| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_decimate_q31.c |
| * Description: Q31 FIR Decimator |
| * |
| * $Date: 18. March 2019 |
| * $Revision: V1.6.0 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved. |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| * |
| * Licensed under the Apache License, Version 2.0 (the License); you may |
| * not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "arm_math.h" |
| |
| /** |
| @ingroup groupFilters |
| */ |
| |
| /** |
| @addtogroup FIR_decimate |
| @{ |
| */ |
| |
| /** |
| @brief Processing function for the Q31 FIR decimator. |
| @param[in] S points to an instance of the Q31 FIR decimator structure |
| @param[in] pSrc points to the block of input data |
| @param[out] pDst points to the block of output data |
| @param[in] blockSize number of samples to process |
| @return none |
| |
| @par Scaling and Overflow Behavior |
| The function is implemented using an internal 64-bit accumulator. |
| The accumulator has a 2.62 format and maintains full precision of the intermediate multiplication results but provides only a single guard bit. |
| Thus, if the accumulator result overflows it wraps around rather than clip. |
| In order to avoid overflows completely the input signal must be scaled down by log2(numTaps) bits (where log2 is read as log to the base 2). |
| After all multiply-accumulates are performed, the 2.62 accumulator is truncated to 1.32 format and then saturated to 1.31 format. |
| |
| @remark |
| Refer to \ref arm_fir_decimate_fast_q31() for a faster but less precise implementation of this function. |
| */ |
| |
| #if defined(ARM_MATH_MVEI) |
| |
| #include "arm_helium_utils.h" |
| |
| void arm_fir_decimate_q31( |
| const arm_fir_decimate_instance_q31 * S, |
| const q31_t * pSrc, |
| q31_t * pDst, |
| uint32_t blockSize) |
| { |
| q31_t *pState = S->pState; /* State pointer */ |
| const q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q31_t *pStateCurnt; /* Points to the current sample of the state */ |
| const q31_t *px, *pb; /* Temporary pointers for state and coefficient buffers */ |
| uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */ |
| uint32_t blkCntN4; |
| const q31_t *px0, *px1, *px2, *px3; |
| q63_t acc0v, acc1v, acc2v, acc3v; |
| q31x4_t x0v, x1v, x2v, x3v; |
| q31x4_t c0v; |
| |
| /* |
| * S->pState buffer contains previous frame (numTaps - 1) samples |
| * pStateCurnt points to the location where the new input data should be written |
| */ |
| pStateCurnt = S->pState + (numTaps - 1U); |
| /* |
| * Total number of output samples to be computed |
| */ |
| blkCnt = outBlockSize / 4; |
| blkCntN4 = outBlockSize - (4 * blkCnt); |
| |
| while (blkCnt > 0U) |
| { |
| /* |
| * Copy 4 * decimation factor number of new input samples into the state buffer |
| */ |
| i = (4 * S->M) >> 2; |
| do |
| { |
| vst1q(pStateCurnt, vldrwq_s32(pSrc)); |
| pSrc += 4; |
| pStateCurnt += 4; |
| i--; |
| } |
| while (i > 0U); |
| |
| /* |
| * Clear all accumulators |
| */ |
| acc0v = 0LL; |
| acc1v = 0LL; |
| acc2v = 0LL; |
| acc3v = 0LL; |
| /* |
| * Initialize state pointer for all the samples |
| */ |
| px0 = pState; |
| px1 = pState + S->M; |
| px2 = pState + 2 * S->M; |
| px3 = pState + 3 * S->M; |
| /* |
| * Initialize coeff. pointer |
| */ |
| pb = pCoeffs; |
| /* |
| * Loop unrolling. Process 4 taps at a time. |
| */ |
| tapCnt = numTaps >> 2; |
| /* |
