text: /* ----------------------------------------------------------------------
   * Project:      CMSIS DSP Library
   * Title:        arm_conv_q7.c
   * Description:  Convolution of Q7 sequences
   *
   * $Date:        27. January 2017
   * $Revision:    V.1.5.1
   *
   * Target Processor: Cortex-M cores
   * -------------------------------------------------------------------- */
  /*
   * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
   *
   * SPDX-License-Identifier: Apache-2.0
   *
   * Licensed under the Apache License, Version 2.0 (the License); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an AS IS BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include "arm_math.h"
  
  /**
   * @ingroup groupFilters
   */
  
  /**
   * @addtogroup Conv
   * @{
   */
  
  /**
   * @brief Convolution of Q7 sequences.
   * @param[in] *pSrcA points to the first input sequence.
   * @param[in] srcALen length of the first input sequence.
   * @param[in] *pSrcB points to the second input sequence.
   * @param[in] srcBLen length of the second input sequence.
   * @param[out] *pDst points to the location where the output result is written.  Length srcALen+srcBLen-1.
   * @return none.
   *
   * @details
   * <b>Scaling and Overflow Behavior:</b>
   *
   * \par
   * The function is implemented using a 32-bit internal accumulator.
   * Both the inputs are represented in 1.7 format and multiplications yield a 2.14 result.
   * The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format.
   * This approach provides 17 guard bits and there is no risk of overflow as long as <code>max(srcALen, srcBLen)<131072</code>.
   * The 18.14 result is then truncated to 18.7 format by discarding the low 7 bits and then saturated to 1.7 format.
   *
   * \par
   * Refer the function <code>arm_conv_opt_q7()</code> for a faster implementation of this function.
   *
   */
  
  void arm_conv_q7(
    q7_t * pSrcA,
    uint32_t srcALen,
    q7_t * pSrcB,
    uint32_t srcBLen,
    q7_t * pDst)
  {
  
  
  #if defined (ARM_MATH_DSP)
  
    /* Run the below code for Cortex-M4 and Cortex-M3 */
  
    q7_t *pIn1;                                    /* inputA pointer */
    q7_t *pIn2;                                    /* inputB pointer */
    q7_t *pOut = pDst;                             /* output pointer */
    q7_t *px;                                      /* Intermediate inputA pointer */
    q7_t *py;                                      /* Intermediate inputB pointer */
    q7_t *pSrc1, *pSrc2;                           /* Intermediate pointers */
    q7_t x0, x1, x2, x3, c0, c1;                   /* Temporary variables to hold state and coefficient values */
    q31_t sum, acc0, acc1, acc2, acc3;             /* Accumulator */
    q31_t input1, input2;                          /* Temporary input variables */
    q15_t in1, in2;                                /* Temporary input variables */
    uint32_t j, k, count, blkCnt, blockSize1, blockSize2, blockSize3;     /* loop counter */
  
    /* The algorithm implementation is based on the lengths of the inputs. */
    /* srcB is always made to slide across srcA. */
    /* So srcBLen is always considered as shorter or equal to srcALen */
    if (srcALen >= srcBLen)
    {
      /* Initialization of inputA pointer */
      pIn1 = pSrcA;
  
      /* Initialization of inputB pointer */
      pIn2 = pSrcB;
    }
    else
    {
      /* Initialization of inputA pointer */
      pIn1 = pSrcB;
  
      /* Initialization of inputB pointer */
      pIn2 = pSrcA;
  
      /* srcBLen is always considered as shorter or equal to srcALen */
      j = srcBLen;
      srcBLen = srcALen;
      srcALen = j;
    }
  
    /* conv(x,y) at n = x[n] * y[0] + x[n-1] * y[1] + x[n-2] * y[2] + ...+ x[n-N+1] * y[N -1] */
    /* The function is internally
     * divided into three stages according to the number of multiplications that has to be
     * taken place between inputA samples and inputB samples. In the first stage of the
     * algorithm, the multiplications increase by one for every iteration.
     * In the second stage of the algorithm, srcBLen number of multiplications are done.
     * In the third stage of the algorithm, the multiplications decrease by one
     * for every iteration. */
  
    /* The algorithm is implemented in three stages.
       The loop counters of each stage is initiated here. */
    blockSize1 = srcBLen - 1u;
    blockSize2 = (srcALen - srcBLen) + 1u;
    blockSize3 = blockSize1;
  
