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Justine Tunney 2020-06-15 07:18:57 -07:00
commit c91b3c5006
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tool/viz/lib/doublechrominance.S Normal file
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/*-*- mode:asm; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
│vi: set et ft=asm ts=8 tw=8 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/macros.h"
/ Duplicates chrominance samples horizontally, e.g.
/
/ 12345678--------
/ → 1122334455667788
/
/ @param %edi is size of %rsi array in bytes
/ @param %rsi is char[edi/16][16] output and %rsi==%rdx is OK
/ @param %rdx is char[edi/16][8] input
/ @return %rax is %rsi
doublechrominance:
.leafprologue
.profilable
shr $1,%edi # backwards algorithm
jbe 1f # do nothing if !n || n%2
mov %edi,%ecx
shr $4,%ecx
shl $4,%ecx
0: cmp %edi,%ecx
je 0f
dec %edi
movzbl (%rdx,%rdi),%eax
mov %al,(%rsi,%rdi,2)
mov %al,1(%rsi,%rdi,2)
jmp 0b
0: sub $8,%edi
movq (%rdx,%rdi),%xmm0
punpcklbw %xmm0,%xmm0
movdqu %xmm0,(%rsi,%rdi,2)
jnz 0b
1: mov %rsi,%rax
.leafepilogue
.endfn doublechrominance,globl
.yoink __FILE__