mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 19:43:32 +00:00
425c055116
- Polyfill readlink("foo/") dir check on Windows
- Support asynchronous signal delivery on Windows
- Restore Windows Console from execve() daisy chain
- Work around bug in AARCH64 Optimized Routines memcmp()
- Disable unbourne.com shell completion on Windows for now
- Don't always set virtual terminal input state on console
- Remove Musl Libc's unusual preservation of realpath("//")
- Make realpath() strongly link malloc() to pass configure test
- Delete cosh.com shell, now that unbourne.com works on Windows!
84 lines
4.6 KiB
C
84 lines
4.6 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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typedef char xmm_t __attribute__((__vector_size__(16), __aligned__(1)));
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/**
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* Compares memory byte by byte.
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*
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* memcmp n=0 2 nanoseconds
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* memcmp n=1 2 ns/byte 357 mb/s
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* memcmp n=2 1 ns/byte 530 mb/s
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* memcmp n=3 1 ns/byte 631 mb/s
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* 𝗺𝗲𝗺𝗰𝗺𝗽 n=4 1 ns/byte 849 mb/s
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* memcmp n=5 816 ps/byte 1,195 mb/s
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* memcmp n=6 888 ps/byte 1,098 mb/s
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* memcmp n=7 829 ps/byte 1,176 mb/s
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* 𝗺𝗲𝗺𝗰𝗺𝗽 n=8 773 ps/byte 1,261 mb/s
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* memcmp n=9 629 ps/byte 1,551 mb/s
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* memcmp n=15 540 ps/byte 1,805 mb/s
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* 𝗺𝗲𝗺𝗰𝗺𝗽 n=16 211 ps/byte 4,623 mb/s
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* memcmp n=17 268 ps/byte 3,633 mb/s
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* memcmp n=31 277 ps/byte 3,524 mb/s
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* memcmp n=32 153 ps/byte 6,351 mb/s
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* memcmp n=33 179 ps/byte 5,431 mb/s
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* memcmp n=79 148 ps/byte 6,576 mb/s
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* 𝗺𝗲𝗺𝗰𝗺𝗽 n=80 81 ps/byte 11 GB/s
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* memcmp n=128 76 ps/byte 12 GB/s
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* memcmp n=256 60 ps/byte 15 GB/s
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* memcmp n=16384 51 ps/byte 18 GB/s
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* memcmp n=32768 51 ps/byte 18 GB/s
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* memcmp n=131072 52 ps/byte 18 GB/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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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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#if defined(__x86_64__) && !defined(__chibicc__)
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unsigned u;
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while (n >= 16 && (((uintptr_t)p & 0xfff) <= 0x1000 - 16 &&
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((uintptr_t)q & 0xfff) <= 0x1000 - 16)) {
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if (!(u = __builtin_ia32_pmovmskb128(*(xmm_t *)p == *(xmm_t *)q) ^
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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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#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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