FFmpeg
cabac.h
Go to the documentation of this file.
1 /*
2  * This file is part of FFmpeg.
3  *
4  * FFmpeg is free software; you can redistribute it and/or
5  * modify it under the terms of the GNU Lesser General Public
6  * License as published by the Free Software Foundation; either
7  * version 2.1 of the License, or (at your option) any later version.
8  *
9  * FFmpeg is distributed in the hope that it will be useful,
10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12  * Lesser General Public License for more details.
13  *
14  * You should have received a copy of the GNU Lesser General Public
15  * License along with FFmpeg; if not, write to the Free Software
16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #ifndef AVCODEC_AARCH64_CABAC_H
20 #define AVCODEC_AARCH64_CABAC_H
21 
22 #include "config.h"
23 #if HAVE_INLINE_ASM
24 
25 #include "libavutil/attributes.h"
26 #include "libavutil/internal.h"
27 #include "libavcodec/cabac.h"
28 
29 #define get_cabac_inline get_cabac_inline_aarch64
30 static av_always_inline int get_cabac_inline_aarch64(CABACContext *c,
31  uint8_t *const state)
32 {
33  int bit;
34  void *reg_a, *reg_b, *reg_c, *tmp;
35 
36  __asm__ volatile(
37  "ldrb %w[bit] , [%[state]] \n\t"
38  "add %[r_b] , %[tables] , %[lps_off] \n\t"
39  "mov %w[tmp] , %w[range] \n\t"
40  "and %w[range] , %w[range] , #0xC0 \n\t"
41  "lsl %w[r_c] , %w[range] , #1 \n\t"
42  "add %[r_b] , %[r_b] , %w[bit], UXTW \n\t"
43  "ldrb %w[range] , [%[r_b], %w[r_c], SXTW] \n\t"
44  "sub %w[r_c] , %w[tmp] , %w[range] \n\t"
45  "lsl %w[tmp] , %w[r_c] , #17 \n\t"
46  "cmp %w[tmp] , %w[low] \n\t"
47  "csel %w[tmp] , %w[tmp] , wzr , cc \n\t"
48  "csel %w[range] , %w[r_c] , %w[range], gt \n\t"
49  "cinv %w[bit] , %w[bit] , cc \n\t"
50  "sub %w[low] , %w[low] , %w[tmp] \n\t"
51  "add %[r_b] , %[tables] , %[norm_off] \n\t"
52  "add %[r_a] , %[tables] , %[mlps_off] \n\t"
53  "ldrb %w[tmp] , [%[r_b], %w[range], SXTW] \n\t"
54  "ldrb %w[r_a] , [%[r_a], %w[bit], SXTW] \n\t"
55  "lsl %w[low] , %w[low] , %w[tmp] \n\t"
56  "lsl %w[range] , %w[range] , %w[tmp] \n\t"
57  "uxth %w[r_c] , %w[low] \n\t"
58  "strb %w[r_a] , [%[state]] \n\t"
59  "cbnz %w[r_c] , 2f \n\t"
60  "ldr %[r_c] , [%[c], %[byte]] \n\t"
61  "ldr %[r_a] , [%[c], %[end]] \n\t"
62  "ldrh %w[tmp] , [%[r_c]] \n\t"
63  "cmp %[r_c] , %[r_a] \n\t"
64  "b.ge 1f \n\t"
65  "add %[r_a] , %[r_c] , #2 \n\t"
66  "str %[r_a] , [%[c], %[byte]] \n\t"
67  "1: \n\t"
68  "sub %w[r_c] , %w[low] , #1 \n\t"
69  "eor %w[r_c] , %w[r_c] , %w[low] \n\t"
70  "rev %w[tmp] , %w[tmp] \n\t"
71  "lsr %w[r_c] , %w[r_c] , #15 \n\t"
72  "lsr %w[tmp] , %w[tmp] , #15 \n\t"
73  "ldrb %w[r_c] , [%[r_b], %w[r_c], SXTW] \n\t"
74  "mov %w[r_b] , #0xFFFF \n\t"
75  "mov %w[r_a] , #7 \n\t"
76  "sub %w[tmp] , %w[tmp] , %w[r_b] \n\t"
77  "sub %w[r_c] , %w[r_a] , %w[r_c] \n\t"
78  "lsl %w[tmp] , %w[tmp] , %w[r_c] \n\t"
79  "add %w[low] , %w[low] , %w[tmp] \n\t"
80  "2: \n\t"
81  : [bit]"=&r"(bit),
82  [low]"+&r"(c->low),
83  [range]"+&r"(c->range),
84  [r_a]"=&r"(reg_a),
85  [r_b]"=&r"(reg_b),
86  [r_c]"=&r"(reg_c),
87  [tmp]"=&r"(tmp)
88  : [c]"r"(c),
89  [state]"r"(state),
91  [byte]"i"(offsetof(CABACContext, bytestream)),
92  [end]"i"(offsetof(CABACContext, bytestream_end)),
93  [norm_off]"I"(H264_NORM_SHIFT_OFFSET),
94  [lps_off]"I"(H264_LPS_RANGE_OFFSET),
95  [mlps_off]"I"(H264_MLPS_STATE_OFFSET + 128)
96  : "memory", "cc"
97  );
98 
99  return bit & 1;
100 }
101 
102 #endif /* HAVE_INLINE_ASM */
103 
104 #endif /* AVCODEC_AARCH64_CABAC_H */
#define r_b
Macro definitions for various function/variable attributes.
uint8_t
static av_cold int end(AVCodecContext *avctx)
Definition: avrndec.c:90
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
common internal API header
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_WB16 unsigned int_TMPL byte
Definition: bytestream.h:87
int range
Definition: cabac.h:45
#define H264_MLPS_STATE_OFFSET
Definition: cabac.h:37
Writing a table generator This documentation is preliminary Parts of the API are not good and should be changed Basic concepts A table generator consists of two *_tablegen c and *_tablegen h The h file will provide the variable declarations and initialization code for the tables
Definition: tablegen.txt:8
#define H264_NORM_SHIFT_OFFSET
Definition: cabac.h:35
int low
Definition: cabac.h:44
const uint8_t ff_h264_cabac_tables[512+4 *2 *64+4 *64+63]
#define av_always_inline
Definition: attributes.h:39
static struct @304 state
Context Adaptive Binary Arithmetic Coder.
#define H264_LPS_RANGE_OFFSET
Definition: cabac.h:36
static uint8_t tmp[11]
Definition: aes_ctr.c:26