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  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_abs_q31.c
  4.  * Description:  Q31 vector absolute value
  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 BasicAbs
  37.  * @{
  38.  */
  39.  
  40.  
  41. /**
  42.  * @brief Q31 vector absolute value.
  43.  * @param[in]       *pSrc points to the input buffer
  44.  * @param[out]      *pDst points to the output buffer
  45.  * @param[in]       blockSize number of samples in each vector
  46.  * @return none.
  47.  *
  48.  * <b>Scaling and Overflow Behavior:</b>
  49.  * \par
  50.  * The function uses saturating arithmetic.
  51.  * The Q31 value -1 (0x80000000) will be saturated to the maximum allowable positive value 0x7FFFFFFF.
  52.  */
  53.  
  54. void arm_abs_q31(
  55.   q31_t * pSrc,
  56.   q31_t * pDst,
  57.   uint32_t blockSize)
  58. {
  59.   uint32_t blkCnt;                               /* loop counter */
  60.   q31_t in;                                      /* Input value */
  61.  
  62. #if defined (ARM_MATH_DSP)
  63.  
  64.   /* Run the below code for Cortex-M4 and Cortex-M3 */
  65.   q31_t in1, in2, in3, in4;
  66.  
  67.   /*loop Unrolling */
  68.   blkCnt = blockSize >> 2U;
  69.  
  70.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  71.    ** a second loop below computes the remaining 1 to 3 samples. */
  72.   while (blkCnt > 0U)
  73.   {
  74.     /* C = |A| */
  75.     /* Calculate absolute of input (if -1 then saturated to 0x7fffffff) and then store the results in the destination buffer. */
  76.     in1 = *pSrc++;
  77.     in2 = *pSrc++;
  78.     in3 = *pSrc++;
  79.     in4 = *pSrc++;
  80.  
  81.     *pDst++ = (in1 > 0) ? in1 : (q31_t)__QSUB(0, in1);
  82.     *pDst++ = (in2 > 0) ? in2 : (q31_t)__QSUB(0, in2);
  83.     *pDst++ = (in3 > 0) ? in3 : (q31_t)__QSUB(0, in3);
  84.     *pDst++ = (in4 > 0) ? in4 : (q31_t)__QSUB(0, in4);
  85.  
  86.     /* Decrement the loop counter */
  87.     blkCnt--;
  88.   }
  89.  
  90.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  91.    ** No loop unrolling is used. */
  92.   blkCnt = blockSize % 0x4U;
  93.  
  94. #else
  95.  
  96.   /* Run the below code for Cortex-M0 */
  97.  
  98.   /* Initialize blkCnt with number of samples */
  99.   blkCnt = blockSize;
  100.  
  101. #endif /*   #if defined (ARM_MATH_DSP)   */
  102.  
  103.   while (blkCnt > 0U)
  104.   {
  105.     /* C = |A| */
  106.     /* Calculate absolute value of the input (if -1 then saturated to 0x7fffffff) and then store the results in the destination buffer. */
  107.     in = *pSrc++;
  108.     *pDst++ = (in > 0) ? in : ((in == INT32_MIN) ? INT32_MAX : -in);
  109.  
  110.     /* Decrement the loop counter */
  111.     blkCnt--;
  112.   }
  113.  
  114. }
  115.  
  116. /**
  117.  * @} end of BasicAbs group
  118.  */
  119.