arm_fir_sparse_q7.c

/* ----------------------------------------------------------------------    
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
*    
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*    
* Project: 	    CMSIS DSP Library    
* Title:	    arm_fir_sparse_q7.c    
*    
* Description:	Q7 sparse FIR filter processing function.   
*    
* 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;
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* ------------------------------------------------------------------- */
#include "arm_math.h"


/**    
 * @ingroup groupFilters    
 */

/**    
 * @addtogroup FIR_Sparse    
 * @{    
 */


/**   
 * @brief Processing function for the Q7 sparse FIR filter.   
 * @param[in]  *S           points to an instance of the Q7 sparse FIR structure.   
 * @param[in]  *pSrc        points to the block of input data.   
 * @param[out] *pDst        points to the block of output data   
 * @param[in]  *pScratchIn  points to a temporary buffer of size blockSize.   
 * @param[in]  *pScratchOut points to a temporary buffer of size blockSize.   
 * @param[in]  blockSize    number of input samples to process per call.   
 * @return none.   
 *    
 * <b>Scaling and Overflow Behavior:</b>    
 * \par    
 * The function is implemented using a 32-bit internal accumulator.    
 * Both coefficients and state variables 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.    
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.    
 * The accumulator is then converted to 18.7 format by discarding the low 7 bits.   
 * Finally, the result is truncated to 1.7 format.   
 */

void arm_fir_sparse_q7(
  arm_fir_sparse_instance_q7 * S,
  q7_t * pSrc,
  q7_t * pDst,
  q7_t * pScratchIn,
  q31_t * pScratchOut,
  uint32_t blockSize)
{

  q7_t *pState = S->pState;                      /* State pointer */
  q7_t *pCoeffs = S->pCoeffs;                    /* Coefficient pointer */
  q7_t *px;                                      /* Scratch buffer pointer */
  q7_t *py = pState;                             /* Temporary pointers for state buffer */
  q7_t *pb = pScratchIn;                         /* Temporary pointers for scratch buffer */
  q7_t *pOut = pDst;                             /* Destination pointer */
  int32_t *pTapDelay = S->pTapDelay;             /* Pointer to the array containing offset of the non-zero tap values. */
  uint32_t delaySize = S->maxDelay + blockSize;  /* state length */
  uint16_t numTaps = S->numTaps;                 /* Filter order */
  int32_t readIndex;                             /* Read index of the state buffer */
  uint32_t tapCnt, blkCnt;                       /* loop counters */
  q7_t coeff = *pCoeffs++;                       /* Read the coefficient value */
  q31_t *pScr2 = pScratchOut;                    /* Working pointer for scratch buffer of output values */
  q31_t in;


#ifndef ARM_MATH_CM0_FAMILY

  /* Run the below code for Cortex-M4 and Cortex-M3 */

  q7_t in1, in2, in3, in4;

  /* BlockSize of Input samples are copied into the state buffer */
  /* StateIndex points to the starting position to write in the state buffer */
  arm_circularWrite_q7(py, (int32_t) delaySize, &S->stateIndex, 1, pSrc, 1,
                       blockSize);

  /* Loop over the number of taps. */
  tapCnt = numTaps;

  /* Read Index, from where the state buffer should be read, is calculated. */
  readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

  /* Wraparound of readIndex */
  if(readIndex < 0)
  {
    readIndex += (int32_t) delaySize;
  }

  /* Working pointer for state buffer is updated */
  py = pState;

  /* blockSize samples are read from the state buffer */
  arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
                      (int32_t) blockSize, 1, blockSize);

  /* Working pointer for the scratch buffer of state values */
  px = pb;

  /* Working pointer for scratch buffer of output values */
  pScratchOut = pScr2;

  /* Loop over the blockSize. Unroll by a factor of 4.    
   * Compute 4 multiplications at a time. */
  blkCnt = blockSize >> 2;

  while(blkCnt > 0u)
  {
    /* Perform multiplication and store in the scratch buffer */
    *pScratchOut++ = ((q31_t) * px++ * coeff);
    *pScratchOut++ = ((q31_t) * px++ * coeff);
    *pScratchOut++ = ((q31_t) * px++ * coeff);
    *pScratchOut++ = ((q31_t) * px++ * coeff);

    /* Decrement the loop counter */
    blkCnt--;
  }

  /* If the blockSize is not a multiple of 4,    
   * compute the remaining samples */
  blkCnt = blockSize % 0x4u;

  while(blkCnt > 0u)
  {
    /* Perform multiplication and store in the scratch buffer */
    *pScratchOut++ = ((q31_t) * px++ * coeff);

