| @ |
| @ Copyright (c) 2012 The WebRTC project authors. All Rights Reserved. |
| @ |
| @ Use of this source code is governed by a BSD-style license |
| @ that can be found in the LICENSE file in the root of the source |
| @ tree. An additional intellectual property rights grant can be found |
| @ in the file PATENTS. All contributing project authors may |
| @ be found in the AUTHORS file in the root of the source tree. |
| @ |
| |
| @ This file contains the function WebRtcSpl_DownsampleFast(), optimized for |
| @ ARM Neon platform. The description header can be found in |
| @ signal_processing_library.h |
| @ |
| @ The reference C code is in file downsample_fast.c. Bit-exact. |
| |
| .arch armv7-a |
| .fpu neon |
| |
| .align 2 |
| .global WebRtcSpl_DownsampleFast |
| |
| WebRtcSpl_DownsampleFast: |
| |
| .fnstart |
| |
| .save {r4-r11} |
| push {r4-r11} |
| |
| cmp r3, #0 @ data_out_length <= 0? |
| movle r0, #-1 |
| ble END |
| |
| ldrsh r12, [sp, #44] |
| ldr r5, [sp, #40] @ r5: factor |
| add r4, r12, #1 @ r4: delay + 1 |
| sub r3, r3, #1 @ r3: data_out_length - 1 |
| smulbb r3, r5, r3 |
| ldr r8, [sp, #32] @ &coefficients[0] |
| mov r9, r12 @ Iteration counter for outer loops. |
| add r3, r4 @ delay + factor * (out_length-1) +1 |
| |
| cmp r3, r1 @ data_in_length < endpos? |
| movgt r0, #-1 |
| bgt END |
| |
| @ Initializations. |
| sub r3, r5, asl #3 |
| add r11, r0, r12, asl #1 @ &data_in[delay] |
| ldr r0, [sp, #36] @ coefficients_length |
| add r3, r5 @ endpos - factor * 7 |
| |
| cmp r0, #0 @ coefficients_length <= 0 ? |
| movle r0, #-1 |
| ble END |
| |
| add r8, r0, asl #1 @ &coeffieient[coefficients_length] |
| cmp r9, r3 |
| bge POST_LOOP_ENDPOS @ branch when Iteration < 8 times. |
| |
| @ |
| @ First part, unroll the loop 8 times, with 3 subcases (factor == 2, 4, others) |
| @ |
| mov r4, #-2 |
| |
| @ Direct program flow to the right channel. |
| |
| @ r10 is an offset to &data_in[] in the loop. After an iteration, we need to |
| @ move the pointer back to original after advancing 16 bytes by a vld1, and |
| @ then move 2 bytes forward to increment one more sample. |
| cmp r5, #2 |
| moveq r10, #-14 |
| beq LOOP_ENDPOS_FACTOR2 @ Branch when factor == 2 |
| |
| @ Similar here, for r10, we need to move the pointer back to original after |
| @ advancing 32 bytes, then move 2 bytes forward to increment one sample. |
| cmp r5, #4 |
| moveq r10, #-30 |
| beq LOOP_ENDPOS_FACTOR4 @ Branch when factor == 4 |
| |
| @ For r10, we need to move the pointer back to original after advancing |
| @ (factor * 7 * 2) bytes, then move 2 bytes forward to increment one sample. |
| mov r10, r5, asl #4 |
| rsb r10, #2 |
| add r10, r5, asl #1 |
| lsl r5, #1 @ r5 = factor * sizeof(data_in) |
| |
| @ The general case (factor != 2 && factor != 4) |
| LOOP_ENDPOS_GENERAL: |
| @ Initializations. |
| vmov.i32 q2, #2048 |
| vmov.i32 q3, #2048 |
| sub r7, r8, #2 |
| sub r12, r0, #1 @ coefficients_length - 1 |
| sub r1, r11, r12, asl #1 @ &data_in[i - j] |
| |
| LOOP_COEFF_LENGTH_GENERAL: |
| vld1.16 {d2[], d3[]}, [r7], r4 @ coefficients[j] |
| vld1.16 d0[0], [r1], r5 @ data_in[i - j] |
| vld1.16 d0[1], [r1], r5 @ data_in[i + factor - j] |
| vld1.16 d0[2], [r1], r5 @ data_in[i + factor * 2 - j] |
| vld1.16 d0[3], [r1], r5 @ data_in[i + factor * 3 - j] |
