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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
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8  *
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12  * Lesser General Public License for more details.
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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_ARM_CABAC_H
20 #define AVCODEC_ARM_CABAC_H
21 
22 #include "config.h"
23 #if HAVE_ARMV6T2_INLINE
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_arm
30 static av_always_inline int get_cabac_inline_arm(CABACContext *c,
31  uint8_t *const state)
32 {
33  int bit;
34  void *reg_b, *reg_c, *tmp;
35 
36  __asm__ volatile(
37  "ldrb %[bit] , [%[state]] \n\t"
38  "add %[r_b] , %[tables] , %[lps_off] \n\t"
39  "mov %[tmp] , %[range] \n\t"
40  "and %[range] , %[range] , #0xC0 \n\t"
41  "add %[r_b] , %[r_b] , %[bit] \n\t"
42  "ldrb %[range] , [%[r_b], %[range], lsl #1] \n\t"
43  "add %[r_b] , %[tables] , %[norm_off] \n\t"
44  "sub %[r_c] , %[tmp] , %[range] \n\t"
45  "lsl %[tmp] , %[r_c] , #17 \n\t"
46  "cmp %[tmp] , %[low] \n\t"
47  "it gt \n\t"
48  "movgt %[range] , %[r_c] \n\t"
49  "itt cc \n\t"
50  "mvncc %[bit] , %[bit] \n\t"
51  "subcc %[low] , %[low] , %[tmp] \n\t"
52  "add %[r_c] , %[tables] , %[mlps_off] \n\t"
53  "ldrb %[tmp] , [%[r_b], %[range]] \n\t"
54  "ldrb %[r_b] , [%[r_c], %[bit]] \n\t"
55  "lsl %[low] , %[low] , %[tmp] \n\t"
56  "lsl %[range] , %[range] , %[tmp] \n\t"
57  "uxth %[r_c] , %[low] \n\t"
58  "strb %[r_b] , [%[state]] \n\t"
59  "tst %[r_c] , %[r_c] \n\t"
60  "bne 2f \n\t"
61  "ldr %[r_c] , [%[c], %[byte]] \n\t"
62 #if UNCHECKED_BITSTREAM_READER
63  "ldrh %[tmp] , [%[r_c]] \n\t"
64  "add %[r_c] , %[r_c] , #2 \n\t"
65  "str %[r_c] , [%[c], %[byte]] \n\t"
66 #else
67  "ldr %[r_b] , [%[c], %[end]] \n\t"
68  "ldrh %[tmp] , [%[r_c]] \n\t"
69  "cmp %[r_c] , %[r_b] \n\t"
70  "itt lt \n\t"
71  "addlt %[r_c] , %[r_c] , #2 \n\t"
72  "strlt %[r_c] , [%[c], %[byte]] \n\t"
73 #endif
74  "sub %[r_c] , %[low] , #1 \n\t"
75  "add %[r_b] , %[tables] , %[norm_off] \n\t"
76  "eor %[r_c] , %[low] , %[r_c] \n\t"
77  "rev %[tmp] , %[tmp] \n\t"
78  "lsr %[r_c] , %[r_c] , #15 \n\t"
79  "lsr %[tmp] , %[tmp] , #15 \n\t"
80  "ldrb %[r_c] , [%[r_b], %[r_c]] \n\t"
81  "movw %[r_b] , #0xFFFF \n\t"
82  "sub %[tmp] , %[tmp] , %[r_b] \n\t"
83  "rsb %[r_c] , %[r_c] , #7 \n\t"
84  "lsl %[tmp] , %[tmp] , %[r_c] \n\t"
85  "add %[low] , %[low] , %[tmp] \n\t"
86  "2: \n\t"
87  : [bit]"=&r"(bit),
88  [low]"+&r"(c->low),
89  [range]"+&r"(c->range),
90  [r_b]"=&r"(reg_b),
91  [r_c]"=&r"(reg_c),
92  [tmp]"=&r"(tmp)
93  : [c]"r"(c),
94  [state]"r"(state),
95  [tables]"r"(ff_h264_cabac_tables),
96  [byte]"M"(offsetof(CABACContext, bytestream)),
97  [end]"M"(offsetof(CABACContext, bytestream_end)),
98  [norm_off]"I"(H264_NORM_SHIFT_OFFSET),
99  [lps_off]"I"(H264_LPS_RANGE_OFFSET),
100  [mlps_off]"I"(H264_MLPS_STATE_OFFSET + 128)
101  : "memory", "cc"
102  );
103 
104  return bit & 1;
105 }
106 #endif /* HAVE_ARMV6T2_INLINE */
107 
108 #endif /* AVCODEC_ARM_CABAC_H */
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