55 lines
2.6 KiB
ArmAsm
55 lines
2.6 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.h"
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/ Duplicates chrominance samples horizontally, e.g.
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/
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/ 12345678--------
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/ → 1122334455667788
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/
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/ @param %edi is size of %rsi array in bytes
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/ @param %rsi is char[edi/16][16] output and %rsi==%rdx is OK
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/ @param %rdx is char[edi/16][8] input
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/ @return %rax is %rsi
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doublechrominance:
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.leafprologue
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.profilable
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shr $1,%edi # backwards algorithm
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jbe 1f # do nothing if !n || n%2
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mov %edi,%ecx
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shr $4,%ecx
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shl $4,%ecx
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0: cmp %edi,%ecx
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je 0f
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dec %edi
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movzbl (%rdx,%rdi),%eax
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mov %al,(%rsi,%rdi,2)
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mov %al,1(%rsi,%rdi,2)
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jmp 0b
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0: sub $8,%edi
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movq (%rdx,%rdi),%xmm0
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punpcklbw %xmm0,%xmm0
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movdqu %xmm0,(%rsi,%rdi,2)
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jnz 0b
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1: mov %rsi,%rax
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.leafepilogue
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.endfn doublechrominance,globl
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.source __FILE__
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