| /* ---------------------------------------------------------------------- |
| * Project: CMSIS DSP Library |
| * Title: arm_sub_q15.c |
| * Description: Q15 vector subtraction |
| * |
| * $Date: 27. January 2017 |
| * $Revision: V.1.5.1 |
| * |
| * Target Processor: Cortex-M cores |
| * -------------------------------------------------------------------- */ |
| /* |
| * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved. |
| * |
| * SPDX-License-Identifier: Apache-2.0 |
| * |
| * Licensed under the Apache License, Version 2.0 (the License); you may |
| * not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an AS IS BASIS, WITHOUT |
| * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #include "arm_math.h" |
| |
| /** |
| * @ingroup groupMath |
| */ |
| |
| /** |
| * @addtogroup BasicSub |
| * @{ |
| */ |
| |
| /** |
| * @brief Q15 vector subtraction. |
| * @param[in] *pSrcA points to the first input vector |
| * @param[in] *pSrcB points to the second input vector |
| * @param[out] *pDst points to the output vector |
| * @param[in] blockSize number of samples in each vector |
| * @return none. |
| * |
| * <b>Scaling and Overflow Behavior:</b> |
| * \par |
| * The function uses saturating arithmetic. |
| * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated. |
| */ |
| |
| void arm_sub_q15( |
| q15_t * pSrcA, |
| q15_t * pSrcB, |
| q15_t * pDst, |
| uint32_t blockSize) |
| { |
| uint32_t blkCnt; /* loop counter */ |
| |
| |
| #if defined (ARM_MATH_DSP) |
| |
| /* Run the below code for Cortex-M4 and Cortex-M3 */ |
| q31_t inA1, inA2; |
| q31_t inB1, inB2; |
| |
| /*loop Unrolling */ |
| blkCnt = blockSize >> 2U; |
| |
| /* First part of the processing with loop unrolling. Compute 4 outputs at a time. |
| ** a second loop below computes the remaining 1 to 3 samples. */ |
| while (blkCnt > 0U) |
| { |
| /* C = A - B */ |
| /* Subtract and then store the results in the destination buffer two samples at a time. */ |
| inA1 = *__SIMD32(pSrcA)++; |
| inA2 = *__SIMD32(pSrcA)++; |
| inB1 = *__SIMD32(pSrcB)++; |
| inB2 = *__SIMD32(pSrcB)++; |
| |
| *__SIMD32(pDst)++ = __QSUB16(inA1, inB1); |
| *__SIMD32(pDst)++ = __QSUB16(inA2, inB2); |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| /* If the blockSize is not a multiple of 4, compute any remaining output samples here. |
| ** No loop unrolling is used. */ |
| blkCnt = blockSize % 0x4U; |
| |
| while (blkCnt > 0U) |
| { |
| /* C = A - B */ |
| /* Subtract and then store the result in the destination buffer. */ |
| *pDst++ = (q15_t) __QSUB16(*pSrcA++, *pSrcB++); |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| #else |
| |
| /* Run the below code for Cortex-M0 */ |
| |
| /* Initialize blkCnt with number of samples */ |
| blkCnt = blockSize; |
| |
| while (blkCnt > 0U) |
| { |
| /* C = A - B */ |
| /* Subtract and then store the result in the destination buffer. */ |
| *pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16); |
| |
| /* Decrement the loop counter */ |
| blkCnt--; |
| } |
| |
| #endif /* #if defined (ARM_MATH_DSP) */ |
| |
| |
| } |
| |
| /** |
| * @} end of BasicSub group |
| */ |