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CMSIS-DSP/Source/TransformFunctions/arm_cfft_radix4_f16.c

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/* ----------------------------------------------------------------------
* Project: CMSIS DSP Library
* Title: arm_cfft_radix4_f16.c
* Description: Radix-4 Decimation in Frequency CFFT & CIFFT Floating point processing function
*
* $Date: 23 April 2021
* $Revision: V1.9.0
*
* Target Processor: Cortex-M and Cortex-A cores
* -------------------------------------------------------------------- */
/*
* Copyright (C) 2010-2021 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 "dsp/transform_functions_f16.h"
#if defined(ARM_FLOAT16_SUPPORTED)
extern void arm_bitreversal_f16(
float16_t * pSrc,
uint16_t fftSize,
uint16_t bitRevFactor,
const uint16_t * pBitRevTab);
void arm_radix4_butterfly_f16(
float16_t * pSrc,
uint16_t fftLen,
const float16_t * pCoef,
uint16_t twidCoefModifier);
void arm_radix4_butterfly_inverse_f16(
float16_t * pSrc,
uint16_t fftLen,
const float16_t * pCoef,
uint16_t twidCoefModifier,
float16_t onebyfftLen);
void arm_cfft_radix4by2_f16(
float16_t * pSrc,
uint32_t fftLen,
const float16_t * pCoef);
/**
@ingroup groupTransforms
*/
/**
@addtogroup ComplexFFT
@{
*/
/*
* @brief Core function for the floating-point CFFT butterfly process.
* @param[in, out] *pSrc points to the in-place buffer of floating-point data type.
* @param[in] fftLen length of the FFT.
* @param[in] *pCoef points to the twiddle coefficient buffer.
* @param[in] twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
* @return none.
*/
void arm_cfft_radix4by2_f16(
float16_t * pSrc,
uint32_t fftLen,
const float16_t * pCoef)
{
uint32_t i, l;
uint32_t n2, ia;
float16_t xt, yt, cosVal, sinVal;
float16_t p0, p1,p2,p3,a0,a1;
n2 = fftLen >> 1;
ia = 0;
for (i = 0; i < n2; i++)
{
cosVal = pCoef[2*ia];
sinVal = pCoef[2*ia + 1];
ia++;
l = i + n2;
/* Butterfly implementation */
a0 = (_Float16)pSrc[2 * i] + (_Float16)pSrc[2 * l];
xt = (_Float16)pSrc[2 * i] - (_Float16)pSrc[2 * l];
yt = (_Float16)pSrc[2 * i + 1] - (_Float16)pSrc[2 * l + 1];
a1 = (_Float16)pSrc[2 * l + 1] + (_Float16)pSrc[2 * i + 1];
p0 = (_Float16)xt * (_Float16)cosVal;
p1 = (_Float16)yt * (_Float16)sinVal;
p2 = (_Float16)yt * (_Float16)cosVal;
p3 = (_Float16)xt * (_Float16)sinVal;
pSrc[2 * i] = a0;
pSrc[2 * i + 1] = a1;
pSrc[2 * l] = (_Float16)p0 + (_Float16)p1;
pSrc[2 * l + 1] = (_Float16)p2 - (_Float16)p3;
}
// first col
arm_radix4_butterfly_f16( pSrc, n2, (float16_t*)pCoef, 2U);
// second col
arm_radix4_butterfly_f16( pSrc + fftLen, n2, (float16_t*)pCoef, 2U);
}
/**
@brief Processing function for the floating-point Radix-4 CFFT/CIFFT.
@deprecated Do not use this function. It has been superseded by \ref arm_cfft_f16 and will be removed in the future.
@param[in] S points to an instance of the floating-point Radix-4 CFFT/CIFFT structure
@param[in,out] pSrc points to the complex data buffer of size <code>2*fftLen</code>. Processing occurs in-place
@return none
*/
void arm_cfft_radix4_f16(
const arm_cfft_radix4_instance_f16 * S,
float16_t * pSrc)
{
if (S->ifftFlag == 1U)
{
/* Complex IFFT radix-4 */
arm_radix4_butterfly_inverse_f16(pSrc, S->fftLen, S->pTwiddle, S->twidCoefModifier, S->onebyfftLen);
}
else
{
/* Complex FFT radix-4 */
arm_radix4_butterfly_f16(pSrc, S->fftLen, S->pTwiddle, S->twidCoefModifier);
}
if (S->bitReverseFlag == 1U)
{
/* Bit Reversal */
arm_bitreversal_f16(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
}
}
/**
@} end of ComplexFFT group
*/
/* ----------------------------------------------------------------------
* Internal helper function used by the FFTs
* ---------------------------------------------------------------------- */
/*
* @brief Core function for the floating-point CFFT butterfly process.
* @param[in, out] *pSrc points to the in-place buffer of floating-point data type.
* @param[in] fftLen length of the FFT.
* @param[in] *pCoef points to the twiddle coefficient buffer.
* @param[in] twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
* @return none.
