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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_negate_q15.c
  4.  * Description:  Negates Q15 vectors
  5.  *
  6.  * $Date:        27. January 2017
  7.  * $Revision:    V.1.5.1
  8.  *
  9.  * Target Processor: Cortex-M cores
  10.  * -------------------------------------------------------------------- */
  11. /*
  12.  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
  13.  *
  14.  * SPDX-License-Identifier: Apache-2.0
  15.  *
  16.  * Licensed under the Apache License, Version 2.0 (the License); you may
  17.  * not use this file except in compliance with the License.
  18.  * You may obtain a copy of the License at
  19.  *
  20.  * www.apache.org/licenses/LICENSE-2.0
  21.  *
  22.  * Unless required by applicable law or agreed to in writing, software
  23.  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  24.  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  25.  * See the License for the specific language governing permissions and
  26.  * limitations under the License.
  27.  */
  28.  
  29. #include "arm_math.h"
  30.  
  31. /**
  32.  * @ingroup groupMath
  33.  */
  34.  
  35. /**
  36.  * @addtogroup negate
  37.  * @{
  38.  */
  39.  
  40. /**
  41.  * @brief  Negates the elements of a Q15 vector.
  42.  * @param[in]  *pSrc points to the input vector
  43.  * @param[out]  *pDst points to the output vector
  44.  * @param[in]  blockSize number of samples in the vector
  45.  * @return none.
  46.  *
  47.  * \par Conditions for optimum performance
  48.  *  Input and output buffers should be aligned by 32-bit
  49.  *
  50.  *
  51.  * <b>Scaling and Overflow Behavior:</b>
  52.  * \par
  53.  * The function uses saturating arithmetic.
  54.  * The Q15 value -1 (0x8000) will be saturated to the maximum allowable positive value 0x7FFF.
  55.  */
  56.  
  57. void arm_negate_q15(
  58.   q15_t * pSrc,
  59.   q15_t * pDst,
  60.   uint32_t blockSize)
  61. {
  62.   uint32_t blkCnt;                               /* loop counter */
  63.   q15_t in;
  64.  
  65. #if defined (ARM_MATH_DSP)
  66.  
  67. /* Run the below code for Cortex-M4 and Cortex-M3 */
  68.  
  69.   q31_t in1, in2;                                /* Temporary variables */
  70.  
  71.  
  72.   /*loop Unrolling */
  73.   blkCnt = blockSize >> 2U;
  74.  
  75.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  76.    ** a second loop below computes the remaining 1 to 3 samples. */
  77.   while (blkCnt > 0U)
  78.   {
  79.     /* C = -A */
  80.     /* Read two inputs at a time */
  81.     in1 = _SIMD32_OFFSET(pSrc);
  82.     in2 = _SIMD32_OFFSET(pSrc + 2);
  83.  
  84.     /* negate two samples at a time */
  85.     in1 = __QSUB16(0, in1);
  86.  
  87.     /* negate two samples at a time */
  88.     in2 = __QSUB16(0, in2);
  89.  
  90.     /* store the result to destination 2 samples at a time */
  91.     _SIMD32_OFFSET(pDst) = in1;
  92.     /* store the result to destination 2 samples at a time */
  93.     _SIMD32_OFFSET(pDst + 2) = in2;
  94.  
  95.  
  96.     /* update pointers to process next samples */
  97.     pSrc += 4U;
  98.     pDst += 4U;
  99.  
  100.     /* Decrement the loop counter */
  101.     blkCnt--;
  102.   }
  103.  
  104.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  105.    ** No loop unrolling is used. */
  106.   blkCnt = blockSize % 0x4U;
  107.  
  108. #else
  109.  
  110.   /* Run the below code for Cortex-M0 */
  111.  
  112.   /* Initialize blkCnt with number of samples */
  113.   blkCnt = blockSize;
  114.  
  115. #endif /* #if defined (ARM_MATH_DSP) */
  116.  
  117.   while (blkCnt > 0U)
  118.   {
  119.     /* C = -A */
  120.     /* Negate and then store the result in the destination buffer. */
  121.     in = *pSrc++;
  122.     *pDst++ = (in == (q15_t) 0x8000) ? 0x7fff : -in;
  123.  
  124.     /* Decrement the loop counter */
  125.     blkCnt--;
  126.   }
  127. }
  128.  
  129. /**
  130.  * @} end of negate group
  131.  */
  132.