arm_abs_q15.c

00001 /* ----------------------------------------------------------------------  
00002 * Copyright (C) 2010 ARM Limited. All rights reserved.  
00003 *  
00004 * $Date:        29. November 2010  
00005 * $Revision:    V1.0.3  
00006 *  
00007 * Project:      CMSIS DSP Library  
00008 * Title:        arm_abs_q15.c  
00009 *  
00010 * Description:  Q15 vector absolute value.  
00011 *  
00012 * Target Processor: Cortex-M4/Cortex-M3
00013 *  
00014 * Version 1.0.3 2010/11/29 
00015 *    Re-organized the CMSIS folders and updated documentation.  
00016 *   
00017 * Version 1.0.2 2010/11/11  
00018 *    Documentation updated.   
00019 *  
00020 * Version 1.0.1 2010/10/05   
00021 *    Production release and review comments incorporated.  
00022 *  
00023 * Version 1.0.0 2010/09/20   
00024 *    Production release and review comments incorporated.  
00025 *  
00026 * Version 0.0.7  2010/06/10   
00027 *    Misra-C changes done  
00028 * -------------------------------------------------------------------- */ 
00029  
00030 #include "arm_math.h" 
00031  
00032 /**  
00033  * @ingroup groupMath  
00034  */ 
00035  
00036 /**  
00037  * @addtogroup BasicAbs  
00038  * @{  
00039  */ 
00040  
00041 /**  
00042  * @brief Q15 vector absolute value.  
00043  * @param[in]       *pSrc points to the input buffer  
00044  * @param[out]      *pDst points to the output buffer  
00045  * @param[in]       blockSize number of samples in each vector  
00046  * @return none.  
00047  *  
00048  * <b>Scaling and Overflow Behavior:</b>  
00049  * \par  
00050  * The function uses saturating arithmetic.  
00051  * The Q15 value -1 (0x8000) will be saturated to the maximum allowable positive value 0x7FFF.  
00052  */ 
00053  
00054 void arm_abs_q15( 
00055   q15_t * pSrc, 
00056   q15_t * pDst, 
00057   uint32_t blockSize) 
00058 { 
00059   uint32_t blkCnt;                               /* loop counter */ 
00060   q15_t in1;                                     /* Input value1 */ 
00061   q15_t in2;                                     /* Input value2 */ 
00062  
00063  
00064   /*loop Unrolling */ 
00065   blkCnt = blockSize >> 2u; 
00066  
00067   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00068    ** a second loop below computes the remaining 1 to 3 samples. */ 
00069   while(blkCnt > 0u) 
00070   { 
00071     /* C = |A| */ 
00072     /* Read two inputs */ 
00073     in1 = *pSrc++; 
00074     in2 = *pSrc++; 
00075     /* Store the Absolute result in the destination buffer by packing the two values, in a single cycle */ 
00076     *__SIMD32(pDst)++ = 
00077       __PKHBT(((in1 > 0) ? in1 : __SSAT(-in1, 16)), 
00078               ((in2 > 0) ? in2 : __SSAT(-in2, 16)), 16); 
00079  
00080     in1 = *pSrc++; 
00081     in2 = *pSrc++; 
00082     *__SIMD32(pDst)++ = 
00083       __PKHBT(((in1 > 0) ? in1 : __SSAT(-in1, 16)), 
00084               ((in2 > 0) ? in2 : __SSAT(-in2, 16)), 16); 
00085  
00086     /* Decrement the loop counter */ 
00087     blkCnt--; 
00088   } 
00089  
00090   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00091    ** No loop unrolling is used. */ 
00092   blkCnt = blockSize % 0x4u; 
00093  
00094   while(blkCnt > 0u) 
00095   { 
00096     /* C = |A| */ 
00097     /* Read the input */ 
00098     in1 = *pSrc++; 
00099  
00100     /* Calculate absolute value of input and then store the result in the destination buffer. */ 
00101     *pDst++ = (in1 > 0) ? in1 : __SSAT(-in1, 16); 
00102  
00103     /* Decrement the loop counter */ 
00104     blkCnt--; 
00105   } 
00106 } 
00107  
00108 /**  
00109  * @} end of BasicAbs group  
00110  */