1  /* ----------------------------------------------------------------------
  2   * Project:      CMSIS DSP Library
  3   * Title:        arm_sub_q31.c
  4   * Description:  Q31 vector subtraction
  5   *
  6   * $Date:        23 April 2021
  7   * $Revision:    V1.9.0
  8   *
  9   * Target Processor: Cortex-M and Cortex-A cores
 10   * -------------------------------------------------------------------- */
 11  /*
 12   * Copyright (C) 2010-2021 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 "dsp/basic_math_functions.h"
 30  
 31  /**
 32    @ingroup groupMath
 33   */
 34  
 35  /**
 36    @addtogroup BasicSub
 37    @{
 38   */
 39  
 40  /**
 41    @brief         Q31 vector subtraction.
 42    @param[in]     pSrcA      points to the first input vector
 43    @param[in]     pSrcB      points to the second input vector
 44    @param[out]    pDst       points to the output vector
 45    @param[in]     blockSize  number of samples in each vector
 46    @return        none
 47  
 48    @par           Scaling and Overflow Behavior
 49                     The function uses saturating arithmetic.
 50                     Results outside of the allowable Q31 range [0x80000000 0x7FFFFFFF] are saturated.
 51   */
 52  
 53  #if defined(ARM_MATH_MVEI) && !defined(ARM_MATH_AUTOVECTORIZE)
 54  
 55  #include "arm_helium_utils.h"
 56  
 57  void arm_sub_q31(
 58    const q31_t * pSrcA,
 59    const q31_t * pSrcB,
 60          q31_t * pDst,
 61          uint32_t blockSize)
 62  {
 63      uint32_t blkCnt;   
 64      q31x4_t vecA;
 65      q31x4_t vecB;
 66  
 67      /* Compute 4 outputs at a time */
 68      blkCnt = blockSize >> 2;
 69      while (blkCnt > 0U)
 70      {
 71          /*
 72           * C = A + B
 73           * Add and then store the results in the destination buffer.
 74           */
 75          vecA = vld1q(pSrcA);
 76          vecB = vld1q(pSrcB);
 77          vst1q(pDst, vqsubq(vecA, vecB));
 78          /*
 79           * Decrement the blockSize loop counter
 80           */
 81          blkCnt--;
 82          /*
 83           * advance vector source and destination pointers
 84           */
 85          pSrcA  += 4;
 86          pSrcB  += 4;
 87          pDst   += 4;
 88      }
 89      /*
 90       * tail
 91       */
 92      blkCnt = blockSize & 3;
 93      if (blkCnt > 0U)
 94      {
 95          mve_pred16_t p0 = vctp32q(blkCnt);
 96          vecA = vld1q(pSrcA);
 97          vecB = vld1q(pSrcB);
 98          vstrwq_p(pDst, vqsubq(vecA, vecB), p0);
 99      }
100  }
101  
102  #else
103  void arm_sub_q31(
104    const q31_t * pSrcA,
105    const q31_t * pSrcB,
106          q31_t * pDst,
107          uint32_t blockSize)
108  {
109          uint32_t blkCnt;                               /* Loop counter */
110  
111  #if defined (ARM_MATH_LOOPUNROLL)
112  
113    /* Loop unrolling: Compute 4 outputs at a time */
114    blkCnt = blockSize >> 2U;
115  
116    while (blkCnt > 0U)
117    {
118      /* C = A - B */
119  
120      /* Subtract and store result in destination buffer. */
121      *pDst++ = __QSUB(*pSrcA++, *pSrcB++);
122  
123      *pDst++ = __QSUB(*pSrcA++, *pSrcB++);
124  
125      *pDst++ = __QSUB(*pSrcA++, *pSrcB++);
126  
127      *pDst++ = __QSUB(*pSrcA++, *pSrcB++);
128  
129      /* Decrement loop counter */
130      blkCnt--;
131    }
132  
133    /* Loop unrolling: Compute remaining outputs */
134    blkCnt = blockSize % 0x4U;
135  
136  #else
137  
138    /* Initialize blkCnt with number of samples */
139    blkCnt = blockSize;
140  
141  #endif /* #if defined (ARM_MATH_LOOPUNROLL) */
142  
143    while (blkCnt > 0U)
144    {
145      /* C = A - B */
146  
147      /* Subtract and store result in destination buffer. */
148      *pDst++ = __QSUB(*pSrcA++, *pSrcB++);
149  
150      /* Decrement loop counter */
151      blkCnt--;
152    }
153  
154  }
155  #endif /* defined(ARM_MATH_MVEI) */
156  
157  /**
158    @} end of BasicSub group
159   */