*/
void arm_radix4_butterfly_f16(
float16_t * pSrc,
uint16_t fftLen,
const float16_t * pCoef,
uint16_t twidCoefModifier)
{
float16_t co1, co2, co3, si1, si2, si3;
uint32_t ia1, ia2, ia3;
uint32_t i0, i1, i2, i3;
uint32_t n1, n2, j, k;
#if defined (ARM_MATH_DSP)
/* Run the below code for Cortex-M4 and Cortex-M3 */
float16_t xaIn, yaIn, xbIn, ybIn, xcIn, ycIn, xdIn, ydIn;
float16_t Xaplusc, Xbplusd, Yaplusc, Ybplusd, Xaminusc, Xbminusd, Yaminusc,
Ybminusd;
float16_t Xb12C_out, Yb12C_out, Xc12C_out, Yc12C_out, Xd12C_out, Yd12C_out;
float16_t Xb12_out, Yb12_out, Xc12_out, Yc12_out, Xd12_out, Yd12_out;
float16_t *ptr1;
float16_t p0,p1,p2,p3,p4,p5;
float16_t a0,a1,a2,a3,a4,a5,a6,a7;
/* Initializations for the first stage */
n2 = fftLen;
n1 = n2;
/* n2 = fftLen/4 */
n2 >>= 2U;
i0 = 0U;
ia1 = 0U;
j = n2;
/* Calculation of first stage */
do
{
/* index calculation for the input as, */
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
xaIn = pSrc[(2U * i0)];
yaIn = pSrc[(2U * i0) + 1U];
xbIn = pSrc[(2U * i1)];
ybIn = pSrc[(2U * i1) + 1U];
xcIn = pSrc[(2U * i2)];
ycIn = pSrc[(2U * i2) + 1U];
xdIn = pSrc[(2U * i3)];
ydIn = pSrc[(2U * i3) + 1U];
/* xa + xc */
Xaplusc = (_Float16)xaIn + (_Float16)xcIn;
/* xb + xd */
Xbplusd = (_Float16)xbIn + (_Float16)xdIn;
/* ya + yc */
Yaplusc = (_Float16)yaIn + (_Float16)ycIn;
/* yb + yd */
Ybplusd = (_Float16)ybIn + (_Float16)ydIn;
/* index calculation for the coefficients */
ia2 = ia1 + ia1;
co2 = pCoef[ia2 * 2U];
si2 = pCoef[(ia2 * 2U) + 1U];
/* xa - xc */
Xaminusc = (_Float16)xaIn - (_Float16)xcIn;
/* xb - xd */
Xbminusd = (_Float16)xbIn - (_Float16)xdIn;
/* ya - yc */
Yaminusc = (_Float16)yaIn - (_Float16)ycIn;
/* yb - yd */
Ybminusd = (_Float16)ybIn - (_Float16)ydIn;
/* xa' = xa + xb + xc + xd */
pSrc[(2U * i0)] = (_Float16)Xaplusc + (_Float16)Xbplusd;
/* ya' = ya + yb + yc + yd */
pSrc[(2U * i0) + 1U] = (_Float16)Yaplusc + (_Float16)Ybplusd;
/* (xa - xc) + (yb - yd) */
Xb12C_out = ((_Float16)Xaminusc + (_Float16)Ybminusd);
/* (ya - yc) + (xb - xd) */
Yb12C_out = ((_Float16)Yaminusc - (_Float16)Xbminusd);
/* (xa + xc) - (xb + xd) */
Xc12C_out = ((_Float16)Xaplusc - (_Float16)Xbplusd);
/* (ya + yc) - (yb + yd) */
Yc12C_out = ((_Float16)Yaplusc - (_Float16)Ybplusd);
/* (xa - xc) - (yb - yd) */
Xd12C_out = ((_Float16)Xaminusc - (_Float16)Ybminusd);
/* (ya - yc) + (xb - xd) */
Yd12C_out = ((_Float16)Xbminusd + (_Float16)Yaminusc);
co1 = pCoef[ia1 * 2U];
si1 = pCoef[(ia1 * 2U) + 1U];
/* index calculation for the coefficients */
ia3 = ia2 + ia1;
co3 = pCoef[ia3 * 2U];
si3 = pCoef[(ia3 * 2U) + 1U];
Xb12_out = (_Float16)Xb12C_out * (_Float16)co1;
Yb12_out = (_Float16)Yb12C_out * (_Float16)co1;
Xc12_out = (_Float16)Xc12C_out * (_Float16)co2;
Yc12_out = (_Float16)Yc12C_out * (_Float16)co2;
Xd12_out = (_Float16)Xd12C_out * (_Float16)co3;
Yd12_out = (_Float16)Yd12C_out * (_Float16)co3;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
//Xb12_out -= Yb12C_out * si1;
p0 = (_Float16)Yb12C_out * (_Float16)si1;
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
//Yb12_out += Xb12C_out * si1;
p1 = (_Float16)Xb12C_out * (_Float16)si1;
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
//Xc12_out -= Yc12C_out * si2;
p2 = (_Float16)Yc12C_out * (_Float16)si2;
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
//Yc12_out += Xc12C_out * si2;
p3 = (_Float16)Xc12C_out * (_Float16)si2;
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
//Xd12_out -= Yd12C_out * si3;
p4 = (_Float16)Yd12C_out * (_Float16)si3;
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
//Yd12_out += Xd12C_out * si3;
p5 = (_Float16)Xd12C_out * (_Float16)si3;
Xb12_out += (_Float16)p0;
Yb12_out -= (_Float16)p1;
Xc12_out += (_Float16)p2;
Yc12_out -= (_Float16)p3;
Xd12_out += (_Float16)p4;
Yd12_out -= (_Float16)p5;
/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */
pSrc[2U * i1] = Xc12_out;
/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */
pSrc[(2U * i1) + 1U] = Yc12_out;
/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */
pSrc[2U * i2] = Xb12_out;
/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */
pSrc[(2U * i2) + 1U] = Yb12_out;
/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */
