lib/main/CMSIS/DSP/Source/BasicMathFunctions/arm_shift_q15.c

   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  */