    /* --------------------------
     * Initializations of stage1
     * -------------------------*/
  
    /* sum = x[0] * y[0]
     * sum = x[0] * y[1] + x[1] * y[0]
     * ....
     * sum = x[0] * y[srcBlen - 1] + x[1] * y[srcBlen - 2] +...+ x[srcBLen - 1] * y[0]
     */
  
    /* In this stage the MAC operations are increased by 1 for every iteration.
       The count variable holds the number of MAC operations performed */
    count = 1u;
  
    /* Working pointer of inputA */
    px = pIn1;
  
    /* Working pointer of inputB */
    py = pIn2;
  
  
    /* ------------------------
     * Stage1 process
     * ----------------------*/
  
    /* The first stage starts here */
    while (blockSize1 > 0u)
    {
      /* Accumulator is made zero for every iteration */
      sum = 0;
  
      /* Apply loop unrolling and compute 4 MACs simultaneously. */
      k = count >> 2u;
  
      /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
       ** a second loop below computes MACs for the remaining 1 to 3 samples. */
      while (k > 0u)
      {
        /* x[0] , x[1] */
        in1 = (q15_t) * px++;
        in2 = (q15_t) * px++;
        input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* y[srcBLen - 1] , y[srcBLen - 2] */
        in1 = (q15_t) * py--;
        in2 = (q15_t) * py--;
        input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* x[0] * y[srcBLen - 1] */
        /* x[1] * y[srcBLen - 2] */
        sum = __SMLAD(input1, input2, sum);
  
        /* x[2] , x[3] */
        in1 = (q15_t) * px++;
        in2 = (q15_t) * px++;
        input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* y[srcBLen - 3] , y[srcBLen - 4] */
        in1 = (q15_t) * py--;
        in2 = (q15_t) * py--;
        input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* x[2] * y[srcBLen - 3] */
        /* x[3] * y[srcBLen - 4] */
        sum = __SMLAD(input1, input2, sum);
  
        /* Decrement the loop counter */
        k--;
      }
  
      /* If the count is not a multiple of 4, compute any remaining MACs here.
       ** No loop unrolling is used. */
      k = count % 0x4u;
  
      while (k > 0u)
      {
        /* Perform the multiply-accumulates */
        sum += ((q15_t) * px++ * *py--);
  
        /* Decrement the loop counter */
        k--;
      }
  
      /* Store the result in the accumulator in the destination buffer. */
      *pOut++ = (q7_t) (__SSAT(sum >> 7u, 8));
  
      /* Update the inputA and inputB pointers for next MAC calculation */
      py = pIn2 + count;
      px = pIn1;
  
      /* Increment the MAC count */
      count++;
  
      /* Decrement the loop counter */
      blockSize1--;
    }
  
    /* --------------------------
     * Initializations of stage2
     * ------------------------*/
  
    /* sum = x[0] * y[srcBLen-1] + x[1] * y[srcBLen-2] +...+ x[srcBLen-1] * y[0]
     * sum = x[1] * y[srcBLen-1] + x[2] * y[srcBLen-2] +...+ x[srcBLen] * y[0]
     * ....
     * sum = x[srcALen-srcBLen-2] * y[srcBLen-1] + x[srcALen] * y[srcBLen-2] +...+ x[srcALen-1] * y[0]
     */
  
    /* Working pointer of inputA */
    px = pIn1;
  
    /* Working pointer of inputB */
    pSrc2 = pIn2 + (srcBLen - 1u);
    py = pSrc2;
  
    /* count is index by which the pointer pIn1 to be incremented */
    count = 0u;
  
    /* -------------------
     * Stage2 process
     * ------------------*/
  
    /* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed.
     * So, to loop unroll over blockSize2,
     * srcBLen should be greater than or equal to 4 */
    if (srcBLen >= 4u)
    {
      /* Loop unroll over blockSize2, by 4 */
      blkCnt = blockSize2 >> 2u;
  
      while (blkCnt > 0u)
      {
        /* Set all accumulators to zero */
        acc0 = 0;
        acc1 = 0;
        acc2 = 0;
        acc3 = 0;
  
        /* read x[0], x[1], x[2] samples */
        x0 = *(px++);
        x1 = *(px++);
        x2 = *(px++);
  
        /* Apply loop unrolling and compute 4 MACs simultaneously. */
        k = srcBLen >> 2u;
  
