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56 mjames 1 
/* ----------------------------------------------------------------------
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 * Project:      CMSIS DSP Library
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 * Title:        arm_shift_q15.c
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 * Description:  Shifts the elements of a Q15 vector by a specified number of bits
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 *
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 * $Date:        27. January 2017
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 * $Revision:    V.1.5.1
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 *
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 * Target Processor: Cortex-M cores
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 * -------------------------------------------------------------------- */
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/*
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 * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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 *
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 * SPDX-License-Identifier: Apache-2.0
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 *
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 * Licensed under the Apache License, Version 2.0 (the License); you may
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 * not use this file except in compliance with the License.
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 * You may obtain a copy of the License at
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 *
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 * www.apache.org/licenses/LICENSE-2.0
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 *
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 * Unless required by applicable law or agreed to in writing, software
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 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
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 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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 * See the License for the specific language governing permissions and
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 * limitations under the License.
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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[in]  *pSrc points to the input vector
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 * @param[in]  shiftBits number of bits to shift.  A positive value shifts left; a negative value shifts right.
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 * @param[out]  *pDst points to the output vector
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 * @param[in]  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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#if defined (ARM_MATH_DSP)
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/* Run the below code for Cortex-M4 and Cortex-M3 */
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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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#ifndef  ARM_MATH_BIG_ENDIAN
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      *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
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                                  __SSAT((in2 << shiftBits), 16), 16);
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#else
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      *__SIMD32(pDst)++ = __PKHBT(__SSAT((in2 << shiftBits), 16),
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                                  __SSAT((in1 << shiftBits), 16), 16);
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#endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
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      in1 = *pSrc++;
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      in2 = *pSrc++;
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#ifndef  ARM_MATH_BIG_ENDIAN
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      *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
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                                  __SSAT((in2 << shiftBits), 16), 16);
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#else
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      *__SIMD32(pDst)++ = __PKHBT(__SSAT((in2 << shiftBits), 16),
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                                  __SSAT((in1 << shiftBits), 16), 16);
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#endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
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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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    {
139 
      /* 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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#ifndef  ARM_MATH_BIG_ENDIAN
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      *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
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                                  (in2 >> -shiftBits), 16);
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#else
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      *__SIMD32(pDst)++ = __PKHBT((in2 >> -shiftBits),
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                                  (in1 >> -shiftBits), 16);
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#endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
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      in1 = *pSrc++;
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      in2 = *pSrc++;
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#ifndef  ARM_MATH_BIG_ENDIAN
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      *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
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                                  (in2 >> -shiftBits), 16);
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#else
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      *__SIMD32(pDst)++ = __PKHBT((in2 >> -shiftBits),
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                                  (in1 >> -shiftBits), 16);
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#endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
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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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180 
    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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186 
      /* Decrement the loop counter */
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      blkCnt--;
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    }
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  }
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#else
192 
 
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  /* Run the below code for Cortex-M0 */
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195 
  /* Getting the sign of shiftBits */
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  sign = (shiftBits & 0x80);
197 
 
198 
  /* If the shift value is positive then do right shift else left shift */
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  if (sign == 0U)
200 
  {
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    /* Initialize blkCnt with number of samples */
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    blkCnt = blockSize;
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204 
    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(((q31_t) * 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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    /* Initialize blkCnt with number of samples */
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    blkCnt = blockSize;
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219 
    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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#endif /* #if defined (ARM_MATH_DSP) */
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}
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/**
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 * @} end of shift group
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 */