pigweed / third_party / github / STMicroelectronics / cmsis_core / refs/heads/cm4 / . / DSP / Source / FilteringFunctions / arm_correlate_fast_q31.c

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

* Project: CMSIS DSP Library | |

* Title: arm_correlate_fast_q31.c | |

* Description: Fast Q31 Correlation | |

* | |

* $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 Corr | |

@{ | |

*/ | |

/** | |

@brief Correlation of Q31 sequences (fast version). | |

@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 2 * max(srcALen, srcBLen) - 1. | |

@return none | |

@par Scaling and Overflow Behavior | |

This function is optimized for speed at the expense of fixed-point precision and overflow protection. | |

The result of each 1.31 x 1.31 multiplication is truncated to 2.30 format. | |

These intermediate results are accumulated in a 32-bit register in 2.30 format. | |

Finally, the accumulator is saturated and converted to a 1.31 result. | |

@par | |

The fast version has the same overflow behavior as the standard version but provides less precision since it discards the low 32 bits of each multiplication result. | |

In order to avoid overflows completely the input signals must be scaled down. | |

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

Scale down one of the inputs by 1/min(srcALen, srcBLen)to avoid overflows since a | |

maximum of min(srcALen, srcBLen) number of additions is carried internally. | |

@remark | |

Refer to \ref arm_correlate_q31() for a slower implementation of this function which uses 64-bit accumulation to provide higher precision. | |

*/ | |

void arm_correlate_fast_q31( | |

const q31_t * pSrcA, | |

uint32_t srcALen, | |

const q31_t * pSrcB, | |

uint32_t srcBLen, | |

q31_t * pDst) | |

{ | |

const q31_t *pIn1; /* InputA pointer */ | |

const q31_t *pIn2; /* InputB pointer */ | |

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

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

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

const q31_t *pSrc1; /* Intermediate pointers */ | |

q31_t sum, acc0, acc1, acc2, acc3; /* Accumulators */ | |

q31_t x0, x1, x2, x3, c0; /* Temporary variables for holding input and coefficient values */ | |

uint32_t blockSize1, blockSize2, blockSize3; /* Loop counters */ | |

uint32_t j, k, count, blkCnt; /* Loop counters */ | |

uint32_t outBlockSize; | |

int32_t inc = 1; /* Destination address modifier */ | |

/* 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; | |

/* Number of output samples is calculated */ | |

outBlockSize = (2U * srcALen) - 1U; | |

/* When srcALen > srcBLen, zero padding is done to srcB | |

* to make their lengths equal. | |

* Instead, (outBlockSize - (srcALen + srcBLen - 1)) | |

* number of output samples are made zero */ | |

j = outBlockSize - (srcALen + (srcBLen - 1U)); | |

/* Updating the pointer position to non zero value */ | |

pOut += j; | |

} | |

else | |

{ | |

/* Initialization of inputA pointer */ | |

pIn1 = pSrcB; | |

/* Initialization of inputB pointer */ | |

pIn2 = pSrcA; | |

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

j = srcBLen; | |

srcBLen = srcALen; | |

srcALen = j; | |

/* CORR(x, y) = Reverse order(CORR(y, x)) */ | |

/* Hence set the destination pointer to point to the last output sample */ | |

pOut = pDst + ((srcALen + srcBLen) - 2U); | |

/* Destination address modifier is set to -1 */ | |

inc = -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[srcBlen - 1] | |

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

* .... | |

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

*/ | |

/* 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 */ | |

pSrc1 = pIn2 + (srcBLen - 1U); | |

py = pSrc1; | |

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

* 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 - 4] */ | |

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* x[1] * y[srcBLen - 3] */ | |

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

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

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* x[3] * y[srcBLen - 1] */ | |

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* Decrement 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 */ | |

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

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* Decrement loop counter */ | |

k--; | |

} | |

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

*pOut = sum << 1; | |

/* Destination pointer is updated according to the address modifier, inc */ | |

pOut += inc; | |

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

py = pSrc1 - count; | |

px = pIn1; | |

/* Increment MAC count */ | |

count++; | |

/* Decrement loop counter */ | |

blockSize1--; | |

} | |

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

* Initializations of stage2 | |

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

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

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

* .... | |

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

*/ | |

/* Working pointer of inputA */ | |

px = pIn1; | |

/* Working pointer of inputB */ | |

py = pIn2; | |

/* 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 over blockSize2, by 4 */ | |

