pigweed / third_party / github / STMicroelectronics / cmsis_core / 7dd288b23bf605a3a2fafa81a29d2c96a2fd83ce / . / DSP_Lib / Source / FilteringFunctions / arm_conv_q31.c

/* ---------------------------------------------------------------------- | |

* Copyright (C) 2010-2014 ARM Limited. All rights reserved. | |

* | |

* $Date: 19. March 2015 | |

* $Revision: V.1.4.5 | |

* | |

* Project: CMSIS DSP Library | |

* Title: arm_conv_q31.c | |

* | |

* Description: Convolution of Q31 sequences. | |

* | |

* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0 | |

* | |

* Redistribution and use in source and binary forms, with or without | |

* modification, are permitted provided that the following conditions | |

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* - Redistributions in binary form must reproduce the above copyright | |

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* distribution. | |

* - Neither the name of ARM LIMITED nor the names of its contributors | |

* may be used to endorse or promote products derived from this | |

* software without specific prior written permission. | |

* | |

* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |

* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |

* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS | |

* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE | |

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* -------------------------------------------------------------------- */ | |

#include "arm_math.h" | |

/** | |

* @ingroup groupFilters | |

*/ | |

/** | |

* @addtogroup Conv | |

* @{ | |

*/ | |

/** | |

* @brief Convolution of Q31 sequences. | |

* @param[in] *pSrcA points to the first input sequence. | |

* @param[in] srcALen length of the first input sequence. | |

* @param[in] *pSrcB points to the second input sequence. | |

* @param[in] srcBLen length of the second input sequence. | |

* @param[out] *pDst points to the location where the output result is written. Length srcALen+srcBLen-1. | |

* @return none. | |

* | |

* @details | |

* <b>Scaling and Overflow Behavior:</b> | |

* | |

* \par | |

* 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. | |

* There is no saturation on intermediate additions. | |

* Thus, if the accumulator overflows it wraps around and distorts the result. | |

* The input signals should be scaled down to avoid intermediate overflows. | |

* Scale down the inputs by log2(min(srcALen, srcBLen)) (log2 is read as log to the base 2) times to avoid overflows, | |

* as maximum of min(srcALen, srcBLen) number of additions are carried internally. | |

* The 2.62 accumulator is right shifted by 31 bits and saturated to 1.31 format to yield the final result. | |

* | |

* \par | |

* See <code>arm_conv_fast_q31()</code> for a faster but less precise implementation of this function for Cortex-M3 and Cortex-M4. | |

*/ | |

void arm_conv_q31( | |

q31_t * pSrcA, | |

uint32_t srcALen, | |

q31_t * pSrcB, | |

uint32_t srcBLen, | |

q31_t * pDst) | |

{ | |

#ifndef ARM_MATH_CM0_FAMILY | |

/* Run the below code for Cortex-M4 and Cortex-M3 */ | |

q31_t *pIn1; /* inputA pointer */ | |

q31_t *pIn2; /* inputB pointer */ | |

q31_t *pOut = pDst; /* output pointer */ | |

q31_t *px; /* Intermediate inputA pointer */ | |

q31_t *py; /* Intermediate inputB pointer */ | |

q31_t *pSrc1, *pSrc2; /* Intermediate pointers */ | |

q63_t sum; /* Accumulator */ | |

q63_t acc0, acc1, acc2; /* Accumulator */ | |

q31_t x0, x1, x2, c0; /* Temporary variables to hold state and coefficient values */ | |

uint32_t j, k, count, blkCnt, blockSize1, blockSize2, blockSize3; /* loop counter */ | |

/* The algorithm implementation is based on the lengths of the inputs. */ | |

/* srcB is always made to slide across srcA. */ | |

/* So srcBLen is always considered as shorter or equal to srcALen */ | |

if(srcALen >= srcBLen) | |

{ | |

/* Initialization of inputA pointer */ | |

pIn1 = pSrcA; | |

/* Initialization of inputB pointer */ | |

pIn2 = pSrcB; | |

} | |

else | |

{ | |

/* Initialization of inputA pointer */ | |

pIn1 = (q31_t *) pSrcB; | |

/* Initialization of inputB pointer */ | |

pIn2 = (q31_t *) pSrcA; | |

/* srcBLen is always considered as shorter or equal to srcALen */ | |

j = srcBLen; | |

srcBLen = srcALen; | |

srcALen = j; | |

} | |

/* conv(x,y) at n = x[n] * y[0] + x[n-1] * y[1] + x[n-2] * y[2] + ...+ x[n-N+1] * y[N -1] */ | |

