lib/main/CMSIS/DSP/Source/BasicMathFunctions/arm_negate_q15.c

   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  */