lib/main/CMSIS/DSP/Source/BasicMathFunctions/arm_scale_q15.c

   1 /* ----------------------------------------------------------------------
   2  * Project:      CMSIS DSP Library
   3  * Title:        arm_scale_q15.c
   4  * Description:  Multiplies a Q15 vector by a scalar
   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 scale
  37  * @{
  38  */
  39
  40 /**
  41  * @brief Multiplies a Q15 vector by a scalar.
  42  * @param[in]       *pSrc points to the input vector
  43  * @param[in]       scaleFract fractional portion of the scale value
  44  * @param[in]       shift number of bits to shift the result by
  45  * @param[out]      *pDst points to the output vector
  46  * @param[in]       blockSize number of samples in the vector
  47  * @return none.
  48  *
  49  * <b>Scaling and Overflow Behavior:</b>
  50  * \par
  51  * The input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.15 format.
  52  * These are multiplied to yield a 2.30 intermediate result and this is shifted with saturation to 1.15 format.
  53  */
  54
  55
  56 void arm_scale_q15(
  57   q15_t * pSrc,
  58   q15_t scaleFract,
  59   int8_t shift,
  60   q15_t * pDst,
  61   uint32_t blockSize)
  62 {
  63   int8_t kShift = 15 - shift;                    /* shift to apply after scaling */
  64   uint32_t blkCnt;                               /* loop counter */
  65
  66 #if defined (ARM_MATH_DSP)
  67
  68 /* Run the below code for Cortex-M4 and Cortex-M3 */
  69   q15_t in1, in2, in3, in4;
  70   q31_t inA1, inA2;                              /* Temporary variables */
  71   q31_t out1, out2, out3, out4;
  72
  73
  74   /*loop Unrolling */
  75   blkCnt = blockSize >> 2U;
  76
  77   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
  78    ** a second loop below computes the remaining 1 to 3 samples. */
  79   while (blkCnt > 0U)
  80   {
  81     /* Reading 2 inputs from memory */
  82     inA1 = *__SIMD32(pSrc)++;
  83     inA2 = *__SIMD32(pSrc)++;
  84
  85     /* C = A * scale */
  86     /* Scale the inputs and then store the 2 results in the destination buffer
  87      * in single cycle by packing the outputs */
  88     out1 = (q31_t) ((q15_t) (inA1 >> 16) * scaleFract);
  89     out2 = (q31_t) ((q15_t) inA1 * scaleFract);
  90     out3 = (q31_t) ((q15_t) (inA2 >> 16) * scaleFract);
  91     out4 = (q31_t) ((q15_t) inA2 * scaleFract);
  92
  93     /* apply shifting */
  94     out1 = out1 >> kShift;
  95     out2 = out2 >> kShift;
  96     out3 = out3 >> kShift;
  97     out4 = out4 >> kShift;
  98
  99     /* saturate the output */
 100     in1 = (q15_t) (__SSAT(out1, 16));
 101     in2 = (q15_t) (__SSAT(out2, 16));
 102     in3 = (q15_t) (__SSAT(out3, 16));
 103     in4 = (q15_t) (__SSAT(out4, 16));
 104
 105     /* store the result to destination */
 106     *__SIMD32(pDst)++ = __PKHBT(in2, in1, 16);
 107     *__SIMD32(pDst)++ = __PKHBT(in4, in3, 16);
 108
 109     /* Decrement the loop counter */
 110     blkCnt--;
 111   }
 112
 113   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
 114    ** No loop unrolling is used. */
 115   blkCnt = blockSize % 0x4U;
 116
 117   while (blkCnt > 0U)
 118   {
 119     /* C = A * scale */
 120     /* Scale the input and then store the result in the destination buffer. */
 121     *pDst++ = (q15_t) (__SSAT(((*pSrc++) * scaleFract) >> kShift, 16));
 122
 123     /* Decrement the loop counter */
 124     blkCnt--;
 125   }
 126
 127 #else
 128
 129   /* Run the below code for Cortex-M0 */
 130
 131   /* Initialize blkCnt with number of samples */
 132   blkCnt = blockSize;
 133
 134   while (blkCnt > 0U)
 135   {
 136     /* C = A * scale */
 137     /* Scale the input and then store the result in the destination buffer. */
 138     *pDst++ = (q15_t) (__SSAT(((q31_t) * pSrc++ * scaleFract) >> kShift, 16));
 139
 140     /* Decrement the loop counter */
 141     blkCnt--;
 142   }
 143
 144 #endif /* #if defined (ARM_MATH_DSP) */
 145
 146 }
 147
 148 /**
 149  * @} end of scale group
 150  */