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bzero.c
170 lines (165 loc) · 7.51 KB
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bzero.c
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/*-*- 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/nexgen32e.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/str/str.h"
typedef char xmm_t __attribute__((__vector_size__(16), __aligned__(1)));
typedef long long xmm_a __attribute__((__vector_size__(16), __aligned__(16)));
static void bzero128(char *p, size_t n) {
xmm_t v = {0};
if (n <= 32) {
*(xmm_t *)(p + n - 16) = v;
*(xmm_t *)p = v;
} else {
do {
n -= 32;
*(xmm_t *)(p + n) = v;
*(xmm_t *)(p + n + 16) = v;
} while (n > 32);
*(xmm_t *)(p + 16) = v;
*(xmm_t *)p = v;
}
}
#if defined(__x86_64__) && !defined(__chibicc__)
_Microarchitecture("avx") static void bzero_avx(char *p, size_t n) {
xmm_t v = {0};
if (n <= 32) {
*(xmm_t *)(p + n - 16) = v;
*(xmm_t *)p = v;
} else if (n >= 1024 && X86_HAVE(ERMS)) {
asm("rep stosb" : "+D"(p), "+c"(n), "=m"(*(char(*)[n])p) : "a"(0));
} else {
if (n < kHalfCache3 || !kHalfCache3) {
do {
n -= 32;
*(xmm_t *)(p + n) = v;
*(xmm_t *)(p + n + 16) = v;
} while (n > 32);
} else {
while ((uintptr_t)(p + n) & 15) {
p[--n] = 0;
}
do {
n -= 32;
__builtin_ia32_movntdq((xmm_a *)(p + n), (xmm_a)v);
__builtin_ia32_movntdq((xmm_a *)(p + n + 16), (xmm_a)v);
} while (n > 32);
asm("sfence");
}
*(xmm_t *)(p + 16) = v;
*(xmm_t *)p = v;
}
}
#endif
/**
* Sets memory to zero.
*
* bzero n=0 661 picoseconds
* bzero n=1 661 ps/byte 1,476 mb/s
* bzero n=2 330 ps/byte 2,952 mb/s
* bzero n=3 220 ps/byte 4,428 mb/s
* bzero n=4 165 ps/byte 5,904 mb/s
* bzero n=7 94 ps/byte 10,333 mb/s
* bzero n=8 41 ps/byte 23,618 mb/s
* bzero n=15 44 ps/byte 22,142 mb/s
* bzero n=16 20 ps/byte 47,236 mb/s
* bzero n=31 21 ps/byte 45,760 mb/s
* bzero n=32 20 ps/byte 47,236 mb/s
* bzero n=63 10 ps/byte 92,997 mb/s
* bzero n=64 15 ps/byte 62,982 mb/s
* bzero n=127 15 ps/byte 62,490 mb/s
* bzero n=128 10 ps/byte 94,473 mb/s
* bzero n=255 14 ps/byte 68,439 mb/s
* bzero n=256 9 ps/byte 105 gb/s
* bzero n=511 15 ps/byte 62,859 mb/s
* bzero n=512 11 ps/byte 83,976 mb/s
* bzero n=1023 15 ps/byte 61,636 mb/s
* bzero n=1024 10 ps/byte 88,916 mb/s
* bzero n=2047 9 ps/byte 105 gb/s
* bzero n=2048 8 ps/byte 109 gb/s
* bzero n=4095 8 ps/byte 115 gb/s
* bzero n=4096 8 ps/byte 118 gb/s
* bzero n=8191 7 ps/byte 129 gb/s
* bzero n=8192 7 ps/byte 130 gb/s
* bzero n=16383 6 ps/byte 136 gb/s
* bzero n=16384 6 ps/byte 137 gb/s
* bzero n=32767 6 ps/byte 140 gb/s
* bzero n=32768 6 ps/byte 141 gb/s
* bzero n=65535 15 ps/byte 64,257 mb/s
* bzero n=65536 15 ps/byte 64,279 mb/s
* bzero n=131071 15 ps/byte 63,166 mb/s
* bzero n=131072 15 ps/byte 63,115 mb/s
* bzero n=262143 15 ps/byte 62,052 mb/s
* bzero n=262144 15 ps/byte 62,097 mb/s
* bzero n=524287 15 ps/byte 61,699 mb/s
* bzero n=524288 15 ps/byte 61,674 mb/s
* bzero n=1048575 16 ps/byte 60,179 mb/s
* bzero n=1048576 15 ps/byte 61,330 mb/s
* bzero n=2097151 15 ps/byte 61,071 mb/s
* bzero n=2097152 15 ps/byte 61,065 mb/s
* bzero n=4194303 16 ps/byte 60,942 mb/s
* bzero n=4194304 16 ps/byte 60,947 mb/s
* bzero n=8388607 16 ps/byte 60,872 mb/s
* bzero n=8388608 16 ps/byte 60,879 mb/s
*
* @param p is memory address
* @param n is byte length
* @return p
* @asyncsignalsafe
*/
void bzero(void *p, size_t n) {
char *b;
uint64_t x;
b = p;
#ifdef __x86_64__
asm("xorl\t%k0,%k0" : "=r"(x));
#else
if (1) {
memset(p, 0, n);
return;
}
x = 0;
#endif
if (n <= 16) {
if (n >= 8) {
__builtin_memcpy(b, &x, 8);
__builtin_memcpy(b + n - 8, &x, 8);
} else if (n >= 4) {
__builtin_memcpy(b, &x, 4);
__builtin_memcpy(b + n - 4, &x, 4);
} else if (n) {
do {
asm volatile("" ::: "memory");
b[--n] = x;
} while (n);
}
#if defined(__x86_64__) && !defined(__chibicc__)
} else if (IsTiny()) {
asm("rep stosb" : "+D"(b), "+c"(n), "=m"(*(char(*)[n])b) : "a"(0));
return;
} else if (X86_HAVE(AVX)) {
bzero_avx(b, n);
#endif
} else {
bzero128(b, n);
}
}
__weak_reference(bzero, explicit_bzero);