/* The function is internally | |

* divided into three stages according to the number of multiplications that has to be | |

* taken place between inputA samples and inputB samples. In the first stage of the | |

* algorithm, the multiplications increase by one for every iteration. | |

* In the second stage of the algorithm, srcBLen number of multiplications are done. | |

* In the third stage of the algorithm, the multiplications decrease by one | |

* for every iteration. */ | |

/* The algorithm is implemented in three stages. | |

The loop counters of each stage is initiated here. */ | |

blockSize1 = srcBLen - 1u; | |

blockSize2 = srcALen - (srcBLen - 1u); | |

blockSize3 = blockSize1; | |

/* -------------------------- | |

* Initializations of stage1 | |

* -------------------------*/ | |

/* sum = x[0] * y[0] | |

* sum = x[0] * y[1] + x[1] * y[0] | |

* .... | |

* sum = x[0] * y[srcBlen - 1] + x[1] * y[srcBlen - 2] +...+ x[srcBLen - 1] * y[0] | |

*/ | |

/* In this stage the MAC operations are increased by 1 for every iteration. | |

The count variable holds the number of MAC operations performed */ | |

count = 1u; | |

/* Working pointer of inputA */ | |

px = pIn1; | |

/* Working pointer of inputB */ | |

py = pIn2; | |

/* ------------------------ | |

* Stage1 process | |

* ----------------------*/ | |

/* The first stage starts here */ | |

while(blockSize1 > 0u) | |

{ | |

/* Accumulator is made zero for every iteration */ | |

sum = 0; | |

/* Apply loop unrolling and compute 4 MACs simultaneously. */ | |

k = count >> 2u; | |

/* First part of the processing with loop unrolling. Compute 4 MACs at a time. | |

** a second loop below computes MACs for the remaining 1 to 3 samples. */ | |

while(k > 0u) | |

{ | |

/* x[0] * y[srcBLen - 1] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* x[1] * y[srcBLen - 2] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* x[2] * y[srcBLen - 3] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* x[3] * y[srcBLen - 4] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* If the count is not a multiple of 4, compute any remaining MACs here. | |

** No loop unrolling is used. */ | |

k = count % 0x4u; | |

while(k > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += (q63_t) * px++ * (*py--); | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut++ = (q31_t) (sum >> 31); | |

/* Update the inputA and inputB pointers for next MAC calculation */ | |

py = pIn2 + count; | |

px = pIn1; | |

/* Increment the MAC count */ | |

count++; | |

/* Decrement the loop counter */ | |

blockSize1--; | |

} | |

/* -------------------------- | |

* Initializations of stage2 | |

* ------------------------*/ | |

/* sum = x[0] * y[srcBLen-1] + x[1] * y[srcBLen-2] +...+ x[srcBLen-1] * y[0] | |

* sum = x[1] * y[srcBLen-1] + x[2] * y[srcBLen-2] +...+ x[srcBLen] * y[0] | |

* .... | |

* sum = x[srcALen-srcBLen-2] * y[srcBLen-1] + x[srcALen] * y[srcBLen-2] +...+ x[srcALen-1] * y[0] | |

*/ | |

/* Working pointer of inputA */ | |

px = pIn1; | |

/* Working pointer of inputB */ | |

pSrc2 = pIn2 + (srcBLen - 1u); | |

py = pSrc2; | |

/* count is index by which the pointer pIn1 to be incremented */ | |

count = 0u; | |

/* ------------------- | |

* Stage2 process | |

* ------------------*/ | |

/* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed. | |

* So, to loop unroll over blockSize2, | |

* srcBLen should be greater than or equal to 4 */ | |

if(srcBLen >= 4u) | |

{ | |

/* Loop unroll by 3 */ | |

blkCnt = blockSize2 / 3; | |

while(blkCnt > 0u) | |

{ | |

/* Set all accumulators to zero */ | |

acc0 = 0; | |

acc1 = 0; | |

acc2 = 0; | |

/* read x[0], x[1], x[2] samples */ | |

x0 = *(px++); | |

x1 = *(px++); | |

/* Apply loop unrolling and compute 3 MACs simultaneously. */ | |

k = srcBLen / 3; | |

/* First part of the processing with loop unrolling. Compute 3 MACs at a time. | |

