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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_negate_q7.c
  4.  * Description:  Negates Q7 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 Q7 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.  * <b>Scaling and Overflow Behavior:</b>
  48.  * \par
  49.  * The function uses saturating arithmetic.
  50.  * The Q7 value -1 (0x80) will be saturated to the maximum allowable positive value 0x7F.
  51.  */
  52.  
  53. void arm_negate_q7(
  54.   q7_t * pSrc,
  55.   q7_t * pDst,
  56.   uint32_t blockSize)
  57. {
  58.   uint32_t blkCnt;                               /* loop counter */
  59.   q7_t in;
  60.  
  61. #if defined (ARM_MATH_DSP)
  62.  
  63. /* Run the below code for Cortex-M4 and Cortex-M3 */
  64.   q31_t input;                                   /* Input values1-4 */
  65.   q31_t zero = 0x00000000;
  66.  
  67.  
  68.   /*loop Unrolling */
  69.   blkCnt = blockSize >> 2U;
  70.  
  71.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  72.    ** a second loop below computes the remaining 1 to 3 samples. */
  73.   while (blkCnt > 0U)
  74.   {
  75.     /* C = -A */
  76.     /* Read four inputs */
  77.     input = *__SIMD32(pSrc)++;
  78.  
  79.     /* Store the Negated results in the destination buffer in a single cycle by packing the results */
  80.     *__SIMD32(pDst)++ = __QSUB8(zero, input);
  81.  
  82.     /* Decrement the loop counter */
  83.     blkCnt--;
  84.   }
  85.  
  86.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  87.    ** No loop unrolling is used. */
  88.   blkCnt = blockSize % 0x4U;
  89.  
  90. #else
  91.  
  92.   /* Run the below code for Cortex-M0 */
  93.  
  94.   /* Initialize blkCnt with number of samples */
  95.   blkCnt = blockSize;
  96.  
  97. #endif /* #if defined (ARM_MATH_DSP) */
  98.  
  99.   while (blkCnt > 0U)
  100.   {
  101.     /* C = -A */
  102.     /* Negate and then store the results in the destination buffer. */ \
  103.       in = *pSrc++;
  104.     *pDst++ = (in == (q7_t) 0x80) ? 0x7f : -in;
  105.  
  106.     /* Decrement the loop counter */
  107.     blkCnt--;
  108.   }
  109. }
  110.  
  111. /**
  112.  * @} end of negate group
  113.  */
  114.