CMSIS DSP Software Library: arm_scale_q15.c Source File

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# arm_scale_q15.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_scale_q15.c
    00009 *
    00010 * Description:  Multiplies a Q15 vector by a scalar.
    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
    00060 void arm_scale_q15(
    00061   q15_t * pSrc,
    00062   q15_t scaleFract,
    00063   int8_t shift,
    00064   q15_t * pDst,
    00065   uint32_t blockSize)
    00066 {
    00067   int8_t kShift = 15 - shift;                    /* shift to apply after scaling */
    00068   uint32_t blkCnt;                               /* loop counter */
    00069
    00070 #ifndef ARM_MATH_CM0
    00071
    00072 /* Run the below code for Cortex-M4 and Cortex-M3 */
    00073
    00074   q15_t in1, in2;                                /* Temporary variables */
    00075
    00076
    00077   /*loop Unrolling */
    00078   blkCnt = blockSize >> 2u;
    00079
    00080   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
    00081    ** a second loop below computes the remaining 1 to 3 samples. */
    00082   while(blkCnt > 0u)
    00083   {
    00084     /* Reading 2 inputs from memory */
    00085     in1 = *pSrc++;
    00086     in2 = *pSrc++;
    00087     /* C = A * scale */
    00088     /* Scale the inputs and then store the 2 results in the destination buffer
    00089      * in single cycle by packing the outputs */
    00090 #ifndef  ARM_MATH_BIG_ENDIAN
    00091
    00092     *__SIMD32(pDst)++ =
    00093       __PKHBT(__SSAT((in1 * scaleFract) >> kShift, 16),
    00094               __SSAT((in2 * scaleFract) >> kShift, 16), 16);
    00095
    00096 #else
    00097
    00098     *__SIMD32(pDst)++ =
    00099       __PKHBT(__SSAT((in2 * scaleFract) >> kShift, 16),
    00100               __SSAT((in1 * scaleFract) >> kShift, 16), 16);
    00101
    00102 #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
    00103
    00104     in1 = *pSrc++;
    00105     in2 = *pSrc++;
    00106
    00107 #ifndef  ARM_MATH_BIG_ENDIAN
    00108
    00109     *__SIMD32(pDst)++ =
    00110       __PKHBT(__SSAT((in1 * scaleFract) >> kShift, 16),
    00111               __SSAT((in2 * scaleFract) >> kShift, 16), 16);
    00112
    00113 #else
    00114
    00115     *__SIMD32(pDst)++ =
    00116       __PKHBT(__SSAT((in2 * scaleFract) >> kShift, 16),
    00117               __SSAT((in1 * scaleFract) >> kShift, 16), 16);
    00118
    00119 #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
    00120
    00121     /* Decrement the loop counter */
    00122     blkCnt--;
    00123   }
    00124
    00125   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
    00126    ** No loop unrolling is used. */
    00127   blkCnt = blockSize % 0x4u;
    00128
    00129   while(blkCnt > 0u)
    00130   {
    00131     /* C = A * scale */
    00132     /* Scale the input and then store the result in the destination buffer. */
    00133     *pDst++ = (q15_t) (__SSAT(((*pSrc++) * scaleFract) >> kShift, 16));
    00134
    00135     /* Decrement the loop counter */
    00136     blkCnt--;
    00137   }
    00138
    00139 #else
    00140
    00141   /* Run the below code for Cortex-M0 */
    00142
    00143   /* Initialize blkCnt with number of samples */
    00144   blkCnt = blockSize;
    00145
    00146   while(blkCnt > 0u)
    00147   {
    00148     /* C = A * scale */
    00149     /* Scale the input and then store the result in the destination buffer. */
    00150     *pDst++ = (q15_t) (__SSAT(((q31_t) * pSrc++ * scaleFract) >> kShift, 16));
    00151
    00152     /* Decrement the loop counter */
    00153     blkCnt--;
    00154   }
    00155
    00156 #endif /* #ifndef ARM_MATH_CM0 */
    00157
    00158 }
    00159

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