| #include "u.h" |
| #include "libc.h" |
| |
| /* |
| * first argument (l) is in r3 at entry. |
| * r3 contains return value upon return. |
| */ |
| int |
| _tas(int *x) |
| { |
| int v; |
| /* |
| * this __asm__ works with gcc 2.95.2 (mac os x 10.1). |
| * this assembly language destroys r0 (0), some other register (v), |
| * r4 (x) and r5 (temp). |
| */ |
| __asm__("\n sync\n" |
| " li r0,0\n" |
| " mr r4,%1 /* &l->val */\n" |
| " lis r5,0xdead /* assemble constant 0xdeaddead */\n" |
| " ori r5,r5,0xdead /* \" */\n" |
| "tas1:\n" |
| " dcbf r4,r0 /* cache flush; \"fix for 603x bug\" */\n" |
| " lwarx %0,r4,r0 /* v = l->val with reservation */\n" |
| " cmp cr0,0,%0,r0 /* v == 0 */\n" |
| " bne tas0\n" |
| " stwcx. r5,r4,r0 /* if (l->val same) l->val = 0xdeaddead */\n" |
| " bne tas1\n" |
| "tas0:\n" |
| " sync\n" |
| " isync\n" |
| : "=r" (v) |
| : "r" (x) |
| : "cc", "memory", "r0", "r4", "r5" |
| ); |
| switch(v) { |
| case 0: return 0; |
| case 0xdeaddead: return 1; |
| default: fprint(2, "tas: corrupted 0x%lux\n", v); |
| } |
| return 0; |
| } |
