text: /* ----------------------------------------------------------------------    
  * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
  *    
  * $Date:        19. March 2015
  * $Revision: 	V.1.4.5
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:		arm_conv_opt_q7.c    
  *    
  * Description:	Convolution of Q7 sequences.  
  *    
  * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  *  
  * Redistribution and use in source and binary forms, with or without 
  * modification, are permitted provided that the following conditions
  * are met:
  *   - Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  *   - Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in
  *     the documentation and/or other materials provided with the 
  *     distribution.
  *   - Neither the name of ARM LIMITED nor the names of its contributors
  *     may be used to endorse or promote products derived from this
  *     software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.  
  * -------------------------------------------------------------------- */
  
  #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.    
   * @param[in]  *pScratch1 points to scratch buffer(of type q15_t) of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.   
   * @param[in]  *pScratch2 points to scratch buffer (of type q15_t) of size min(srcALen, srcBLen).   
   * @return none.    
   *    
   * \par Restrictions    
   *  If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE    
   *	In this case input, output, scratch1 and scratch2 buffers should be aligned by 32-bit     
   *       
   * @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.    
   *
   */
  
  void arm_conv_opt_q7(
    q7_t * pSrcA,
    uint32_t srcALen,
    q7_t * pSrcB,
    uint32_t srcBLen,
    q7_t * pDst,
    q15_t * pScratch1,
    q15_t * pScratch2)
  {
  
    q15_t *pScr2, *pScr1;                          /* Intermediate pointers for scratch pointers */
    q15_t x4;                                      /* Temporary input variable */
    q7_t *pIn1, *pIn2;                             /* inputA and inputB pointer */
    uint32_t j, k, blkCnt, tapCnt;                 /* loop counter */
    q7_t *px;                                      /* Temporary input1 pointer */
    q15_t *py;                                     /* Temporary input2 pointer */
    q31_t acc0, acc1, acc2, acc3;                  /* Accumulator */
    q31_t x1, x2, x3, y1;                          /* Temporary input variables */
    q7_t *pOut = pDst;                             /* output pointer */
    q7_t out0, out1, out2, out3;                   /* temporary variables */
  
    /* 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;
    }
  
    /* pointer to take end of scratch2 buffer */
    pScr2 = pScratch2;
  
    /* points to smaller length sequence */
    px = pIn2 + srcBLen - 1;
  
    /* Apply loop unrolling and do 4 Copies simultaneously. */
    k = srcBLen >> 2u;
  
    /* First part of the processing with loop unrolling copies 4 data points at a time.       
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
      /* copy second buffer in reversal manner */
      x4 = (q15_t) * px--;
      *pScr2++ = x4;
      x4 = (q15_t) * px--;
      *pScr2++ = x4;
      x4 = (q15_t) * px--;
      *pScr2++ = x4;
      x4 = (q15_t) * px--;
      *pScr2++ = x4;
  
      /* Decrement the loop counter */
      k--;
    }
  
    /* If the count is not a multiple of 4, copy remaining samples here.       
     ** No loop unrolling is used. */
    k = srcBLen % 0x4u;
  
    while(k > 0u)
    {
      /* copy second buffer in reversal manner for remaining samples */
      x4 = (q15_t) * px--;
      *pScr2++ = x4;
  
      /* Decrement the loop counter */
      k--;
    }
  
    /* Initialze temporary scratch pointer */
    pScr1 = pScratch1;
  
    /* Fill (srcBLen - 1u) zeros in scratch buffer */
    arm_fill_q15(0, pScr1, (srcBLen - 1u));
  
    /* Update temporary scratch pointer */
    pScr1 += (srcBLen - 1u);
  
    /* Copy (srcALen) samples in scratch buffer */
    /* Apply loop unrolling and do 4 Copies simultaneously. */
    k = srcALen >> 2u;
  
    /* First part of the processing with loop unrolling copies 4 data points at a time.       
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
      /* copy second buffer in reversal manner */
      x4 = (q15_t) * pIn1++;
      *pScr1++ = x4;
      x4 = (q15_t) * pIn1++;
      *pScr1++ = x4;
      x4 = (q15_t) * pIn1++;
      *pScr1++ = x4;
      x4 = (q15_t) * pIn1++;
      *pScr1++ = x4;
  
      /* Decrement the loop counter */
      k--;
    }
  
    /* If the count is not a multiple of 4, copy remaining samples here.       
     ** No loop unrolling is used. */
    k = srcALen % 0x4u;
  
    while(k > 0u)
    {
      /* copy second buffer in reversal manner for remaining samples */
      x4 = (q15_t) * pIn1++;
      *pScr1++ = x4;
  
      /* Decrement the loop counter */
      k--;
    }
  
  #ifndef UNALIGNED_SUPPORT_DISABLE
  
    /* Fill (srcBLen - 1u) zeros at end of scratch buffer */
    arm_fill_q15(0, pScr1, (srcBLen - 1u));
  
    /* Update pointer */
    pScr1 += (srcBLen - 1u);
  
  #else
  
    /* Apply loop unrolling and do 4 Copies simultaneously. */
    k = (srcBLen - 1u) >> 2u;
  
