Subversion Repositories dashGPS

Rev

Rev 2 | Blame | Compare with Previous | Last modification | View Log | Download | RSS feed

  1. /* ----------------------------------------------------------------------
  2.  * Project:      CMSIS DSP Library
  3.  * Title:        arm_shift_q15.c
  4.  * Description:  Shifts the elements of a Q15 vector by a specified number of bits
  5.  *
  6.  * $Date:        27. January 2017
  7.  * $Revision:    V.1.5.1
  8.  *
  9.  * Target Processor: Cortex-M cores
  10.  * -------------------------------------------------------------------- */
  11. /*
  12.  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
  13.  *
  14.  * SPDX-License-Identifier: Apache-2.0
  15.  *
  16.  * Licensed under the Apache License, Version 2.0 (the License); you may
  17.  * not use this file except in compliance with the License.
  18.  * You may obtain a copy of the License at
  19.  *
  20.  * www.apache.org/licenses/LICENSE-2.0
  21.  *
  22.  * Unless required by applicable law or agreed to in writing, software
  23.  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
  24.  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  25.  * See the License for the specific language governing permissions and
  26.  * limitations under the License.
  27.  */
  28.  
  29. #include "arm_math.h"
  30.  
  31. /**
  32.  * @ingroup groupMath
  33.  */
  34.  
  35. /**
  36.  * @addtogroup shift
  37.  * @{
  38.  */
  39.  
  40. /**
  41.  * @brief  Shifts the elements of a Q15 vector a specified number of bits.
  42.  * @param[in]  *pSrc points to the input vector
  43.  * @param[in]  shiftBits number of bits to shift.  A positive value shifts left; a negative value shifts right.
  44.  * @param[out]  *pDst points to the output vector
  45.  * @param[in]  blockSize number of samples in the vector
  46.  * @return none.
  47.  *
  48.  * <b>Scaling and Overflow Behavior:</b>
  49.  * \par
  50.  * The function uses saturating arithmetic.
  51.  * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.
  52.  */
  53.  
  54. void arm_shift_q15(
  55.   q15_t * pSrc,
  56.   int8_t shiftBits,
  57.   q15_t * pDst,
  58.   uint32_t blockSize)
  59. {
  60.   uint32_t blkCnt;                               /* loop counter */
  61.   uint8_t sign;                                  /* Sign of shiftBits */
  62.  
  63. #if defined (ARM_MATH_DSP)
  64.  
  65. /* Run the below code for Cortex-M4 and Cortex-M3 */
  66.  
  67.   q15_t in1, in2;                                /* Temporary variables */
  68.  
  69.  
  70.   /*loop Unrolling */
  71.   blkCnt = blockSize >> 2U;
  72.  
  73.   /* Getting the sign of shiftBits */
  74.   sign = (shiftBits & 0x80);
  75.  
  76.   /* If the shift value is positive then do right shift else left shift */
  77.   if (sign == 0U)
  78.   {
  79.     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  80.      ** a second loop below computes the remaining 1 to 3 samples. */
  81.     while (blkCnt > 0U)
  82.     {
  83.       /* Read 2 inputs */
  84.       in1 = *pSrc++;
  85.       in2 = *pSrc++;
  86.       /* C = A << shiftBits */
  87.       /* Shift the inputs and then store the results in the destination buffer. */
  88. #ifndef  ARM_MATH_BIG_ENDIAN
  89.  
  90.       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
  91.                                   __SSAT((in2 << shiftBits), 16), 16);
  92.  
  93. #else
  94.  
  95.       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in2 << shiftBits), 16),
  96.                                   __SSAT((in1 << shiftBits), 16), 16);
  97.  
  98. #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
  99.  
  100.       in1 = *pSrc++;
  101.       in2 = *pSrc++;
  102.  
  103. #ifndef  ARM_MATH_BIG_ENDIAN
  104.  
  105.       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
  106.                                   __SSAT((in2 << shiftBits), 16), 16);
  107.  
  108. #else
  109.  