pSrc[2U * i3] = Xd12_out;
/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */
pSrc[(2U * i3) + 1U] = Yd12_out;
/* Twiddle coefficients index modifier */
ia1 += twidCoefModifier;
/* Updating input index */
i0++;
}
while (--j);
twidCoefModifier <<= 2U;
/* Calculation of second stage to excluding last stage */
for (k = fftLen >> 2U; k > 4U; k >>= 2U)
{
/* Initializations for the first stage */
n1 = n2;
n2 >>= 2U;
ia1 = 0U;
/* Calculation of first stage */
j = 0;
do
{
/* index calculation for the coefficients */
ia2 = ia1 + ia1;
ia3 = ia2 + ia1;
co1 = pCoef[ia1 * 2U];
si1 = pCoef[(ia1 * 2U) + 1U];
co2 = pCoef[ia2 * 2U];
si2 = pCoef[(ia2 * 2U) + 1U];
co3 = pCoef[ia3 * 2U];
si3 = pCoef[(ia3 * 2U) + 1U];
/* Twiddle coefficients index modifier */
ia1 += twidCoefModifier;
i0 = j;
do
{
/* index calculation for the input as, */
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
xaIn = pSrc[(2U * i0)];
yaIn = pSrc[(2U * i0) + 1U];
xbIn = pSrc[(2U * i1)];
ybIn = pSrc[(2U * i1) + 1U];
xcIn = pSrc[(2U * i2)];
ycIn = pSrc[(2U * i2) + 1U];
xdIn = pSrc[(2U * i3)];
ydIn = pSrc[(2U * i3) + 1U];
/* xa - xc */
Xaminusc = (_Float16)xaIn - (_Float16)xcIn;
/* (xb - xd) */
Xbminusd = (_Float16)xbIn - (_Float16)xdIn;
/* ya - yc */
Yaminusc = (_Float16)yaIn - (_Float16)ycIn;
/* (yb - yd) */
Ybminusd = (_Float16)ybIn - (_Float16)ydIn;
/* xa + xc */
Xaplusc = (_Float16)xaIn + (_Float16)xcIn;
/* xb + xd */
Xbplusd = (_Float16)xbIn + (_Float16)xdIn;
/* ya + yc */
Yaplusc = (_Float16)yaIn + (_Float16)ycIn;
/* yb + yd */
Ybplusd = (_Float16)ybIn + (_Float16)ydIn;
/* (xa - xc) + (yb - yd) */
Xb12C_out = ((_Float16)Xaminusc + (_Float16)Ybminusd);
/* (ya - yc) - (xb - xd) */
Yb12C_out = ((_Float16)Yaminusc - (_Float16)Xbminusd);
/* xa + xc -(xb + xd) */
Xc12C_out = ((_Float16)Xaplusc - (_Float16)Xbplusd);
/* (ya + yc) - (yb + yd) */
Yc12C_out = ((_Float16)Yaplusc - (_Float16)Ybplusd);
/* (xa - xc) - (yb - yd) */
Xd12C_out = ((_Float16)Xaminusc - (_Float16)Ybminusd);
/* (ya - yc) + (xb - xd) */
Yd12C_out = ((_Float16)Xbminusd + (_Float16)Yaminusc);
pSrc[(2U * i0)] = (_Float16)Xaplusc + (_Float16)Xbplusd;
pSrc[(2U * i0) + 1U] = (_Float16)Yaplusc + (_Float16)Ybplusd;
Xb12_out = (_Float16)Xb12C_out * (_Float16)co1;
Yb12_out = (_Float16)Yb12C_out * (_Float16)co1;
Xc12_out = (_Float16)Xc12C_out * (_Float16)co2;
Yc12_out = (_Float16)Yc12C_out * (_Float16)co2;
Xd12_out = (_Float16)Xd12C_out * (_Float16)co3;
Yd12_out = (_Float16)Yd12C_out * (_Float16)co3;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
//Xb12_out -= Yb12C_out * si1;
p0 = (_Float16)Yb12C_out * (_Float16)si1;
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
//Yb12_out += Xb12C_out * si1;
p1 = (_Float16)Xb12C_out * (_Float16)si1;
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
//Xc12_out -= Yc12C_out * si2;
p2 = (_Float16)Yc12C_out * (_Float16)si2;
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
//Yc12_out += Xc12C_out * si2;
p3 = (_Float16)Xc12C_out * (_Float16)si2;
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
//Xd12_out -= Yd12C_out * si3;
p4 = (_Float16)Yd12C_out * (_Float16)si3;
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
//Yd12_out += Xd12C_out * si3;
p5 = (_Float16)Xd12C_out * (_Float16)si3;
Xb12_out += (_Float16)p0;
Yb12_out -= (_Float16)p1;
Xc12_out += (_Float16)p2;
Yc12_out -= (_Float16)p3;
Xd12_out += (_Float16)p4;
Yd12_out -= (_Float16)p5;
/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */
pSrc[2U * i1] = Xc12_out;
/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */
pSrc[(2U * i1) + 1U] = Yc12_out;
/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */
pSrc[2U * i2] = Xb12_out;
/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */
pSrc[(2U * i2) + 1U] = Yb12_out;
/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */
pSrc[2U * i3] = Xd12_out;
/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */
pSrc[(2U * i3) + 1U] = Yd12_out;
i0 += n1;
} while (i0 < fftLen);
j++;
} while (j <= (n2 - 1U));
twidCoefModifier <<= 2U;
}
j = fftLen >> 2;
ptr1 = &pSrc[0];
/* Calculations of last stage */
do
{
xaIn = ptr1[0];
yaIn = ptr1[1];
xbIn = ptr1[2];
ybIn = ptr1[3];
xcIn = ptr1[4];
