tool/mbed/mbed-sdk/libraries/dsp/cmsis_dsp/BasicMathFunctions/arm_shift_q15.c

   1 /* ----------------------------------------------------------------------
   2 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.
   3 *
   4 * $Date:        17. January 2013
   5 * $Revision:    V1.4.1
   6 *
   7 * Project:          CMSIS DSP Library
   8 * Title:                arm_shift_q15.c
   9 *
  10 * Description:  Shifts the elements of a Q15 vector by a specified number of bits.
  11 *
  12 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
  13 *
  14 * Redistribution and use in source and binary forms, with or without
  15 * modification, are permitted provided that the following conditions
  16 * are met:
  17 *   - Redistributions of source code must retain the above copyright
  18 *     notice, this list of conditions and the following disclaimer.
  19 *   - Redistributions in binary form must reproduce the above copyright
  20 *     notice, this list of conditions and the following disclaimer in
  21 *     the documentation and/or other materials provided with the
  22 *     distribution.
  23 *   - Neither the name of ARM LIMITED nor the names of its contributors
  24 *     may be used to endorse or promote products derived from this
  25 *     software without specific prior written permission.
  26 *
  27 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  28 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  29 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  30 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  31 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  33 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  34 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  35 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  37 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  38 * POSSIBILITY OF SUCH DAMAGE.
  39 * -------------------------------------------------------------------- */
  40
  41 #include "arm_math.h"
  42
  43 /**
  44  * @ingroup groupMath
  45  */
  46
  47 /**
  48  * @addtogroup shift
  49  * @{
  50  */
  51
  52 /**
  53  * @brief  Shifts the elements of a Q15 vector a specified number of bits.
  54  * @param[in]  *pSrc points to the input vector
  55  * @param[in]  shiftBits number of bits to shift.  A positive value shifts left; a negative value shifts right.
  56  * @param[out]  *pDst points to the output vector
  57  * @param[in]  blockSize number of samples in the vector
  58  * @return none.
  59  *
  60  * <b>Scaling and Overflow Behavior:</b>
  61  * \par
  62  * The function uses saturating arithmetic.
  63  * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.
  64  */
  65
  66 void arm_shift_q15(
  67   q15_t * pSrc,
  68   int8_t shiftBits,
  69   q15_t * pDst,
  70   uint32_t blockSize)
  71 {
  72   uint32_t blkCnt;                               /* loop counter */
  73   uint8_t sign;                                  /* Sign of shiftBits */
  74
  75 #ifndef ARM_MATH_CM0_FAMILY
  76
  77 /* Run the below code for Cortex-M4 and Cortex-M3 */
  78
  79   q15_t in1, in2;                                /* Temporary variables */
  80
  81
  82   /*loop Unrolling */
  83   blkCnt = blockSize >> 2u;
  84
  85   /* Getting the sign of shiftBits */
  86   sign = (shiftBits & 0x80);
  87
  88   /* If the shift value is positive then do right shift else left shift */
  89   if(sign == 0u)
  90   {
  91     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  92      ** a second loop below computes the remaining 1 to 3 samples. */
  93     while(blkCnt > 0u)
  94     {
  95       /* Read 2 inputs */
  96       in1 = *pSrc++;
  97       in2 = *pSrc++;
  98       /* C = A << shiftBits */
  99       /* Shift the inputs and then store the results in the destination buffer. */
 100 #ifndef  ARM_MATH_BIG_ENDIAN
 101
 102       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
 103                                   __SSAT((in2 << shiftBits), 16), 16);
 104
 105 #else
 106
 107       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in2 << shiftBits), 16),
