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