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#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;
int tmp, tmp2, tmp3;
/*
* this __asm__ works with gcc on linux
*/
__asm__("\n sync\n"
" li %1,0\n"
" mr %2,%4 /* &x->val */\n"
" lis %3,0xdead /* assemble constant 0xdeaddead */\n"
" ori %3,%3,0xdead /* \" */\n"
"tas1:\n"
" dcbf %2,%1 /* cache flush; \"fix for 603x bug\" */\n"
" lwarx %0,%2,%1 /* v = x->val with reservation */\n"
" cmp cr0,0,%0,%1 /* v == 0 */\n"
" bne tas0\n"
" stwcx. %3,%2,%1 /* if (x->val same) x->val = 0xdeaddead */\n"
" bne tas1\n"
"tas0:\n"
" sync\n"
" isync\n"
: "=r" (v), "=&r" (tmp), "=&r"(tmp2), "=&r"(tmp3)
: "r" (x)
: "cr0", "memory"
);
switch(v) {
case 0: return 0;
case 0xdeaddead: return 1;
default: fprint(2, "tas: corrupted 0x%lux\n", v);
}
return 0;
}
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