mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 19:43:32 +00:00
207 lines
8.6 KiB
C
207 lines
8.6 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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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/dce.h"
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#include "libc/intrin/likely.h"
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#include "libc/nexgen32e/x86feature.h"
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#include "libc/str/str.h"
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#ifndef __aarch64__
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#define PMOVMSKB(x) __builtin_ia32_pmovmskb128(x)
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typedef char xmm_t __attribute__((__vector_size__(16), __aligned__(1)));
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#ifdef __x86_64__
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static dontinline antiquity int memcmp_sse(const unsigned char *p,
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const unsigned char *q, size_t n) {
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unsigned u;
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if (n > 32) {
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while (n > 16 + 16) {
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if (!(u = PMOVMSKB(*(xmm_t *)p == *(xmm_t *)q) ^ 0xffff)) {
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n -= 16;
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p += 16;
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q += 16;
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} else {
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u = __builtin_ctzl(u);
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return p[u] - q[u];
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}
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}
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}
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if (!(u = PMOVMSKB(*(xmm_t *)p == *(xmm_t *)q) ^ 0xffff)) {
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if (!(u = PMOVMSKB(*(xmm_t *)(p + n - 16) == *(xmm_t *)(q + n - 16)) ^
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0xffff)) {
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return 0;
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} else {
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u = __builtin_ctzl(u);
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return p[n - 16 + u] - q[n - 16 + u];
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}
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} else {
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u = __builtin_ctzl(u);
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return p[u] - q[u];
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}
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}
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_Microarchitecture("avx") static int memcmp_avx(const unsigned char *p,
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const unsigned char *q,
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size_t n) {
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uint64_t w;
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unsigned u;
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if (n > 32) {
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while (n >= 16 + 64) {
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w = (uint64_t)PMOVMSKB(((xmm_t *)p)[0] == ((xmm_t *)q)[0]) << 000 |
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(uint64_t)PMOVMSKB(((xmm_t *)p)[1] == ((xmm_t *)q)[1]) << 020 |
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(uint64_t)PMOVMSKB(((xmm_t *)p)[2] == ((xmm_t *)q)[2]) << 040 |
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(uint64_t)PMOVMSKB(((xmm_t *)p)[3] == ((xmm_t *)q)[3]) << 060;
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if (w == -1) {
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n -= 64;
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p += 64;
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q += 64;
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} else {
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w = __builtin_ctzll(w ^ -1);
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return p[w] - q[w];
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}
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}
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while (n > 16 + 16) {
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if (!(u = PMOVMSKB(*(xmm_t *)p == *(xmm_t *)q) ^ 0xffff)) {
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n -= 16;
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p += 16;
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q += 16;
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} else {
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u = __builtin_ctzl(u);
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return p[u] - q[u];
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}
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}
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}
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if (!(u = PMOVMSKB(*(xmm_t *)p == *(xmm_t *)q) ^ 0xffff)) {
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if (!(u = PMOVMSKB(*(xmm_t *)(p + n - 16) == *(xmm_t *)(q + n - 16)) ^
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0xffff)) {
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return 0;
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} else {
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u = __builtin_ctzl(u);
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return p[n - 16 + u] - q[n - 16 + u];
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}
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} else {
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u = __builtin_ctzl(u);
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return p[u] - q[u];
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}
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}
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#endif /* __x86_64__ */
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/**
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* Compares memory byte by byte.
