| 1 | /* ----------------------------------------------------------------------
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| 2 | * Project: CMSIS DSP Library
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| 3 | * Title: arm_sub_q15.c
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| 4 | * Description: Q15 vector subtraction
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| 5 | *
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| 6 | * $Date: 27. January 2017
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| 7 | * $Revision: V.1.5.1
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| 8 | *
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| 9 | * Target Processor: Cortex-M cores
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| 10 | * -------------------------------------------------------------------- */
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| 11 | /*
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| 12 | * Copyright (C) 2010-2017 ARM Limited or its affiliates. All rights reserved.
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| 13 | *
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| 14 | * SPDX-License-Identifier: Apache-2.0
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| 15 | *
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| 16 | * Licensed under the Apache License, Version 2.0 (the License); you may
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| 17 | * not use this file except in compliance with the License.
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| 18 | * You may obtain a copy of the License at
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| 19 | *
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| 20 | * www.apache.org/licenses/LICENSE-2.0
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| 21 | *
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| 22 | * Unless required by applicable law or agreed to in writing, software
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| 23 | * distributed under the License is distributed on an AS IS BASIS, WITHOUT
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| 24 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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| 25 | * See the License for the specific language governing permissions and
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| 26 | * limitations under the License.
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| 27 | */
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| 28 |
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| 29 | #include "arm_math.h"
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| 30 |
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| 31 | /**
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| 32 | * @ingroup groupMath
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| 33 | */
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| 34 |
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| 35 | /**
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| 36 | * @addtogroup BasicSub
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| 37 | * @{
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| 38 | */
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| 39 |
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| 40 | /**
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| 41 | * @brief Q15 vector subtraction.
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| 42 | * @param[in] *pSrcA points to the first input vector
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| 43 | * @param[in] *pSrcB points to the second input vector
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| 44 | * @param[out] *pDst points to the output vector
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| 45 | * @param[in] blockSize number of samples in each vector
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| 46 | * @return none.
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| 47 | *
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| 48 | * <b>Scaling and Overflow Behavior:</b>
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| 49 | * \par
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| 50 | * The function uses saturating arithmetic.
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| 51 | * Results outside of the allowable Q15 range [0x8000 0x7FFF] will be saturated.
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| 52 | */
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| 53 |
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| 54 | void arm_sub_q15(
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| 55 | q15_t * pSrcA,
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| 56 | q15_t * pSrcB,
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| 57 | q15_t * pDst,
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| 58 | uint32_t blockSize)
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| 59 | {
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| 60 | uint32_t blkCnt; /* loop counter */
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| 61 |
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| 62 |
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| 63 | #if defined (ARM_MATH_DSP)
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| 64 |
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| 65 | /* Run the below code for Cortex-M4 and Cortex-M3 */
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| 66 | q31_t inA1, inA2;
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| 67 | q31_t inB1, inB2;
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| 68 |
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| 69 | /*loop Unrolling */
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| 70 | blkCnt = blockSize >> 2U;
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| 71 |
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| 72 | /* First part of the processing with loop unrolling. Compute 4 outputs at a time.
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| 73 | ** a second loop below computes the remaining 1 to 3 samples. */
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| 74 | while (blkCnt > 0U)
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| 75 | {
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| 76 | /* C = A - B */
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| 77 | /* Subtract and then store the results in the destination buffer two samples at a time. */
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| 78 | inA1 = *__SIMD32(pSrcA)++;
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| 79 | inA2 = *__SIMD32(pSrcA)++;
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| 80 | inB1 = *__SIMD32(pSrcB)++;
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| 81 | inB2 = *__SIMD32(pSrcB)++;
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| 82 |
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| 83 | *__SIMD32(pDst)++ = __QSUB16(inA1, inB1);
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| 84 | *__SIMD32(pDst)++ = __QSUB16(inA2, inB2);
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| 85 |
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| 86 | /* Decrement the loop counter */
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| 87 | blkCnt--;
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| 88 | }
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| 89 |
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| 90 | /* If the blockSize is not a multiple of 4, compute any remaining output samples here.
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| 91 | ** No loop unrolling is used. */
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| 92 | blkCnt = blockSize % 0x4U;
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| 93 |
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| 94 | while (blkCnt > 0U)
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| 95 | {
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| 96 | /* C = A - B */
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| 97 | /* Subtract and then store the result in the destination buffer. */
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| 98 | *pDst++ = (q15_t) __QSUB16(*pSrcA++, *pSrcB++);
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| 99 |
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| 100 | /* Decrement the loop counter */
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| 101 | blkCnt--;
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| 102 | }
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| 103 |
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| 104 | #else
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| 105 |
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| 106 | /* Run the below code for Cortex-M0 */
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| 107 |
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| 108 | /* Initialize blkCnt with number of samples */
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| 109 | blkCnt = blockSize;
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| 110 |
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| 111 | while (blkCnt > 0U)
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| 112 | {
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| 113 | /* C = A - B */
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| 114 | /* Subtract and then store the result in the destination buffer. */
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| 115 | *pDst++ = (q15_t) __SSAT(((q31_t) * pSrcA++ - *pSrcB++), 16);
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| 116 |
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| 117 | /* Decrement the loop counter */
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| 118 | blkCnt--;
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| 119 | }
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| 120 |
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| 121 | #endif /* #if defined (ARM_MATH_DSP) */
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| 122 |
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| 123 |
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| 124 | }
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| 125 |
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| 126 | /**
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| 127 | * @} end of BasicSub group
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| 128 | */
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