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pigweed / third_party / github / STMicroelectronics / cmsis_core / 7dd288b23bf605a3a2fafa81a29d2c96a2fd83ce / . / DSP_Lib / Source / TransformFunctions / arm_cfft_radix4_q15.c
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/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date: 19. March 2015
* $Revision: V.1.4.5
*
* Project: CMSIS DSP Library
* Title: arm_cfft_radix4_q15.c
*
* Description: This file has function definition of Radix-4 FFT & IFFT function and
* In-place bit reversal using bit reversal table
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* - Neither the name of ARM LIMITED nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */
#include "arm_math.h"
void arm_radix4_butterfly_q15(
q15_t * pSrc16,
uint32_t fftLen,
q15_t * pCoef16,
uint32_t twidCoefModifier);
void arm_radix4_butterfly_inverse_q15(
q15_t * pSrc16,
uint32_t fftLen,
q15_t * pCoef16,
uint32_t twidCoefModifier);
void arm_bitreversal_q15(
q15_t * pSrc,
uint32_t fftLen,
uint16_t bitRevFactor,
uint16_t * pBitRevTab);
/**
* @ingroup groupTransforms
*/
/**
* @addtogroup ComplexFFT
* @{
*/
/**
* @details
* @brief Processing function for the Q15 CFFT/CIFFT.
* @deprecated Do not use this function. It has been superseded by \ref arm_cfft_q15 and will be removed
* @param[in] *S points to an instance of the Q15 CFFT/CIFFT structure.
* @param[in, out] *pSrc points to the complex data buffer. Processing occurs in-place.
* @return none.
*
* \par Input and output formats:
* \par
* Internally input is downscaled by 2 for every stage to avoid saturations inside CFFT/CIFFT process.
* Hence the output format is different for different FFT sizes.
* The input and output formats for different FFT sizes and number of bits to upscale are mentioned in the tables below for CFFT and CIFFT:
* \par
* \image html CFFTQ15.gif "Input and Output Formats for Q15 CFFT"
* \image html CIFFTQ15.gif "Input and Output Formats for Q15 CIFFT"
*/
void arm_cfft_radix4_q15(
const arm_cfft_radix4_instance_q15 * S,
q15_t * pSrc)
{
if(S->ifftFlag == 1u)
{
/* Complex IFFT radix-4 */
arm_radix4_butterfly_inverse_q15(pSrc, S->fftLen, S->pTwiddle,
S->twidCoefModifier);
}
else
{
/* Complex FFT radix-4 */
arm_radix4_butterfly_q15(pSrc, S->fftLen, S->pTwiddle,
S->twidCoefModifier);
}
if(S->bitReverseFlag == 1u)
{
/* Bit Reversal */
arm_bitreversal_q15(pSrc, S->fftLen, S->bitRevFactor, S->pBitRevTable);
}
}
/**
* @} end of ComplexFFT group
*/
/*
* Radix-4 FFT algorithm used is :
*
* Input real and imaginary data:
* x(n) = xa + j * ya
* x(n+N/4 ) = xb + j * yb
* x(n+N/2 ) = xc + j * yc
* x(n+3N 4) = xd + j * yd
*
*
* Output real and imaginary data:
* x(4r) = xa'+ j * ya'
* x(4r+1) = xb'+ j * yb'
* x(4r+2) = xc'+ j * yc'
* x(4r+3) = xd'+ j * yd'
*
*
* Twiddle factors for radix-4 FFT:
* Wn = co1 + j * (- si1)
* W2n = co2 + j * (- si2)
* W3n = co3 + j * (- si3)
* The real and imaginary output values for the radix-4 butterfly are
* xa' = xa + xb + xc + xd
* ya' = ya + yb + yc + yd
* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1)
* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1)
* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2)
* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2)
* xd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3)
* yd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3)
*
*/
/**
* @brief Core function for the Q15 CFFT butterfly process.
* @param[in, out] *pSrc16 points to the in-place buffer of Q15 data type.
* @param[in] fftLen length of the FFT.
