cosmopolitan/libc/str/rawmemchr.c
Justine Tunney 2ab9e9f7fd
Make improvements
- Introduce portable sched_getcpu() api
- Support GCC's __target_clones__ feature
- Make fma() go faster on x86 in default mode
- Remove some asan checks from core libraries
- WinMain() now ensures $HOME and $USER are defined
2024-02-12 10:23:00 -08:00

97 lines
3.8 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/dce.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/str/str.h"
static inline const unsigned char *rawmemchr_pure(const unsigned char *s,
unsigned char c) {
for (;; ++s) {
if (*s == c) {
return s;
}
}
}
#if defined(__x86_64__) && !defined(__chibicc__)
typedef char xmm_t __attribute__((__vector_size__(16), __aligned__(16)));
static inline const char *rawmemchr_sse(const char *s, unsigned char c) {
unsigned k;
unsigned m;
const xmm_t *p;
xmm_t v, n = {c, c, c, c, c, c, c, c, c, c, c, c, c, c, c, c};
k = (uintptr_t)s & 15;
p = (const xmm_t *)((uintptr_t)s & -16);
v = *p;
m = __builtin_ia32_pmovmskb128(v == n);
m >>= k;
m <<= k;
while (!m) {
v = *++p;
m = __builtin_ia32_pmovmskb128(v == n);
}
m = __builtin_ctzll(m);
return (const char *)p + m;
}
#endif
static inline uint64_t UncheckedAlignedRead64(const unsigned char *p) {
return (uint64_t)p[7] << 070 | (uint64_t)p[6] << 060 | (uint64_t)p[5] << 050 |
(uint64_t)p[4] << 040 | (uint64_t)p[3] << 030 | (uint64_t)p[2] << 020 |
(uint64_t)p[1] << 010 | (uint64_t)p[0] << 000;
}
/**
* Returns pointer to first instance of character.
*
* @param m is memory to search
* @param c is search byte which is masked with 255
* @return is pointer to first instance of c
*/
__vex void *rawmemchr(const void *s, int c) {
#if defined(__x86_64__) && !defined(__chibicc__)
const void *r;
if (X86_HAVE(SSE)) {
r = rawmemchr_sse(s, c);
} else {
r = rawmemchr_pure(s, c);
}
return (void *)r;
#else
uint64_t v, w;
const unsigned char *p;
p = s;
c &= 255;
v = 0x0101010101010101ul * c;
for (; (uintptr_t)p & 7; ++p) {
if (*p == c) return (void *)p;
}
for (;; p += 8) {
w = UncheckedAlignedRead64(p);
if ((w = ~(w ^ v) & ((w ^ v) - 0x0101010101010101) & 0x8080808080808080)) {
p += (unsigned)__builtin_ctzll(w) >> 3;
break;
}
}
assert(*p == c);
return (void *)p;
#endif
}