pigweed / third_party / github / STMicroelectronics / cmsis_core / refs/heads/cm4 / . / DSP / Source / FilteringFunctions / arm_correlate_opt_q7.c

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

* Project: CMSIS DSP Library | |

* Title: arm_correlate_opt_q7.c | |

* Description: Correlation of Q7 sequences | |

* | |

* $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 Q7 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 2 * max(srcALen, srcBLen) - 1. | |

@param[in] pScratch1 points to scratch buffer(of type q15_t) of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2. | |

@param[in] pScratch2 points to scratch buffer (of type q15_t) of size min(srcALen, srcBLen). | |

@return none | |

@par Scaling and Overflow Behavior | |

The function is implemented using a 32-bit internal accumulator. | |

Both the inputs are represented in 1.7 format and multiplications yield a 2.14 result. | |

The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format. | |

This approach provides 17 guard bits and there is no risk of overflow as long as <code>max(srcALen, srcBLen)<131072</code>. | |

The 18.14 result is then truncated to 18.7 format by discarding the low 7 bits and then saturated to 1.7 format. | |

*/ | |

void arm_correlate_opt_q7( | |

const q7_t * pSrcA, | |

uint32_t srcALen, | |

const q7_t * pSrcB, | |

uint32_t srcBLen, | |

q7_t * pDst, | |

q15_t * pScratch1, | |

q15_t * pScratch2) | |

{ | |

q15_t *pScr1 = pScratch1; /* Temporary pointer for scratch */ | |

q15_t *pScr2 = pScratch2; /* Temporary pointer for scratch */ | |

q15_t x4; /* Temporary input variable */ | |

q15_t *py; /* Temporary input2 pointer */ | |

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

const q7_t *pIn1, *pIn2; /* InputA and inputB pointer */ | |

uint32_t j, k, blkCnt, tapCnt; /* Loop counter */ | |

int32_t inc = 1; /* Output pointer increment */ | |

uint32_t outBlockSize; /* Loop counter */ | |

q31_t x1, x2, x3, y1; /* Temporary input variables */ | |

q7_t *pOut = pDst; /* Output pointer */ | |

/* 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 */ | |

/* But CORR(x, y) is reverse of CORR(y, x) */ | |

/* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */ | |

/* and the destination pointer modifier, inc is set to -1 */ | |

/* If srcALen > srcBLen, zero pad has to be done to srcB to make the two inputs of same length */ | |

/* But to improve the performance, | |

* we include zeroes in the output instead of zero padding either of the the inputs*/ | |

/* If srcALen > srcBLen, | |

* (srcALen - srcBLen) zeroes has to included in the starting of the output buffer */ | |

/* If srcALen < srcBLen, | |

* (srcALen - srcBLen) zeroes has to included in the ending of the output buffer */ | |

if (srcALen >= srcBLen) | |

{ | |

/* Initialization of inputA pointer */ | |

pIn1 = pSrcA; | |

/* Initialization of inputB pointer */ | |

pIn2 = pSrcB; | |

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

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

} | |

/* Copy (srcBLen) samples in scratch buffer */ | |

k = srcBLen >> 2U; | |

/* First part of the processing with loop unrolling copies 4 data points at a time. | |

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

while (k > 0U) | |

{ | |

/* copy second buffer in reversal manner */ | |

x4 = (q15_t) *pIn2++; | |

*pScr2++ = x4; | |

x4 = (q15_t) *pIn2++; | |

*pScr2++ = x4; | |

x4 = (q15_t) *pIn2++; | |

*pScr2++ = x4; | |

x4 = (q15_t) *pIn2++; | |

*pScr2++ = x4; | |

/* Decrement loop counter */ | |

k--; | |

} | |

/* If the count is not a multiple of 4, copy remaining samples here. | |

No loop unrolling is used. */ | |

k = srcBLen % 0x4U; | |

while (k > 0U) | |

{ | |

/* copy second buffer in reversal manner for remaining samples */ | |

x4 = (q15_t) *pIn2++; | |

*pScr2++ = x4; | |

/* Decrement loop counter */ | |

k--; | |

} | |

/* Fill (srcBLen - 1U) zeros in scratch buffer */ | |

arm_fill_q15(0, pScr1, (srcBLen - 1U)); | |

/* Update temporary scratch pointer */ | |

pScr1 += (srcBLen - 1U); | |

/* Copy (srcALen) samples in scratch buffer */ | |

/* Apply loop unrolling and do 4 Copies simultaneously. */ | |

k = srcALen >> 2U; | |

/* First part of the processing with loop unrolling copies 4 data points at a time. | |

