cosmopolitan/libc/bits/countbits.c
Justine Tunney 39bf41f4eb Make numerous improvements
- Python static hello world now 1.8mb
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- Increase stack size for Python for now
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- Add optimized code path for Intel SHA-NI
- Get more Python unit tests passing faster
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- Python hashlib now supports MbedTLS PBKDF2
- Make memcpy/memmove/memcmp/bcmp/etc. faster
- Add Mersenne Twister and Vigna to LIBC_RAND
- Provide privileged __printf() for error code
- Fix zipos opendir() so that it reports ENOTDIR
- Add basic chmod() implementation for Windows NT
- Add Cosmo's best functions to Python cosmo module
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- Show memory diagram on invalid access in MODE=dbg
- Differentiate stack overflow on crash in MODE=dbg
- Add stb_truetype and tools for analyzing font files
- Upgrade to UNICODE 13 and reduce its binary footprint
- COMPILE.COM now logs resource usage of build commands
- Start implementing basic poll() support on bare metal
- Set getauxval(AT_EXECFN) to GetModuleFileName() on NT
- Add descriptions to strerror() in non-TINY build modes
- Add COUNTBRANCH() macro to help with micro-optimizations
- Make error / backtrace / asan / memory code more unbreakable
- Add fast perfect C implementation of μ-Law and a-Law audio codecs
- Make strtol() functions consistent with other libc implementations
- Improve Linenoise implementation (see also github.com/jart/bestline)
- COMPILE.COM now suppresses stdout/stderr of successful build commands
2021-09-28 01:52:34 -07:00

84 lines
3.6 KiB
C

/*-*- 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 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/bits/bits.h"
#include "libc/dce.h"
#include "libc/nexgen32e/x86feature.h"
/**
* Returns population count of array.
*
* @param a is byte sequence
* @return number of bits set to one
* @note 30gbps on Nehalem (Intel 2008+) otherwise 3gbps
*/
size_t _countbits(const void *a, size_t n) {
int i;
size_t t;
unsigned b;
uint64_t x;
long Ai, Bi, Ci, Di;
long Ao, Bo, Co, Do;
const char *p, *e;
t = 0;
p = a;
e = p + n;
if (!IsTiny()) {
if (X86_HAVE(POPCNT)) {
while (p + sizeof(long) * 4 <= e) {
__builtin_memcpy(&Ai, p + 000, sizeof(long));
__builtin_memcpy(&Bi, p + 010, sizeof(long));
__builtin_memcpy(&Ci, p + 020, sizeof(long));
__builtin_memcpy(&Di, p + 030, sizeof(long));
asm("popcnt\t%1,%0" : "=r"(Ao) : "r"(Ai) : "cc");
asm("popcnt\t%1,%0" : "=r"(Bo) : "r"(Bi) : "cc");
asm("popcnt\t%1,%0" : "=r"(Co) : "r"(Ci) : "cc");
asm("popcnt\t%1,%0" : "=r"(Do) : "r"(Di) : "cc");
t += Ao + Bo + Co + Do;
p += sizeof(long) * 4;
}
while (p + sizeof(long) <= e) {
__builtin_memcpy(&Ai, p, 8);
asm("popcnt\t%1,%0" : "=r"(Ao) : "rm"(Ai) : "cc");
p += sizeof(long);
t += Ao;
}
} else {
while (p + 8 <= e) {
__builtin_memcpy(&x, p, 8);
x = x - ((x >> 1) & 0x5555555555555555);
x = ((x >> 2) & 0x3333333333333333) + (x & 0x3333333333333333);
x = (x + (x >> 4)) & 0x0f0f0f0f0f0f0f0f;
x = (x + (x >> 32)) & 0xffffffff;
x = x + (x >> 16);
x = (x + (x >> 8)) & 0x7f;
t += x;
p += 8;
}
}
}
while (p < e) {
b = *p++ & 255;
b = b - ((b >> 1) & 0x55);
b = ((b >> 2) & 0x33) + (b & 0x33);
b = (b + (b >> 4)) & 15;
t += b;
}
return t;
}