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*
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* memcmp n=0 992 picoseconds
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* memcmp n=1 1 ns/byte 738 mb/s
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* memcmp n=2 661 ps/byte 1,476 mb/s
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* memcmp n=3 551 ps/byte 1,771 mb/s
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* memcmp n=4 248 ps/byte 3,936 mb/s
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* memcmp n=5 198 ps/byte 4,920 mb/s
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* memcmp n=6 165 ps/byte 5,904 mb/s
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* memcmp n=7 141 ps/byte 6,889 mb/s
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* memcmp n=8 124 ps/byte 7,873 mb/s
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* memcmp n=9 110 ps/byte 8,857 mb/s
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* memcmp n=15 44 ps/byte 22,143 mb/s
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* memcmp n=16 41 ps/byte 23,619 mb/s
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* memcmp n=17 77 ps/byte 12,547 mb/s
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* memcmp n=31 42 ps/byte 22,881 mb/s
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* memcmp n=32 41 ps/byte 23,619 mb/s
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* memcmp n=33 60 ps/byte 16,238 mb/s
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* memcmp n=80 53 ps/byte 18,169 mb/s
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* memcmp n=128 38 ps/byte 25,194 mb/s
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* memcmp n=256 32 ps/byte 30,233 mb/s
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* memcmp n=16384 27 ps/byte 35,885 mb/s
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* memcmp n=32768 29 ps/byte 32,851 mb/s
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* memcmp n=131072 33 ps/byte 28,983 mb/s
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*
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* @return an integer that's (1) equal to zero if `a` is equal to `b`,
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* (2) less than zero if `a` is less than `b`, or (3) greater than
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* zero if `a` is greater than `b`
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* @asyncsignalsafe
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*/
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int memcmp(const void *a, const void *b, size_t n) {
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int c;
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unsigned u;
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uint32_t k, i, j;
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uint64_t w, x, y;
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const unsigned char *p, *q;
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if ((p = a) == (q = b) || !n) return 0;
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if ((c = *p - *q)) return c;
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#ifdef __x86_64__
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if (!IsTiny()) {
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if (n <= 16) {
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if (n >= 8) {
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if (!(w = (x = ((uint64_t)p[0] << 000 | (uint64_t)p[1] << 010 |
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(uint64_t)p[2] << 020 | (uint64_t)p[3] << 030 |
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(uint64_t)p[4] << 040 | (uint64_t)p[5] << 050 |
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(uint64_t)p[6] << 060 | (uint64_t)p[7] << 070)) ^
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(y = ((uint64_t)q[0] << 000 | (uint64_t)q[1] << 010 |
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(uint64_t)q[2] << 020 | (uint64_t)q[3] << 030 |
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(uint64_t)q[4] << 040 | (uint64_t)q[5] << 050 |
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(uint64_t)q[6] << 060 | (uint64_t)q[7] << 070)))) {
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p += n - 8;
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q += n - 8;
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if (!(w = (x = ((uint64_t)p[0] << 000 | (uint64_t)p[1] << 010 |
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(uint64_t)p[2] << 020 | (uint64_t)p[3] << 030 |
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(uint64_t)p[4] << 040 | (uint64_t)p[5] << 050 |
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(uint64_t)p[6] << 060 | (uint64_t)p[7] << 070)) ^
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(y = ((uint64_t)q[0] << 000 | (uint64_t)q[1] << 010 |
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(uint64_t)q[2] << 020 | (uint64_t)q[3] << 030 |
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(uint64_t)q[4] << 040 | (uint64_t)q[5] << 050 |
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(uint64_t)q[6] << 060 | (uint64_t)q[7] << 070)))) {
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return 0;
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}
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}
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u = __builtin_ctzll(w);
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u = u & -8;
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return ((x >> u) & 255) - ((y >> u) & 255);
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} else if (n >= 4) {
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if (!(k = (i = ((uint32_t)p[0] << 000 | (uint32_t)p[1] << 010 |
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(uint32_t)p[2] << 020 | (uint32_t)p[3] << 030)) ^
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(j = ((uint32_t)q[0] << 000 | (uint32_t)q[1] << 010 |
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(uint32_t)q[2] << 020 | (uint32_t)q[3] << 030)))) {
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p += n - 4;
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q += n - 4;
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if (!(k = (i = ((uint32_t)p[0] << 000 | (uint32_t)p[1] << 010 |
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(uint32_t)p[2] << 020 | (uint32_t)p[3] << 030)) ^
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(j = ((uint32_t)q[0] << 000 | (uint32_t)q[1] << 010 |
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(uint32_t)q[2] << 020 | (uint32_t)q[3] << 030)))) {
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return 0;
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}
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}
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u = __builtin_ctzl(k);
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u = u & -8;
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return ((i >> u) & 255) - ((j >> u) & 255);
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}
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} else if (LIKELY(X86_HAVE(AVX))) {
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return memcmp_avx(p, q, n);
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} else {
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return memcmp_sse(p, q, n);
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}
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}
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#endif /* __x86_64__ */
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for (; n; ++p, ++q, --n) {
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if ((c = *p - *q)) {
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return c;
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}
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}
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return 0;
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}
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#endif /* __aarch64__ */
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