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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_shift_q7.c
* Description: Processing function for the Q7 Shifting
*
* $Date: 27. January 2017
* $Revision: V.1.5.1
*
* Target Processor: Cortex-M cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the License); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an AS IS BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "arm_math.h"
/**
* @ingroup groupMath
*/
/**
* @addtogroup shift
* @{
*/
/**
* @brief Shifts the elements of a Q7 vector a specified number of bits.
* @param[in] *pSrc points to the input vector
* @param[in] shiftBits number of bits to shift. A positive value shifts left; a negative value shifts right.
* @param[out] *pDst points to the output vector
* @param[in] blockSize number of samples in the vector
* @return none.
*
* \par Conditions for optimum performance
* Input and output buffers should be aligned by 32-bit
*
*
* <b>Scaling and Overflow Behavior:</b>
* \par
* The function uses saturating arithmetic.
* Results outside of the allowable Q7 range [0x8 0x7F] will be saturated.
*/
void arm_shift_q7(
q7_t * pSrc,
int8_t shiftBits,
q7_t * pDst,
uint32_t blockSize)
{
uint32_t blkCnt; /* loop counter */
uint8_t sign; /* Sign of shiftBits */
#if defined (ARM_MATH_DSP)
/* Run the below code for Cortex-M4 and Cortex-M3 */
q7_t in1; /* Input value1 */
q7_t in2; /* Input value2 */
q7_t in3; /* Input value3 */
q7_t in4; /* Input value4 */
/*loop Unrolling */
blkCnt = blockSize >> 2U;
/* Getting the sign of shiftBits */
sign = (shiftBits & 0x80);
/* If the shift value is positive then do right shift else left shift */
if (sign == 0U)
{
/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
** a second loop below computes the remaining 1 to 3 samples. */
while (blkCnt > 0U)
{
/* C = A << shiftBits */
/* Read 4 inputs */
in1 = *pSrc;
in2 = *(pSrc + 1);
in3 = *(pSrc + 2);
in4 = *(pSrc + 3);
/* Store the Shifted result in the destination buffer in single cycle by packing the outputs */
*__SIMD32(pDst)++ = __PACKq7(__SSAT((in1 << shiftBits), 8),
__SSAT((in2 << shiftBits), 8),
__SSAT((in3 << shiftBits), 8),
__SSAT((in4 << shiftBits), 8));
/* Update source pointer to process next sampels */
pSrc += 4U;
/* Decrement the loop counter */
blkCnt--;
}
/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
** No loop unrolling is used. */
blkCnt = blockSize % 0x4U;
while (blkCnt > 0U)
{
/* C = A << shiftBits */
/* Shift the input and then store the result in the destination buffer. */
*pDst++ = (q7_t) __SSAT((*pSrc++ << shiftBits), 8);
/* Decrement the loop counter */
blkCnt--;
}
}
else
{
shiftBits = -shiftBits;
/* First part of the processing with loop unrolling. Compute 4 outputs at a time.
** a second loop below computes the remaining 1 to 3 samples. */
while (blkCnt > 0U)
{
/* C = A >> shiftBits */
/* Read 4 inputs */
in1 = *pSrc;
in2 = *(pSrc + 1);
in3 = *(pSrc + 2);
in4 = *(pSrc + 3);
/* Store the Shifted result in the destination buffer in single cycle by packing the outputs */
*__SIMD32(pDst)++ = __PACKq7((in1 >> shiftBits), (in2 >> shiftBits),
(in3 >> shiftBits), (in4 >> shiftBits));
pSrc += 4U;
/* Decrement the loop counter */
blkCnt--;
}
/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
** No loop unrolling is used. */
blkCnt = blockSize % 0x4U;
while (blkCnt > 0U)
{
/* C = A >> shiftBits */
/* Shift the input and then store the result in the destination buffer. */
in1 = *pSrc++;
*pDst++ = (in1 >> shiftBits);
/* Decrement the loop counter */
blkCnt--;
}
}
#else
/* Run the below code for Cortex-M0 */
/* Getting the sign of shiftBits */
sign = (shiftBits & 0x80);
/* If the shift value is positive then do right shift else left shift */
if (sign == 0U)
{
/* Initialize blkCnt with number of samples */
blkCnt = blockSize;
while (blkCnt > 0U)
{
/* C = A << shiftBits */
/* Shift the input and then store the result in the destination buffer. */
*pDst++ = (q7_t) __SSAT(((q15_t) * pSrc++ << shiftBits), 8);
/* Decrement the loop counter */
blkCnt--;
}
}
else
{
/* Initialize blkCnt with number of samples */
blkCnt = blockSize;
while (blkCnt > 0U)
{
/* C = A >> shiftBits */
/* Shift the input and then store the result in the destination buffer. */
*pDst++ = (*pSrc++ >> -shiftBits);
/* Decrement the loop counter */
blkCnt--;
}
}
#endif /* #if defined (ARM_MATH_DSP) */
}
/**
* @} end of shift group
*/
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