43 lines
943 B
C
43 lines
943 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(long *x)
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{
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int v;
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/*
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* this __asm__ works with gcc 2.95.2 (mac os x 10.1).
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* this assembly language destroys r0 (0), some other register (v),
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* r4 (x) and r5 (temp).
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*/
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__asm__("\n sync\n"
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" li r0,0\n"
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" mr r4,%1 /* &l->val */\n"
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" lis r5,0xdead /* assemble constant 0xdeaddead */\n"
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" ori r5,r5,0xdead /* \" */\n"
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"tas1:\n"
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" dcbf r4,r0 /* cache flush; \"fix for 603x bug\" */\n"
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" lwarx %0,r4,r0 /* v = l->val with reservation */\n"
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" cmp cr0,0,%0,r0 /* v == 0 */\n"
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" bne tas0\n"
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" stwcx. r5,r4,r0 /* if (l->val same) l->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)
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: "r" (x)
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: "cc", "memory", "r0", "r4", "r5"
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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: print("tas: corrupted 0x%lux\n", v);
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}
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return 0;
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}
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