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_correlate_opt_q15.c    
  *    
  * Description:	Correlation of Q15 sequences.  
  *    
  * Target Processor: Cortex-M4/Cortex-M3
  *  
  * 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 Corr    
   * @{    
   */
  
  /**    
   * @brief Correlation of Q15 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 2 * max(srcALen, srcBLen) - 1.    
   * @param[in]  *pScratch points to scratch buffer of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.    
   * @return none.    
   *    
   * \par Restrictions    
   *  If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE    
   *	In this case input, output, scratch buffers should be aligned by 32-bit    
   *     
   * @details    
   * <b>Scaling and Overflow Behavior:</b>    
   *    
   * \par    
   * The function is implemented using a 64-bit internal accumulator.    
   * Both inputs are in 1.15 format and multiplications yield a 2.30 result.    
   * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.    
   * This approach provides 33 guard bits and there is no risk of overflow.    
   * The 34.30 result is then truncated to 34.15 format by discarding the low 15 bits and then saturated to 1.15 format.    
   *    
   * \par    
   * Refer to <code>arm_correlate_fast_q15()</code> for a faster but less precise version of this function for Cortex-M3 and Cortex-M4.   
   *  
   * 
   */
  
  
  void arm_correlate_opt_q15(
    q15_t * pSrcA,
    uint32_t srcALen,
    q15_t * pSrcB,
    uint32_t srcBLen,
    q15_t * pDst,
    q15_t * pScratch)
  {
    q15_t *pIn1;                                   /* inputA pointer               */
    q15_t *pIn2;                                   /* inputB pointer               */
    q63_t acc0, acc1, acc2, acc3;                  /* Accumulators                  */
    q15_t *py;                                     /* Intermediate inputB pointer  */
    q31_t x1, x2, x3;                              /* temporary variables for holding input1 and input2 values */
    uint32_t j, blkCnt, outBlockSize;              /* loop counter                 */
    int32_t inc = 1;                               /* output pointer increment     */
    uint32_t tapCnt;
    q31_t y1, y2;
    q15_t *pScr;                                   /* Intermediate pointers        */
    q15_t *pOut = pDst;                            /* output pointer               */
  #ifdef UNALIGNED_SUPPORT_DISABLE
  
    q15_t a, b;
  
  #endif	/*	#ifndef 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 */
    /* But CORR(x, y) is reverse of CORR(y, x) */
    /* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */
    /* and the destination pointer modifier, inc is set to -1 */
    /* If srcALen > srcBLen, zero pad has to be done to srcB to make the two inputs of same length */
    /* But to improve the performance,        
     * we include zeroes in the output instead of zero padding either of the the inputs*/
    /* If srcALen > srcBLen,        
     * (srcALen - srcBLen) zeroes has to included in the starting of the output buffer */
    /* If srcALen < srcBLen,        
     * (srcALen - srcBLen) zeroes has to included in the ending of the output buffer */
    if(srcALen >= srcBLen)
    {
      /* Initialization of inputA pointer */
      pIn1 = (pSrcA);
  
      /* Initialization of inputB pointer */
      pIn2 = (pSrcB);
  
      /* Number of output samples is calculated */
      outBlockSize = (2u * srcALen) - 1u;
  
      /* When srcALen > srcBLen, zero padding is done to srcB        
       * to make their lengths equal.        
       * Instead, (outBlockSize - (srcALen + srcBLen - 1))        
       * number of output samples are made zero */
      j = outBlockSize - (srcALen + (srcBLen - 1u));
  
      /* Updating the pointer position to non zero value */
      pOut += j;
  
    }
    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;
  
      /* CORR(x, y) = Reverse order(CORR(y, x)) */
      /* Hence set the destination pointer to point to the last output sample */
      pOut = pDst + ((srcALen + srcBLen) - 2u);
  
      /* Destination address modifier is set to -1 */
      inc = -1;
  
    }
  
    pScr = pScratch;
  
    /* Fill (srcBLen - 1u) zeros in scratch buffer */
    arm_fill_q15(0, pScr, (srcBLen - 1u));
  
    /* Update temporary scratch pointer */
    pScr += (srcBLen - 1u);
  
  #ifndef UNALIGNED_SUPPORT_DISABLE
  
    /* Copy (srcALen) samples in scratch buffer */
    arm_copy_q15(pIn1, pScr, srcALen);
  
    /* Update pointers */
    //pIn1 += srcALen;    
    pScr += srcALen;
  
  #else
  
    /* Apply loop unrolling and do 4 Copies simultaneously. */
    j = 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(j > 0u)
    {
      /* copy second buffer in reversal manner */
      *pScr++ = *pIn1++;
      *pScr++ = *pIn1++;
      *pScr++ = *pIn1++;
      *pScr++ = *pIn1++;
  
      /* Decrement the loop counter */
      j--;
    }
  
    /* If the count is not a multiple of 4, copy remaining samples here.       
     ** No loop unrolling is used. */
    j = srcALen % 0x4u;
  
    while(j > 0u)
    {
      /* copy second buffer in reversal manner for remaining samples */
      *pScr++ = *pIn1++;
  
      /* Decrement the loop counter */
      j--;
    }
  
  #endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/
  
  #ifndef UNALIGNED_SUPPORT_DISABLE
  
    /* Fill (srcBLen - 1u) zeros at end of scratch buffer */
    arm_fill_q15(0, pScr, (srcBLen - 1u));
  
    /* Update pointer */
    pScr += (srcBLen - 1u);
  