* @param[in] *pCoef16 points to 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_q15(
q15_t * pSrc16,
uint32_t fftLen,
q15_t * pCoef16,
uint32_t twidCoefModifier)
{
#ifndef ARM_MATH_CM0_FAMILY
/* Run the below code for Cortex-M4 and Cortex-M3 */
q31_t R, S, T, U;
q31_t C1, C2, C3, out1, out2;
uint32_t n1, n2, ic, i0, j, k;
q15_t *ptr1;
q15_t *pSi0;
q15_t *pSi1;
q15_t *pSi2;
q15_t *pSi3;
q31_t xaya, xbyb, xcyc, xdyd;
/* Total process is divided into three stages */
/* process first stage, middle stages, & last stage */
/* Initializations for the first stage */
n2 = fftLen;
n1 = n2;
/* n2 = fftLen/4 */
n2 >>= 2u;
/* Index for twiddle coefficient */
ic = 0u;
/* Index for input read and output write */
j = n2;
pSi0 = pSrc16;
pSi1 = pSi0 + 2 * n2;
pSi2 = pSi1 + 2 * n2;
pSi3 = pSi2 + 2 * n2;
/* Input is in 1.15(q15) format */
/* start of first stage process */
do
{
/* Butterfly implementation */
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T = _SIMD32_OFFSET(pSi0);
T = __SHADD16(T, 0); // this is just a SIMD arithmetic shift right by 1
T = __SHADD16(T, 0); // it turns out doing this twice is 2 cycles, the alternative takes 3 cycles
//in = ((int16_t) (T & 0xFFFF)) >> 2; // alternative code that takes 3 cycles
//T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
/* Read yc (real), xc(imag) input */
S = _SIMD32_OFFSET(pSi2);
S = __SHADD16(S, 0);
S = __SHADD16(S, 0);
/* R = packed((ya + yc), (xa + xc) ) */
R = __QADD16(T, S);
/* S = packed((ya - yc), (xa - xc) ) */
S = __QSUB16(T, S);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T = _SIMD32_OFFSET(pSi1);
T = __SHADD16(T, 0);
T = __SHADD16(T, 0);
/* Read yd (real), xd(imag) input */
U = _SIMD32_OFFSET(pSi3);
U = __SHADD16(U, 0);
U = __SHADD16(U, 0);
/* T = packed((yb + yd), (xb + xd) ) */
T = __QADD16(T, U);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
_SIMD32_OFFSET(pSi0) = __SHADD16(R, T);
pSi0 += 2;
/* R = packed((ya + yc) - (yb + yd), (xa + xc)- (xb + xd)) */
R = __QSUB16(R, T);
/* co2 & si2 are read from SIMD Coefficient pointer */
C2 = _SIMD32_OFFSET(pCoef16 + (4u * ic));
#ifndef ARM_MATH_BIG_ENDIAN
/* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
out1 = __SMUAD(C2, R) >> 16u;
/* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out2 = __SMUSDX(C2, R);
#else
/* xc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out1 = __SMUSDX(R, C2) >> 16u;
/* yc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
out2 = __SMUAD(C2, R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Reading i0+fftLen/4 */
/* T = packed(yb, xb) */
T = _SIMD32_OFFSET(pSi1);
T = __SHADD16(T, 0);
T = __SHADD16(T, 0);
/* writing the butterfly processed i0 + fftLen/4 sample */
/* writing output(xc', yc') in little endian format */
_SIMD32_OFFSET(pSi1) =
(q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi1 += 2;
/* Butterfly calculations */
/* U = packed(yd, xd) */
U = _SIMD32_OFFSET(pSi3);
U = __SHADD16(U, 0);
U = __SHADD16(U, 0);
/* T = packed(yb-yd, xb-xd) */
T = __QSUB16(T, U);
#ifndef ARM_MATH_BIG_ENDIAN
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __QASX(S, T);
/* S = packed((ya-yc) - (xb- xd), (xa-xc) + (yb-yd)) */
S = __QSAX(S, T);
#else
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __QSAX(S, T);
/* S = packed((ya-yc) - (xb- xd), (xa-xc) + (yb-yd)) */
S = __QASX(S, T);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* co1 & si1 are read from SIMD Coefficient pointer */
C1 = _SIMD32_OFFSET(pCoef16 + (2u * ic));
/* Butterfly process for the i0+fftLen/2 sample */
#ifndef ARM_MATH_BIG_ENDIAN
/* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
out1 = __SMUAD(C1, S) >> 16u;
/* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
out2 = __SMUSDX(C1, S);
#else
/* xb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
out1 = __SMUSDX(S, C1) >> 16u;
/* yb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
out2 = __SMUAD(C1, S);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* writing output(xb', yb') in little endian format */
_SIMD32_OFFSET(pSi2) =