** a second loop below computes MACs for the remaining 1 to 2 samples. */ | |

do | |

{ | |

/* Read y[srcBLen - 1] sample */ | |

c0 = *(py); | |

/* Read x[3] sample */ | |

x2 = *(px); | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[0] * y[srcBLen - 1] */ | |

acc0 += ((q63_t) x0 * c0); | |

/* acc1 += x[1] * y[srcBLen - 1] */ | |

acc1 += ((q63_t) x1 * c0); | |

/* acc2 += x[2] * y[srcBLen - 1] */ | |

acc2 += ((q63_t) x2 * c0); | |

/* Read y[srcBLen - 2] sample */ | |

c0 = *(py - 1u); | |

/* Read x[4] sample */ | |

x0 = *(px + 1u); | |

/* Perform the multiply-accumulate */ | |

/* acc0 += x[1] * y[srcBLen - 2] */ | |

acc0 += ((q63_t) x1 * c0); | |

/* acc1 += x[2] * y[srcBLen - 2] */ | |

acc1 += ((q63_t) x2 * c0); | |

/* acc2 += x[3] * y[srcBLen - 2] */ | |

acc2 += ((q63_t) x0 * c0); | |

/* Read y[srcBLen - 3] sample */ | |

c0 = *(py - 2u); | |

/* Read x[5] sample */ | |

x1 = *(px + 2u); | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[2] * y[srcBLen - 3] */ | |

acc0 += ((q63_t) x2 * c0); | |

/* acc1 += x[3] * y[srcBLen - 2] */ | |

acc1 += ((q63_t) x0 * c0); | |

/* acc2 += x[4] * y[srcBLen - 2] */ | |

acc2 += ((q63_t) x1 * c0); | |

/* update scratch pointers */ | |

px += 3u; | |

py -= 3u; | |

} while(--k); | |

/* If the srcBLen is not a multiple of 3, compute any remaining MACs here. | |

** No loop unrolling is used. */ | |

k = srcBLen - (3 * (srcBLen / 3)); | |

while(k > 0u) | |

{ | |

/* Read y[srcBLen - 5] sample */ | |

c0 = *(py--); | |

/* Read x[7] sample */ | |

x2 = *(px++); | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[4] * y[srcBLen - 5] */ | |

acc0 += ((q63_t) x0 * c0); | |

/* acc1 += x[5] * y[srcBLen - 5] */ | |

acc1 += ((q63_t) x1 * c0); | |

/* acc2 += x[6] * y[srcBLen - 5] */ | |

acc2 += ((q63_t) x2 * c0); | |

/* Reuse the present samples for the next MAC */ | |

x0 = x1; | |

x1 = x2; | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the results in the accumulators in the destination buffer. */ | |

*pOut++ = (q31_t) (acc0 >> 31); | |

*pOut++ = (q31_t) (acc1 >> 31); | |

*pOut++ = (q31_t) (acc2 >> 31); | |

/* Increment the pointer pIn1 index, count by 3 */ | |

count += 3u; | |

/* Update the inputA and inputB pointers for next MAC calculation */ | |

px = pIn1 + count; | |

py = pSrc2; | |

/* Decrement the loop counter */ | |

blkCnt--; | |

} | |

/* If the blockSize2 is not a multiple of 3, compute any remaining output samples here. | |

** No loop unrolling is used. */ | |

blkCnt = blockSize2 - 3 * (blockSize2 / 3); | |

while(blkCnt > 0u) | |

{ | |

/* Accumulator is made zero for every iteration */ | |

sum = 0; | |

/* Apply loop unrolling and compute 4 MACs simultaneously. */ | |

k = srcBLen >> 2u; | |

/* First part of the processing with loop unrolling. Compute 4 MACs at a time. | |

** a second loop below computes MACs for the remaining 1 to 3 samples. */ | |

while(k > 0u) | |

{ | |

/* Perform the multiply-accumulates */ | |

sum += (q63_t) * px++ * (*py--); | |

sum += (q63_t) * px++ * (*py--); | |

sum += (q63_t) * px++ * (*py--); | |

sum += (q63_t) * px++ * (*py--); | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* If the srcBLen is not a multiple of 4, compute any remaining MACs here. | |

** No loop unrolling is used. */ | |

k = srcBLen % 0x4u; | |

while(k > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += (q63_t) * px++ * (*py--); | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut++ = (q31_t) (sum >> 31); | |

/* Increment the MAC count */ | |

count++; | |

/* Update the inputA and inputB pointers for next MAC calculation */ | |

px = pIn1 + count; | |

py = pSrc2; | |

/* Decrement the loop counter */ | |

blkCnt--; | |

} | |

} | |

else | |

{ | |

/* If the srcBLen is not a multiple of 4, | |

* the blockSize2 loop cannot be unrolled by 4 */ | |

blkCnt = blockSize2; | |

while(blkCnt > 0u) | |

{ | |

/* Accumulator is made zero for every iteration */ | |

sum = 0; | |

/* srcBLen number of MACS should be performed */ | |

k = srcBLen; | |

while(k > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += (q63_t) * px++ * (*py--); | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut++ = (q31_t) (sum >> 31); | |