| * Loop over the number of taps. Unroll by a factor of 4. |
| * Repeat until we've computed numTaps-4 coefficients. |
| */ |
| while (tapCnt > 0U) |
| { |
| /* |
| * Read the b[numTaps-1] coefficient |
| */ |
| c0v = vldrwq_s32(pb); |
| pb += 4; |
| /* |
| * Read x[n-numTaps-1] sample for acc0 |
| */ |
| x0v = vld1q(px0); |
| x1v = vld1q(px1); |
| x2v = vld1q(px2); |
| x3v = vld1q(px3); |
| px0 += 4; |
| px1 += 4; |
| px2 += 4; |
| px3 += 4; |
| |
| acc0v = vrmlaldavhaq(acc0v, x0v, c0v); |
| acc1v = vrmlaldavhaq(acc1v, x1v, c0v); |
| acc2v = vrmlaldavhaq(acc2v, x2v, c0v); |
| acc3v = vrmlaldavhaq(acc3v, x3v, c0v); |
| /* |
| * Decrement the loop counter |
| */ |
| tapCnt--; |
| } |
| |
| /* |
| * If the filter length is not a multiple of 4, compute the remaining filter taps |
| * should be tail predicated |
| */ |
| tapCnt = numTaps % 0x4U; |
| if (tapCnt > 0U) |
| { |
| mve_pred16_t p0 = vctp32q(tapCnt); |
| /* |
| * Read the b[numTaps-1] coefficient |
| */ |
| c0v = vldrwq_z_s32(pb, p0); |
| pb += 4; |
| /* |
| * Read x[n-numTaps-1] sample for acc0 |
| */ |
| x0v = vld1q(px0); |
| x1v = vld1q(px1); |
| x2v = vld1q(px2); |
| x3v = vld1q(px3); |
| px0 += 4; |
| px1 += 4; |
| px2 += 4; |
| px3 += 4; |
| |
| acc0v = vrmlaldavhaq(acc0v, x0v, c0v); |
| acc1v = vrmlaldavhaq(acc1v, x1v, c0v); |
| acc2v = vrmlaldavhaq(acc2v, x2v, c0v); |
| acc3v = vrmlaldavhaq(acc3v, x3v, c0v); |
| } |
| |
| acc0v = asrl(acc0v, 31 - 8); |
| acc1v = asrl(acc1v, 31 - 8); |
| acc2v = asrl(acc2v, 31 - 8); |
| acc3v = asrl(acc3v, 31 - 8); |
| /* |
| * store in the destination buffer. |
| */ |
| *pDst++ = (q31_t) acc0v; |
| *pDst++ = (q31_t) acc1v; |
| *pDst++ = (q31_t) acc2v; |
| *pDst++ = (q31_t) acc3v; |
| |
| /* |
| * Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples |
| */ |
| pState = pState + 4 * S->M; |
| /* |
| * Decrement the loop counter |
| */ |
| blkCnt--; |
| } |
| |
| while (blkCntN4 > 0U) |
| { |
| /* |
| * Copy decimation factor number of new input samples into the state buffer |
| */ |
| i = S->M; |
| do |
| { |
| *pStateCurnt++ = *pSrc++; |
| } |
| while (--i); |
| /* |
| * Set accumulator to zero |
| */ |
| acc0v = 0LL; |
| /* |
| * Initialize state pointer |
| */ |
| px = pState; |
| /* |
| * Initialize coeff. pointer |
| */ |
| pb = pCoeffs; |
| /* |
| * Loop unrolling. Process 4 taps at a time. |
| */ |
| tapCnt = numTaps >> 2; |
| /* |
| * Loop over the number of taps. Unroll by a factor of 4. |
| * Repeat until we've computed numTaps-4 coefficients. |
| */ |
| while (tapCnt > 0U) |
| { |
| c0v = vldrwq_s32(pb); |
| x0v = vldrwq_s32(px); |
| pb += 4; |
| px += 4; |
| acc0v = vrmlaldavhaq(acc0v, x0v, c0v); |
| /* |
| * Decrement the loop counter |
| */ |
| tapCnt--; |
| } |
| tapCnt = numTaps % 0x4U; |
| if (tapCnt > 0U) |
| { |
| mve_pred16_t p0 = vctp32q(tapCnt); |
| c0v = vldrwq_z_s32(pb, p0); |
| x0v = vldrwq_z_s32(px, p0); |
| acc0v = vrmlaldavhaq_p(acc0v, x0v, c0v, p0); |
| } |
| acc0v = asrl(acc0v, 31 - 8); |
| |
| /* |
| * Advance the state pointer by the decimation factor |
| * * to process the next group of decimation factor number samples |
| */ |
| pState = pState + S->M; |
| /* |
| * The result is in the accumulator, store in the destination buffer. |
| */ |
| *pDst++ = (q31_t) acc0v; |
| /* |
| * Decrement the loop counter |
| */ |
| blkCntN4--; |
| } |
| |
| /* |
| * Processing is complete. |
