cosmopolitan/tool/build/lib/bitscan.c

81 lines
3.6 KiB
C

/*-*- 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 │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "tool/build/lib/bitscan.h"
#include "tool/build/lib/flags.h"
#include "tool/build/lib/machine.h"
#include "tool/build/lib/modrm.h"
uint64_t AluBsr(struct Machine *m, uint32_t rde, uint64_t _, 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;
}
}
uint64_t AluBsf(struct Machine *m, uint32_t rde, uint64_t _, uint64_t x) {
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;
}
}
uint64_t AluPopcnt(struct Machine *m, uint32_t rde, uint64_t _, 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;
}