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  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.  */
  151.