ycIn = ptr1[5];
xdIn = ptr1[6];
ydIn = ptr1[7];
/* xa + xc */
Xaplusc = (_Float16)xaIn + (_Float16)xcIn;
/* xa - xc */
Xaminusc = (_Float16)xaIn - (_Float16)xcIn;
/* ya + yc */
Yaplusc = (_Float16)yaIn + (_Float16)ycIn;
/* ya - yc */
Yaminusc = (_Float16)yaIn - (_Float16)ycIn;
/* xb + xd */
Xbplusd = (_Float16)xbIn + (_Float16)xdIn;
/* yb + yd */
Ybplusd = (_Float16)ybIn + (_Float16)ydIn;
/* (xb-xd) */
Xbminusd = (_Float16)xbIn - (_Float16)xdIn;
/* (yb-yd) */
Ybminusd = (_Float16)ybIn - (_Float16)ydIn;
/* xa' = xa + xb + xc + xd */
a0 = ((_Float16)Xaplusc + (_Float16)Xbplusd);
/* ya' = ya + yb + yc + yd */
a1 = ((_Float16)Yaplusc + (_Float16)Ybplusd);
/* xc' = (xa-xb+xc-xd) */
a2 = ((_Float16)Xaplusc - (_Float16)Xbplusd);
/* yc' = (ya-yb+yc-yd) */
a3 = ((_Float16)Yaplusc - (_Float16)Ybplusd);
/* xb' = (xa+yb-xc-yd) */
a4 = ((_Float16)Xaminusc + (_Float16)Ybminusd);
/* yb' = (ya-xb-yc+xd) */
a5 = ((_Float16)Yaminusc - (_Float16)Xbminusd);
/* xd' = (xa-yb-xc+yd)) */
a6 = ((_Float16)Xaminusc - (_Float16)Ybminusd);
/* yd' = (ya+xb-yc-xd) */
a7 = ((_Float16)Xbminusd + (_Float16)Yaminusc);
ptr1[0] = a0;
ptr1[1] = a1;
ptr1[2] = a2;
ptr1[3] = a3;
ptr1[4] = a4;
ptr1[5] = a5;
ptr1[6] = a6;
ptr1[7] = a7;
/* increment pointer by 8 */
ptr1 += 8U;
} while (--j);
#else
float16_t t1, t2, r1, r2, s1, s2;
/* Run the below code for Cortex-M0 */
/* Initializations for the fft calculation */
n2 = fftLen;
n1 = n2;
for (k = fftLen; k > 1U; k >>= 2U)
{
/* Initializations for the fft calculation */
n1 = n2;
n2 >>= 2U;
ia1 = 0U;
/* FFT Calculation */
j = 0;
do
{
/* index calculation for the coefficients */
ia2 = ia1 + ia1;
ia3 = ia2 + ia1;
co1 = pCoef[ia1 * 2U];
si1 = pCoef[(ia1 * 2U) + 1U];
co2 = pCoef[ia2 * 2U];
si2 = pCoef[(ia2 * 2U) + 1U];
co3 = pCoef[ia3 * 2U];
si3 = pCoef[(ia3 * 2U) + 1U];
/* Twiddle coefficients index modifier */
ia1 = ia1 + twidCoefModifier;
i0 = j;
do
{
/* index calculation for the input as, */
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* xa + xc */
r1 = (_Float16)pSrc[(2U * i0)] + (_Float16)pSrc[(2U * i2)];
/* xa - xc */
r2 = (_Float16)pSrc[(2U * i0)] - (_Float16)pSrc[(2U * i2)];
/* ya + yc */
s1 = (_Float16)pSrc[(2U * i0) + 1U] + (_Float16)pSrc[(2U * i2) + 1U];
/* ya - yc */
s2 = (_Float16)pSrc[(2U * i0) + 1U] - (_Float16)pSrc[(2U * i2) + 1U];
/* xb + xd */
t1 = (_Float16)pSrc[2U * i1] + (_Float16)pSrc[2U * i3];
/* xa' = xa + xb + xc + xd */
pSrc[2U * i0] = (_Float16)r1 + (_Float16)t1;
/* xa + xc -(xb + xd) */
r1 = (_Float16)r1 - (_Float16)t1;
/* yb + yd */
t2 = (_Float16)pSrc[(2U * i1) + 1U] + (_Float16)pSrc[(2U * i3) + 1U];
/* ya' = ya + yb + yc + yd */
pSrc[(2U * i0) + 1U] = (_Float16)s1 + (_Float16)t2;
/* (ya + yc) - (yb + yd) */
s1 = (_Float16)s1 - (_Float16)t2;
/* (yb - yd) */
t1 = (_Float16)pSrc[(2U * i1) + 1U] - (_Float16)pSrc[(2U * i3) + 1U];
/* (xb - xd) */
t2 = (_Float16)pSrc[2U * i1] - (_Float16)pSrc[2U * i3];
/* xc' = (xa-xb+xc-xd)co2 + (ya-yb+yc-yd)(si2) */
pSrc[2U * i1] = ((_Float16)r1 * (_Float16)co2) + ((_Float16)s1 * (_Float16)si2);
/* yc' = (ya-yb+yc-yd)co2 - (xa-xb+xc-xd)(si2) */
pSrc[(2U * i1) + 1U] = ((_Float16)s1 * (_Float16)co2) - ((_Float16)r1 * (_Float16)si2);
/* (xa - xc) + (yb - yd) */
r1 = (_Float16)r2 + (_Float16)t1;
/* (xa - xc) - (yb - yd) */
r2 = (_Float16)r2 - (_Float16)t1;
/* (ya - yc) - (xb - xd) */
s1 = (_Float16)s2 - (_Float16)t2;
/* (ya - yc) + (xb - xd) */
s2 = (_Float16)s2 + (_Float16)t2;
/* xb' = (xa+yb-xc-yd)co1 + (ya-xb-yc+xd)(si1) */
pSrc[2U * i2] = ((_Float16)r1 * (_Float16)co1) + ((_Float16)s1 * (_Float16)si1);
/* yb' = (ya-xb-yc+xd)co1 - (xa+yb-xc-yd)(si1) */
pSrc[(2U * i2) + 1U] = ((_Float16)s1 * (_Float16)co1) - ((_Float16)r1 * (_Float16)si1);
/* xd' = (xa-yb-xc+yd)co3 + (ya+xb-yc-xd)(si3) */
pSrc[2U * i3] = ((_Float16)r2 * (_Float16)co3) + ((_Float16)s2 * (_Float16)si3);
/* yd' = (ya+xb-yc-xd)co3 - (xa-yb-xc+yd)(si3) */
pSrc[(2U * i3) + 1U] = ((_Float16)s2 * (_Float16)co3) - ((_Float16)r2 * (_Float16)si3);
i0 += n1;
} while ( i0 < fftLen);
j++;
} while (j <= (n2 - 1U));
twidCoefModifier <<= 2U;
}
#endif /* #if defined (ARM_MATH_DSP) */
}
/*
* @brief Core function for the floating-point CIFFT butterfly process.