blkCnt = blockSize2 >> 2U; | |

while (blkCnt > 0U) | |

{ | |

/* Set all accumulators to zero */ | |

acc0 = 0; | |

acc1 = 0; | |

acc2 = 0; | |

acc3 = 0; | |

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

x0 = *px++; | |

x1 = *px++; | |

x2 = *px++; | |

/* 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. */ | |

do | |

{ | |

/* Read y[0] sample */ | |

c0 = *py++; | |

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

x3 = *px++; | |

/* Perform the multiply-accumulate */ | |

/* acc0 += x[0] * y[0] */ | |

acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); | |

/* acc1 += x[1] * y[0] */ | |

acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); | |

/* acc2 += x[2] * y[0] */ | |

acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32); | |

/* acc3 += x[3] * y[0] */ | |

acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32); | |

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

c0 = *py++; | |

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

x0 = *px++; | |

/* Perform the multiply-accumulate */ | |

/* acc0 += x[1] * y[1] */ | |

acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x1 * c0)) >> 32); | |

/* acc1 += x[2] * y[1] */ | |

acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x2 * c0)) >> 32); | |

/* acc2 += x[3] * y[1] */ | |

acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x3 * c0)) >> 32); | |

/* acc3 += x[4] * y[1] */ | |

acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x0 * c0)) >> 32); | |

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

c0 = *py++; | |

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

x1 = *px++; | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[2] * y[2] */ | |

acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x2 * c0)) >> 32); | |

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

acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x3 * c0)) >> 32); | |

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

acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x0 * c0)) >> 32); | |

/* acc3 += x[5] * y[2] */ | |

acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x1 * c0)) >> 32); | |

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

c0 = *py++; | |

/* Read x[6] sample */ | |

x2 = *px++; | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[3] * y[3] */ | |

acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x3 * c0)) >> 32); | |

/* acc1 += x[4] * y[3] */ | |

acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x0 * c0)) >> 32); | |

/* acc2 += x[5] * y[3] */ | |

acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x1 * c0)) >> 32); | |

/* acc3 += x[6] * y[3] */ | |

acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x2 * c0)) >> 32); | |

} while (--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) | |

{ | |

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

c0 = *py++; | |

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

x3 = *px++; | |

/* Perform the multiply-accumulates */ | |

/* acc0 += x[4] * y[4] */ | |

acc0 = (q31_t) ((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32); | |

/* acc1 += x[5] * y[4] */ | |

acc1 = (q31_t) ((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32); | |

/* acc2 += x[6] * y[4] */ | |

acc2 = (q31_t) ((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32); | |

/* acc3 += x[7] * y[4] */ | |

acc3 = (q31_t) ((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32); | |

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

x0 = x1; | |

x1 = x2; | |

x2 = x3; | |

/* Decrement loop counter */ | |

k--; | |

} | |

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

*pOut = (q31_t) (acc0 << 1); | |

/* Destination pointer is updated according to the address modifier, inc */ | |

pOut += inc; | |

*pOut = (q31_t) (acc1 << 1); | |

pOut += inc; | |

*pOut = (q31_t) (acc2 << 1); | |

pOut += inc; | |

*pOut = (q31_t) (acc3 << 1); | |

pOut += inc; | |

/* Increment the pointer pIn1 index, count by 4 */ | |

count += 4U; | |

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

px = pIn1 + count; | |

py = pIn2; | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

/* If the blockSize2 is not a multiple of 4, compute any remaining output samples here. | |

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

blkCnt = blockSize2 % 0x4U; | |

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 = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* Decrement 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 = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* Decrement loop counter */ | |

k--; | |

} | |

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

*pOut = sum << 1; | |

/* Destination pointer is updated according to the address modifier, inc */ | |

pOut += inc; | |

/* Increment MAC count */ | |

count++; | |

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

px = pIn1 + count; | |

py = pIn2; | |

/* Decrement 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 = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* Decrement loop counter */ | |

k--; | |

} | |

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

*pOut = sum << 1; | |

/* Destination pointer is updated according to the address modifier, inc */ | |

pOut += inc; | |

/* Increment MAC count */ | |

count++; | |

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

px = pIn1 + count; | |

py = pIn2; | |

/* Decrement loop counter */ | |

blkCnt--; | |

} | |

} | |

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

* Initializations of stage3 | |

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

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

* sum += x[srcALen-srcBLen+2] * y[0] + x[srcALen-srcBLen+3] * y[1] +...+ x[srcALen-1] * y[srcBLen-1] | |

* .... | |

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

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

*/ | |

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

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

count = srcBLen - 1U; | |

/* Working pointer of inputA */ | |

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

px = pSrc1; | |

/* Working pointer of inputB */ | |

py = pIn2; | |

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

* Stage3 process | |

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

while (blockSize3 > 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) | |

{ | |

/* Perform the multiply-accumulate */ | |

/* sum += x[srcALen - srcBLen + 4] * y[3] */ | |

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

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

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

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

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

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

sum = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* Decrement 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 = (q31_t) ((((q63_t) sum << 32) + | |

((q63_t) *px++ * (*py++))) >> 32); | |

/* Decrement loop counter */ | |

k--; | |

} | |

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

*pOut = sum << 1; | |

/* Destination pointer is updated according to the address modifier, inc */ | |

pOut += inc; | |

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

px = ++pSrc1; | |

py = pIn2; | |

/* Decrement MAC count */ | |

count--; | |

/* Decrement loop counter */ | |

blockSize3--; | |

} | |

} | |

/** | |

@} end of Corr group | |

*/ |