arm_negate_q7.c

00001 /* ----------------------------------------------------------------------    
00002 * Copyright (C) 2010-2013 ARM Limited. All rights reserved.    
00003 *    
00004 * $Date:        17. January 2013
00005 * $Revision:    V1.4.1
00006 *    
00007 * Project:      CMSIS DSP Library    
00008 * Title:        arm_negate_q7.c    
00009 *    
00010 * Description:  Negates Q7 vectors.    
00011 *    
00012 * Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
00013 *  
00014 * Redistribution and use in source and binary forms, with or without 
00015 * modification, are permitted provided that the following conditions
00016 * are met:
00017 *   - Redistributions of source code must retain the above copyright
00018 *     notice, this list of conditions and the following disclaimer.
00019 *   - Redistributions in binary form must reproduce the above copyright
00020 *     notice, this list of conditions and the following disclaimer in
00021 *     the documentation and/or other materials provided with the 
00022 *     distribution.
00023 *   - Neither the name of ARM LIMITED nor the names of its contributors
00024 *     may be used to endorse or promote products derived from this
00025 *     software without specific prior written permission.
00026 *
00027 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00028 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00029 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00030 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 
00031 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00032 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00033 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
00034 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
00035 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00036 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
00037 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
00038 * POSSIBILITY OF SUCH DAMAGE.   
00039 * -------------------------------------------------------------------- */
00040 
00041 #include "arm_math.h"
00042 
00043 /**    
00044  * @ingroup groupMath    
00045  */
00046 
00047 /**    
00048  * @addtogroup negate    
00049  * @{    
00050  */
00051 
00052 /**    
00053  * @brief  Negates the elements of a Q7 vector.    
00054  * @param[in]  *pSrc points to the input vector    
00055  * @param[out]  *pDst points to the output vector    
00056  * @param[in]  blockSize number of samples in the vector    
00057  * @return none.    
00058  *    
00059  * <b>Scaling and Overflow Behavior:</b>    
00060  * \par    
00061  * The function uses saturating arithmetic.    
00062  * The Q7 value -1 (0x80) will be saturated to the maximum allowable positive value 0x7F.    
00063  */
00064 
00065 void arm_negate_q7(
00066   q7_t * pSrc,
00067   q7_t * pDst,
00068   uint32_t blockSize)
00069 {
00070   uint32_t blkCnt;                               /* loop counter */
00071   q7_t in;
00072 
00073 #ifndef ARM_MATH_CM0_FAMILY
00074 
00075 /* Run the below code for Cortex-M4 and Cortex-M3 */
00076   q31_t input;                                   /* Input values1-4 */
00077   q31_t zero = 0x00000000;
00078 
00079 
00080   /*loop Unrolling */
00081   blkCnt = blockSize >> 2u;
00082 
00083   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.    
00084    ** a second loop below computes the remaining 1 to 3 samples. */
00085   while(blkCnt > 0u)
00086   {
00087     /* C = -A */
00088     /* Read four inputs */
00089     input = *__SIMD32(pSrc)++;
00090 
00091     /* Store the Negated results in the destination buffer in a single cycle by packing the results */
00092     *__SIMD32(pDst)++ = __QSUB8(zero, input);
00093 
00094     /* Decrement the loop counter */
00095     blkCnt--;
00096   }
00097 
00098   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.    
00099    ** No loop unrolling is used. */
00100   blkCnt = blockSize % 0x4u;
00101 
00102 #else
00103 
00104   /* Run the below code for Cortex-M0 */
00105 
00106   /* Initialize blkCnt with number of samples */
00107   blkCnt = blockSize;
00108 
00109 #endif /* #ifndef ARM_MATH_CM0_FAMILY */
00110 
00111   while(blkCnt > 0u)
00112   {
00113     /* C = -A */
00114     /* Negate and then store the results in the destination buffer. */ \
00115       in = *pSrc++;
00116     *pDst++ = (in == (q7_t) 0x80) ? 0x7f : -in;
00117 
00118     /* Decrement the loop counter */
00119     blkCnt--;
00120   }
00121 }
00122 
00123 /**    
00124  * @} end of negate group    
00125  */