* @param[in, out] *pSrc points to the in-place buffer of floating-point data type.
* @param[in] fftLen length of the FFT.
* @param[in] *pCoef points to twiddle coefficient buffer.
* @param[in] twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
* @param[in] onebyfftLen value of 1/fftLen.
* @return none.
*/
void arm_radix4_butterfly_inverse_f16(
float16_t * pSrc,
uint16_t fftLen,
const float16_t * pCoef,
uint16_t twidCoefModifier,
float16_t onebyfftLen)
{
float16_t co1, co2, co3, si1, si2, si3;
uint32_t ia1, ia2, ia3;
uint32_t i0, i1, i2, i3;
uint32_t n1, n2, j, k;
#if defined (ARM_MATH_DSP)
float16_t xaIn, yaIn, xbIn, ybIn, xcIn, ycIn, xdIn, ydIn;
float16_t Xaplusc, Xbplusd, Yaplusc, Ybplusd, Xaminusc, Xbminusd, Yaminusc,
Ybminusd;
float16_t Xb12C_out, Yb12C_out, Xc12C_out, Yc12C_out, Xd12C_out, Yd12C_out;
float16_t Xb12_out, Yb12_out, Xc12_out, Yc12_out, Xd12_out, Yd12_out;
float16_t *ptr1;
float16_t p0,p1,p2,p3,p4,p5,p6,p7;
float16_t a0,a1,a2,a3,a4,a5,a6,a7;
/* Initializations for the first stage */
n2 = fftLen;
n1 = n2;
/* n2 = fftLen/4 */
n2 >>= 2U;
i0 = 0U;
ia1 = 0U;
j = n2;
/* Calculation of first stage */
do
{
/* index calculation for the input as, */
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Butterfly implementation */
xaIn = pSrc[(2U * i0)];
yaIn = pSrc[(2U * i0) + 1U];
xcIn = pSrc[(2U * i2)];
ycIn = pSrc[(2U * i2) + 1U];
xbIn = pSrc[(2U * i1)];
ybIn = pSrc[(2U * i1) + 1U];
xdIn = pSrc[(2U * i3)];
ydIn = pSrc[(2U * i3) + 1U];
/* xa + xc */
Xaplusc = (_Float16)xaIn + (_Float16)xcIn;
/* xb + xd */
Xbplusd = (_Float16)xbIn + (_Float16)xdIn;
/* ya + yc */
Yaplusc = (_Float16)yaIn + (_Float16)ycIn;
/* yb + yd */
Ybplusd = (_Float16)ybIn + (_Float16)ydIn;
/* index calculation for the coefficients */
ia2 = ia1 + ia1;
co2 = pCoef[ia2 * 2U];
si2 = pCoef[(ia2 * 2U) + 1U];
/* xa - xc */
Xaminusc = (_Float16)xaIn - (_Float16)xcIn;
/* xb - xd */
Xbminusd = (_Float16)xbIn - (_Float16)xdIn;
/* ya - yc */
Yaminusc = (_Float16)yaIn - (_Float16)ycIn;
/* yb - yd */
Ybminusd = (_Float16)ybIn - (_Float16)ydIn;
/* xa' = xa + xb + xc + xd */
pSrc[(2U * i0)] = (_Float16)Xaplusc + (_Float16)Xbplusd;
/* ya' = ya + yb + yc + yd */
pSrc[(2U * i0) + 1U] = (_Float16)Yaplusc + (_Float16)Ybplusd;
/* (xa - xc) - (yb - yd) */
Xb12C_out = ((_Float16)Xaminusc - (_Float16)Ybminusd);
/* (ya - yc) + (xb - xd) */
Yb12C_out = ((_Float16)Yaminusc + (_Float16)Xbminusd);
/* (xa + xc) - (xb + xd) */
Xc12C_out = ((_Float16)Xaplusc - (_Float16)Xbplusd);
/* (ya + yc) - (yb + yd) */
Yc12C_out = ((_Float16)Yaplusc - (_Float16)Ybplusd);
/* (xa - xc) + (yb - yd) */
Xd12C_out = ((_Float16)Xaminusc + (_Float16)Ybminusd);
/* (ya - yc) - (xb - xd) */
Yd12C_out = ((_Float16)Yaminusc - (_Float16)Xbminusd);
co1 = pCoef[ia1 * 2U];
si1 = pCoef[(ia1 * 2U) + 1U];
/* index calculation for the coefficients */
ia3 = ia2 + ia1;
co3 = pCoef[ia3 * 2U];
si3 = pCoef[(ia3 * 2U) + 1U];
Xb12_out = (_Float16)Xb12C_out * (_Float16)co1;
Yb12_out = (_Float16)Yb12C_out * (_Float16)co1;
Xc12_out = (_Float16)Xc12C_out * (_Float16)co2;
Yc12_out = (_Float16)Yc12C_out * (_Float16)co2;
Xd12_out = (_Float16)Xd12C_out * (_Float16)co3;
Yd12_out = (_Float16)Yd12C_out * (_Float16)co3;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
//Xb12_out -= Yb12C_out * si1;
p0 = (_Float16)Yb12C_out * (_Float16)si1;
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
//Yb12_out += Xb12C_out * si1;
p1 = (_Float16)Xb12C_out * (_Float16)si1;
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
//Xc12_out -= Yc12C_out * si2;
p2 = (_Float16)Yc12C_out * (_Float16)si2;
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
//Yc12_out += Xc12C_out * si2;
p3 = (_Float16)Xc12C_out * (_Float16)si2;
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
//Xd12_out -= Yd12C_out * si3;
p4 = (_Float16)Yd12C_out * (_Float16)si3;
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
//Yd12_out += Xd12C_out * si3;
p5 =(_Float16) Xd12C_out * (_Float16)si3;
Xb12_out -= (_Float16)p0;
