text: /* ----------------------------------------------------------------------    
  * Copyright (C) 2010 ARM Limited. All rights reserved.    
  *    
  * $Date:        15. February 2012  
  * $Revision: 	V1.1.0  
  *    
  * Project: 	    CMSIS DSP Library    
  * Title:		arm_conv_fast_opt_q15.c    
  *    
  * Description:	Fast Q15 Convolution.    
  *    
  * Target Processor: Cortex-M4/Cortex-M3
  *  
  * Version 1.1.0 2012/02/15 
  *    Updated with more optimizations, bug fixes and minor API changes.  
  *  
  * Version 1.0.11 2011/10/18  
  *    Bug Fix in conv, correlation, partial convolution.  
  * 
  * Version 1.0.10 2011/7/15  
  *    Big Endian support added and Merged M0 and M3/M4 Source code.   
  *    
  * Version 1.0.3 2010/11/29   
  *    Re-organized the CMSIS folders and updated documentation.    
  *     
  * Version 1.0.2 2010/11/11    
  *    Documentation updated.     
  *    
  * Version 1.0.1 2010/10/05     
  *    Production release and review comments incorporated.    
  *    
  * Version 1.0.0 2010/09/20     
  *    Production release and review comments incorporated.    
  * -------------------------------------------------------------------- */
  
  #include "arm_math.h"
  
  /**    
   * @ingroup groupFilters    
   */
  
  /**    
   * @addtogroup Conv    
   * @{    
   */
  
  /**    
   * @brief Convolution of Q15 sequences (fast version) for Cortex-M3 and Cortex-M4.    
   * @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 size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.   
   * @param[in]  *pScratch2 points to scratch buffer 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    
   *     
   * <b>Scaling and Overflow Behavior:</b>    
   *    
   * \par    
   * This fast version uses a 32-bit accumulator with 2.30 format.    
   * The accumulator maintains full precision of the intermediate multiplication results    
   * but provides only a single guard bit. There is no saturation on intermediate additions.    
   * Thus, if the accumulator overflows it wraps around and distorts the result.    
   * The input signals should be scaled down to avoid intermediate overflows.    
   * Scale down the inputs by log2(min(srcALen, srcBLen)) (log2 is read as log to the base 2) times to avoid overflows,    
   * as maximum of min(srcALen, srcBLen) number of additions are carried internally.    
   * The 2.30 accumulator is right shifted by 15 bits and then saturated to 1.15 format to yield the final result.    
   *    
   * \par    
   * See <code>arm_conv_q15()</code> for a slower implementation of this function which uses 64-bit accumulation to avoid wrap around distortion.    
   */
  
  void arm_conv_fast_opt_q15(
    q15_t * pSrcA,
    uint32_t srcALen,
    q15_t * pSrcB,
    uint32_t srcBLen,
    q15_t * pDst,
    q15_t * pScratch1,
    q15_t * pScratch2)
  {
    q31_t acc0, acc1, acc2, acc3;                  /* Accumulators */
    q31_t x1, x2, x3;                              /* Temporary variables to hold state and coefficient values */
    q31_t y1, y2;                                  /* State variables */
    q15_t *pOut = pDst;                            /* output pointer */
    q15_t *pScr1 = pScratch1;                      /* Temporary pointer for scratch1 */
    q15_t *pScr2 = pScratch2;                      /* Temporary pointer for scratch1 */
    q15_t *pIn1;                                   /* inputA pointer */
    q15_t *pIn2;                                   /* inputB pointer */
    q15_t *px;                                     /* Intermediate inputA pointer  */
    q15_t *py;                                     /* Intermediate inputB pointer  */
    uint32_t j, k, blkCnt;                         /* loop counter */
    uint32_t tapCnt;                               /* loop count */
  #ifdef UNALIGNED_SUPPORT_DISABLE
  
    q15_t a, b;
  
  #endif	/*	#ifdef UNALIGNED_SUPPORT_DISABLE	*/
  
    /* 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 + srcBLen - 1;
  
    /* points to smaller length sequence */
    px = pIn2;
  
    /* 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. */
  
    /* Copy smaller length input sequence in reverse order into second scratch buffer */
    while(k > 0u)
    {
      /* copy second buffer in reversal manner */
      *pScr2-- = *px++;
      *pScr2-- = *px++;
      *pScr2-- = *px++;
      *pScr2-- = *px++;
  
      /* 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 */
      *pScr2-- = *px++;
  
      /* Decrement the loop counter */
      k--;
    }
  
    /* Initialze temporary scratch pointer */
    pScr1 = pScratch1;
  
    /* Assuming scratch1 buffer is aligned by 32-bit */
    /* Fill (srcBLen - 1u) zeros in scratch1 buffer */
    arm_fill_q15(0, pScr1, (srcBLen - 1u));
  
    /* Update temporary scratch pointer */
    pScr1 += (srcBLen - 1u);
  
    /* Copy bigger length sequence(srcALen) samples in scratch1 buffer */
  
  #ifndef UNALIGNED_SUPPORT_DISABLE
  
    /* Copy (srcALen) samples in scratch buffer */
    arm_copy_q15(pIn1, pScr1, srcALen);
  