    /* Decrement the loop counter */
    blkCnt--;
  }

  /* Load the coefficient value and    
   * increment the coefficient buffer for the next set of state values */
  coeff = *pCoeffs++;

  /* Read Index, from where the state buffer should be read, is calculated. */
  readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

  /* Wraparound of readIndex */
  if(readIndex < 0)
  {
    readIndex += (int32_t) delaySize;
  }

  /* Loop over the number of taps. */
  tapCnt = (uint32_t) numTaps - 2u;

  while(tapCnt > 0u)
  {
    /* Working pointer for state buffer is updated */
    py = pState;

    /* blockSize samples are read from the state buffer */
    arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
                        (int32_t) blockSize, 1, blockSize);

    /* Working pointer for the scratch buffer of state values */
    px = pb;

    /* Working pointer for scratch buffer of output values */
    pScratchOut = pScr2;

    /* Loop over the blockSize. Unroll by a factor of 4.    
     * Compute 4 MACS at a time. */
    blkCnt = blockSize >> 2;

    while(blkCnt > 0u)
    {
      /* Perform Multiply-Accumulate */
      in = *pScratchOut + ((q31_t) * px++ * coeff);
      *pScratchOut++ = in;
      in = *pScratchOut + ((q31_t) * px++ * coeff);
      *pScratchOut++ = in;
      in = *pScratchOut + ((q31_t) * px++ * coeff);
      *pScratchOut++ = in;
      in = *pScratchOut + ((q31_t) * px++ * coeff);
      *pScratchOut++ = in;

      /* Decrement the loop counter */
      blkCnt--;
    }

    /* If the blockSize is not a multiple of 4,    
     * compute the remaining samples */
    blkCnt = blockSize % 0x4u;

    while(blkCnt > 0u)
    {
      /* Perform Multiply-Accumulate */
      in = *pScratchOut + ((q31_t) * px++ * coeff);
      *pScratchOut++ = in;

      /* Decrement the loop counter */
      blkCnt--;
    }

    /* Load the coefficient value and    
     * increment the coefficient buffer for the next set of state values */
    coeff = *pCoeffs++;

    /* Read Index, from where the state buffer should be read, is calculated. */
    readIndex = ((int32_t) S->stateIndex -
                 (int32_t) blockSize) - *pTapDelay++;

    /* Wraparound of readIndex */
    if(readIndex < 0)
    {
      readIndex += (int32_t) delaySize;
    }

    /* Decrement the tap loop counter */
    tapCnt--;
  }
	
	/* Compute last tap without the final read of pTapDelay */	
	
	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
											(int32_t) blockSize, 1, blockSize);

	/* Working pointer for the scratch buffer of state values */
	px = pb;

	/* Working pointer for scratch buffer of output values */
	pScratchOut = pScr2;

	/* Loop over the blockSize. Unroll by a factor of 4.    
	 * Compute 4 MACS at a time. */
	blkCnt = blockSize >> 2;

	while(blkCnt > 0u)
	{
		/* Perform Multiply-Accumulate */
		in = *pScratchOut + ((q31_t) * px++ * coeff);
		*pScratchOut++ = in;
		in = *pScratchOut + ((q31_t) * px++ * coeff);
		*pScratchOut++ = in;
		in = *pScratchOut + ((q31_t) * px++ * coeff);
		*pScratchOut++ = in;
		in = *pScratchOut + ((q31_t) * px++ * coeff);
		*pScratchOut++ = in;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4,    
	 * compute the remaining samples */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u)
	{
		/* Perform Multiply-Accumulate */
		in = *pScratchOut + ((q31_t) * px++ * coeff);
		*pScratchOut++ = in;

		/* Decrement the loop counter */
		blkCnt--;
	}

  /* All the output values are in pScratchOut buffer.    
     Convert them into 1.15 format, saturate and store in the destination buffer. */
  /* Loop over the blockSize. */
  blkCnt = blockSize >> 2;

  while(blkCnt > 0u)
  {
    in1 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
    in2 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
    in3 = (q7_t) __SSAT(*pScr2++ >> 7, 8);
    in4 = (q7_t) __SSAT(*pScr2++ >> 7, 8);

    *__SIMD32(pOut)++ = __PACKq7(in1, in2, in3, in4);

