cosmopolitan/libc/intrin/pshuflw.c

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/*-*- 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 2020 Justine Alexandra Roberts Tunney
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
*/
#include "libc/intrin/pshuflw.h"
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/**
* Shuffles lower half of word vector.
* @param 𝑚 needs to be a literal, constexpr, or embedding
* @mayalias
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*/
void(pshuflw)(int16_t b[8], const int16_t a[8], uint8_t m) {
int16_t t[4];
t[0] = a[(m & 0b00000011) >> 0];
t[1] = a[(m & 0b00001100) >> 2];
t[2] = a[(m & 0b00110000) >> 4];
t[3] = a[(m & 0b11000000) >> 6];
b[0] = t[0];
b[1] = t[1];
b[2] = t[2];
b[3] = t[3];
b[4] = a[4];
b[5] = a[5];
b[6] = a[6];
b[7] = a[7];
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}