| vld1.16 d1[0], [r1], r5 @ data_in[i + factor * 4 - j] |
| vld1.16 d1[1], [r1], r5 @ data_in[i + factor * 5 - j] |
| vld1.16 d1[2], [r1], r5 @ data_in[i + factor * 6 - j] |
| vld1.16 d1[3], [r1], r10 @ data_in[i + factor * 7 - j] |
| subs r12, #1 |
| vmlal.s16 q2, d0, d2 |
| vmlal.s16 q3, d1, d3 |
| bge LOOP_COEFF_LENGTH_GENERAL |
| |
| @ Shift, saturate, and store the result. |
| vqshrn.s32 d0, q2, #12 |
| vqshrn.s32 d1, q3, #12 |
| vst1.16 {d0, d1}, [r2]! |
| |
| add r11, r5, asl #3 @ r11 -> &data_in[i + factor * 8] |
| add r9, r5, asl #2 @ Counter i = delay + factor * 8. |
| cmp r9, r3 @ i < endpos - factor * 7 ? |
| blt LOOP_ENDPOS_GENERAL |
| asr r5, #1 @ Restore r5 to the value of factor. |
| b POST_LOOP_ENDPOS |
| |
| @ The case for factor == 2. |
| LOOP_ENDPOS_FACTOR2: |
| @ Initializations. |
| vmov.i32 q2, #2048 |
| vmov.i32 q3, #2048 |
| sub r7, r8, #2 |
| sub r12, r0, #1 @ coefficients_length - 1 |
| sub r1, r11, r12, asl #1 @ &data_in[i - j] |
| |
| LOOP_COEFF_LENGTH_FACTOR2: |
| vld1.16 {d16[], d17[]}, [r7], r4 @ coefficients[j] |
| vld2.16 {d0, d1}, [r1]! @ data_in[] |
| vld2.16 {d2, d3}, [r1], r10 @ data_in[] |
| subs r12, #1 |
| vmlal.s16 q2, d0, d16 |
| vmlal.s16 q3, d2, d17 |
| bge LOOP_COEFF_LENGTH_FACTOR2 |
| |
| @ Shift, saturate, and store the result. |
| vqshrn.s32 d0, q2, #12 |
| vqshrn.s32 d1, q3, #12 |
| vst1.16 {d0, d1}, [r2]! |
| |
| add r11, r5, asl #4 @ r11 -> &data_in[i + factor * 8] |
| add r9, r5, asl #3 @ Counter i = delay + factor * 8. |
| cmp r9, r3 @ i < endpos - factor * 7 ? |
| blt LOOP_ENDPOS_FACTOR2 |
| b POST_LOOP_ENDPOS |
| |
| @ The case for factor == 4. |
| LOOP_ENDPOS_FACTOR4: |
| @ Initializations. |
| vmov.i32 q2, #2048 |
| vmov.i32 q3, #2048 |
| sub r7, r8, #2 |
| sub r12, r0, #1 @ coefficients_length - 1 |
| sub r1, r11, r12, asl #1 @ &data_in[i - j] |
| |
| LOOP_COEFF_LENGTH_FACTOR4: |
| vld1.16 {d16[], d17[]}, [r7], r4 @ coefficients[j] |
| vld4.16 {d0, d1, d2, d3}, [r1]! @ data_in[] |
| vld4.16 {d18, d19, d20, d21}, [r1], r10 @ data_in[] |
| subs r12, #1 |
| vmlal.s16 q2, d0, d16 |
| vmlal.s16 q3, d18, d17 |
| bge LOOP_COEFF_LENGTH_FACTOR4 |
| |
| @ Shift, saturate, and store the result. |
| vqshrn.s32 d0, q2, #12 |
| vqshrn.s32 d1, q3, #12 |
| vst1.16 {d0, d1}, [r2]! |
| |
| add r11, r5, asl #4 @ r11 -> &data_in[i + factor * 8] |
| add r9, r5, asl #3 @ Counter i = delay + factor * 8. |
| cmp r9, r3 @ i < endpos - factor * 7 ? |
| blt LOOP_ENDPOS_FACTOR4 |
| |
| @ |
| @ Second part, do the rest iterations (if any). |
| @ |
| |
| POST_LOOP_ENDPOS: |
| add r3, r5, asl #3 |
| sub r3, r5 @ Restore r3 to endpos. |
| cmp r9, r3 |
| movge r0, #0 |
| bge END |
| |
| LOOP2_ENDPOS: |
| @ Initializations. |
| mov r7, r8 |
| sub r12, r0, #1 @ coefficients_length - 1 |
| sub r6, r11, r12, asl #1 @ &data_in[i - j] |
| |
| mov r1, #2048 |
| |
| LOOP2_COEFF_LENGTH: |
| ldrsh r4, [r7, #-2]! @ coefficients[j] |
| ldrsh r10, [r6], #2 @ data_in[i - j] |
| smlabb r1, r4, r10, r1 |
| subs r12, #1 |
| bge LOOP2_COEFF_LENGTH |
| |
| @ Shift, saturate, and store the result. |
| ssat r1, #16, r1, asr #12 |
| strh r1, [r2], #2 |
| |
| add r11, r5, asl #1 @ r11 -> &data_in[i + factor] |
| add r9, r5 @ Counter i = delay + factor. |
| cmp r9, r3 @ i < endpos? |
| blt LOOP2_ENDPOS |
| |
| mov r0, #0 |
| |
| END: |
| pop {r4-r11} |
| bx lr |
| |
| .fnend |
