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_DownsampleFastNeon(), optimized for 12 @ ARM Neon platform. The description header can be found in 13 @ signal_processing_library.h 14 @ 15 @ The reference C code is in file downsample_fast.c. Bit-exact. 16 17 #include "webrtc/system_wrappers/interface/asm_defines.h" 18 19 GLOBAL_FUNCTION WebRtcSpl_DownsampleFastNeon 20 .align 2 21 DEFINE_FUNCTION WebRtcSpl_DownsampleFastNeon 22 push {r4-r11} 23 24 cmp r3, #0 @ data_out_length <= 0? 25 movle r0, #-1 26 ble END 27 28 ldrsh r12, [sp, #44] 29 ldr r5, [sp, #40] @ r5: factor 30 add r4, r12, #1 @ r4: delay + 1 31 sub r3, r3, #1 @ r3: data_out_length - 1 32 smulbb r3, r5, r3 33 ldr r8, [sp, #32] @ &coefficients[0] 34 mov r9, r12 @ Iteration counter for outer loops. 35 add r3, r4 @ delay + factor * (out_length-1) +1 36 37 cmp r3, r1 @ data_in_length < endpos? 38 movgt r0, #-1 39 bgt END 40 41 @ Initializations. 42 sub r3, r5, asl #3 43 add r11, r0, r12, asl #1 @ &data_in[delay] 44 ldr r0, [sp, #36] @ coefficients_length 45 add r3, r5 @ endpos - factor * 7 46 47 cmp r0, #0 @ coefficients_length <= 0 ? 48 movle r0, #-1 49 ble END 50 51 add r8, r0, asl #1 @ &coeffieient[coefficients_length] 52 cmp r9, r3 53 bge POST_LOOP_ENDPOS @ branch when Iteration < 8 times. 54 55 @ 56 @ First part, unroll the loop 8 times, with 3 subcases (factor == 2, 4, others) 57 @ 58 mov r4, #-2 59 60 @ Direct program flow to the right channel. 61 62 @ r10 is an offset to &data_in[] in the loop. After an iteration, we need to 63 @ move the pointer back to original after advancing 16 bytes by a vld1, and 64 @ then move 2 bytes forward to increment one more sample. 65 cmp r5, #2 66 moveq r10, #-14 67 beq LOOP_ENDPOS_FACTOR2 @ Branch when factor == 2 68 69 @ Similar here, for r10, we need to move the pointer back to original after 70 @ advancing 32 bytes, then move 2 bytes forward to increment one sample. 71 cmp r5, #4 72 moveq r10, #-30 73 beq LOOP_ENDPOS_FACTOR4 @ Branch when factor == 4 74 75 @ For r10, we need to move the pointer back to original after advancing 76 @ (factor * 7 * 2) bytes, then move 2 bytes forward to increment one sample. 77 mov r10, r5, asl #4 78 rsb r10, #2 79 add r10, r5, asl #1 80 lsl r5, #1 @ r5 = factor * sizeof(data_in) 81 82 @ The general case (factor != 2 && factor != 4) 83 LOOP_ENDPOS_GENERAL: 84 @ Initializations. 85 vmov.i32 q2, #2048 86 vmov.i32 q3, #2048 87 sub r7, r8, #2 88 sub r12, r0, #1 @ coefficients_length - 1 89 sub r1, r11, r12, asl #1 @ &data_in[i - j] 90 91 LOOP_COEFF_LENGTH_GENERAL: 92 vld1.16 {d2[], d3[]}, [r7], r4 @ coefficients[j] 93 vld1.16 d0[0], [r1], r5 @ data_in[i - j] 94 vld1.16 d0[1], [r1], r5 @ data_in[i + factor - j] 95 vld1.16 d0[2], [r1], r5 @ data_in[i + factor * 2 - j] 96 vld1.16 d0[3], [r1], r5 @ data_in[i + factor * 3 - j] 97 vld1.16 d1[0], [r1], r5 @ data_in[i + factor * 4 - j] 98 vld1.16 d1[1], [r1], r5 @ data_in[i + factor * 5 - j] 99 vld1.16 d1[2], [r1], r5 @ data_in[i + factor * 6 - j] 100 vld1.16 d1[3], [r1], r10 @ data_in[i + factor * 7 - j] 101 subs r12, #1 102 vmlal.s16 q2, d0, d2 103 vmlal.s16 q3, d1, d3 104 bge LOOP_COEFF_LENGTH_GENERAL 105 106 @ Shift, saturate, and store the result. 