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103 lines
3.2 KiB
C
103 lines
3.2 KiB
C
/* ----------------------------------------------------------------------
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* Project: CMSIS DSP Library
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* Title: arm_bitreversal_f16.c
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* Description: Bitreversal functions
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*
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* $Date: 23 April 2021
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* $Revision: V1.9.0
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*
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* Target Processor: Cortex-M and Cortex-A cores
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* -------------------------------------------------------------------- */
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/*
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* Copyright (C) 2010-2021 ARM Limited or its affiliates. All rights reserved.
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the License); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an AS IS BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "dsp/transform_functions_f16.h"
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/*
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* @brief In-place bit reversal function.
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* @param[in, out] *pSrc points to the in-place buffer of floating-point data type.
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* @param[in] fftSize length of the FFT.
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* @param[in] bitRevFactor bit reversal modifier that supports different size FFTs with the same bit reversal table.
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* @param[in] *pBitRevTab points to the bit reversal table.
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* @return none.
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*/
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#if defined(ARM_FLOAT16_SUPPORTED)
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void arm_bitreversal_f16(
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float16_t * pSrc,
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uint16_t fftSize,
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uint16_t bitRevFactor,
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const uint16_t * pBitRevTab)
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{
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uint16_t fftLenBy2, fftLenBy2p1;
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uint16_t i, j;
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float16_t in;
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/* Initializations */
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j = 0U;
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fftLenBy2 = fftSize >> 1U;
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fftLenBy2p1 = (fftSize >> 1U) + 1U;
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/* Bit Reversal Implementation */
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for (i = 0U; i <= (fftLenBy2 - 2U); i += 2U)
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{
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if (i < j)
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{
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/* pSrc[i] <-> pSrc[j]; */
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in = pSrc[2U * i];
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pSrc[2U * i] = pSrc[2U * j];
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pSrc[2U * j] = in;
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/* pSrc[i+1U] <-> pSrc[j+1U] */
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in = pSrc[(2U * i) + 1U];
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pSrc[(2U * i) + 1U] = pSrc[(2U * j) + 1U];
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pSrc[(2U * j) + 1U] = in;
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/* pSrc[i+fftLenBy2p1] <-> pSrc[j+fftLenBy2p1] */
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in = pSrc[2U * (i + fftLenBy2p1)];
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pSrc[2U * (i + fftLenBy2p1)] = pSrc[2U * (j + fftLenBy2p1)];
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pSrc[2U * (j + fftLenBy2p1)] = in;
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/* pSrc[i+fftLenBy2p1+1U] <-> pSrc[j+fftLenBy2p1+1U] */
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in = pSrc[(2U * (i + fftLenBy2p1)) + 1U];
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pSrc[(2U * (i + fftLenBy2p1)) + 1U] =
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pSrc[(2U * (j + fftLenBy2p1)) + 1U];
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pSrc[(2U * (j + fftLenBy2p1)) + 1U] = in;
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}
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/* pSrc[i+1U] <-> pSrc[j+1U] */
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in = pSrc[2U * (i + 1U)];
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pSrc[2U * (i + 1U)] = pSrc[2U * (j + fftLenBy2)];
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pSrc[2U * (j + fftLenBy2)] = in;
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/* pSrc[i+2U] <-> pSrc[j+2U] */
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in = pSrc[(2U * (i + 1U)) + 1U];
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pSrc[(2U * (i + 1U)) + 1U] = pSrc[(2U * (j + fftLenBy2)) + 1U];
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pSrc[(2U * (j + fftLenBy2)) + 1U] = in;
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/* Reading the index for the bit reversal */
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j = *pBitRevTab;
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/* Updating the bit reversal index depending on the fft length */
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pBitRevTab += bitRevFactor;
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}
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}
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#endif /* #if defined(ARM_FLOAT16_SUPPORTED) */
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