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cabac.h
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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),
90  [tables]"r"(ff_h264_cabac_tables),
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 */
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