107 vqshrn.s32 d0, q2, #12 108 vqshrn.s32 d1, q3, #12 109 vst1.16 {d0, d1}, [r2]! 110 111 add r11, r5, asl #3 @ r11 -> &data_in[i + factor * 8] 112 add r9, r5, asl #2 @ Counter i = delay + factor * 8. 113 cmp r9, r3 @ i < endpos - factor * 7 ? 114 blt LOOP_ENDPOS_GENERAL 115 asr r5, #1 @ Restore r5 to the value of factor. 116 b POST_LOOP_ENDPOS 117 118 @ The case for factor == 2. 119 LOOP_ENDPOS_FACTOR2: 120 @ Initializations. 121 vmov.i32 q2, #2048 122 vmov.i32 q3, #2048 123 sub r7, r8, #2 124 sub r12, r0, #1 @ coefficients_length - 1 125 sub r1, r11, r12, asl #1 @ &data_in[i - j] 126 127 LOOP_COEFF_LENGTH_FACTOR2: 128 vld1.16 {d16[], d17[]}, [r7], r4 @ coefficients[j] 129 vld2.16 {d0, d1}, [r1]! @ data_in[] 130 vld2.16 {d2, d3}, [r1], r10 @ data_in[] 131 subs r12, #1 132 vmlal.s16 q2, d0, d16 133 vmlal.s16 q3, d2, d17 134 bge LOOP_COEFF_LENGTH_FACTOR2 135 136 @ Shift, saturate, and store the result. 137 vqshrn.s32 d0, q2, #12 138 vqshrn.s32 d1, q3, #12 139 vst1.16 {d0, d1}, [r2]! 140 141 add r11, r5, asl #4 @ r11 -> &data_in[i + factor * 8] 142 add r9, r5, asl #3 @ Counter i = delay + factor * 8. 143 cmp r9, r3 @ i < endpos - factor * 7 ? 144 blt LOOP_ENDPOS_FACTOR2 145 b POST_LOOP_ENDPOS 146 147 @ The case for factor == 4. 148 LOOP_ENDPOS_FACTOR4: 149 @ Initializations. 150 vmov.i32 q2, #2048 151 vmov.i32 q3, #2048 152 sub r7, r8, #2 153 sub r12, r0, #1 @ coefficients_length - 1 154 sub r1, r11, r12, asl #1 @ &data_in[i - j] 155 156 LOOP_COEFF_LENGTH_FACTOR4: 157 vld1.16 {d16[], d17[]}, [r7], r4 @ coefficients[j] 158 vld4.16 {d0, d1, d2, d3}, [r1]! @ data_in[] 159 vld4.16 {d18, d19, d20, d21}, [r1], r10 @ data_in[] 160 subs r12, #1 161 vmlal.s16 q2, d0, d16 162 vmlal.s16 q3, d18, d17 163 bge LOOP_COEFF_LENGTH_FACTOR4 164 165 add r11, r5, asl #4 @ r11 -> &data_in[i + factor * 8] 166 add r9, r5, asl #3 @ Counter i = delay + factor * 8. 167 168 @ Shift, saturate, and store the result. 169 vqshrn.s32 d0, q2, #12 170 vqshrn.s32 d1, q3, #12 171 cmp r9, r3 @ i < endpos - factor * 7 ? 172 vst1.16 {d0, d1}, [r2]! 173 174 blt LOOP_ENDPOS_FACTOR4 175 176 @ 177 @ Second part, do the rest iterations (if any). 178 @ 179 180 POST_LOOP_ENDPOS: 181 add r3, r5, asl #3 182 sub r3, r5 @ Restore r3 to endpos. 183 cmp r9, r3 184 movge r0, #0 185 bge END 186 187 LOOP2_ENDPOS: 188 @ Initializations. 189 mov r7, r8 190 sub r12, r0, #1 @ coefficients_length - 1 191 sub r6, r11, r12, asl #1 @ &data_in[i - j] 192 193 mov r1, #2048 194 195 LOOP2_COEFF_LENGTH: 196 ldrsh r4, [r7, #-2]! @ coefficients[j] 197 ldrsh r10, [r6], #2 @ data_in[i - j] 198 smlabb r1, r4, r10, r1 199 subs r12, #1 200 bge LOOP2_COEFF_LENGTH 201 202 @ Shift, saturate, and store the result. 203 ssat r1, #16, r1, asr #12 204 strh r1, [r2], #2 205 206 add r11, r5, asl #1 @ r11 -> &data_in[i + factor] 207 add r9, r5 @ Counter i = delay + factor. 208 cmp r9, r3 @ i < endpos? 209 blt LOOP2_ENDPOS 210 211 mov r0, #0 212 213 END: 214 pop {r4-r11} 215 bx lr 216
