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  1. /* ----------------------------------------------------------------------    
  2. * Copyright (C) 2010-2014 ARM Limited. All rights reserved.    
  3. *    
  4. * $Date:        19. March 2015
  5. * $Revision:    V.1.4.5
  6. *    
  7. * Project:          CMSIS DSP Library    
  8. * Title:                arm_scale_q15.c    
  9. *    
  10. * Description:  Multiplies a Q15 vector by a scalar.    
  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 scale    
  49.  * @{    
  50.  */
  51.  
  52. /**    
  53.  * @brief Multiplies a Q15 vector by a scalar.    
  54.  * @param[in]       *pSrc points to the input vector    
  55.  * @param[in]       scaleFract fractional portion of the scale value    
  56.  * @param[in]       shift number of bits to shift the result by    
  57.  * @param[out]      *pDst points to the output vector    
  58.  * @param[in]       blockSize number of samples in the vector    
  59.  * @return none.    
  60.  *    
  61.  * <b>Scaling and Overflow Behavior:</b>    
  62.  * \par    
  63.  * The input data <code>*pSrc</code> and <code>scaleFract</code> are in 1.15 format.    
  64.  * These are multiplied to yield a 2.30 intermediate result and this is shifted with saturation to 1.15 format.    
  65.  */
  66.  
  67.  
  68. void arm_scale_q15(
  69.   q15_t * pSrc,
  70.   q15_t scaleFract,
  71.   int8_t shift,
  72.   q15_t * pDst,
  73.   uint32_t blockSize)
  74. {
  75.   int8_t kShift = 15 - shift;                    /* shift to apply after scaling */
  76.   uint32_t blkCnt;                               /* loop counter */
  77.  
  78. #ifndef ARM_MATH_CM0_FAMILY
  79.  
  80. /* Run the below code for Cortex-M4 and Cortex-M3 */
  81.   q15_t in1, in2, in3, in4;
  82.   q31_t inA1, inA2;                              /* Temporary variables */
  83.   q31_t out1, out2, out3, out4;
  84.  
  85.  
  86.   /*loop Unrolling */
  87.   blkCnt = blockSize >> 2u;
  88.  
  89.   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.        
  90.    ** a second loop below computes the remaining 1 to 3 samples. */
  91.   while(blkCnt > 0u)
  92.   {
  93.     /* Reading 2 inputs from memory */
  94.     inA1 = *__SIMD32(pSrc)++;
  95.     inA2 = *__SIMD32(pSrc)++;
  96.  
  97.     /* C = A * scale */
  98.     /* Scale the inputs and then store the 2 results in the destination buffer        
  99.      * in single cycle by packing the outputs */
  100.     out1 = (q31_t) ((q15_t) (inA1 >> 16) * scaleFract);
  101.     out2 = (q31_t) ((q15_t) inA1 * scaleFract);
  102.     out3 = (q31_t) ((q15_t) (inA2 >> 16) * scaleFract);
  103.     out4 = (q31_t) ((q15_t) inA2 * scaleFract);
  104.  
  105.     /* apply shifting */
  106.     out1 = out1 >> kShift;
  107.     out2 = out2 >> kShift;
  108.     out3 = out3 >> kShift;
  109.     out4 = out4 >> kShift;
  110.  
  111.     /* saturate the output */
  112.     in1 = (q15_t) (__SSAT(out1, 16));
  113.     in2 = (q15_t) (__SSAT(out2, 16));
  114.     in3 = (q15_t) (__SSAT(out3, 16));
  115.     in4 = (q15_t) (__SSAT(out4, 16));
  116.  
  117.     /* store the result to destination */
  118.     *__SIMD32(pDst)++ = __PKHBT(in2, in1, 16);
  119.     *__SIMD32(pDst)++ = __PKHBT(in4, in3, 16);
  120.  
  121.     /* Decrement the loop counter */
  122.     blkCnt--;
  123.   }
  124.  
  125.   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
  126.    ** No loop unrolling is used. */
  127.   blkCnt = blockSize % 0x4u;
  128.  
  129.   while(blkCnt > 0u)
  130.   {
  131.     /* C = A * scale */
  132.     /* Scale the input and then store the result in the destination buffer. */
  133.     *pDst++ = (q15_t) (__SSAT(((*pSrc++) * scaleFract) >> kShift, 16));
  134.  
  135.     /* Decrement the loop counter */
  136.     blkCnt--;
  137.   }
  138.  
  139. #else
  140.  
  141.   /* Run the below code for Cortex-M0 */
  142.  
  143.   /* Initialize blkCnt with number of samples */
  144.   blkCnt = blockSize;
  145.  
  146.   while(blkCnt > 0u)
  147.   {
  148.     /* C = A * scale */
  149.     /* Scale the input and then store the result in the destination buffer. */
  150.     *pDst++ = (q15_t) (__SSAT(((q31_t) * pSrc++ * scaleFract) >> kShift, 16));
  151.  
  152.     /* Decrement the loop counter */
  153.     blkCnt--;
  154.   }
  155.  
  156. #endif /* #ifndef ARM_MATH_CM0_FAMILY */
  157.  
  158. }
  159.  
  160. /**    
  161.  * @} end of scale group    
  162.  */
  163.