 108                                   __SSAT((in1 << shiftBits), 16), 16);
 109
 110 #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
 111
 112       in1 = *pSrc++;
 113       in2 = *pSrc++;
 114
 115 #ifndef  ARM_MATH_BIG_ENDIAN
 116
 117       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in1 << shiftBits), 16),
 118                                   __SSAT((in2 << shiftBits), 16), 16);
 119
 120 #else
 121
 122       *__SIMD32(pDst)++ = __PKHBT(__SSAT((in2 << shiftBits), 16),
 123                                   __SSAT((in1 << shiftBits), 16), 16);
 124
 125 #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
 126
 127       /* Decrement the loop counter */
 128       blkCnt--;
 129     }
 130
 131     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 132      ** No loop unrolling is used. */
 133     blkCnt = blockSize % 0x4u;
 134
 135     while(blkCnt > 0u)
 136     {
 137       /* C = A << shiftBits */
 138       /* Shift and then store the results in the destination buffer. */
 139       *pDst++ = __SSAT((*pSrc++ << shiftBits), 16);
 140
 141       /* Decrement the loop counter */
 142       blkCnt--;
 143     }
 144   }
 145   else
 146   {
 147     /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
 148      ** a second loop below computes the remaining 1 to 3 samples. */
 149     while(blkCnt > 0u)
 150     {
 151       /* Read 2 inputs */
 152       in1 = *pSrc++;
 153       in2 = *pSrc++;
 154
 155       /* C = A >> shiftBits */
 156       /* Shift the inputs and then store the results in the destination buffer. */
 157 #ifndef  ARM_MATH_BIG_ENDIAN
 158
 159       *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
 160                                   (in2 >> -shiftBits), 16);
 161
 162 #else
 163
 164       *__SIMD32(pDst)++ = __PKHBT((in2 >> -shiftBits),
 165                                   (in1 >> -shiftBits), 16);
 166
 167 #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
 168
 169       in1 = *pSrc++;
 170       in2 = *pSrc++;
 171
 172 #ifndef  ARM_MATH_BIG_ENDIAN
 173
 174       *__SIMD32(pDst)++ = __PKHBT((in1 >> -shiftBits),
 175                                   (in2 >> -shiftBits), 16);
 176
 177 #else
 178
 179       *__SIMD32(pDst)++ = __PKHBT((in2 >> -shiftBits),
 180                                   (in1 >> -shiftBits), 16);
 181
 182 #endif /* #ifndef  ARM_MATH_BIG_ENDIAN    */
 183
 184       /* Decrement the loop counter */
 185       blkCnt--;
 186     }
 187
 188     /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 189      ** No loop unrolling is used. */
 190     blkCnt = blockSize % 0x4u;
 191
 192     while(blkCnt > 0u)
 193     {
 194       /* C = A >> shiftBits */
 195       /* Shift the inputs and then store the results in the destination buffer. */
 196       *pDst++ = (*pSrc++ >> -shiftBits);
 197
 198       /* Decrement the loop counter */
 199       blkCnt--;
 200     }
 201   }
 202
 203 #else
 204
 205   /* Run the below code for Cortex-M0 */
 206
 207   /* Getting the sign of shiftBits */
 208   sign = (shiftBits & 0x80);
 209
 210   /* If the shift value is positive then do right shift else left shift */
 211   if(sign == 0u)
 212   {
 213     /* Initialize blkCnt with number of samples */
 214     blkCnt = blockSize;
 215
 216     while(blkCnt > 0u)
 217     {
 218       /* C = A << shiftBits */
 219       /* Shift and then store the results in the destination buffer. */
 220       *pDst++ = __SSAT(((q31_t) * pSrc++ << shiftBits), 16);
 221
 222       /* Decrement the loop counter */
 223       blkCnt--;
 224     }
 225   }
 226   else
 227   {
 228     /* Initialize blkCnt with number of samples */
 229     blkCnt = blockSize;
 230
 231     while(blkCnt > 0u)
 232     {
 233       /* C = A >> shiftBits */
 234       /* Shift the inputs and then store the results in the destination buffer. */
 235       *pDst++ = (*pSrc++ >> -shiftBits);
 236
 237       /* Decrement the loop counter */
 238       blkCnt--;
 239     }
 240   }
 241
 242 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
 243
 244 }
 245
 246 /**
 247  * @} end of shift group
 248  */