        /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
         ** a second loop below computes MACs for the remaining 1 to 3 samples. */
        do
        {
          /* Read y[srcBLen - 1] sample */
          c0 = *(py--);
          /* Read y[srcBLen - 2] sample */
          c1 = *(py--);
  
          /* Read x[3] sample */
          x3 = *(px++);
  
          /* x[0] and x[1] are packed */
          in1 = (q15_t) x0;
          in2 = (q15_t) x1;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* y[srcBLen - 1]   and y[srcBLen - 2] are packed */
          in1 = (q15_t) c0;
          in2 = (q15_t) c1;
  
          input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc0 += x[0] * y[srcBLen - 1] + x[1] * y[srcBLen - 2]  */
          acc0 = __SMLAD(input1, input2, acc0);
  
          /* x[1] and x[2] are packed */
          in1 = (q15_t) x1;
          in2 = (q15_t) x2;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc1 += x[1] * y[srcBLen - 1] + x[2] * y[srcBLen - 2]  */
          acc1 = __SMLAD(input1, input2, acc1);
  
          /* x[2] and x[3] are packed */
          in1 = (q15_t) x2;
          in2 = (q15_t) x3;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc2 += x[2] * y[srcBLen - 1] + x[3] * y[srcBLen - 2]  */
          acc2 = __SMLAD(input1, input2, acc2);
  
          /* Read x[4] sample */
          x0 = *(px++);
  
          /* x[3] and x[4] are packed */
          in1 = (q15_t) x3;
          in2 = (q15_t) x0;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc3 += x[3] * y[srcBLen - 1] + x[4] * y[srcBLen - 2]  */
          acc3 = __SMLAD(input1, input2, acc3);
  
          /* Read y[srcBLen - 3] sample */
          c0 = *(py--);
          /* Read y[srcBLen - 4] sample */
          c1 = *(py--);
  
          /* Read x[5] sample */
          x1 = *(px++);
  
          /* x[2] and x[3] are packed */
          in1 = (q15_t) x2;
          in2 = (q15_t) x3;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* y[srcBLen - 3] and y[srcBLen - 4] are packed */
          in1 = (q15_t) c0;
          in2 = (q15_t) c1;
  
          input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc0 += x[2] * y[srcBLen - 3] + x[3] * y[srcBLen - 4]  */
          acc0 = __SMLAD(input1, input2, acc0);
  
          /* x[3] and x[4] are packed */
          in1 = (q15_t) x3;
          in2 = (q15_t) x0;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc1 += x[3] * y[srcBLen - 3] + x[4] * y[srcBLen - 4]  */
          acc1 = __SMLAD(input1, input2, acc1);
  
          /* x[4] and x[5] are packed */
          in1 = (q15_t) x0;
          in2 = (q15_t) x1;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc2 += x[4] * y[srcBLen - 3] + x[5] * y[srcBLen - 4]  */
          acc2 = __SMLAD(input1, input2, acc2);
  
          /* Read x[6] sample */
          x2 = *(px++);
  
          /* x[5] and x[6] are packed */
          in1 = (q15_t) x1;
          in2 = (q15_t) x2;
  
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* acc3 += x[5] * y[srcBLen - 3] + x[6] * y[srcBLen - 4]  */
          acc3 = __SMLAD(input1, input2, acc3);
  
        } while (--k);
  
        /* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
         ** No loop unrolling is used. */
        k = srcBLen % 0x4u;
  
        while (k > 0u)
        {
          /* Read y[srcBLen - 5] sample */
          c0 = *(py--);
  
          /* Read x[7] sample */
          x3 = *(px++);
  
          /* Perform the multiply-accumulates */
          /* acc0 +=  x[4] * y[srcBLen - 5] */
          acc0 += ((q15_t) x0 * c0);
          /* acc1 +=  x[5] * y[srcBLen - 5] */
          acc1 += ((q15_t) x1 * c0);
          /* acc2 +=  x[6] * y[srcBLen - 5] */
          acc2 += ((q15_t) x2 * c0);
          /* acc3 +=  x[7] * y[srcBLen - 5] */
          acc3 += ((q15_t) x3 * c0);
  
          /* Reuse the present samples for the next MAC */
          x0 = x1;
          x1 = x2;
          x2 = x3;
  
