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arm: get_cabac inline asm

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Based on the aarch64 asm. CPU cycle counts on cortex-a9 compared to
gcc 4.8.2:
before: 475 decicycles in get_cabac_noinline, 67106035 runs, 2829 skips
after:  393 decicycles in get_cabac_noinline, 67106474 runs, 2390 skips

Overall speedup is above 2%. Code generated by clang 3.4 is slower on
the same hardware and the relative change is a little larger.
This commit is contained in:
Janne Grunau 2014-01-29 14:48:22 +01:00
parent dfe224f377
commit 634d9d8b39
2 changed files with 105 additions and 0 deletions
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102
libavcodec/arm/cabac.h Normal file
View File

@ -0,0 +1,102 @@
/*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#ifndef AVCODEC_ARM_CABAC_H
#define AVCODEC_ARM_CABAC_H
#include "config.h"
#if HAVE_ARMV6T2_INLINE
#include "libavutil/attributes.h"
#include "libavutil/internal.h"
#include "libavcodec/cabac.h"
#define get_cabac_inline get_cabac_inline_arm
static av_always_inline int get_cabac_inline_arm(CABACContext *c,
uint8_t *const state)
{
int bit;
void *reg_b, *reg_c, *tmp;
__asm__ volatile(
"ldrb %[bit] , [%[state]] \n\t"
"add %[r_b] , %[tables] , %[lps_off] \n\t"
"mov %[tmp] , %[range] \n\t"
"and %[range] , %[range] , #0xC0 \n\t"
"add %[r_b] , %[r_b] , %[bit] \n\t"
"ldrb %[range] , [%[r_b], %[range], lsl #1] \n\t"
"add %[r_b] , %[tables] , %[norm_off] \n\t"
"sub %[r_c] , %[tmp] , %[range] \n\t"
"lsl %[tmp] , %[r_c] , #17 \n\t"
"cmp %[tmp] , %[low] \n\t"
"it gt \n\t"
"movgt %[range] , %[r_c] \n\t"
"itt cc \n\t"
"mvncc %[bit] , %[bit] \n\t"
"subcc %[low] , %[low] , %[tmp] \n\t"
"add %[r_c] , %[tables] , %[mlps_off] \n\t"
"ldrb %[tmp] , [%[r_b], %[range]] \n\t"
"ldrb %[r_b] , [%[r_c], %[bit]] \n\t"
"lsl %[low] , %[low] , %[tmp] \n\t"
"lsl %[range] , %[range] , %[tmp] \n\t"
"uxth %[r_c] , %[low] \n\t"
"strb %[r_b] , [%[state]] \n\t"
"tst %[r_c] , %[r_c] \n\t"
"bne 2f \n\t"
"ldr %[r_c] , [%[c], %[byte]] \n\t"
"ldr %[r_b] , [%[c], %[end]] \n\t"
"ldrh %[tmp] , [%[r_c]] \n\t"
"cmp %[r_c] , %[r_b] \n\t"
"itt lt \n\t"
"addlt %[r_c] , %[r_c] , #2 \n\t"
"strlt %[r_c] , [%[c], %[byte]] \n\t"
"sub %[r_c] , %[low] , #1 \n\t"
"add %[r_b] , %[tables] , %[norm_off] \n\t"
"eor %[r_c] , %[low] , %[r_c] \n\t"
"rev %[tmp] , %[tmp] \n\t"
"lsr %[r_c] , %[r_c] , #15 \n\t"
"lsr %[tmp] , %[tmp] , #15 \n\t"
"ldrb %[r_c] , [%[r_b], %[r_c]] \n\t"
"movw %[r_b] , #0xFFFF \n\t"
"sub %[tmp] , %[tmp] , %[r_b] \n\t"
"rsb %[r_c] , %[r_c] , #7 \n\t"
"lsl %[tmp] , %[tmp] , %[r_c] \n\t"
"add %[low] , %[low] , %[tmp] \n\t"
"2: \n\t"
: [bit]"=&r"(bit),
[low]"+&r"(c->low),
[range]"+&r"(c->range),
[r_b]"=&r"(reg_b),
[r_c]"=&r"(reg_c),
[tmp]"=&r"(tmp)
: [c]"r"(c),
[state]"r"(state),
[tables]"r"(ff_h264_cabac_tables),
[byte]"M"(offsetof(CABACContext, bytestream)),
[end]"M"(offsetof(CABACContext, bytestream_end)),
[norm_off]"I"(H264_NORM_SHIFT_OFFSET),
[lps_off]"I"(H264_LPS_RANGE_OFFSET),
[mlps_off]"I"(H264_MLPS_STATE_OFFSET + 128)
: "memory", "cc"
);
return bit & 1;
}
#endif /* HAVE_ARMV6T2_INLINE */
#endif /* AVCODEC_ARM_CABAC_H */

3
libavcodec/cabac_functions.h
View File

@ -35,6 +35,9 @@
#if ARCH_AARCH64
# include "aarch64/cabac.h"
#endif
#if ARCH_ARM
# include "arm/cabac.h"
#endif
#if ARCH_X86
# include "x86/cabac.h"
#endif