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/* ----------------------------------------------------------------------
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* Copyright (C) 2010 ARM Limited. All rights reserved.
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*
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* $Date: 29. November 2010
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* $Revision: V1.0.3
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*
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* Project: CMSIS DSP Library
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* Title: arm_shift_q15.c
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*
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* Description: Shifts elements of a Q15 vector a specified number of bits.
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*
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* Target Processor: Cortex-M4/Cortex-M3
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*
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* Version 1.0.3 2010/11/29
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* Re-organized the CMSIS folders and updated documentation.
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*
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* Version 1.0.2 2010/11/11
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* Documentation updated.
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*
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* Version 1.0.1 2010/10/05
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* Production release and review comments incorporated.
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*
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* Version 1.0.0 2010/09/20
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* Production release and review comments incorporated.
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*
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* Version 0.0.7 2010/06/10
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* Misra-C changes done
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* -------------------------------------------------------------------- */
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#include "arm_math.h"
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/**
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* @ingroup groupMath
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*/
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/**
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* @addtogroup shift
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* @{
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*/
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/**
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* @brief Shifts the elements of a Q15 vector a specified number of bits.
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* @param *pSrc points to the input vector
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* @param shiftBits number of bits to shift. A positive value shifts left; a negative value shifts right.
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* @param *pDst points to the output vector
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* @param blockSize number of samples in the vector
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* @return none.
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*
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* <b>Scaling and Overflow Behavior:</b>
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* \par
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* The function uses saturating arithmetic.
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* Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.
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*/
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void arm_shift_q15(
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q15_t * pSrc,
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int8_t shiftBits,
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q15_t * pDst,
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uint32_t blockSize)
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{
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uint32_t blkCnt; /* loop counter */
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uint8_t sign; /* Sign of shiftBits */
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q15_t in1, in2; /* Temporary variables */
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/*loop Unrolling */
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blkCnt = blockSize >> 2u;
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/* Getting the sign of shiftBits */
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sign = (shiftBits & 0x80);
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/* If the shift value is positive then do right shift else left shift */
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if(sign == 0u)
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{
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/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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** a second loop below computes the remaining 1 to 3 samples. */
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while(blkCnt > 0u)
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{
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/* Read 2 inputs */
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in1 = *pSrc++;
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in2 = *pSrc++;
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/* C = A << shiftBits */
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/* Shift the inputs and then store the results in the destination buffer. */
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*__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
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__SSAT((in2 << shiftBits), 16), 16);
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in1 = *pSrc++;
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in2 = *pSrc++;
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*__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
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__SSAT((in2 << shiftBits), 16), 16);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x4u;
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while(blkCnt > 0u)
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{
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/* C = A << shiftBits */
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/* Shift and then store the results in the destination buffer. */
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*pDst++ = __SSAT((*pSrc++ << shiftBits), 16);
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/* Decrement the loop counter */
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blkCnt--;
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}
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}
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else
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{
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/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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** a second loop below computes the remaining 1 to 3 samples. */
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while(blkCnt > 0u)
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{
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/* Read 2 inputs */
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in1 = *pSrc++;
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in2 = *pSrc++;
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/* C = A >> shiftBits */
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/* Shift the inputs and then store the results in the destination buffer. */
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*__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
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(in2 >> -shiftBits), 16);
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in1 = *pSrc++;
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in2 = *pSrc++;
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*__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
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(in2 >> -shiftBits), 16);
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/* Decrement the loop counter */
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blkCnt--;
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}
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/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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** No loop unrolling is used. */
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blkCnt = blockSize % 0x4u;
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while(blkCnt > 0u)
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{
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/* C = A >> shiftBits */
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/* Shift the inputs and then store the results in the destination buffer. */
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*pDst++ = (*pSrc++ >> -shiftBits);
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/* Decrement the loop counter */
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blkCnt--;
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}
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}
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}
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/**
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* @} end of shift group
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*/
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