((out2) & 0xFFFF0000) | ((out1) & 0x0000FFFF);
pSi2 += 2;
/* co3 & si3 are read from SIMD Coefficient pointer */
C3 = _SIMD32_OFFSET(pCoef16 + (6u * ic));
/* Butterfly process for the i0+3fftLen/4 sample */
#ifndef ARM_MATH_BIG_ENDIAN
/* xd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */
out1 = __SMUAD(C3, R) >> 16u;
/* yd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */
out2 = __SMUSDX(C3, R);
#else
/* xd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */
out1 = __SMUSDX(R, C3) >> 16u;
/* yd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */
out2 = __SMUAD(C3, R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* writing output(xd', yd') in little endian format */
_SIMD32_OFFSET(pSi3) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi3 += 2;
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
} while(--j);
/* data is in 4.11(q11) format */
/* end of first stage process */
/* start of middle stage process */
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
/* Calculation of Middle stage */
for (k = fftLen / 4u; k > 4u; k >>= 2u)
{
/* Initializations for the middle stage */
n1 = n2;
n2 >>= 2u;
ic = 0u;
for (j = 0u; j <= (n2 - 1u); j++)
{
/* index calculation for the coefficients */
C1 = _SIMD32_OFFSET(pCoef16 + (2u * ic));
C2 = _SIMD32_OFFSET(pCoef16 + (4u * ic));
C3 = _SIMD32_OFFSET(pCoef16 + (6u * ic));
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
pSi0 = pSrc16 + 2 * j;
pSi1 = pSi0 + 2 * n2;
pSi2 = pSi1 + 2 * n2;
pSi3 = pSi2 + 2 * n2;
/* Butterfly implementation */
for (i0 = j; i0 < fftLen; i0 += n1)
{
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T = _SIMD32_OFFSET(pSi0);
/* Read yc (real), xc(imag) input */
S = _SIMD32_OFFSET(pSi2);
/* R = packed( (ya + yc), (xa + xc)) */
R = __QADD16(T, S);
/* S = packed((ya - yc), (xa - xc)) */
S = __QSUB16(T, S);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T = _SIMD32_OFFSET(pSi1);
/* Read yd (real), xd(imag) input */
U = _SIMD32_OFFSET(pSi3);
/* T = packed( (yb + yd), (xb + xd)) */
T = __QADD16(T, U);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
out1 = __SHADD16(R, T);
out1 = __SHADD16(out1, 0);
_SIMD32_OFFSET(pSi0) = out1;
pSi0 += 2 * n1;
/* R = packed( (ya + yc) - (yb + yd), (xa + xc) - (xb + xd)) */
R = __SHSUB16(R, T);
#ifndef ARM_MATH_BIG_ENDIAN
/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */
out1 = __SMUAD(C2, R) >> 16u;
/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out2 = __SMUSDX(C2, R);
#else
/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out1 = __SMUSDX(R, C2) >> 16u;
/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */
out2 = __SMUAD(C2, R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Reading i0+3fftLen/4 */
/* Read yb (real), xb(imag) input */
T = _SIMD32_OFFSET(pSi1);
/* writing the butterfly processed i0 + fftLen/4 sample */
/* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
/* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
_SIMD32_OFFSET(pSi1) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi1 += 2 * n1;
/* Butterfly calculations */
/* Read yd (real), xd(imag) input */
U = _SIMD32_OFFSET(pSi3);
/* T = packed(yb-yd, xb-xd) */
T = __QSUB16(T, U);
#ifndef ARM_MATH_BIG_ENDIAN
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __SHASX(S, T);
/* S = packed((ya-yc) - (xb- xd), (xa-xc) + (yb-yd)) */
S = __SHSAX(S, T);
/* Butterfly process for the i0+fftLen/2 sample */
out1 = __SMUAD(C1, S) >> 16u;
out2 = __SMUSDX(C1, S);
#else
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __SHSAX(S, T);
/* S = packed((ya-yc) - (xb- xd), (xa-xc) + (yb-yd)) */
S = __SHASX(S, T);
/* Butterfly process for the i0+fftLen/2 sample */
out1 = __SMUSDX(S, C1) >> 16u;
out2 = __SMUAD(C1, S);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
/* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
_SIMD32_OFFSET(pSi2) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi2 += 2 * n1;
/* Butterfly process for the i0+3fftLen/4 sample */
#ifndef ARM_MATH_BIG_ENDIAN
out1 = __SMUAD(C3, R) >> 16u;
