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