Yb12_out += (_Float16)p1;
Xc12_out -= (_Float16)p2;
Yc12_out += (_Float16)p3;
Xd12_out -= (_Float16)p4;
Yd12_out += (_Float16)p5;
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
pSrc[2U * i1] = Xc12_out;
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
pSrc[(2U * i1) + 1U] = Yc12_out;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
pSrc[2U * i2] = Xb12_out;
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
pSrc[(2U * i2) + 1U] = Yb12_out;
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
pSrc[2U * i3] = Xd12_out;
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
pSrc[(2U * i3) + 1U] = Yd12_out;
/* Twiddle coefficients index modifier */
ia1 = ia1 + twidCoefModifier;
/* Updating input index */
i0 = i0 + 1U;
} while (--j);
twidCoefModifier <<= 2U;
/* Calculation of second stage to excluding last stage */
for (k = fftLen >> 2U; k > 4U; k >>= 2U)
{
/* Initializations for the first stage */
n1 = n2;
n2 >>= 2U;
ia1 = 0U;
/* Calculation of first stage */
j = 0;
do
{
/* index calculation for the coefficients */
ia2 = ia1 + ia1;
ia3 = ia2 + ia1;
co1 = pCoef[ia1 * 2U];
si1 = pCoef[(ia1 * 2U) + 1U];
co2 = pCoef[ia2 * 2U];
si2 = pCoef[(ia2 * 2U) + 1U];
co3 = pCoef[ia3 * 2U];
si3 = pCoef[(ia3 * 2U) + 1U];
/* Twiddle coefficients index modifier */
ia1 = ia1 + twidCoefModifier;
i0 = j;
do
{
/* index calculation for the input as, */
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
xaIn = pSrc[(2U * i0)];
yaIn = pSrc[(2U * i0) + 1U];
xbIn = pSrc[(2U * i1)];
ybIn = pSrc[(2U * i1) + 1U];
xcIn = pSrc[(2U * i2)];
ycIn = pSrc[(2U * i2) + 1U];
xdIn = pSrc[(2U * i3)];
ydIn = pSrc[(2U * i3) + 1U];
/* xa - xc */
Xaminusc = (_Float16)xaIn - (_Float16)xcIn;
/* (xb - xd) */
Xbminusd = (_Float16)xbIn - (_Float16)xdIn;
/* ya - yc */
Yaminusc = (_Float16)yaIn - (_Float16)ycIn;
/* (yb - yd) */
Ybminusd = (_Float16)ybIn - (_Float16)ydIn;
/* xa + xc */
Xaplusc = (_Float16)xaIn + (_Float16)xcIn;
/* xb + xd */
Xbplusd = (_Float16)xbIn + (_Float16)xdIn;
/* ya + yc */
Yaplusc = (_Float16)yaIn + (_Float16)ycIn;
/* yb + yd */
Ybplusd = (_Float16)ybIn + (_Float16)ydIn;
/* (xa - xc) - (yb - yd) */
Xb12C_out = ((_Float16)Xaminusc - (_Float16)Ybminusd);
/* (ya - yc) + (xb - xd) */
Yb12C_out = ((_Float16)Yaminusc + (_Float16)Xbminusd);
/* xa + xc -(xb + xd) */
Xc12C_out = ((_Float16)Xaplusc - (_Float16)Xbplusd);
/* (ya + yc) - (yb + yd) */
Yc12C_out = ((_Float16)Yaplusc - (_Float16)Ybplusd);
/* (xa - xc) + (yb - yd) */
Xd12C_out = ((_Float16)Xaminusc + (_Float16)Ybminusd);
/* (ya - yc) - (xb - xd) */
Yd12C_out = ((_Float16)Yaminusc - (_Float16)Xbminusd);
pSrc[(2U * i0)] = (_Float16)Xaplusc + (_Float16)Xbplusd;
pSrc[(2U * i0) + 1U] = (_Float16)Yaplusc + (_Float16)Ybplusd;
Xb12_out = (_Float16)Xb12C_out * (_Float16)co1;
Yb12_out = (_Float16)Yb12C_out * (_Float16)co1;
Xc12_out = (_Float16)Xc12C_out * (_Float16)co2;
Yc12_out = (_Float16)Yc12C_out * (_Float16)co2;
Xd12_out = (_Float16)Xd12C_out * (_Float16)co3;
Yd12_out = (_Float16)Yd12C_out * (_Float16)co3;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
//Xb12_out -= Yb12C_out * si1;
p0 = (_Float16)Yb12C_out * (_Float16)si1;
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
//Yb12_out += Xb12C_out * si1;
p1 = (_Float16)Xb12C_out * (_Float16)si1;
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
//Xc12_out -= Yc12C_out * si2;
p2 = (_Float16)Yc12C_out * (_Float16)si2;
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
//Yc12_out += Xc12C_out * si2;
p3 = (_Float16)Xc12C_out * (_Float16)si2;
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
//Xd12_out -= Yd12C_out * si3;
p4 = (_Float16)Yd12C_out * (_Float16)si3;
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
//Yd12_out += Xd12C_out * si3;
p5 = (_Float16)Xd12C_out * (_Float16)si3;
Xb12_out -= (_Float16)p0;
Yb12_out += (_Float16)p1;
Xc12_out -= (_Float16)p2;
Yc12_out += (_Float16)p3;
Xd12_out -= (_Float16)p4;
Yd12_out += (_Float16)p5;
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
