43 lines
2.4 KiB
C
43 lines
2.4 KiB
C
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/bits/bits.h"
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#include "libc/nexgen32e/x86feature.h"
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static noinline uint32_t popcount$swar32(uint32_t x) {
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x -= (x >> 1) & 0x55555555;
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x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
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return (((x + (x >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
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}
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unsigned long(popcount)(unsigned long x) {
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size_t i;
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unsigned long r;
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if (X86_HAVE(POPCNT)) {
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return popcount$nehalem(x);
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} else {
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r = 0;
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for (i = 0; i < sizeof(x); i += 4) {
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r |= popcount$swar32(x);
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x >>= 32;
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}
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return r;
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}
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}
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