CMSIS DSP Software Library: arm_shift_q31.c Source File

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# arm_shift_q31.c

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    00001 /* ----------------------------------------------------------------------
    00002 * Copyright (C) 2010 ARM Limited. All rights reserved.
    00003 *
    00004 * $Date:        15. July 2011
    00005 * $Revision:    V1.0.10
    00006 *
    00007 * Project:      CMSIS DSP Library
    00008 * Title:        arm_shift_q31.c
    00009 *
    00010 * Description:  Shifts the elements of a Q31 vector by a specified number of bits.
    00011 *
    00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
    00013 *
    00014 * Version 1.0.10 2011/7/15
    00015 *    Big Endian support added and Merged M0 and M3/M4 Source code.
    00016 *
    00017 * Version 1.0.3 2010/11/29
    00018 *    Re-organized the CMSIS folders and updated documentation.
    00019 *
    00020 * Version 1.0.2 2010/11/11
    00021 *    Documentation updated.
    00022 *
    00023 * Version 1.0.1 2010/10/05
    00024 *    Production release and review comments incorporated.
    00025 *
    00026 * Version 1.0.0 2010/09/20
    00027 *    Production release and review comments incorporated.
    00028 *
    00029 * Version 0.0.7  2010/06/10
    00030 *    Misra-C changes done
    00031 * -------------------------------------------------------------------- */
    00032
    00033 #include "arm_math.h"
    00034
    00073 void arm_shift_q31(
    00074   q31_t * pSrc,
    00075   int8_t shiftBits,
    00076   q31_t * pDst,
    00077   uint32_t blockSize)
    00078 {
    00079   uint32_t blkCnt;                               /* loop counter */
    00080   uint8_t sign;                                  /* Sign of shiftBits */
    00081   /* Getting the sign of shiftBits */
    00082   sign = (shiftBits & 0x80);
    00083
    00084
    00085 #ifndef ARM_MATH_CM0
    00086
    00087 /* Run the below code for Cortex-M4 and Cortex-M3 */
    00088   /*loop Unrolling */
    00089   blkCnt = blockSize >> 2u;
    00090
    00091
    00092   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00093    ** a second loop below computes the remaining 1 to 3 samples. */
    00094   while(blkCnt > 0u)
    00095   {
    00096     /* C = A (>> or <<) shiftBits */
    00097     /* Shift the input and then store the results in the destination buffer. */
    00098     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00099       (*pSrc++ >> -shiftBits);
    00100     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00101       (*pSrc++ >> -shiftBits);
    00102     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00103       (*pSrc++ >> -shiftBits);
    00104     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00105       (*pSrc++ >> -shiftBits);
    00106
    00107     /* Decrement the loop counter */
    00108     blkCnt--;
    00109   }
    00110
    00111   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00112    ** No loop unrolling is used. */
    00113   blkCnt = blockSize % 0x4u;
    00114
    00115 #else
    00116
    00117   /* Run the below code for Cortex-M0 */
    00118
    00119
    00120   /* Initialize blkCnt with number of samples */
    00121   blkCnt = blockSize;
    00122
    00123 #endif /* #ifndef ARM_MATH_CM0 */
    00124
    00125
    00126   while(blkCnt > 0u)
    00127   {
    00128     /* C = A (>> or <<) shiftBits */
    00129     /* Shift the input and then store the result in the destination buffer. */
    00130     *pDst++ = (sign == 0u) ? clip_q63_to_q31((q63_t) * pSrc++ << shiftBits) :
    00131       (*pSrc++ >> -shiftBits);
    00132
    00133     /* Decrement the loop counter */
    00134     blkCnt--;
    00135   }
    00136
    00137 }
    00138

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