1@
2@ Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
3@
4@ Use of this source code is governed by a BSD-style license
5@ that can be found in the LICENSE file in the root of the source
6@ tree. An additional intellectual property rights grant can be found
7@ in the file PATENTS.  All contributing project authors may
8@ be found in the AUTHORS file in the root of the source tree.
9@
10
11@ This file contains the function WebRtcSpl_ComplexBitReverse(), optimized
12@ for ARMv5 platforms.
13@ Reference C code is in file complex_bit_reverse.c. Bit-exact.
14
15#include "webrtc/system_wrappers/include/asm_defines.h"
16
17GLOBAL_FUNCTION WebRtcSpl_ComplexBitReverse
18.align  2
19DEFINE_FUNCTION WebRtcSpl_ComplexBitReverse
20  push {r4-r7}
21
22  cmp r1, #7
23  adr r3, index_7                 @ Table pointer.
24  mov r4, #112                    @ Number of interations.
25  beq PRE_LOOP_STAGES_7_OR_8
26
27  cmp r1, #8
28  adr r3, index_8                 @ Table pointer.
29  mov r4, #240                    @ Number of interations.
30  beq PRE_LOOP_STAGES_7_OR_8
31
32  mov r3, #1                      @ Initialize m.
33  mov r1, r3, asl r1              @ n = 1 << stages;
34  subs r6, r1, #1                 @ nn = n - 1;
35  ble END
36
37  mov r5, r0                      @ &complex_data
38  mov r4, #0                      @ ml
39
40LOOP_GENERIC:
41  rsb r12, r4, r6                 @ l > nn - mr
42  mov r2, r1                      @ n
43
44LOOP_SHIFT:
45  asr r2, #1                      @ l >>= 1;
46  cmp r2, r12
47  bgt LOOP_SHIFT
48
49  sub r12, r2, #1
50  and r4, r12, r4
51  add r4, r2                      @ mr = (mr & (l - 1)) + l;
52  cmp r4, r3                      @ mr <= m ?
53  ble UPDATE_REGISTERS
54
55  mov r12, r4, asl #2
56  ldr r7, [r5, #4]                @ complex_data[2 * m, 2 * m + 1].
57                                  @   Offset 4 due to m incrementing from 1.
58  ldr r2, [r0, r12]               @ complex_data[2 * mr, 2 * mr + 1].
59  str r7, [r0, r12]
60  str r2, [r5, #4]
61
62UPDATE_REGISTERS:
63  add r3, r3, #1
64  add r5, #4
65  cmp r3, r1
66  bne LOOP_GENERIC
67
68  b END
69
70PRE_LOOP_STAGES_7_OR_8:
71  add r4, r3, r4, asl #1
72
73LOOP_STAGES_7_OR_8:
74  ldrsh r2, [r3], #2              @ index[m]
75  ldrsh r5, [r3], #2              @ index[m + 1]
76  ldr r1, [r0, r2]                @ complex_data[index[m], index[m] + 1]
77  ldr r12, [r0, r5]               @ complex_data[index[m + 1], index[m + 1] + 1]
78  cmp r3, r4
79  str r1, [r0, r5]
80  str r12, [r0, r2]
81  bne LOOP_STAGES_7_OR_8
82
83END:
84  pop {r4-r7}
85  bx lr
86
87@ The index tables. Note the values are doubles of the actual indexes for 16-bit
88@ elements, different from the generic C code. It actually provides byte offsets
89@ for the indexes.
90
91.align  2
92index_7:  @ Indexes for stages == 7.
93  .short 4, 256, 8, 128, 12, 384, 16, 64, 20, 320, 24, 192, 28, 448, 36, 288
94  .short 40, 160, 44, 416, 48, 96, 52, 352, 56, 224, 60, 480, 68, 272, 72, 144
95  .short 76, 400, 84, 336, 88, 208, 92, 464, 100, 304, 104, 176, 108, 432, 116
96  .short 368, 120, 240, 124, 496, 132, 264, 140, 392, 148, 328, 152, 200, 156
97  .short 456, 164, 296, 172, 424, 180, 360, 184, 232, 188, 488, 196, 280, 204
98  .short 408, 212, 344, 220, 472, 228, 312, 236, 440, 244, 376, 252, 504, 268
99  .short 388, 276, 324, 284, 452, 300, 420, 308, 356, 316, 484, 332, 404, 348
100  .short 468, 364, 436, 380, 500, 412, 460, 444, 492
101
102index_8:  @ Indexes for stages == 8.
103  .short 4, 512, 8, 256, 12, 768, 16, 128, 20, 640, 24, 384, 28, 896, 32, 64
104  .short 36, 576, 40, 320, 44, 832, 48, 192, 52, 704, 56, 448, 60, 960, 68, 544
105  .short 72, 288, 76, 800, 80, 160, 84, 672, 88, 416, 92, 928, 100, 608, 104
106  .short 352, 108, 864, 112, 224, 116, 736, 120, 480, 124, 992, 132, 528, 136
107  .short 272, 140, 784, 148, 656, 152, 400, 156, 912, 164, 592, 168, 336, 172
108  .short 848, 176, 208, 180, 720, 184, 464, 188, 976, 196, 560, 200, 304, 204
109  .short 816, 212, 688, 216, 432, 220, 944, 228, 624, 232, 368, 236, 880, 244
110  .short 752, 248, 496, 252, 1008, 260, 520, 268, 776, 276, 648, 280, 392, 284
111  .short 904, 292, 584, 296, 328, 300, 840, 308, 712, 312, 456, 316, 968, 324
112  .short 552, 332, 808, 340, 680, 344, 424, 348, 936, 356, 616, 364, 872, 372
113  .short 744, 376, 488, 380, 1000, 388, 536, 396, 792, 404, 664, 412, 920, 420
114  .short 600, 428, 856, 436, 728, 440, 472, 444, 984, 452, 568, 460, 824, 468
115  .short 696, 476, 952, 484, 632, 492, 888, 500, 760, 508, 1016, 524, 772, 532
116  .short 644, 540, 900, 548, 580, 556, 836, 564, 708, 572, 964, 588, 804, 596
117  .short 676, 604, 932, 620, 868, 628, 740, 636, 996, 652, 788, 668, 916, 684
118  .short 852, 692, 724, 700, 980, 716, 820, 732, 948, 748, 884, 764, 1012, 796
119  .short 908, 812, 844, 828, 972, 860, 940, 892, 1004, 956, 988
120