  110.       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in2 << shiftBits), 16),
  111.                                   __SSAT((in1 << shiftBits), 16), 16);
  112.  
  113. #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
  114.  
  115.       /* Decrement the loop counter */
  116.       blkCnt--;
  117.     }
  118.  
  119.     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  120.      ** No loop unrolling is used. */
  121.     blkCnt = blockSize % 0x4U;
  122.  
  123.     while (blkCnt > 0U)
  124.     {
  125.       /* C = A << shiftBits */
  126.       /* Shift and then store the results in the destination buffer. */
  127.       *pDst++ = __SSAT((*pSrc++ << shiftBits), 16);
  128.  
  129.       /* Decrement the loop counter */
  130.       blkCnt--;
  131.     }
  132.   }
  133.   else
  134.   {
  135.     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  136.      ** a second loop below computes the remaining 1 to 3 samples. */
  137.     while (blkCnt > 0U)
  138.     {
  139.       /* Read 2 inputs */
  140.       in1 = *pSrc++;
  141.       in2 = *pSrc++;
  142.  
  143.       /* C = A >> shiftBits */
  144.       /* Shift the inputs and then store the results in the destination buffer. */
  145. #ifndef  ARM_MATH_BIG_ENDIAN
  146.  
  147.       *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
  148.                                   (in2 >> -shiftBits), 16);
  149.  
  150. #else
  151.  
  152.       *__SIMD32(pDst)++ = __PKHBT((in2 >> -shiftBits),
  153.                                   (in1 >> -shiftBits), 16);
  154.  
  155. #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
  156.  
  157.       in1 = *pSrc++;
  158.       in2 = *pSrc++;
  159.  
  160. #ifndef  ARM_MATH_BIG_ENDIAN
  161.  
  162.       *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
  163.                                   (in2 >> -shiftBits), 16);
  164.  
  165. #else
  166.  
  167.       *__SIMD32(pDst)++ = __PKHBT((in2 >> -shiftBits),
  168.                                   (in1 >> -shiftBits), 16);
  169.  
  170. #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
  171.  
  172.       /* Decrement the loop counter */
  173.       blkCnt--;
  174.     }
  175.  
  176.     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
  177.      ** No loop unrolling is used. */
  178.     blkCnt = blockSize % 0x4U;
  179.  
  180.     while (blkCnt > 0U)
  181.     {
  182.       /* C = A >> shiftBits */
  183.       /* Shift the inputs and then store the results in the destination buffer. */
  184.       *pDst++ = (*pSrc++ >> -shiftBits);
  185.  
  186.       /* Decrement the loop counter */
  187.       blkCnt--;
  188.     }
  189.   }
  190.  
  191. #else
  192.  
  193.   /* Run the below code for Cortex-M0 */
  194.  
  195.   /* Getting the sign of shiftBits */
  196.   sign = (shiftBits & 0x80);
  197.  
  198.   /* If the shift value is positive then do right shift else left shift */
  199.   if (sign == 0U)
  200.   {
  201.     /* Initialize blkCnt with number of samples */
  202.     blkCnt = blockSize;
  203.  
  204.     while (blkCnt > 0U)
  205.     {
  206.       /* C = A << shiftBits */
  207.       /* Shift and then store the results in the destination buffer. */
  208.       *pDst++ = __SSAT(((q31_t) * pSrc++ << shiftBits), 16);
  209.  
  210.       /* Decrement the loop counter */
  211.       blkCnt--;
  212.     }
  213.   }
  214.   else
  215.   {
  216.     /* Initialize blkCnt with number of samples */
  217.     blkCnt = blockSize;
  218.  
  219.     while (blkCnt > 0U)
  220.     {
  221.       /* C = A >> shiftBits */
  222.       /* Shift the inputs and then store the results in the destination buffer. */
  223.       *pDst++ = (*pSrc++ >> -shiftBits);
  224.  
  225.       /* Decrement the loop counter */
  226.       blkCnt--;
  227.     }
  228.   }
  229.  
  230. #endif /* #if defined (ARM_MATH_DSP) */
  231.  
  232. }
  233.  
  234. /**
  235.  * @} end of shift group
  236.  */
  237.