cosmopolitan/tool/build/lib/bitscan.c

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
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Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted, provided that the
above copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
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*/
#include "tool/build/lib/bitscan.h"
#include "tool/build/lib/flags.h"
#include "tool/build/lib/machine.h"
#include "tool/build/lib/modrm.h"
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uint64_t AluBsr(struct Machine *m, uint32_t rde, uint64_t x) {
unsigned i;
if (Rexw(rde)) {
x &= 0xffffffffffffffff;
m->flags = SetFlag(m->flags, FLAGS_ZF, !x);
if (!x) return 0;
return 63 ^ __builtin_clzll(x);
} else if (!Osz(rde)) {
x &= 0xffffffff;
m->flags = SetFlag(m->flags, FLAGS_ZF, !x);
if (!x) return 0;
return 31 ^ __builtin_clz(x);
} else {
x &= 0xffff;
m->flags = SetFlag(m->flags, FLAGS_ZF, !x);
if (!x) return 0;
for (i = 15; !(x & 0x8000); --i) x <<= 1;
return i;
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}
}
uint64_t AluBsf(struct Machine *m, uint32_t rde, uint64_t x) {
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unsigned i;
if (Rexw(rde)) {
x &= 0xffffffffffffffff;
m->flags = SetFlag(m->flags, FLAGS_ZF, !x);
if (!x) return 0;
return __builtin_ctzll(x);
} else if (!Osz(rde)) {
x &= 0xffffffff;
m->flags = SetFlag(m->flags, FLAGS_ZF, !x);
if (!x) return 0;
return __builtin_ctz(x);
} else {
x &= 0xffff;
m->flags = SetFlag(m->flags, FLAGS_ZF, !x);
if (!x) return 0;
for (i = 0; !(x & 1); ++i) x >>= 1;
return i;
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}
}
uint64_t AluPopcnt(struct Machine *m, uint32_t rde, uint64_t x) {
m->flags = SetFlag(m->flags, FLAGS_ZF, !x);
m->flags = SetFlag(m->flags, FLAGS_CF, false);
m->flags = SetFlag(m->flags, FLAGS_SF, false);
m->flags = SetFlag(m->flags, FLAGS_OF, false);
m->flags = SetFlag(m->flags, FLAGS_PF, false);
x = x - ((x >> 1) & 0x5555555555555555);
x = ((x >> 2) & 0x3333333333333333) + (x & 0x3333333333333333);
x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f;
x = (x + (x >> 32)) & 0xffffffff;
x = x + (x >> 16);
x = (x + (x >> 8)) & 0x7f;
return x;
}