/* Increment the MAC count */ | |

count++; | |

/* Update the inputA and inputB pointers for next MAC calculation */ | |

px = pIn1 + count; | |

py = pSrc2; | |

/* Decrement the loop counter */ | |

blkCnt--; | |

} | |

} | |

/* -------------------------- | |

* Initializations of stage3 | |

* -------------------------*/ | |

/* sum += x[srcALen-srcBLen+1] * y[srcBLen-1] + x[srcALen-srcBLen+2] * y[srcBLen-2] +...+ x[srcALen-1] * y[1] | |

* sum += x[srcALen-srcBLen+2] * y[srcBLen-1] + x[srcALen-srcBLen+3] * y[srcBLen-2] +...+ x[srcALen-1] * y[2] | |

* .... | |

* sum += x[srcALen-2] * y[srcBLen-1] + x[srcALen-1] * y[srcBLen-2] | |

* sum += x[srcALen-1] * y[srcBLen-1] | |

*/ | |

/* In this stage the MAC operations are decreased by 1 for every iteration. | |

The blockSize3 variable holds the number of MAC operations performed */ | |

/* Working pointer of inputA */ | |

pSrc1 = (pIn1 + srcALen) - (srcBLen - 1u); | |

px = pSrc1; | |

/* Working pointer of inputB */ | |

pSrc2 = pIn2 + (srcBLen - 1u); | |

py = pSrc2; | |

/* ------------------- | |

* Stage3 process | |

* ------------------*/ | |

while(blockSize3 > 0u) | |

{ | |

/* Accumulator is made zero for every iteration */ | |

sum = 0; | |

/* Apply loop unrolling and compute 4 MACs simultaneously. */ | |

k = blockSize3 >> 2u; | |

/* First part of the processing with loop unrolling. Compute 4 MACs at a time. | |

** a second loop below computes MACs for the remaining 1 to 3 samples. */ | |

while(k > 0u) | |

{ | |

/* sum += x[srcALen - srcBLen + 1] * y[srcBLen - 1] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* sum += x[srcALen - srcBLen + 2] * y[srcBLen - 2] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* sum += x[srcALen - srcBLen + 3] * y[srcBLen - 3] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* sum += x[srcALen - srcBLen + 4] * y[srcBLen - 4] */ | |

sum += (q63_t) * px++ * (*py--); | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* If the blockSize3 is not a multiple of 4, compute any remaining MACs here. | |

** No loop unrolling is used. */ | |

k = blockSize3 % 0x4u; | |

while(k > 0u) | |

{ | |

/* Perform the multiply-accumulate */ | |

sum += (q63_t) * px++ * (*py--); | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Store the result in the accumulator in the destination buffer. */ | |

*pOut++ = (q31_t) (sum >> 31); | |

/* Update the inputA and inputB pointers for next MAC calculation */ | |

px = ++pSrc1; | |

py = pSrc2; | |

/* Decrement the loop counter */ | |

blockSize3--; | |

} | |

#else | |

/* Run the below code for Cortex-M0 */ | |

q31_t *pIn1 = pSrcA; /* input pointer */ | |

q31_t *pIn2 = pSrcB; /* coefficient pointer */ | |

q63_t sum; /* Accumulator */ | |

uint32_t i, j; /* loop counter */ | |

/* Loop to calculate output of convolution for output length number of times */ | |

for (i = 0; i < (srcALen + srcBLen - 1); i++) | |

{ | |

/* Initialize sum with zero to carry on MAC operations */ | |

sum = 0; | |

/* Loop to perform MAC operations according to convolution equation */ | |

for (j = 0; j <= i; j++) | |

{ | |

/* Check the array limitations */ | |

if(((i - j) < srcBLen) && (j < srcALen)) | |

{ | |

/* z[i] += x[i-j] * y[j] */ | |

sum += ((q63_t) pIn1[j] * (pIn2[i - j])); | |

} | |

} | |

/* Store the output in the destination buffer */ | |

pDst[i] = (q31_t) (sum >> 31u); | |

} | |

#endif /* #ifndef ARM_MATH_CM0_FAMILY */ | |

} | |

/** | |

* @} end of Conv group | |

*/ |