43 lines
882 B
C
43 lines
882 B
C
#include "u.h"
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#include "libc.h"
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/*
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* first argument (l) is in r3 at entry.
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* r3 contains return value upon return.
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*/
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int
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_tas(int *x)
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{
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int v;
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int tmp, tmp2, tmp3;
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/*
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* this __asm__ works with gcc on linux
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*/
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__asm__("\n sync\n"
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" li %1,0\n"
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" mr %2,%4 /* &x->val */\n"
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" lis %3,0xdead /* assemble constant 0xdeaddead */\n"
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" ori %3,%3,0xdead /* \" */\n"
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"tas1:\n"
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" dcbf %2,%1 /* cache flush; \"fix for 603x bug\" */\n"
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" lwarx %0,%2,%1 /* v = x->val with reservation */\n"
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" cmp cr0,0,%0,%1 /* v == 0 */\n"
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" bne tas0\n"
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" stwcx. %3,%2,%1 /* if (x->val same) x->val = 0xdeaddead */\n"
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" bne tas1\n"
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"tas0:\n"
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" sync\n"
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" isync\n"
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: "=r" (v), "=&r" (tmp), "=&r"(tmp2), "=&r"(tmp3)
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: "r" (x)
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: "cr0", "memory"
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);
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switch(v) {
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case 0: return 0;
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case 0xdeaddead: return 1;
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default: fprint(2, "tas: corrupted 0x%lux\n", v);
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}
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return 0;
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}
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