63 lines
3.4 KiB
C
63 lines
3.4 KiB
C
/*-*- 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/str/internal.h"
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#define kVectorSize 32 /* x86+avx2 is 256-bit cpu */
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typedef uint8_t uint8_v _Vector_size(kVectorSize);
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typedef uint32_t vbitmask_t;
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/**
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* Returns how many bytes the utf16 string would be as utf8.
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*/
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int strcmp$avx2(const char *s1, const char *s2) {
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if (s1 == s2) return 0;
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const unsigned char *p1 = (const unsigned char *)s1;
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const unsigned char *p2 = (const unsigned char *)s2;
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size_t i = -kVectorSize;
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vLoop:
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i += kVectorSize;
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bLoop:
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if (!IsPointerDangerous(p1 + i) && !IsPointerDangerous(p2 + i)) {
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unsigned char zf;
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vbitmask_t r1;
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uint8_v v1, v2;
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const uint8_v kZero = {0};
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asm(ZFLAG_ASM("vmovdqu\t%5,%2\n\t" /* move because gcc problematic */
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"vpcmpeqb\t%4,%2,%1\n\t" /* check for equality in p1 and p2 */
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"vpcmpeqb\t%6,%2,%2\n\t" /* check for nul in p1 */
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"vpandn\t%7,%1,%2\n\t" /* most complicated bitwise not ever */
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"vpor\t%2,%1,%1\n\t" /* check for nul in p2 */
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"pmovmskb\t%1,%3\n\t" /* turn 256 bits into 32 bits */
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"bsf\t%3,%3") /* find stop byte */
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: ZFLAG_CONSTRAINT(zf), "=x"(v1), "=x"(v2), "=r"(r1)
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: "m"(*(const uint8_v *)(p1 + i)), "m"(*(const uint8_v *)(p2 + i)),
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"x"(kZero), "m"(kVectorSize));
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if (zf) goto vLoop;
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return p1[i + r1] - p2[i + r1];
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} else {
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i += 1;
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int c;
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if (!(c = p1[i - 1] - p2[i - 1]) && p1[i - 1] + p1[i - 1] != 0) goto bLoop;
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return c;
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}
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}
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