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# arm_shift_q15.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_q15.c
    00009 *
    00010 * Description:  Shifts elements of a Q15 vector a specified number of bits.
    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
    00055 void arm_shift_q15(
    00056   q15_t * pSrc,
    00057   int8_t shiftBits,
    00058   q15_t * pDst,
    00059   uint32_t blockSize)
    00060 {
    00061   uint32_t blkCnt;                               /* loop counter */
    00062   uint8_t sign;                                  /* Sign of shiftBits */
    00063   q15_t in1, in2;                                /* Temporary variables */
    00064
    00065
    00066   /*loop Unrolling */
    00067   blkCnt = blockSize >> 2u;
    00068
    00069   /* Getting the sign of shiftBits */
    00070   sign = (shiftBits & 0x80);
    00071
    00072   /* If the shift value is positive then do right shift else left shift */
    00073   if(sign == 0u)
    00074   {
    00075     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00076      ** a second loop below computes the remaining 1 to 3 samples. */
    00077     while(blkCnt > 0u)
    00078     {
    00079       /* Read 2 inputs */
    00080       in1 = *pSrc++;
    00081       in2 = *pSrc++;
    00082       /* C = A << shiftBits */
    00083       /* Shift the inputs and then store the results in the destination buffer. */
    00084       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
    00085                                   __SSAT((in2 << shiftBits), 16), 16);
    00086
    00087       in1 = *pSrc++;
    00088       in2 = *pSrc++;
    00089
    00090       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
    00091                                   __SSAT((in2 << shiftBits), 16), 16);
    00092
    00093       /* Decrement the loop counter */
    00094       blkCnt--;
    00095     }
    00096
    00097     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00098      ** No loop unrolling is used. */
    00099     blkCnt = blockSize % 0x4u;
    00100
    00101     while(blkCnt > 0u)
    00102     {
    00103       /* C = A << shiftBits */
    00104       /* Shift and then store the results in the destination buffer. */
    00105       *pDst++ = __SSAT((*pSrc++ << shiftBits), 16);
    00106
    00107       /* Decrement the loop counter */
    00108       blkCnt--;
    00109     }
    00110   }
    00111   else
    00112   {
    00113     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00114      ** a second loop below computes the remaining 1 to 3 samples. */
    00115     while(blkCnt > 0u)
    00116     {
    00117       /* Read 2 inputs */
    00118       in1 = *pSrc++;
    00119       in2 = *pSrc++;
    00120       /* C = A >> shiftBits */
    00121       /* Shift the inputs and then store the results in the destination buffer. */
    00122       *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
    00123                                   (in2 >> -shiftBits), 16);
    00124       in1 = *pSrc++;
    00125       in2 = *pSrc++;
    00126
    00127       *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
    00128                                   (in2 >> -shiftBits), 16);
    00129
    00130       /* Decrement the loop counter */
    00131       blkCnt--;
    00132     }
    00133
    00134     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00135      ** No loop unrolling is used. */
    00136     blkCnt = blockSize % 0x4u;
    00137
    00138     while(blkCnt > 0u)
    00139     {
    00140       /* C = A >> shiftBits */
    00141       /* Shift the inputs and then store the results in the destination buffer. */
    00142       *pDst++ = (*pSrc++ >> -shiftBits);
    00143
    00144       /* Decrement the loop counter */
    00145       blkCnt--;
    00146     }
    00147   }
    00148 }
    00149

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