    /* Decrement the blockSize loop counter */
    blkCnt--;
  }

  /* If the blockSize is not a multiple of 4,    
     remaining samples are processed in the below loop */
  blkCnt = blockSize % 0x4u;

  while(blkCnt > 0u)
  {
    *pOut++ = (q7_t) __SSAT(*pScr2++ >> 7, 8);

    /* Decrement the blockSize loop counter */
    blkCnt--;
  }

#else

  /* Run the below code for Cortex-M0 */

  /* BlockSize of Input samples are copied into the state buffer */
  /* StateIndex points to the starting position to write in the state buffer */
  arm_circularWrite_q7(py, (int32_t) delaySize, &S->stateIndex, 1, pSrc, 1,
                       blockSize);

  /* Loop over the number of taps. */
  tapCnt = numTaps;

  /* Read Index, from where the state buffer should be read, is calculated. */
  readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

  /* Wraparound of readIndex */
  if(readIndex < 0)
  {
    readIndex += (int32_t) delaySize;
  }

  /* Working pointer for state buffer is updated */
  py = pState;

  /* blockSize samples are read from the state buffer */
  arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
                      (int32_t) blockSize, 1, blockSize);

  /* Working pointer for the scratch buffer of state values */
  px = pb;

  /* Working pointer for scratch buffer of output values */
  pScratchOut = pScr2;

  /* Loop over the blockSize */
  blkCnt = blockSize;

  while(blkCnt > 0u)
  {
    /* Perform multiplication and store in the scratch buffer */
    *pScratchOut++ = ((q31_t) * px++ * coeff);

    /* Decrement the loop counter */
    blkCnt--;
  }

  /* Load the coefficient value and           
   * increment the coefficient buffer for the next set of state values */
  coeff = *pCoeffs++;

  /* Read Index, from where the state buffer should be read, is calculated. */
  readIndex = ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

  /* Wraparound of readIndex */
  if(readIndex < 0)
  {
    readIndex += (int32_t) delaySize;
  }

  /* Loop over the number of taps. */
  tapCnt = (uint32_t) numTaps - 2u;

  while(tapCnt > 0u)
  {
    /* Working pointer for state buffer is updated */
    py = pState;

    /* blockSize samples are read from the state buffer */
    arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
                        (int32_t) blockSize, 1, blockSize);

    /* Working pointer for the scratch buffer of state values */
    px = pb;

    /* Working pointer for scratch buffer of output values */
    pScratchOut = pScr2;

    /* Loop over the blockSize */
    blkCnt = blockSize;

    while(blkCnt > 0u)
    {
      /* Perform Multiply-Accumulate */
      in = *pScratchOut + ((q31_t) * px++ * coeff);
      *pScratchOut++ = in;

      /* Decrement the loop counter */
      blkCnt--;
    }

    /* Load the coefficient value and           
     * increment the coefficient buffer for the next set of state values */
    coeff = *pCoeffs++;

    /* Read Index, from where the state buffer should be read, is calculated. */
    readIndex =
      ((int32_t) S->stateIndex - (int32_t) blockSize) - *pTapDelay++;

    /* Wraparound of readIndex */
    if(readIndex < 0)
    {
      readIndex += (int32_t) delaySize;
    }

    /* Decrement the tap loop counter */
    tapCnt--;
  }
	
	/* Compute last tap without the final read of pTapDelay */	
	
	/* Working pointer for state buffer is updated */
	py = pState;

	/* blockSize samples are read from the state buffer */
	arm_circularRead_q7(py, (int32_t) delaySize, &readIndex, 1, pb, pb,
											(int32_t) blockSize, 1, blockSize);

	/* Working pointer for the scratch buffer of state values */
	px = pb;

	/* Working pointer for scratch buffer of output values */
	pScratchOut = pScr2;

	/* Loop over the blockSize */
	blkCnt = blockSize;

	while(blkCnt > 0u)
	{
		/* Perform Multiply-Accumulate */
		in = *pScratchOut + ((q31_t) * px++ * coeff);
		*pScratchOut++ = in;

		/* Decrement the loop counter */
		blkCnt--;
	}

  /* All the output values are in pScratchOut buffer.       
     Convert them into 1.15 format, saturate and store in the destination buffer. */
  /* Loop over the blockSize. */
  blkCnt = blockSize;

  while(blkCnt > 0u)
  {
    *pOut++ = (q7_t) __SSAT(*pScr2++ >> 7, 8);

    /* Decrement the blockSize loop counter */
    blkCnt--;
  }

#endif /*   #ifndef ARM_MATH_CM0_FAMILY */

}

/**    
 * @} end of FIR_Sparse group    
 */