    /* Update pointers */
    pScr1 += srcALen;
  
  #else
  
    /* 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 */
      *pScr1++ = *pIn1++;
      *pScr1++ = *pIn1++;
      *pScr1++ = *pIn1++;
      *pScr1++ = *pIn1++;
  
      /* 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 */
      *pScr1++ = *pIn1++;
  
      /* Decrement the loop counter */
      k--;
    }
  
  #endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/
  
  
  #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	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/
  
    /* Temporary pointer for scratch2 */
    py = pScratch2;
  
  
    /* Initialization of pIn2 pointer */
    pIn2 = py;
  
    /* First part of the processing with loop unrolling process 4 data points at a time.       
     ** a second loop below process for the remaining 1 to 3 samples. */
  
    /* 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)
      {
  
  #ifndef UNALIGNED_SUPPORT_DISABLE
  
        /* Read four samples from smaller buffer */
        y1 = _SIMD32_OFFSET(pIn2);
        y2 = _SIMD32_OFFSET(pIn2 + 2u);
  
        /* 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_OFFSET(pScr1);
  
        /* multiply and accumlate */
        acc0 = __SMLAD(x2, y2, acc0);
        acc2 = __SMLAD(x1, y2, acc2);
  
        /* 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);
        acc1 = __SMLADX(x3, y2, acc1);
  
        x2 = _SIMD32_OFFSET(pScr1 + 2u);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        acc3 = __SMLADX(x3, y2, acc3);
  
  #else	 
  
        /* Read four samples from smaller buffer */
  	  a = *pIn2;
  	  b = *(pIn2 + 1);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        y1 = __PKHBT(a, b, 16);
  #else
        y1 = __PKHBT(b, a, 16);
  #endif
  	  
  	  a = *(pIn2 + 2);
  	  b = *(pIn2 + 3);
  #ifndef ARM_MATH_BIG_ENDIAN
        y2 = __PKHBT(a, b, 16);
  #else
        y2 = __PKHBT(b, a, 16);
  #endif				
  
        acc0 = __SMLAD(x1, y1, acc0);
  
        acc2 = __SMLAD(x2, y1, acc2);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        acc1 = __SMLADX(x3, y1, acc1);
  
  	  a = *pScr1;
  	  b = *(pScr1 + 1);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x1 = __PKHBT(a, b, 16);
  #else
        x1 = __PKHBT(b, a, 16);
  #endif
  
        acc0 = __SMLAD(x2, y2, acc0);
  
        acc2 = __SMLAD(x1, y2, acc2);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x1, x2, 0);
  #else
        x3 = __PKHBT(x2, x1, 0);
  #endif
  
        acc3 = __SMLADX(x3, y1, acc3);
  
        acc1 = __SMLADX(x3, y2, acc1);
  
  	  a = *(pScr1 + 2);
  	  b = *(pScr1 + 3);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x2 = __PKHBT(a, b, 16);
  #else
        x2 = __PKHBT(b, a, 16);
  #endif
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        acc3 = __SMLADX(x3, y2, acc3);
  
  #endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/
  
        /* update scratch pointers */
        pIn2 += 4u;
        pScr1 += 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++ * *pIn2);
        acc1 += (*pScr1++ * *pIn2);
        acc2 += (*pScr1++ * *pIn2);
        acc3 += (*pScr1++ * *pIn2++);
  
        pScr1 -= 3u;
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
      blkCnt--;
  
  
      /* Store the results in the accumulators in the destination buffer. */
  
  #ifndef ARM_MATH_BIG_ENDIAN
  
      *__SIMD32(pOut)++ =
        __PKHBT(__SSAT((acc0 >> 15), 16), __SSAT((acc1 >> 15), 16), 16);
  
      *__SIMD32(pOut)++ =
        __PKHBT(__SSAT((acc2 >> 15), 16), __SSAT((acc3 >> 15), 16), 16);
  
  
  #else
  
      *__SIMD32(pOut)++ =
        __PKHBT(__SSAT((acc1 >> 15), 16), __SSAT((acc0 >> 15), 16), 16);
  
      *__SIMD32(pOut)++ =
        __PKHBT(__SSAT((acc3 >> 15), 16), __SSAT((acc2 >> 15), 16), 16);
  
  
  
  #endif /*      #ifndef ARM_MATH_BIG_ENDIAN       */
  
      /* Initialization of inputB pointer */
      pIn2 = 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++ * *pIn2++);
        acc0 += (*pScr1++ * *pIn2++);
  
        /* 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++ * *pIn2++);
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
      blkCnt--;
  
      /* The result is in 2.30 format.  Convert to 1.15 with saturation.       
       ** Then store the output in the destination buffer. */
      *pOut++ = (q15_t) (__SSAT((acc0 >> 15), 16));
  
      /* Initialization of inputB pointer */
      pIn2 = py;
  
      pScratch1 += 1u;
  
    }
  
  }
  
  /**    
   * @} end of Conv group    
   */
  