          /* Decrement the loop counter */
          k--;
        }
  
  
        /* Store the result in the accumulator in the destination buffer. */
        *pOut++ = (q7_t) (__SSAT(acc0 >> 7u, 8));
        *pOut++ = (q7_t) (__SSAT(acc1 >> 7u, 8));
        *pOut++ = (q7_t) (__SSAT(acc2 >> 7u, 8));
        *pOut++ = (q7_t) (__SSAT(acc3 >> 7u, 8));
  
        /* Increment the pointer pIn1 index, count by 4 */
        count += 4u;
  
        /* Update the inputA and inputB pointers for next MAC calculation */
        px = pIn1 + count;
        py = pSrc2;
  
        /* Decrement the loop counter */
        blkCnt--;
      }
  
      /* If the blockSize2 is not a multiple of 4, compute any remaining output samples here.
       ** No loop unrolling is used. */
      blkCnt = blockSize2 % 0x4u;
  
      while (blkCnt > 0u)
      {
        /* Accumulator is made zero for every iteration */
        sum = 0;
  
        /* Apply loop unrolling and compute 4 MACs simultaneously. */
        k = srcBLen >> 2u;
  
        /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
         ** a second loop below computes MACs for the remaining 1 to 3 samples. */
        while (k > 0u)
        {
  
          /* Reading two inputs of SrcA buffer and packing */
          in1 = (q15_t) * px++;
          in2 = (q15_t) * px++;
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* Reading two inputs of SrcB buffer and packing */
          in1 = (q15_t) * py--;
          in2 = (q15_t) * py--;
          input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* Perform the multiply-accumulates */
          sum = __SMLAD(input1, input2, sum);
  
          /* Reading two inputs of SrcA buffer and packing */
          in1 = (q15_t) * px++;
          in2 = (q15_t) * px++;
          input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* Reading two inputs of SrcB buffer and packing */
          in1 = (q15_t) * py--;
          in2 = (q15_t) * py--;
          input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
          /* Perform the multiply-accumulates */
          sum = __SMLAD(input1, input2, sum);
  
          /* Decrement the loop counter */
          k--;
        }
  
        /* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
         ** No loop unrolling is used. */
        k = srcBLen % 0x4u;
  
        while (k > 0u)
        {
          /* Perform the multiply-accumulates */
          sum += ((q15_t) * px++ * *py--);
  
          /* Decrement the loop counter */
          k--;
        }
  
        /* Store the result in the accumulator in the destination buffer. */
        *pOut++ = (q7_t) (__SSAT(sum >> 7u, 8));
  
        /* Increment the pointer pIn1 index, count by 1 */
        count++;
  
        /* Update the inputA and inputB pointers for next MAC calculation */
        px = pIn1 + count;
        py = pSrc2;
  
        /* Decrement the loop counter */
        blkCnt--;
      }
    }
    else
    {
      /* If the srcBLen is not a multiple of 4,
       * the blockSize2 loop cannot be unrolled by 4 */
      blkCnt = blockSize2;
  
      while (blkCnt > 0u)
      {
        /* Accumulator is made zero for every iteration */
        sum = 0;
  
        /* srcBLen number of MACS should be performed */
        k = srcBLen;
  
        while (k > 0u)
        {
          /* Perform the multiply-accumulate */
          sum += ((q15_t) * px++ * *py--);
  
          /* Decrement the loop counter */
          k--;
        }
  
        /* Store the result in the accumulator in the destination buffer. */
        *pOut++ = (q7_t) (__SSAT(sum >> 7u, 8));
  
        /* Increment the MAC count */
        count++;
  
        /* Update the inputA and inputB pointers for next MAC calculation */
        px = pIn1 + count;
        py = pSrc2;
  
        /* Decrement the loop counter */
        blkCnt--;
      }
    }
  
  
    /* --------------------------
     * Initializations of stage3
     * -------------------------*/
  
    /* sum += x[srcALen-srcBLen+1] * y[srcBLen-1] + x[srcALen-srcBLen+2] * y[srcBLen-2] +...+ x[srcALen-1] * y[1]
     * sum += x[srcALen-srcBLen+2] * y[srcBLen-1] + x[srcALen-srcBLen+3] * y[srcBLen-2] +...+ x[srcALen-1] * y[2]
     * ....
     * sum +=  x[srcALen-2] * y[srcBLen-1] + x[srcALen-1] * y[srcBLen-2]
     * sum +=  x[srcALen-1] * y[srcBLen-1]
     */
  
