132 lines
3.3 KiB
C
132 lines
3.3 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_negate_q15.c
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* Description: Negates Q15 vectors
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*
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* $Date: 27. January 2017
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* $Revision: V.1.5.1
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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) 2010-2017 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 negate
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* @{
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*/
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/**
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* @brief Negates the elements of a Q15 vector.
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* @param[in] *pSrc points to the 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 the vector
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* @return none.
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*
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* \par Conditions for optimum performance
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* Input and output buffers should be aligned by 32-bit
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*
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*
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* <b>Scaling and Overflow Behavior:</b>
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* \par
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* The function uses saturating arithmetic.
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* The Q15 value -1 (0x8000) will be saturated to the maximum allowable positive value 0x7FFF.
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*/
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void arm_negate_q15(
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q15_t * pSrc,
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q15_t * pDst,
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uint32_t blockSize)
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{
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uint32_t blkCnt; /* loop counter */
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q15_t in;
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#if defined (ARM_MATH_DSP)
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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q31_t in1, in2; /* Temporary variables */
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/*loop Unrolling */
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blkCnt = blockSize >> 2U;
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/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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** a second loop below computes the remaining 1 to 3 samples. */
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while (blkCnt > 0U)
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{
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/* C = -A */
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/* Read two inputs at a time */
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in1 = _SIMD32_OFFSET(pSrc);
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in2 = _SIMD32_OFFSET(pSrc + 2);
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/* negate two samples at a time */
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in1 = __QSUB16(0, in1);
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/* negate two samples at a time */
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in2 = __QSUB16(0, in2);
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/* store the result to destination 2 samples at a time */
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_SIMD32_OFFSET(pDst) = in1;
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/* store the result to destination 2 samples at a time */
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_SIMD32_OFFSET(pDst + 2) = in2;
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/* update pointers to process next samples */
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pSrc += 4U;
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pDst += 4U;
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x4U;
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#else
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/* Run the below code for Cortex-M0 */
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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_DSP) */
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while (blkCnt > 0U)
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{
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/* C = -A */
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/* Negate and then store the result in the destination buffer. */
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in = *pSrc++;
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*pDst++ = (in == (q15_t) 0x8000) ? 0x7fff : -in;
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/* Decrement the 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 negate group
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*/
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