arm_negate_q15.c

00001 /* ----------------------------------------------------------------------
00002  * Project:      CMSIS DSP Library
00003  * Title:        arm_negate_q15.c
00004  * Description:  Negates Q15 vectors
00005  *
00006  * $Date:        27. January 2017
00007  * $Revision:    V.1.5.1
00008  *
00009  * Target Processor: Cortex-M cores
00010  * -------------------------------------------------------------------- */
00011 /*
00012  * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
00013  *
00014  * SPDX-License-Identifier: Apache-2.0
00015  *
00016  * Licensed under the Apache License, Version 2.0 (the License); you may
00017  * not use this file except in compliance with the License.
00018  * You may obtain a copy of the License at
00019  *
00020  * www.apache.org/licenses/LICENSE-2.0
00021  *
00022  * Unless required by applicable law or agreed to in writing, software
00023  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00024  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00025  * See the License for the specific language governing permissions and
00026  * limitations under the License.
00027  */
00028 
00029 #include "arm_math.h"
00030 
00031 /**
00032  * @ingroup groupMath
00033  */
00034 
00035 /**
00036  * @addtogroup negate
00037  * @{
00038  */
00039 
00040 /**
00041  * @brief  Negates the elements of a Q15 vector.
00042  * @param[in]  *pSrc points to the input vector
00043  * @param[out]  *pDst points to the output vector
00044  * @param[in]  blockSize number of samples in the vector
00045  * @return none.
00046  *
00047  * \par Conditions for optimum performance
00048  *  Input and output buffers should be aligned by 32-bit
00049  *
00050  *
00051  * <b>Scaling and Overflow Behavior:</b>
00052  * \par
00053  * The function uses saturating arithmetic.
00054  * The Q15 value -1 (0x8000) will be saturated to the maximum allowable positive value 0x7FFF.
00055  */
00056 
00057 void arm_negate_q15(
00058   q15_t * pSrc,
00059   q15_t * pDst,
00060   uint32_t blockSize)
00061 {
00062   uint32_t blkCnt;                               /* loop counter */
00063   q15_t in;
00064 
00065 #if defined (ARM_MATH_DSP)
00066 
00067 /* Run the below code for Cortex-M4 and Cortex-M3 */
00068 
00069   q31_t in1, in2;                                /* Temporary variables */
00070 
00071 
00072   /*loop Unrolling */
00073   blkCnt = blockSize >> 2U;
00074 
00075   /* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
00076    ** a second loop below computes the remaining 1 to 3 samples. */
00077   while (blkCnt > 0U)
00078   {
00079     /* C = -A */
00080     /* Read two inputs at a time */
00081     in1 = _SIMD32_OFFSET(pSrc);
00082     in2 = _SIMD32_OFFSET(pSrc + 2);
00083 
00084     /* negate two samples at a time */
00085     in1 = __QSUB16(0, in1);
00086 
00087     /* negate two samples at a time */
00088     in2 = __QSUB16(0, in2);
00089 
00090     /* store the result to destination 2 samples at a time */
00091     _SIMD32_OFFSET(pDst) = in1;
00092     /* store the result to destination 2 samples at a time */
00093     _SIMD32_OFFSET(pDst + 2) = in2;
00094 
00095 
00096     /* update pointers to process next samples */
00097     pSrc += 4U;
00098     pDst += 4U;
00099 
00100     /* Decrement the loop counter */
00101     blkCnt--;
00102   }
00103 
00104   /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
00105    ** No loop unrolling is used. */
00106   blkCnt = blockSize % 0x4U;
00107 
00108 #else
00109 
00110   /* Run the below code for Cortex-M0 */
00111 
00112   /* Initialize blkCnt with number of samples */
00113   blkCnt = blockSize;
00114 
00115 #endif /* #if defined (ARM_MATH_DSP) */
00116 
00117   while (blkCnt > 0U)
00118   {
00119     /* C = -A */
00120     /* Negate and then store the result in the destination buffer. */
00121     in = *pSrc++;
00122     *pDst++ = (in == (q15_t) 0x8000) ? 0x7fff : -in;
00123 
00124     /* Decrement the loop counter */
00125     blkCnt--;
00126   }
00127 }
00128 
00129 /**
00130  * @} end of negate group
00131  */
00132