    /* In this stage the MAC operations are decreased by 1 for every iteration.
       The blockSize3 variable holds the number of MAC operations performed */
  
    /* Working pointer of inputA */
    pSrc1 = pIn1 + (srcALen - (srcBLen - 1u));
    px = pSrc1;
  
    /* Working pointer of inputB */
    pSrc2 = pIn2 + (srcBLen - 1u);
    py = pSrc2;
  
    /* -------------------
     * Stage3 process
     * ------------------*/
  
    while (blockSize3 > 0u)
    {
      /* Accumulator is made zero for every iteration */
      sum = 0;
  
      /* Apply loop unrolling and compute 4 MACs simultaneously. */
      k = blockSize3 >> 2u;
  
      /* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
       ** a second loop below computes MACs for the remaining 1 to 3 samples. */
      while (k > 0u)
      {
        /* Reading two inputs, x[srcALen - srcBLen + 1] and x[srcALen - srcBLen + 2] of SrcA buffer and packing */
        in1 = (q15_t) * px++;
        in2 = (q15_t) * px++;
        input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* Reading two inputs, y[srcBLen - 1] and y[srcBLen - 2] of SrcB buffer and packing */
        in1 = (q15_t) * py--;
        in2 = (q15_t) * py--;
        input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* sum += x[srcALen - srcBLen + 1] * y[srcBLen - 1] */
        /* sum += x[srcALen - srcBLen + 2] * y[srcBLen - 2] */
        sum = __SMLAD(input1, input2, sum);
  
        /* Reading two inputs, x[srcALen - srcBLen + 3] and x[srcALen - srcBLen + 4] of SrcA buffer and packing */
        in1 = (q15_t) * px++;
        in2 = (q15_t) * px++;
        input1 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* Reading two inputs, y[srcBLen - 3] and y[srcBLen - 4] of SrcB buffer and packing */
        in1 = (q15_t) * py--;
        in2 = (q15_t) * py--;
        input2 = ((q31_t) in1 & 0x0000FFFF) | ((q31_t) in2 << 16u);
  
        /* sum += x[srcALen - srcBLen + 3] * y[srcBLen - 3] */
        /* sum += x[srcALen - srcBLen + 4] * y[srcBLen - 4] */
        sum = __SMLAD(input1, input2, sum);
  
        /* Decrement the loop counter */
        k--;
      }
  
      /* If the blockSize3 is not a multiple of 4, compute any remaining MACs here.
       ** No loop unrolling is used. */
      k = blockSize3 % 0x4u;
  
      while (k > 0u)
      {
        /* Perform the multiply-accumulates */
        sum += ((q15_t) * px++ * *py--);
  
        /* Decrement the loop counter */
        k--;
      }
  
      /* Store the result in the accumulator in the destination buffer. */
      *pOut++ = (q7_t) (__SSAT(sum >> 7u, 8));
  
      /* Update the inputA and inputB pointers for next MAC calculation */
      px = ++pSrc1;
      py = pSrc2;
  
      /* Decrement the loop counter */
      blockSize3--;
    }
  
  #else
  
    /* Run the below code for Cortex-M0 */
  
    q7_t *pIn1 = pSrcA;                            /* input pointer */
    q7_t *pIn2 = pSrcB;                            /* coefficient pointer */
    q31_t sum;                                     /* Accumulator */
    uint32_t i, j;                                 /* loop counter */
  
    /* Loop to calculate output of convolution for output length number of times */
    for (i = 0; i < (srcALen + srcBLen - 1); i++)
    {
      /* Initialize sum with zero to carry on MAC operations */
      sum = 0;
  
      /* Loop to perform MAC operations according to convolution equation */
      for (j = 0; j <= i; j++)
      {
        /* Check the array limitations */
        if (((i - j) < srcBLen) && (j < srcALen))
        {
          /* z[i] += x[i-j] * y[j] */
          sum += (q15_t) pIn1[j] * (pIn2[i - j]);
        }
      }
  
      /* Store the output in the destination buffer */
      pDst[i] = (q7_t) __SSAT((sum >> 7u), 8u);
    }
  
  #endif /*   #if defined (ARM_MATH_DSP)        */
  
  }
  
  /**
   * @} end of Conv group
   */
  