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# arm_shift_q7.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        29. November 2010
    00005 * $Revision:    V1.0.3
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_shift_q7.c
    00009 *
    00010 * Description:  Processing function for the Q7 Shifting
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3
    00013 *
    00014 * Version 1.0.3 2010/11/29
    00015 *    Re-organized the CMSIS folders and updated documentation.
    00016 *
    00017 * Version 1.0.2 2010/11/11
    00018 *    Documentation updated.
    00019 *
    00020 * Version 1.0.1 2010/10/05
    00021 *    Production release and review comments incorporated.
    00022 *
    00023 * Version 1.0.0 2010/09/20
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 0.0.7  2010/06/10
    00027 *    Misra-C changes done
    00028 * -------------------------------------------------------------------- */
    00029
    00030 #include "arm_math.h"
    00031
    00056 void arm_shift_q7(
    00057   q7_t * pSrc,
    00058   int8_t shiftBits,
    00059   q7_t * pDst,
    00060   uint32_t blockSize)
    00061 {
    00062   uint32_t blkCnt;                               /* loop counter */
    00063   uint8_t sign;                                  /* Sign of shiftBits */
    00064   q7_t in1;                                      /* Input value1 */
    00065   q7_t in2;                                      /* Input value2 */
    00066   q7_t in3;                                      /* Input value3 */
    00067   q7_t in4;                                      /* Input value4 */
    00068
    00069
    00070   /*loop Unrolling */
    00071   blkCnt = blockSize >> 2u;
    00072
    00073   /* Getting the sign of shiftBits */
    00074   sign = (shiftBits & 0x80);
    00075
    00076   /* If the shift value is positive then do right shift else left shift */
    00077   if(sign == 0u)
    00078   {
    00079     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00080      ** a second loop below computes the remaining 1 to 3 samples. */
    00081     while(blkCnt > 0u)
    00082     {
    00083       /* C = A << shiftBits */
    00084       /* Read 4 inputs */
    00085       in1 = *pSrc++;
    00086       in2 = *pSrc++;
    00087       in3 = *pSrc++;
    00088       in4 = *pSrc++;
    00089
    00090       /* Store the Shifted result in the destination buffer in single cycle by packing the outputs */
    00091       *__SIMD32(pDst)++ = __PACKq7(__SSAT((in1 << shiftBits), 8),
    00092                                    __SSAT((in2 << shiftBits), 8),
    00093                                    __SSAT((in3 << shiftBits), 8),
    00094                                    __SSAT((in4 << shiftBits), 8));
    00095
    00096       /* Decrement the loop counter */
    00097       blkCnt--;
    00098     }
    00099
    00100     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00101      ** No loop unrolling is used. */
    00102     blkCnt = blockSize % 0x4u;
    00103
    00104     while(blkCnt > 0u)
    00105     {
    00106       /* C = A << shiftBits */
    00107       /* Shift the input and then store the result in the destination buffer. */
    00108       *pDst++ = (q7_t) __SSAT((*pSrc++ << shiftBits), 8);
    00109
    00110       /* Decrement the loop counter */
    00111       blkCnt--;
    00112     }
    00113   }
    00114   else
    00115   {
    00116     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00117      ** a second loop below computes the remaining 1 to 3 samples. */
    00118     while(blkCnt > 0u)
    00119     {
    00120       /* C = A >> shiftBits */
    00121       /* Read 4 inputs */
    00122       in1 = *pSrc++;
    00123       in2 = *pSrc++;
    00124       in3 = *pSrc++;
    00125       in4 = *pSrc++;
    00126
    00127       /* Store the Shifted result in the destination buffer in single cycle by packing the outputs */
    00128       *__SIMD32(pDst)++ = __PACKq7((in1 >> -shiftBits), (in2 >> -shiftBits),
    00129                                    (in3 >> -shiftBits), (in4 >> -shiftBits));
    00130
    00131       /* Decrement the loop counter */
    00132       blkCnt--;
    00133     }
    00134
    00135     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00136      ** No loop unrolling is used. */
    00137     blkCnt = blockSize % 0x4u;
    00138
    00139     while(blkCnt > 0u)
    00140     {
    00141       /* C = A >> shiftBits */
    00142       /* Shift the input and then store the result in the destination buffer. */
    00143       *pDst++ = (*pSrc++ >> -shiftBits);
    00144
    00145       /* Decrement the loop counter */
    00146       blkCnt--;
    00147     }
    00148   }
    00149 }
    00150

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