| * Now copy the last numTaps - 1 samples to the start of the state buffer. |
| * This prepares the state buffer for the next function call. |
| */ |
| pStateCurnt = S->pState; |
| blkCnt = (numTaps - 1) >> 2; |
| while (blkCnt > 0U) |
| { |
| vst1q(pStateCurnt, vldrwq_s32(pState)); |
| pState += 4; |
| pStateCurnt += 4; |
| blkCnt--; |
| } |
| blkCnt = (numTaps - 1) & 3; |
| if (blkCnt > 0U) |
| { |
| mve_pred16_t p0 = vctp32q(blkCnt); |
| vstrwq_p_s32(pStateCurnt, vldrwq_s32(pState), p0); |
| } |
| } |
| #else |
| void arm_fir_decimate_q31( |
| const arm_fir_decimate_instance_q31 * S, |
| const q31_t * pSrc, |
| q31_t * pDst, |
| uint32_t blockSize) |
| { |
| q31_t *pState = S->pState; /* State pointer */ |
| const q31_t *pCoeffs = S->pCoeffs; /* Coefficient pointer */ |
| q31_t *pStateCur; /* Points to the current sample of the state */ |
| q31_t *px0; /* Temporary pointer for state buffer */ |
| const q31_t *pb; /* Temporary pointer for coefficient buffer */ |
| q31_t x0, c0; /* Temporary variables to hold state and coefficient values */ |
| q63_t acc0; /* Accumulator */ |
| uint32_t numTaps = S->numTaps; /* Number of filter coefficients in the filter */ |
| uint32_t i, tapCnt, blkCnt, outBlockSize = blockSize / S->M; /* Loop counters */ |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| q31_t *px1, *px2, *px3; |
| q31_t x1, x2, x3; |
| q63_t acc1, acc2, acc3; |
| #endif |
| |
| /* S->pState buffer contains previous frame (numTaps - 1) samples */ |
| /* pStateCur points to the location where the new input data should be written */ |
| pStateCur = S->pState + (numTaps - 1U); |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 samples at a time */ |
| blkCnt = outBlockSize >> 2U; |
| |
| /* Samples loop unrolled by 4 */ |
| while (blkCnt > 0U) |
| { |
| /* Copy 4 * decimation factor number of new input samples into the state buffer */ |
| i = S->M * 4; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulators to zero */ |
| acc0 = 0; |
| acc1 = 0; |
| acc2 = 0; |
| acc3 = 0; |
| |
| /* Initialize state pointer for all the samples */ |
| px0 = pState; |
| px1 = pState + S->M; |
| px2 = pState + 2 * S->M; |
| px3 = pState + 3 * S->M; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-1] sample for acc0 */ |
| x0 = *(px0++); |
| /* Read x[n-numTaps-1] sample for acc1 */ |
| x1 = *(px1++); |
| /* Read x[n-numTaps-1] sample for acc2 */ |
| x2 = *(px2++); |
| /* Read x[n-numTaps-1] sample for acc3 */ |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| acc1 += (q63_t) x1 * c0; |
| acc2 += (q63_t) x2 * c0; |
| acc3 += (q63_t) x3 * c0; |
| |
| /* Read the b[numTaps-2] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-2] sample for acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| acc1 += (q63_t) x1 * c0; |
| acc2 += (q63_t) x2 * c0; |
| acc3 += (q63_t) x3 * c0; |
| |
| /* Read the b[numTaps-3] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-3] sample acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| acc1 += (q63_t) x1 * c0; |
| acc2 += (q63_t) x2 * c0; |
| acc3 += (q63_t) x3 * c0; |
| |
| /* Read the b[numTaps-4] coefficient */ |
| c0 = *(pb++); |
| |
| /* Read x[n-numTaps-4] sample acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| acc1 += (q63_t) x1 * c0; |
| acc2 += (q63_t) x2 * c0; |
| acc3 += (q63_t) x3 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *(pb++); |
| |
| /* Fetch state variables for acc0, acc1, acc2, acc3 */ |
