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