombier  * r3 contains return value upon return.
7*8ccd4a63SDavid du Colombier  */
8*8ccd4a63SDavid du Colombier int
tas(long * x)9*8ccd4a63SDavid du Colombier tas(long *x)
10*8ccd4a63SDavid du Colombier {
11*8ccd4a63SDavid du Colombier 	int     v;
12*8ccd4a63SDavid du Colombier 	/*
13*8ccd4a63SDavid du Colombier 	 * this __asm__ works with gcc 2.95.2 (mac os x 10.1).
14*8ccd4a63SDavid du Colombier 	 * this assembly language destroys r0 (0), some other register (v),
15*8ccd4a63SDavid du Colombier 	 * r4 (x) and r5 (temp).
16*8ccd4a63SDavid du Colombier 	 */
17*8ccd4a63SDavid du Colombier 	__asm__("\n	sync\n"
18*8ccd4a63SDavid du Colombier 	"	li	r0,0\n"
19*8ccd4a63SDavid du Colombier 	"	mr	r4,%1		/* &l->val */\n"
20*8ccd4a63SDavid du Colombier 	"	lis	r5,0xdead	/* assemble constant 0xdeaddead */\n"
21*8ccd4a63SDavid du Colombier 	"	ori	r5,r5,0xdead	/* \" */\n"
22*8ccd4a63SDavid du Colombier 	"tas1:\n"
23*8ccd4a63SDavid du Colombier 	"	dcbf	r4,r0	/* cache flush; \"fix for 603x bug\" */\n"
24*8ccd4a63SDavid du Colombier 	"	lwarx	%0,r4,r0	/* v = l->val with reservation */\n"
25*8ccd4a63SDavid du Colombier 	"	cmp	cr0,0,%0,r0	/* v == 0 */\n"
26*8ccd4a63SDavid du Colombier 	"	bne	tas0\n"
27*8ccd4a63SDavid du Colombier 	"	stwcx.	r5,r4,r0   /* if (l->val same) l->val = 0xdeaddead */\n"
28*8ccd4a63SDavid du Colombier 	"	bne	tas1\n"
29*8ccd4a63SDavid du Colombier 	"tas0:\n"
30*8ccd4a63SDavid du Colombier 	"	sync\n"
31*8ccd4a63SDavid du Colombier 	"	isync\n"
32*8ccd4a63SDavid du Colombier 	: "=r" (v)
33*8ccd4a63SDavid du Colombier 	: "r"  (x)
34*8ccd4a63SDavid du Colombier 	: "cc", "memory", "r0", "r4", "r5"
35*8ccd4a63SDavid du Colombier 	);
36*8ccd4a63SDavid du Colombier 	switch(v) {
37*8ccd4a63SDavid du Colombier 	case 0:		return 0;
38*8ccd4a63SDavid du Colombier 	case 0xdeaddead: return 1;
39*8ccd4a63SDavid du Colombier 	default:	print("tas: corrupted 0x%lux\n", v);
40*8ccd4a63SDavid du Colombier 	}
41*8ccd4a63SDavid du Colombier 	return 0;
42*8ccd4a63SDavid du Colombier }
43