pSrc[2U * i1] = Xc12_out;
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
pSrc[(2U * i1) + 1U] = Yc12_out;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
pSrc[2U * i2] = Xb12_out;
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
pSrc[(2U * i2) + 1U] = Yb12_out;
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
pSrc[2U * i3] = Xd12_out;
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
pSrc[(2U * i3) + 1U] = Yd12_out;
i0 += n1;
} while (i0 < fftLen);
j++;
} while (j <= (n2 - 1U));
twidCoefModifier <<= 2U;
}
/* Initializations of last stage */
j = fftLen >> 2;
ptr1 = &pSrc[0];
/* Calculations of last stage */
do
{
xaIn = ptr1[0];
yaIn = ptr1[1];
xbIn = ptr1[2];
ybIn = ptr1[3];
xcIn = ptr1[4];
ycIn = ptr1[5];
xdIn = ptr1[6];
ydIn = ptr1[7];
/* Butterfly implementation */
/* xa + xc */
Xaplusc = (_Float16)xaIn + (_Float16)xcIn;
/* xa - xc */
Xaminusc = (_Float16)xaIn - (_Float16)xcIn;
/* ya + yc */
Yaplusc = (_Float16)yaIn + (_Float16)ycIn;
/* ya - yc */
Yaminusc = (_Float16)yaIn - (_Float16)ycIn;
/* xb + xd */
Xbplusd = (_Float16)xbIn + (_Float16)xdIn;
/* yb + yd */
Ybplusd = (_Float16)ybIn + (_Float16)ydIn;
/* (xb-xd) */
Xbminusd = (_Float16)xbIn - (_Float16)xdIn;
/* (yb-yd) */
Ybminusd = (_Float16)ybIn - (_Float16)ydIn;
/* xa' = (xa+xb+xc+xd) * onebyfftLen */
a0 = ((_Float16)Xaplusc + (_Float16)Xbplusd);
/* ya' = (ya+yb+yc+yd) * onebyfftLen */
a1 = ((_Float16)Yaplusc + (_Float16)Ybplusd);
/* xc' = (xa-xb+xc-xd) * onebyfftLen */
a2 = ((_Float16)Xaplusc - (_Float16)Xbplusd);
/* yc' = (ya-yb+yc-yd) * onebyfftLen */
a3 = ((_Float16)Yaplusc - (_Float16)Ybplusd);
/* xb' = (xa-yb-xc+yd) * onebyfftLen */
a4 = ((_Float16)Xaminusc - (_Float16)Ybminusd);
/* yb' = (ya+xb-yc-xd) * onebyfftLen */
a5 = ((_Float16)Yaminusc + (_Float16)Xbminusd);
/* xd' = (xa-yb-xc+yd) * onebyfftLen */
a6 = ((_Float16)Xaminusc + (_Float16)Ybminusd);
/* yd' = (ya-xb-yc+xd) * onebyfftLen */
a7 = ((_Float16)Yaminusc - (_Float16)Xbminusd);
p0 = (_Float16)a0 * (_Float16)onebyfftLen;
p1 = (_Float16)a1 * (_Float16)onebyfftLen;
p2 = (_Float16)a2 * (_Float16)onebyfftLen;
p3 = (_Float16)a3 * (_Float16)onebyfftLen;
p4 = (_Float16)a4 * (_Float16)onebyfftLen;
p5 = (_Float16)a5 * (_Float16)onebyfftLen;
p6 = (_Float16)a6 * (_Float16)onebyfftLen;
p7 = (_Float16)a7 * (_Float16)onebyfftLen;
/* xa' = (xa+xb+xc+xd) * onebyfftLen */
ptr1[0] = p0;
/* ya' = (ya+yb+yc+yd) * onebyfftLen */
ptr1[1] = p1;
/* xc' = (xa-xb+xc-xd) * onebyfftLen */
ptr1[2] = p2;
/* yc' = (ya-yb+yc-yd) * onebyfftLen */
ptr1[3] = p3;
/* xb' = (xa-yb-xc+yd) * onebyfftLen */
ptr1[4] = p4;
/* yb' = (ya+xb-yc-xd) * onebyfftLen */
ptr1[5] = p5;
/* xd' = (xa-yb-xc+yd) * onebyfftLen */
ptr1[6] = p6;
/* yd' = (ya-xb-yc+xd) * onebyfftLen */
ptr1[7] = p7;
/* increment source pointer by 8 for next calculations */
ptr1 = ptr1 + 8U;
} while (--j);
#else
float16_t t1, t2, r1, r2, s1, s2;
/* Run the below code for Cortex-M0 */
/* Initializations for the first stage */
n2 = fftLen;
n1 = n2;
/* Calculation of first stage */
for (k = fftLen; k > 4U; k >>= 2U)
{
/* Initializations for the first stage */
n1 = n2;
n2 >>= 2U;
ia1 = 0U;
/* Calculation of first stage */
j = 0;
do
{
/* index calculation for the coefficients */
ia2 = ia1 + ia1;
ia3 = ia2 + ia1;
co1 = pCoef[ia1 * 2U];
si1 = pCoef[(ia1 * 2U) + 1U];
co2 = pCoef[ia2 * 2U];
si2 = pCoef[(ia2 * 2U) + 1U];
co3 = pCoef[ia3 * 2U];
si3 = pCoef[(ia3 * 2U) + 1U];
/* Twiddle coefficients index modifier */
ia1 = ia1 + twidCoefModifier;
i0 = j;
do
{
/* index calculation for the input as, */
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* xa + xc */
r1 = (_Float16)pSrc[(2U * i0)] + (_Float16)pSrc[(2U * i2)];
/* xa - xc */
r2 = (_Float16)pSrc[(2U * i0)] - (_Float16)pSrc[(2U * i2)];
/* ya + yc */
s1 = (_Float16)pSrc[(2U * i0) + 1U] + (_Float16)pSrc[(2U * i2) + 1U];
/* ya - yc */
s2 = (_Float16)pSrc[(2U * i0) + 1U] - (_Float16)pSrc[(2U * i2) + 1U];
/* xb + xd */
t1 = (_Float16)pSrc[2U * i1] + (_Float16)pSrc[2U * i3];
/* xa' = xa + xb + xc + xd */
