arm_negate_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_negate_q15.c  
00009 *  
00010 * Description:  Negates Q15 vectors.  
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 negate  
00038  * @{  
00039  */ 
00040  
00041 /**  
00042  * @brief  Negates the elements of a Q15 vector.  
00043  * @param  *pSrc points to the input vector  
00044  * @param  *pDst points to the output vector  
00045  * @param  blockSize number of samples in the 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_negate_q15( 
00055   q15_t * pSrc, 
00056   q15_t * pDst, 
00057   uint32_t blockSize) 
00058 { 
00059   uint32_t blkCnt;                               /* loop counter */ 
00060   q15_t in1, in2;                                /* Temporary variables */ 
00061  
00062  
00063   /*loop Unrolling */ 
00064   blkCnt = blockSize >> 2u; 
00065  
00066   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.  
00067    ** a second loop below computes the remaining 1 to 3 samples. */ 
00068   while(blkCnt > 0u) 
00069   { 
00070     /* C = ~A */ 
00071     /* Read two inputs */ 
00072     in1 = *pSrc++; 
00073     in2 = *pSrc++; 
00074     /* Negate and then store the results in the destination buffer by packing. */ 
00075     *__SIMD32(pDst)++ = __PKHBT(__SSAT(-in1, 16), __SSAT(-in2, 16), 16); 
00076  
00077     in1 = *pSrc++; 
00078     in2 = *pSrc++; 
00079  
00080     *__SIMD32(pDst)++ = __PKHBT(__SSAT(-in1, 16), __SSAT(-in2, 16), 16); 
00081  
00082     /* Decrement the loop counter */ 
00083     blkCnt--; 
00084   } 
00085  
00086   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.  
00087    ** No loop unrolling is used. */ 
00088   blkCnt = blockSize % 0x4u; 
00089  
00090   while(blkCnt > 0u) 
00091   { 
00092     /* C = ~A */ 
00093     /* Negate and then store the result in the destination buffer. */ 
00094     *pDst++ = __SSAT(-*pSrc++, 16); 
00095  
00096     /* Decrement the loop counter */ 
00097     blkCnt--; 
00098   } 
00099 } 
00100  
00101 /**  
00102  * @} end of negate group  
00103  */