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

while (k > 0U) | |

{ | |

/* copy second buffer in reversal manner */ | |

x4 = (q15_t) *pIn1++; | |

*pScr1++ = x4; | |

x4 = (q15_t) *pIn1++; | |

*pScr1++ = x4; | |

x4 = (q15_t) *pIn1++; | |

*pScr1++ = x4; | |

x4 = (q15_t) *pIn1++; | |

*pScr1++ = x4; | |

/* Decrement loop counter */ | |

k--; | |

} | |

/* If the count is not a multiple of 4, copy remaining samples here. | |

No loop unrolling is used. */ | |

k = srcALen % 0x4U; | |

while (k > 0U) | |

{ | |

/* copy second buffer in reversal manner for remaining samples */ | |

x4 = (q15_t) * pIn1++; | |

*pScr1++ = x4; | |

/* Decrement the loop counter */ | |

k--; | |

} | |

/* Fill (srcBLen - 1U) zeros at end of scratch buffer */ | |

arm_fill_q15(0, pScr1, (srcBLen - 1U)); | |

/* Update pointer */ | |

pScr1 += (srcBLen - 1U); | |

/* Temporary pointer for scratch2 */ | |

py = pScratch2; | |

/* Initialization of pScr2 pointer */ | |

pScr2 = pScratch2; | |

/* Actual correlation process starts here */ | |

blkCnt = (srcALen + srcBLen - 1U) >> 2; | |

while (blkCnt > 0) | |

{ | |

/* Initialze temporary scratch pointer as scratch1 */ | |

pScr1 = pScratch1; | |

/* Clear Accumlators */ | |

acc0 = 0; | |

acc1 = 0; | |

acc2 = 0; | |

acc3 = 0; | |

/* Read two samples from scratch1 buffer */ | |

x1 = read_q15x2_ia (&pScr1); | |

/* Read next two samples from scratch1 buffer */ | |

x2 = read_q15x2_ia (&pScr1); | |

tapCnt = (srcBLen) >> 2U; | |

while (tapCnt > 0U) | |

{ | |

/* Read four samples from smaller buffer */ | |

y1 = read_q15x2_ia (&pScr2); | |

/* multiply and accumlate */ | |

acc0 = __SMLAD(x1, y1, acc0); | |

acc2 = __SMLAD(x2, y1, acc2); | |

/* pack input data */ | |

#ifndef ARM_MATH_BIG_ENDIAN | |

x3 = __PKHBT(x2, x1, 0); | |

#else | |

x3 = __PKHBT(x1, x2, 0); | |

#endif | |

/* multiply and accumlate */ | |

acc1 = __SMLADX(x3, y1, acc1); | |

/* Read next two samples from scratch1 buffer */ | |

x1 = read_q15x2_ia (&pScr1); | |

/* pack input data */ | |

#ifndef ARM_MATH_BIG_ENDIAN | |

x3 = __PKHBT(x1, x2, 0); | |

#else | |

x3 = __PKHBT(x2, x1, 0); | |

#endif | |

acc3 = __SMLADX(x3, y1, acc3); | |

/* Read four samples from smaller buffer */ | |

y1 = read_q15x2_ia (&pScr2); | |

acc0 = __SMLAD(x2, y1, acc0); | |

acc2 = __SMLAD(x1, y1, acc2); | |

acc1 = __SMLADX(x3, y1, acc1); | |

x2 = read_q15x2_ia (&pScr1); | |

#ifndef ARM_MATH_BIG_ENDIAN | |

x3 = __PKHBT(x2, x1, 0); | |

#else | |

x3 = __PKHBT(x1, x2, 0); | |

#endif | |

acc3 = __SMLADX(x3, y1, acc3); | |

/* Decrement loop counter */ | |

tapCnt--; | |

} | |

/* Update scratch pointer for remaining samples of smaller length sequence */ | |

pScr1 -= 4U; | |

/* apply same above for remaining samples of smaller length sequence */ | |

tapCnt = (srcBLen) & 3U; | |

while (tapCnt > 0U) | |

{ | |

/* accumlate the results */ | |

acc0 += (*pScr1++ * *pScr2); | |

acc1 += (*pScr1++ * *pScr2); | |

acc2 += (*pScr1++ * *pScr2); | |

acc3 += (*pScr1++ * *pScr2++); | |

pScr1 -= 3U; | |

/* Decrement loop counter */ | |

tapCnt--; | |

} | |

blkCnt--; | |

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

*pOut = (q7_t) (__SSAT(acc0 >> 7U, 8)); | |

pOut += inc; | |

*pOut = (q7_t) (__SSAT(acc1 >> 7U, 8)); | |

pOut += inc; | |

*pOut = (q7_t) (__SSAT(acc2 >> 7U, 8)); | |

pOut += inc; | |

*pOut = (q7_t) (__SSAT(acc3 >> 7U, 8)); | |

pOut += inc; | |

/* Initialization of inputB pointer */ | |

pScr2 = py; | |

pScratch1 += 4U; | |

} | |

blkCnt = (srcALen + srcBLen - 1U) & 0x3; | |

/* Calculate correlation for remaining samples of Bigger length sequence */ | |

while (blkCnt > 0) | |

{ | |

/* Initialze temporary scratch pointer as scratch1 */ | |

pScr1 = pScratch1; | |

/* Clear Accumlators */ | |

acc0 = 0; | |

tapCnt = (srcBLen) >> 1U; | |

while (tapCnt > 0U) | |

{ | |

acc0 += (*pScr1++ * *pScr2++); | |

acc0 += (*pScr1++ * *pScr2++); | |

/* Decrement loop counter */ | |

tapCnt--; | |

} | |

tapCnt = (srcBLen) & 1U; | |

/* apply same above for remaining samples of smaller length sequence */ | |

while (tapCnt > 0U) | |

{ | |

/* accumlate the results */ | |

acc0 += (*pScr1++ * *pScr2++); | |

/* Decrement loop counter */ | |

tapCnt--; | |

} | |

blkCnt--; | |

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

*pOut = (q7_t) (__SSAT(acc0 >> 7U, 8)); | |

pOut += inc; | |

/* Initialization of inputB pointer */ | |

pScr2 = py; | |

pScratch1 += 1U; | |

} | |

} | |

/** | |

@} end of Corr group | |

*/ |