lib/main/CMSIS/DSP/Source/BasicMathFunctions/arm_negate_q7.c

   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  */