    /* First part of the processing with loop unrolling copies 4 data points at a time.       
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
      /* copy second buffer in reversal manner */
      *pScr1++ = 0;
      *pScr1++ = 0;
      *pScr1++ = 0;
      *pScr1++ = 0;
  
      /* Decrement the loop counter */
      k--;
    }
  
    /* If the count is not a multiple of 4, copy remaining samples here.       
     ** No loop unrolling is used. */
    k = (srcBLen - 1u) % 0x4u;
  
    while(k > 0u)
    {
      /* copy second buffer in reversal manner for remaining samples */
      *pScr1++ = 0;
  
      /* Decrement the loop counter */
      k--;
    }
  
  #endif
  
    /* Temporary pointer for scratch2 */
    py = pScratch2;
  
    /* Initialization of pIn2 pointer */
    pIn2 = (q7_t *) py;
  
    pScr2 = py;
  
    /* Actual convolution process starts here */
    blkCnt = (srcALen + srcBLen - 1u) >> 2;
  
    while(blkCnt > 0)
    {
      /* Initialze temporary scratch pointer as scratch1 */
      pScr1 = pScratch1;
  
      /* Clear Accumlators */
      acc0 = 0;
      acc1 = 0;
      acc2 = 0;
      acc3 = 0;
  
      /* Read two samples from scratch1 buffer */
      x1 = *__SIMD32(pScr1)++;
  
      /* Read next two samples from scratch1 buffer */
      x2 = *__SIMD32(pScr1)++;
  
      tapCnt = (srcBLen) >> 2u;
  
      while(tapCnt > 0u)
      {
  
        /* Read four samples from smaller buffer */
        y1 = _SIMD32_OFFSET(pScr2);
  
        /* multiply and accumlate */
        acc0 = __SMLAD(x1, y1, acc0);
        acc2 = __SMLAD(x2, y1, acc2);
  
        /* pack input data */
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        /* multiply and accumlate */
        acc1 = __SMLADX(x3, y1, acc1);
  
        /* Read next two samples from scratch1 buffer */
        x1 = *__SIMD32(pScr1)++;
  
        /* pack input data */
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x1, x2, 0);
  #else
        x3 = __PKHBT(x2, x1, 0);
  #endif
  
        acc3 = __SMLADX(x3, y1, acc3);
  
        /* Read four samples from smaller buffer */
        y1 = _SIMD32_OFFSET(pScr2 + 2u);
  
        acc0 = __SMLAD(x2, y1, acc0);
  
        acc2 = __SMLAD(x1, y1, acc2);
  
        acc1 = __SMLADX(x3, y1, acc1);
  
        x2 = *__SIMD32(pScr1)++;
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        acc3 = __SMLADX(x3, y1, acc3);
  
        pScr2 += 4u;
  
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
  
  
      /* Update scratch pointer for remaining samples of smaller length sequence */
      pScr1 -= 4u;
  
  
      /* apply same above for remaining samples of smaller length sequence */
      tapCnt = (srcBLen) & 3u;
  
      while(tapCnt > 0u)
      {
  
        /* accumlate the results */
        acc0 += (*pScr1++ * *pScr2);
        acc1 += (*pScr1++ * *pScr2);
        acc2 += (*pScr1++ * *pScr2);
        acc3 += (*pScr1++ * *pScr2++);
  
        pScr1 -= 3u;
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
      blkCnt--;
  
      /* Store the result in the accumulator in the destination buffer. */
      out0 = (q7_t) (__SSAT(acc0 >> 7u, 8));
      out1 = (q7_t) (__SSAT(acc1 >> 7u, 8));
      out2 = (q7_t) (__SSAT(acc2 >> 7u, 8));
      out3 = (q7_t) (__SSAT(acc3 >> 7u, 8));
  
      *__SIMD32(pOut)++ = __PACKq7(out0, out1, out2, out3);
  
      /* Initialization of inputB pointer */
      pScr2 = py;
  
      pScratch1 += 4u;
  
    }
  
  
    blkCnt = (srcALen + srcBLen - 1u) & 0x3;
  
    /* Calculate convolution for remaining samples of Bigger length sequence */
    while(blkCnt > 0)
    {
      /* Initialze temporary scratch pointer as scratch1 */
      pScr1 = pScratch1;
  
      /* Clear Accumlators */
      acc0 = 0;
  
      tapCnt = (srcBLen) >> 1u;
  
      while(tapCnt > 0u)
      {
        acc0 += (*pScr1++ * *pScr2++);
        acc0 += (*pScr1++ * *pScr2++);
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
      tapCnt = (srcBLen) & 1u;
  
      /* apply same above for remaining samples of smaller length sequence */
      while(tapCnt > 0u)
      {
  
        /* accumlate the results */
        acc0 += (*pScr1++ * *pScr2++);
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
      blkCnt--;
  
      /* Store the result in the accumulator in the destination buffer. */
      *pOut++ = (q7_t) (__SSAT(acc0 >> 7u, 8));
  
      /* Initialization of inputB pointer */
      pScr2 = py;
  
      pScratch1 += 1u;
  
    }
  
  }
  
  
  /**    
   * @} end of Conv group    
   */
  