out2 = __SMUSDX(C3, R);
#else
out1 = __SMUSDX(R, C3) >> 16u;
out2 = __SMUAD(C3, R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* xd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */
/* yd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */
_SIMD32_OFFSET(pSi3) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi3 += 2 * n1;
}
}
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
}
/* end of middle stage process */
/* data is in 10.6(q6) format for the 1024 point */
/* data is in 8.8(q8) format for the 256 point */
/* data is in 6.10(q10) format for the 64 point */
/* data is in 4.12(q12) format for the 16 point */
/* Initializations for the last stage */
j = fftLen >> 2;
ptr1 = &pSrc16[0];
/* start of last stage process */
/* Butterfly implementation */
do
{
/* Read xa (real), ya(imag) input */
xaya = *__SIMD32(ptr1)++;
/* Read xb (real), yb(imag) input */
xbyb = *__SIMD32(ptr1)++;
/* Read xc (real), yc(imag) input */
xcyc = *__SIMD32(ptr1)++;
/* Read xd (real), yd(imag) input */
xdyd = *__SIMD32(ptr1)++;
/* R = packed((ya + yc), (xa + xc)) */
R = __QADD16(xaya, xcyc);
/* T = packed((yb + yd), (xb + xd)) */
T = __QADD16(xbyb, xdyd);
/* pointer updation for writing */
ptr1 = ptr1 - 8u;
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
*__SIMD32(ptr1)++ = __SHADD16(R, T);
/* T = packed((yb + yd), (xb + xd)) */
T = __QADD16(xbyb, xdyd);
/* xc' = (xa-xb+xc-xd) */
/* yc' = (ya-yb+yc-yd) */
*__SIMD32(ptr1)++ = __SHSUB16(R, T);
/* S = packed((ya - yc), (xa - xc)) */
S = __QSUB16(xaya, xcyc);
/* Read yd (real), xd(imag) input */
/* T = packed( (yb - yd), (xb - xd)) */
U = __QSUB16(xbyb, xdyd);
#ifndef ARM_MATH_BIG_ENDIAN
/* xb' = (xa+yb-xc-yd) */
/* yb' = (ya-xb-yc+xd) */
*__SIMD32(ptr1)++ = __SHSAX(S, U);
/* xd' = (xa-yb-xc+yd) */
/* yd' = (ya+xb-yc-xd) */
*__SIMD32(ptr1)++ = __SHASX(S, U);
#else
/* xb' = (xa+yb-xc-yd) */
/* yb' = (ya-xb-yc+xd) */
*__SIMD32(ptr1)++ = __SHASX(S, U);
/* xd' = (xa-yb-xc+yd) */
/* yd' = (ya+xb-yc-xd) */
*__SIMD32(ptr1)++ = __SHSAX(S, U);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
} while(--j);
/* end of last stage process */
/* output is in 11.5(q5) format for the 1024 point */
/* output is in 9.7(q7) format for the 256 point */
/* output is in 7.9(q9) format for the 64 point */
/* output is in 5.11(q11) format for the 16 point */
#else
/* Run the below code for Cortex-M0 */
q15_t R0, R1, S0, S1, T0, T1, U0, U1;
q15_t Co1, Si1, Co2, Si2, Co3, Si3, out1, out2;
uint32_t n1, n2, ic, i0, i1, i2, i3, j, k;
/* Total process is divided into three stages */
/* process first stage, middle stages, & last stage */
/* Initializations for the first stage */
n2 = fftLen;
n1 = n2;
/* n2 = fftLen/4 */
n2 >>= 2u;
/* Index for twiddle coefficient */
ic = 0u;
/* Index for input read and output write */
i0 = 0u;
j = n2;
/* Input is in 1.15(q15) format */
/* start of first stage process */
do
{
/* Butterfly implementation */
/* index calculation for the input as, */
/* pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Reading i0, i0+fftLen/2 inputs */
/* input is down scale by 4 to avoid overflow */
/* Read ya (real), xa(imag) input */
T0 = pSrc16[i0 * 2u] >> 2u;
T1 = pSrc16[(i0 * 2u) + 1u] >> 2u;
/* input is down scale by 4 to avoid overflow */
/* Read yc (real), xc(imag) input */
S0 = pSrc16[i2 * 2u] >> 2u;
S1 = pSrc16[(i2 * 2u) + 1u] >> 2u;
/* R0 = (ya + yc) */
R0 = __SSAT(T0 + S0, 16u);
/* R1 = (xa + xc) */
R1 = __SSAT(T1 + S1, 16u);
/* S0 = (ya - yc) */
S0 = __SSAT(T0 - S0, 16);
/* S1 = (xa - xc) */
S1 = __SSAT(T1 - S1, 16);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* input is down scale by 4 to avoid overflow */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u] >> 2u;
T1 = pSrc16[(i1 * 2u) + 1u] >> 2u;
/* input is down scale by 4 to avoid overflow */
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u] >> 2u;
U1 = pSrc16[(i3 * 2u) + 1] >> 2u;
/* T0 = (yb + yd) */
T0 = __SSAT(T0 + U0, 16u);
/* T1 = (xb + xd) */
T1 = __SSAT(T1 + U1, 16u);
/* writing the butterfly processed i0 sample */