  #else
  
  /* Apply loop unrolling and do 4 Copies simultaneously. */
    j = (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(j > 0u)
    {
      /* copy second buffer in reversal manner */
      *pScr++ = 0;
      *pScr++ = 0;
      *pScr++ = 0;
      *pScr++ = 0;
  
      /* Decrement the loop counter */
      j--;
    }
  
    /* If the count is not a multiple of 4, copy remaining samples here.       
     ** No loop unrolling is used. */
    j = (srcBLen - 1u) % 0x4u;
  
    while(j > 0u)
    {
      /* copy second buffer in reversal manner for remaining samples */
      *pScr++ = 0;
  
      /* Decrement the loop counter */
      j--;
    }
  
  #endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/
  
    /* Temporary pointer for scratch2 */
    py = pIn2;
  
  
    /* Actual correlation process starts here */
    blkCnt = (srcALen + srcBLen - 1u) >> 2;
  
    while(blkCnt > 0)
    {
      /* Initialze temporary scratch pointer as scratch1 */
      pScr = pScratch;
  
      /* Clear Accumlators */
      acc0 = 0;
      acc1 = 0;
      acc2 = 0;
      acc3 = 0;
  
      /* Read four samples from scratch1 buffer */
      x1 = *__SIMD32(pScr)++;
  
      /* Read next four samples from scratch1 buffer */
      x2 = *__SIMD32(pScr)++;
  
      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);
  
        acc0 = __SMLALD(x1, y1, acc0);
  
        acc2 = __SMLALD(x2, y1, acc2);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        acc1 = __SMLALDX(x3, y1, acc1);
  
        x1 = _SIMD32_OFFSET(pScr);
  
        acc0 = __SMLALD(x2, y2, acc0);
  
        acc2 = __SMLALD(x1, y2, acc2);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x1, x2, 0);
  #else
        x3 = __PKHBT(x2, x1, 0);
  #endif
  
        acc3 = __SMLALDX(x3, y1, acc3);
  
        acc1 = __SMLALDX(x3, y2, acc1);
  
        x2 = _SIMD32_OFFSET(pScr + 2u);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        acc3 = __SMLALDX(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 = __SMLALD(x1, y1, acc0);
  
        acc2 = __SMLALD(x2, y1, acc2);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x2, x1, 0);
  #else
        x3 = __PKHBT(x1, x2, 0);
  #endif
  
        acc1 = __SMLALDX(x3, y1, acc1);
  
  	  a = *pScr;
  	  b = *(pScr + 1);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x1 = __PKHBT(a, b, 16);
  #else
        x1 = __PKHBT(b, a, 16);
  #endif
  
        acc0 = __SMLALD(x2, y2, acc0);
  
        acc2 = __SMLALD(x1, y2, acc2);
  
  #ifndef ARM_MATH_BIG_ENDIAN
        x3 = __PKHBT(x1, x2, 0);
  #else
        x3 = __PKHBT(x2, x1, 0);
  #endif
  
        acc3 = __SMLALDX(x3, y1, acc3);
  
        acc1 = __SMLALDX(x3, y2, acc1);
  
  	  a = *(pScr + 2);
  	  b = *(pScr + 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 = __SMLALDX(x3, y2, acc3);
  
  #endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/
  
        pIn2 += 4u;
  
        pScr += 4u;
  
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
  
  
      /* Update scratch pointer for remaining samples of smaller length sequence */
      pScr -= 4u;
  
  
      /* apply same above for remaining samples of smaller length sequence */
      tapCnt = (srcBLen) & 3u;
  
      while(tapCnt > 0u)
      {
  
        /* accumlate the results */
        acc0 += (*pScr++ * *pIn2);
        acc1 += (*pScr++ * *pIn2);
        acc2 += (*pScr++ * *pIn2);
        acc3 += (*pScr++ * *pIn2++);
  
        pScr -= 3u;
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
      blkCnt--;
  
  
      /* Store the results in the accumulators in the destination buffer. */
      *pOut = (__SSAT(acc0 >> 15u, 16));
      pOut += inc;
      *pOut = (__SSAT(acc1 >> 15u, 16));
      pOut += inc;
      *pOut = (__SSAT(acc2 >> 15u, 16));
      pOut += inc;
      *pOut = (__SSAT(acc3 >> 15u, 16));
      pOut += inc;
  
      /* Initialization of inputB pointer */
      pIn2 = py;
  
      pScratch += 4u;
  
    }
  
  
    blkCnt = (srcALen + srcBLen - 1u) & 0x3;
  
    /* Calculate correlation for remaining samples of Bigger length sequence */
    while(blkCnt > 0)
    {
      /* Initialze temporary scratch pointer as scratch1 */
      pScr = pScratch;
  
      /* Clear Accumlators */
      acc0 = 0;
  
      tapCnt = (srcBLen) >> 1u;
  
      while(tapCnt > 0u)
      {
  
        acc0 += (*pScr++ * *pIn2++);
        acc0 += (*pScr++ * *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 += (*pScr++ * *pIn2++);
  
        /* Decrement the loop counter */
        tapCnt--;
      }
  
      blkCnt--;
  
      /* Store the result in the accumulator in the destination buffer. */
      *pOut = (q15_t) (__SSAT((acc0 >> 15), 16));
  
      pOut += inc;
  
      /* Initialization of inputB pointer */
      pIn2 = py;
  
      pScratch += 1u;
  
    }
  
  
  }
  
  /**    
   * @} end of Corr group    
   */
  