| x0 = *(px0++); |
| x1 = *(px1++); |
| x2 = *(px2++); |
| x3 = *(px3++); |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| acc1 += (q63_t) x1 * c0; |
| acc2 += (q63_t) x2 * c0; |
| acc3 += (q63_t) x3 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M * 4; |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = (q31_t) (acc0 >> 31); |
| *pDst++ = (q31_t) (acc1 >> 31); |
| *pDst++ = (q31_t) (acc2 >> 31); |
| *pDst++ = (q31_t) (acc3 >> 31); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining samples */ |
| blkCnt = outBlockSize % 0x4U; |
| |
| #else |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = outBlockSize; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (blkCnt > 0U) |
| { |
| /* Copy decimation factor number of new input samples into the state buffer */ |
| i = S->M; |
| |
| do |
| { |
| *pStateCur++ = *pSrc++; |
| |
| } while (--i); |
| |
| /* Set accumulator to zero */ |
| acc0 = 0; |
| |
| /* Initialize state pointer */ |
| px0 = pState; |
| |
| /* Initialize coeff pointer */ |
| pb = pCoeffs; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = numTaps >> 2U; |
| |
| while (tapCnt > 0U) |
| { |
| /* Read the b[numTaps-1] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-1] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| |
| /* Read the b[numTaps-2] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-2] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| |
| /* Read the b[numTaps-3] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-3] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| |
| /* Read the b[numTaps-4] coefficient */ |
| c0 = *pb++; |
| |
| /* Read x[n-numTaps-4] sample */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = numTaps % 0x4U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = numTaps; |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| while (tapCnt > 0U) |
| { |
| /* Read coefficients */ |
| c0 = *pb++; |
| |
| /* Fetch 1 state variable */ |
| x0 = *px0++; |
| |
| /* Perform the multiply-accumulate */ |
| acc0 += (q63_t) x0 * c0; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Advance the state pointer by the decimation factor |
| * to process the next group of decimation factor number samples */ |
| pState = pState + S->M; |
| |
| /* The result is in the accumulator, store in the destination buffer. */ |
| *pDst++ = (q31_t) (acc0 >> 31); |
| |
| /* Decrement loop counter */ |
| blkCnt--; |
| } |
| |
| /* Processing is complete. |
| Now copy the last numTaps - 1 samples to the satrt of the state buffer. |
| This prepares the state buffer for the next function call. */ |
| |
| /* Points to the start of the state buffer */ |
| pStateCur = S->pState; |
| |
| #if defined (ARM_MATH_LOOPUNROLL) |
| |
| /* Loop unrolling: Compute 4 taps at a time */ |
| tapCnt = (numTaps - 1U) >> 2U; |
| |
| /* Copy data */ |
| while (tapCnt > 0U) |
| { |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| /* Loop unrolling: Compute remaining taps */ |
| tapCnt = (numTaps - 1U) % 0x04U; |
| |
| #else |
| |
| /* Initialize tapCnt with number of taps */ |
| tapCnt = (numTaps - 1U); |
| |
| #endif /* #if defined (ARM_MATH_LOOPUNROLL) */ |
| |
| /* Copy data */ |
| while (tapCnt > 0U) |
| { |
| *pStateCur++ = *pState++; |
| |
| /* Decrement loop counter */ |
| tapCnt--; |
| } |
| |
| } |
| #endif /* defined(ARM_MATH_MVEI) */ |
| /** |
| @} end of FIR_decimate group |
| */ |