/* ya' = ya + yb + yc + yd */
/* xa' = xa + xb + xc + xd */
pSrc16[i0 * 2u] = (R0 >> 1u) + (T0 >> 1u);
pSrc16[(i0 * 2u) + 1u] = (R1 >> 1u) + (T1 >> 1u);
/* R0 = (ya + yc) - (yb + yd) */
/* R1 = (xa + xc) - (xb + xd) */
R0 = __SSAT(R0 - T0, 16u);
R1 = __SSAT(R1 - T1, 16u);
/* co2 & si2 are read from Coefficient pointer */
Co2 = pCoef16[2u * ic * 2u];
Si2 = pCoef16[(2u * ic * 2u) + 1];
/* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
out1 = (q15_t) ((Co2 * R0 + Si2 * R1) >> 16u);
/* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out2 = (q15_t) ((-Si2 * R0 + Co2 * R1) >> 16u);
/* Reading i0+fftLen/4 */
/* input is down scale by 4 to avoid overflow */
/* T0 = yb, T1 = xb */
T0 = pSrc16[i1 * 2u] >> 2;
T1 = pSrc16[(i1 * 2u) + 1] >> 2;
/* writing the butterfly processed i0 + fftLen/4 sample */
/* writing output(xc', yc') in little endian format */
pSrc16[i1 * 2u] = out1;
pSrc16[(i1 * 2u) + 1] = out2;
/* Butterfly calculations */
/* input is down scale by 4 to avoid overflow */
/* U0 = yd, U1 = xd */
U0 = pSrc16[i3 * 2u] >> 2;
U1 = pSrc16[(i3 * 2u) + 1] >> 2;
/* T0 = yb-yd */
T0 = __SSAT(T0 - U0, 16);
/* T1 = xb-xd */
T1 = __SSAT(T1 - U1, 16);
/* R1 = (ya-yc) + (xb- xd), R0 = (xa-xc) - (yb-yd)) */
R0 = (q15_t) __SSAT((q31_t) (S0 - T1), 16);
R1 = (q15_t) __SSAT((q31_t) (S1 + T0), 16);
/* S1 = (ya-yc) - (xb- xd), S0 = (xa-xc) + (yb-yd)) */
S0 = (q15_t) __SSAT(((q31_t) S0 + T1), 16u);
S1 = (q15_t) __SSAT(((q31_t) S1 - T0), 16u);
/* co1 & si1 are read from Coefficient pointer */
Co1 = pCoef16[ic * 2u];
Si1 = pCoef16[(ic * 2u) + 1];
/* Butterfly process for the i0+fftLen/2 sample */
/* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
out1 = (q15_t) ((Si1 * S1 + Co1 * S0) >> 16);
/* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
out2 = (q15_t) ((-Si1 * S0 + Co1 * S1) >> 16);
/* writing output(xb', yb') in little endian format */
pSrc16[i2 * 2u] = out1;
pSrc16[(i2 * 2u) + 1] = out2;
/* Co3 & si3 are read from Coefficient pointer */
Co3 = pCoef16[3u * (ic * 2u)];
Si3 = pCoef16[(3u * (ic * 2u)) + 1];
/* Butterfly process for the i0+3fftLen/4 sample */
/* xd' = (xa-yb-xc+yd)* Co3 + (ya+xb-yc-xd)* (si3) */
out1 = (q15_t) ((Si3 * R1 + Co3 * R0) >> 16u);
/* yd' = (ya+xb-yc-xd)* Co3 - (xa-yb-xc+yd)* (si3) */
out2 = (q15_t) ((-Si3 * R0 + Co3 * R1) >> 16u);
/* writing output(xd', yd') in little endian format */
pSrc16[i3 * 2u] = out1;
pSrc16[(i3 * 2u) + 1] = out2;
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
/* Updating input index */
i0 = i0 + 1u;
} while(--j);
/* data is in 4.11(q11) format */
/* end of first stage process */
/* start of middle stage process */
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
/* Calculation of Middle stage */
for (k = fftLen / 4u; k > 4u; k >>= 2u)
{
/* Initializations for the middle stage */
n1 = n2;
n2 >>= 2u;
ic = 0u;
for (j = 0u; j <= (n2 - 1u); j++)
{
/* index calculation for the coefficients */
Co1 = pCoef16[ic * 2u];
Si1 = pCoef16[(ic * 2u) + 1u];
Co2 = pCoef16[2u * (ic * 2u)];
Si2 = pCoef16[(2u * (ic * 2u)) + 1u];
Co3 = pCoef16[3u * (ic * 2u)];
Si3 = pCoef16[(3u * (ic * 2u)) + 1u];
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
/* Butterfly implementation */
for (i0 = j; i0 < fftLen; i0 += n1)
{
/* index calculation for the input as, */
/* pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T0 = pSrc16[i0 * 2u];
T1 = pSrc16[(i0 * 2u) + 1u];
/* Read yc (real), xc(imag) input */
S0 = pSrc16[i2 * 2u];
S1 = pSrc16[(i2 * 2u) + 1u];
/* R0 = (ya + yc), R1 = (xa + xc) */
R0 = __SSAT(T0 + S0, 16);
R1 = __SSAT(T1 + S1, 16);
/* S0 = (ya - yc), S1 =(xa - xc) */
S0 = __SSAT(T0 - S0, 16);
S1 = __SSAT(T1 - S1, 16);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = (yb + yd), T1 = (xb + xd) */
T0 = __SSAT(T0 + U0, 16);
T1 = __SSAT(T1 + U1, 16);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
out1 = ((R0 >> 1u) + (T0 >> 1u)) >> 1u;
out2 = ((R1 >> 1u) + (T1 >> 1u)) >> 1u;
pSrc16[i0 * 2u] = out1;
pSrc16[(2u * i0) + 1u] = out2;
/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */
R0 = (R0 >> 1u) - (T0 >> 1u);
R1 = (R1 >> 1u) - (T1 >> 1u);
/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */
out1 = (q15_t) ((Co2 * R0 + Si2 * R1) >> 16u);
/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out2 = (q15_t) ((-Si2 * R0 + Co2 * R1) >> 16u);
/* Reading i0+3fftLen/4 */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* writing the butterfly processed i0 + fftLen/4 sample */
/* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
/* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
pSrc16[i1 * 2u] = out1;
pSrc16[(i1 * 2u) + 1u] = out2;
/* Butterfly calculations */
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = yb-yd, T1 = xb-xd */
T0 = __SSAT(T0 - U0, 16);
T1 = __SSAT(T1 - U1, 16);
/* R0 = (ya-yc) + (xb- xd), R1 = (xa-xc) - (yb-yd)) */
R0 = (S0 >> 1u) - (T1 >> 1u);
R1 = (S1 >> 1u) + (T0 >> 1u);
/* S0 = (ya-yc) - (xb- xd), S1 = (xa-xc) + (yb-yd)) */
S0 = (S0 >> 1u) + (T1 >> 1u);
S1 = (S1 >> 1u) - (T0 >> 1u);
/* Butterfly process for the i0+fftLen/2 sample */
out1 = (q15_t) ((Co1 * S0 + Si1 * S1) >> 16u);
out2 = (q15_t) ((-Si1 * S0 + Co1 * S1) >> 16u);
/* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
/* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
pSrc16[i2 * 2u] = out1;
pSrc16[(i2 * 2u) + 1u] = out2;
/* Butterfly process for the i0+3fftLen/4 sample */
out1 = (q15_t) ((Si3 * R1 + Co3 * R0) >> 16u);
out2 = (q15_t) ((-Si3 * R0 + Co3 * R1) >> 16u);
/* xd' = (xa-yb-xc+yd)* Co3 + (ya+xb-yc-xd)* (si3) */
/* yd' = (ya+xb-yc-xd)* Co3 - (xa-yb-xc+yd)* (si3) */
pSrc16[i3 * 2u] = out1;
pSrc16[(i3 * 2u) + 1u] = out2;
}
}
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
}
/* end of middle stage process */
/* data is in 10.6(q6) format for the 1024 point */
/* data is in 8.8(q8) format for the 256 point */
/* data is in 6.10(q10) format for the 64 point */
/* data is in 4.12(q12) format for the 16 point */
/* Initializations for the last stage */
n1 = n2;
n2 >>= 2u;
/* start of last stage process */
/* Butterfly implementation */
for (i0 = 0u; i0 <= (fftLen - n1); i0 += n1)
{
/* index calculation for the input as, */
/* pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T0 = pSrc16[i0 * 2u];
T1 = pSrc16[(i0 * 2u) + 1u];
/* Read yc (real), xc(imag) input */
S0 = pSrc16[i2 * 2u];
S1 = pSrc16[(i2 * 2u) + 1u];
/* R0 = (ya + yc), R1 = (xa + xc) */
R0 = __SSAT(T0 + S0, 16u);
R1 = __SSAT(T1 + S1, 16u);
/* S0 = (ya - yc), S1 = (xa - xc) */
S0 = __SSAT(T0 - S0, 16u);
S1 = __SSAT(T1 - S1, 16u);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = (yb + yd), T1 = (xb + xd)) */
T0 = __SSAT(T0 + U0, 16u);
T1 = __SSAT(T1 + U1, 16u);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
pSrc16[i0 * 2u] = (R0 >> 1u) + (T0 >> 1u);
pSrc16[(i0 * 2u) + 1u] = (R1 >> 1u) + (T1 >> 1u);
/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */
R0 = (R0 >> 1u) - (T0 >> 1u);
R1 = (R1 >> 1u) - (T1 >> 1u);
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* writing the butterfly processed i0 + fftLen/4 sample */
/* xc' = (xa-xb+xc-xd) */
/* yc' = (ya-yb+yc-yd) */
pSrc16[i1 * 2u] = R0;
pSrc16[(i1 * 2u) + 1u] = R1;
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = (yb - yd), T1 = (xb - xd) */
T0 = __SSAT(T0 - U0, 16u);
T1 = __SSAT(T1 - U1, 16u);
/* writing the butterfly processed i0 + fftLen/2 sample */
/* xb' = (xa+yb-xc-yd) */
/* yb' = (ya-xb-yc+xd) */
pSrc16[i2 * 2u] = (S0 >> 1u) + (T1 >> 1u);
pSrc16[(i2 * 2u) + 1u] = (S1 >> 1u) - (T0 >> 1u);
/* writing the butterfly processed i0 + 3fftLen/4 sample */
/* xd' = (xa-yb-xc+yd) */
/* yd' = (ya+xb-yc-xd) */
pSrc16[i3 * 2u] = (S0 >> 1u) - (T1 >> 1u);
pSrc16[(i3 * 2u) + 1u] = (S1 >> 1u) + (T0 >> 1u);
}
/* end of last stage process */
/* output is in 11.5(q5) format for the 1024 point */
/* output is in 9.7(q7) format for the 256 point */
/* output is in 7.9(q9) format for the 64 point */
/* output is in 5.11(q11) format for the 16 point */
#endif /* #ifndef ARM_MATH_CM0_FAMILY */
}
/**
* @brief Core function for the Q15 CIFFT butterfly process.