pSrc[2U * i0] = (_Float16)r1 + (_Float16)t1;
/* xa + xc -(xb + xd) */
r1 = (_Float16)r1 - (_Float16)t1;
/* yb + yd */
t2 = (_Float16)pSrc[(2U * i1) + 1U] + (_Float16)pSrc[(2U * i3) + 1U];
/* ya' = ya + yb + yc + yd */
pSrc[(2U * i0) + 1U] = (_Float16)s1 + (_Float16)t2;
/* (ya + yc) - (yb + yd) */
s1 = (_Float16)s1 - (_Float16)t2;
/* (yb - yd) */
t1 = (_Float16)pSrc[(2U * i1) + 1U] - (_Float16)pSrc[(2U * i3) + 1U];
/* (xb - xd) */
t2 = (_Float16)pSrc[2U * i1] - (_Float16)pSrc[2U * i3];
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
pSrc[2U * i1] = ((_Float16)r1 * (_Float16)co2) - ((_Float16)s1 * (_Float16)si2);
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
pSrc[(2U * i1) + 1U] = ((_Float16)s1 * (_Float16)co2) + ((_Float16)r1 * (_Float16)si2);
/* (xa - xc) - (yb - yd) */
r1 = (_Float16)r2 - (_Float16)t1;
/* (xa - xc) + (yb - yd) */
r2 = (_Float16)r2 + (_Float16)t1;
/* (ya - yc) + (xb - xd) */
s1 = (_Float16)s2 + (_Float16)t2;
/* (ya - yc) - (xb - xd) */
s2 = (_Float16)s2 - (_Float16)t2;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
pSrc[2U * i2] = ((_Float16)r1 * (_Float16)co1) - ((_Float16)s1 * (_Float16)si1);
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
pSrc[(2U * i2) + 1U] = ((_Float16)s1 * (_Float16)co1) + ((_Float16)r1 * (_Float16)si1);
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
pSrc[2U * i3] = ((_Float16)r2 * (_Float16)co3) - ((_Float16)s2 * (_Float16)si3);
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
pSrc[(2U * i3) + 1U] = ((_Float16)s2 * (_Float16)co3) + ((_Float16)r2 * (_Float16)si3);
i0 += n1;
} while ( i0 < fftLen);
j++;
} while (j <= (n2 - 1U));
twidCoefModifier <<= 2U;
}
/* Initializations of last stage */
n1 = n2;
n2 >>= 2U;
/* Calculations of last stage */
for (i0 = 0U; i0 <= (fftLen - n1); i0 += n1)
{
/* index calculation for the input as, */
/* pSrc[i0 + 0], pSrc[i0 + fftLen/4], pSrc[i0 + fftLen/2], pSrc[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Butterfly implementation */
/* xa + xc */
r1 = (_Float16)pSrc[2U * i0] + (_Float16)pSrc[2U * i2];
/* xa - xc */
r2 = (_Float16)pSrc[2U * i0] - (_Float16)pSrc[2U * i2];
/* ya + yc */
s1 = (_Float16)pSrc[(2U * i0) + 1U] + (_Float16)pSrc[(2U * i2) + 1U];
/* ya - yc */
s2 = (_Float16)pSrc[(2U * i0) + 1U] - (_Float16)pSrc[(2U * i2) + 1U];
/* xc + xd */
t1 = (_Float16)pSrc[2U * i1] + (_Float16)pSrc[2U * i3];
/* xa' = xa + xb + xc + xd */
pSrc[2U * i0] = ((_Float16)r1 + (_Float16)t1) * (_Float16)onebyfftLen;
/* (xa + xb) - (xc + xd) */
r1 = (_Float16)r1 - (_Float16)t1;
/* yb + yd */
t2 = (_Float16)pSrc[(2U * i1) + 1U] + (_Float16)pSrc[(2U * i3) + 1U];
/* ya' = ya + yb + yc + yd */
pSrc[(2U * i0) + 1U] = ((_Float16)s1 + (_Float16)t2) * (_Float16)onebyfftLen;
/* (ya + yc) - (yb + yd) */
s1 = (_Float16)s1 - (_Float16)t2;
/* (yb-yd) */
t1 = (_Float16)pSrc[(2U * i1) + 1U] - (_Float16)pSrc[(2U * i3) + 1U];
/* (xb-xd) */
t2 = (_Float16)pSrc[2U * i1] - (_Float16)pSrc[2U * i3];
/* xc' = (xa-xb+xc-xd)co2 - (ya-yb+yc-yd)(si2) */
pSrc[2U * i1] = (_Float16)r1 * (_Float16)onebyfftLen;
/* yc' = (ya-yb+yc-yd)co2 + (xa-xb+xc-xd)(si2) */
pSrc[(2U * i1) + 1U] = (_Float16)s1 * (_Float16)onebyfftLen;
/* (xa - xc) - (yb-yd) */
r1 = (_Float16)r2 - (_Float16)t1;
/* (xa - xc) + (yb-yd) */
r2 = (_Float16)r2 + (_Float16)t1;
/* (ya - yc) + (xb-xd) */
s1 = (_Float16)s2 + (_Float16)t2;
/* (ya - yc) - (xb-xd) */
s2 = (_Float16)s2 - (_Float16)t2;
/* xb' = (xa+yb-xc-yd)co1 - (ya-xb-yc+xd)(si1) */
pSrc[2U * i2] = (_Float16)r1 * (_Float16)onebyfftLen;
/* yb' = (ya-xb-yc+xd)co1 + (xa+yb-xc-yd)(si1) */
pSrc[(2U * i2) + 1U] = (_Float16)s1 * (_Float16)onebyfftLen;
/* xd' = (xa-yb-xc+yd)co3 - (ya+xb-yc-xd)(si3) */
pSrc[2U * i3] = (_Float16)r2 * (_Float16)onebyfftLen;
/* yd' = (ya+xb-yc-xd)co3 + (xa-yb-xc+yd)(si3) */
pSrc[(2U * i3) + 1U] = (_Float16)s2 * (_Float16)onebyfftLen;
}
#endif /* #if defined (ARM_MATH_DSP) */
}
#endif /* #if defined(ARM_FLOAT16_SUPPORTED) */
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