121 lines
3.3 KiB
C
121 lines
3.3 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_sub_q15.c
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* Description: Q15 vector subtraction
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*
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* $Date: 18. March 2019
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* $Revision: V1.6.0
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*
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* Target Processor: Cortex-M cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "arm_math.h"
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/**
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@ingroup groupMath
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*/
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/**
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@addtogroup BasicSub
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@{
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*/
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/**
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@brief Q15 vector subtraction.
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@param[in] pSrcA points to the first input vector
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@param[in] pSrcB points to the second input vector
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@param[out] pDst points to the output vector
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@param[in] blockSize number of samples in each vector
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@return none
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@par Scaling and Overflow Behavior
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The function uses saturating arithmetic.
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Results outside of the allowable Q15 range [0x8000 0x7FFF]
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are saturated.
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*/
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void arm_sub_q15(const q15_t *pSrcA, const q15_t *pSrcB, q15_t *pDst,
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uint32_t blockSize) {
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uint32_t blkCnt; /* Loop counter */
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#if defined(ARM_MATH_LOOPUNROLL)
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#if defined(ARM_MATH_DSP)
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q31_t inA1, inA2;
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q31_t inB1, inB2;
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#endif
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/* Loop unrolling: Compute 4 outputs at a time */
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blkCnt = blockSize >> 2U;
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while (blkCnt > 0U) {
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/* C = A - B */
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#if defined(ARM_MATH_DSP)
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/* read 2 times 2 samples at a time from sourceA */
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inA1 = read_q15x2_ia((q15_t **)&pSrcA);
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inA2 = read_q15x2_ia((q15_t **)&pSrcA);
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/* read 2 times 2 samples at a time from sourceB */
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inB1 = read_q15x2_ia((q15_t **)&pSrcB);
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inB2 = read_q15x2_ia((q15_t **)&pSrcB);
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/* Subtract and store 2 times 2 samples at a time */
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write_q15x2_ia(&pDst, __QSUB16(inA1, inB1));
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write_q15x2_ia(&pDst, __QSUB16(inA2, inB2));
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#else
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*pDst++ = (q15_t)__SSAT(((q31_t)*pSrcA++ - *pSrcB++), 16);
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*pDst++ = (q15_t)__SSAT(((q31_t)*pSrcA++ - *pSrcB++), 16);
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*pDst++ = (q15_t)__SSAT(((q31_t)*pSrcA++ - *pSrcB++), 16);
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*pDst++ = (q15_t)__SSAT(((q31_t)*pSrcA++ - *pSrcB++), 16);
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#endif
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/* Decrement loop counter */
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blkCnt--;
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}
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/* Loop unrolling: Compute remaining outputs */
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blkCnt = blockSize % 0x4U;
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#else
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/* Initialize blkCnt with number of samples */
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blkCnt = blockSize;
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#endif /* #if defined (ARM_MATH_LOOPUNROLL) */
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while (blkCnt > 0U) {
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/* C = A - B */
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/* Subtract and store result in destination buffer. */
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#if defined(ARM_MATH_DSP)
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*pDst++ = (q15_t)__QSUB16(*pSrcA++, *pSrcB++);
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#else
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*pDst++ = (q15_t)__SSAT(((q31_t)*pSrcA++ - *pSrcB++), 16);
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#endif
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/* Decrement loop counter */
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blkCnt--;
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}
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}
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/**
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@} end of BasicSub group
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*/
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