* @param[in, out] *pSrc16 points to the in-place buffer of Q15 data type.
* @param[in] fftLen length of the FFT.
* @param[in] *pCoef16 points to twiddle coefficient buffer.
* @param[in] twidCoefModifier twiddle coefficient modifier that supports different size FFTs with the same twiddle factor table.
* @return none.
*/
/*
* Radix-4 IFFT algorithm used is :
*
* CIFFT uses same twiddle coefficients as CFFT function
* x[k] = x[n] + (j)k * x[n + fftLen/4] + (-1)k * x[n+fftLen/2] + (-j)k * x[n+3*fftLen/4]
*
*
* IFFT is implemented with following changes in equations from FFT
*
* Input real and imaginary data:
* x(n) = xa + j * ya
* x(n+N/4 ) = xb + j * yb
* x(n+N/2 ) = xc + j * yc
* x(n+3N 4) = xd + j * yd
*
*
* Output real and imaginary data:
* x(4r) = xa'+ j * ya'
* x(4r+1) = xb'+ j * yb'
* x(4r+2) = xc'+ j * yc'
* x(4r+3) = xd'+ j * yd'
*
*
* Twiddle factors for radix-4 IFFT:
* Wn = co1 + j * (si1)
* W2n = co2 + j * (si2)
* W3n = co3 + j * (si3)
* The real and imaginary output values for the radix-4 butterfly are
* xa' = xa + xb + xc + xd
* ya' = ya + yb + yc + yd
* xb' = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1)
* yb' = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1)
* xc' = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2)
* yc' = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2)
* xd' = (xa+yb-xc-yd)* co3 - (ya-xb-yc+xd)* (si3)
* yd' = (ya-xb-yc+xd)* co3 + (xa+yb-xc-yd)* (si3)
*
*/
void arm_radix4_butterfly_inverse_q15(
q15_t * pSrc16,
uint32_t fftLen,
q15_t * pCoef16,
uint32_t twidCoefModifier)
{
#ifndef ARM_MATH_CM0_FAMILY
/* Run the below code for Cortex-M4 and Cortex-M3 */
q31_t R, S, T, U;
q31_t C1, C2, C3, out1, out2;
uint32_t n1, n2, ic, i0, j, k;
q15_t *ptr1;
q15_t *pSi0;
q15_t *pSi1;
q15_t *pSi2;
q15_t *pSi3;
q31_t xaya, xbyb, xcyc, xdyd;
/* Total process is divided into three stages */
/* process first stage, middle stages, & last stage */
/* Initializations for the first stage */
n2 = fftLen;
n1 = n2;
/* n2 = fftLen/4 */
n2 >>= 2u;
/* Index for twiddle coefficient */
ic = 0u;
/* Index for input read and output write */
j = n2;
pSi0 = pSrc16;
pSi1 = pSi0 + 2 * n2;
pSi2 = pSi1 + 2 * n2;
pSi3 = pSi2 + 2 * n2;
/* Input is in 1.15(q15) format */
/* start of first stage process */
do
{
/* Butterfly implementation */
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T = _SIMD32_OFFSET(pSi0);
T = __SHADD16(T, 0);
T = __SHADD16(T, 0);
/* Read yc (real), xc(imag) input */
S = _SIMD32_OFFSET(pSi2);
S = __SHADD16(S, 0);
S = __SHADD16(S, 0);
/* R = packed((ya + yc), (xa + xc) ) */
R = __QADD16(T, S);
/* S = packed((ya - yc), (xa - xc) ) */
S = __QSUB16(T, S);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T = _SIMD32_OFFSET(pSi1);
T = __SHADD16(T, 0);
T = __SHADD16(T, 0);
/* Read yd (real), xd(imag) input */
U = _SIMD32_OFFSET(pSi3);
U = __SHADD16(U, 0);
U = __SHADD16(U, 0);
/* T = packed((yb + yd), (xb + xd) ) */
T = __QADD16(T, U);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
_SIMD32_OFFSET(pSi0) = __SHADD16(R, T);
pSi0 += 2;
/* R = packed((ya + yc) - (yb + yd), (xa + xc)- (xb + xd)) */
R = __QSUB16(R, T);
/* co2 & si2 are read from SIMD Coefficient pointer */
C2 = _SIMD32_OFFSET(pCoef16 + (4u * ic));
#ifndef ARM_MATH_BIG_ENDIAN
/* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
out1 = __SMUSD(C2, R) >> 16u;
/* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out2 = __SMUADX(C2, R);
#else
