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| 2 | mjames | 1 | /* ---------------------------------------------------------------------- |
| 2 | * Project: CMSIS DSP Library |
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| 3 | * Title: arm_q15_to_q7.c |
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| 4 | * Description: Converts the elements of the Q15 vector to Q7 vector |
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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 | |||
| 29 | #include "arm_math.h" |
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| 30 | |||
| 31 | /** |
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| 32 | * @ingroup groupSupport |
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| 33 | */ |
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| 34 | |||
| 35 | /** |
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| 36 | * @addtogroup q15_to_x |
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| 37 | * @{ |
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| 38 | */ |
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| 39 | |||
| 40 | |||
| 41 | /** |
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| 42 | * @brief Converts the elements of the Q15 vector to Q7 vector. |
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| 43 | * @param[in] *pSrc points to the Q15 input vector |
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| 44 | * @param[out] *pDst points to the Q7 output vector |
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| 45 | * @param[in] blockSize length of the input vector |
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| 46 | * @return none. |
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| 47 | * |
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| 48 | * \par Description: |
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| 49 | * |
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| 50 | * The equation used for the conversion process is: |
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| 51 | * |
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| 52 | * <pre> |
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| 53 | * pDst[n] = (q7_t) pSrc[n] >> 8; 0 <= n < blockSize. |
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| 54 | * </pre> |
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| 55 | * |
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| 56 | */ |
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| 57 | |||
| 58 | |||
| 59 | void arm_q15_to_q7( |
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| 60 | q15_t * pSrc, |
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| 61 | q7_t * pDst, |
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| 62 | uint32_t blockSize) |
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| 63 | { |
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| 64 | q15_t *pIn = pSrc; /* Src pointer */ |
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| 65 | uint32_t blkCnt; /* loop counter */ |
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| 66 | |||
| 67 | #if defined (ARM_MATH_DSP) |
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| 68 | |||
| 69 | /* Run the below code for Cortex-M4 and Cortex-M3 */ |
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| 70 | q31_t in1, in2; |
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| 71 | q31_t out1, out2; |
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| 72 | |||
| 73 | /*loop Unrolling */ |
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| 74 | blkCnt = blockSize >> 2U; |
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| 75 | |||
| 76 | /* First part of the processing with loop unrolling. Compute 4 outputs at a time. |
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| 77 | ** a second loop below computes the remaining 1 to 3 samples. */ |
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| 78 | while (blkCnt > 0U) |
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| 79 | { |
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| 80 | /* C = (q7_t) A >> 8 */ |
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| 81 | /* convert from q15 to q7 and then store the results in the destination buffer */ |
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| 82 | in1 = *__SIMD32(pIn)++; |
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| 83 | in2 = *__SIMD32(pIn)++; |
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| 84 | |||
| 85 | #ifndef ARM_MATH_BIG_ENDIAN |
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| 86 | |||
| 87 | out1 = __PKHTB(in2, in1, 16); |
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| 88 | out2 = __PKHBT(in2, in1, 16); |
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| 89 | |||
| 90 | #else |
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| 91 | |||
| 92 | out1 = __PKHTB(in1, in2, 16); |
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| 93 | out2 = __PKHBT(in1, in2, 16); |
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| 94 | |||
| 95 | #endif // #ifndef ARM_MATH_BIG_ENDIAN |
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| 96 | |||
| 97 | /* rotate packed value by 24 */ |
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| 98 | out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24); |
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| 99 | |||
| 100 | /* anding with 0xff00ff00 to get two 8 bit values */ |
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| 101 | out1 = out1 & 0xFF00FF00; |
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| 102 | /* anding with 0x00ff00ff to get two 8 bit values */ |
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| 103 | out2 = out2 & 0x00FF00FF; |
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| 104 | |||
| 105 | /* oring two values(contains two 8 bit values) to get four packed 8 bit values */ |
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| 106 | out1 = out1 | out2; |
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| 107 | |||
| 108 | /* store 4 samples at a time to destiantion buffer */ |
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| 109 | *__SIMD32(pDst)++ = out1; |
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| 110 | |||
| 111 | /* Decrement the loop counter */ |
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| 112 | blkCnt--; |
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| 113 | } |
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| 114 | |||
| 115 | /* If the blockSize is not a multiple of 4, compute any remaining output samples here. |
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| 116 | ** No loop unrolling is used. */ |
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| 117 | blkCnt = blockSize % 0x4U; |
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| 118 | |||
| 119 | #else |
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| 120 | |||
| 121 | /* Run the below code for Cortex-M0 */ |
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| 122 | |||
| 123 | /* Loop over blockSize number of values */ |
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| 124 | blkCnt = blockSize; |
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| 125 | |||
| 126 | #endif /* #if defined (ARM_MATH_DSP) */ |
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| 127 | |||
| 128 | while (blkCnt > 0U) |
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| 129 | { |
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| 130 | /* C = (q7_t) A >> 8 */ |
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| 131 | /* convert from q15 to q7 and then store the results in the destination buffer */ |
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| 132 | *pDst++ = (q7_t) (*pIn++ >> 8); |
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| 133 | |||
| 134 | /* Decrement the loop counter */ |
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| 135 | blkCnt--; |
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| 136 | } |
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| 137 | |||
| 138 | } |
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| 139 | |||
| 140 | /** |
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| 141 | * @} end of q15_to_x group |
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| 142 | */ |