/* xc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out1 = __SMUADX(C2, R) >> 16u;
/* yc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
out2 = __SMUSD(__QSUB16(0, C2), R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Reading i0+fftLen/4 */
/* T = packed(yb, xb) */
T = _SIMD32_OFFSET(pSi1);
T = __SHADD16(T, 0);
T = __SHADD16(T, 0);
/* writing the butterfly processed i0 + fftLen/4 sample */
/* writing output(xc', yc') in little endian format */
_SIMD32_OFFSET(pSi1) =
(q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi1 += 2;
/* Butterfly calculations */
/* U = packed(yd, xd) */
U = _SIMD32_OFFSET(pSi3);
U = __SHADD16(U, 0);
U = __SHADD16(U, 0);
/* T = packed(yb-yd, xb-xd) */
T = __QSUB16(T, U);
#ifndef ARM_MATH_BIG_ENDIAN
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __QSAX(S, T);
/* S = packed((ya-yc) + (xb- xd), (xa-xc) - (yb-yd)) */
S = __QASX(S, T);
#else
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __QASX(S, T);
/* S = packed((ya-yc) - (xb- xd), (xa-xc) + (yb-yd)) */
S = __QSAX(S, T);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* co1 & si1 are read from SIMD Coefficient pointer */
C1 = _SIMD32_OFFSET(pCoef16 + (2u * ic));
/* Butterfly process for the i0+fftLen/2 sample */
#ifndef ARM_MATH_BIG_ENDIAN
/* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
out1 = __SMUSD(C1, S) >> 16u;
/* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
out2 = __SMUADX(C1, S);
#else
/* xb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
out1 = __SMUADX(C1, S) >> 16u;
/* yb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
out2 = __SMUSD(__QSUB16(0, C1), S);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* writing output(xb', yb') in little endian format */
_SIMD32_OFFSET(pSi2) =
((out2) & 0xFFFF0000) | ((out1) & 0x0000FFFF);
pSi2 += 2;
/* co3 & si3 are read from SIMD Coefficient pointer */
C3 = _SIMD32_OFFSET(pCoef16 + (6u * ic));
/* Butterfly process for the i0+3fftLen/4 sample */
#ifndef ARM_MATH_BIG_ENDIAN
/* xd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */
out1 = __SMUSD(C3, R) >> 16u;
/* yd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */
out2 = __SMUADX(C3, R);
#else
/* xd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */
out1 = __SMUADX(C3, R) >> 16u;
/* yd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */
out2 = __SMUSD(__QSUB16(0, C3), R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* writing output(xd', yd') in little endian format */
_SIMD32_OFFSET(pSi3) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi3 += 2;
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
} while(--j);
/* data is in 4.11(q11) format */
/* end of first stage process */
/* start of middle stage process */
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
/* Calculation of Middle stage */
for (k = fftLen / 4u; k > 4u; k >>= 2u)
{
/* Initializations for the middle stage */
n1 = n2;
n2 >>= 2u;
ic = 0u;
for (j = 0u; j <= (n2 - 1u); j++)
{
/* index calculation for the coefficients */
C1 = _SIMD32_OFFSET(pCoef16 + (2u * ic));
C2 = _SIMD32_OFFSET(pCoef16 + (4u * ic));
C3 = _SIMD32_OFFSET(pCoef16 + (6u * ic));
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
pSi0 = pSrc16 + 2 * j;
pSi1 = pSi0 + 2 * n2;
pSi2 = pSi1 + 2 * n2;
pSi3 = pSi2 + 2 * n2;
/* Butterfly implementation */
for (i0 = j; i0 < fftLen; i0 += n1)
{
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T = _SIMD32_OFFSET(pSi0);
/* Read yc (real), xc(imag) input */
S = _SIMD32_OFFSET(pSi2);
/* R = packed( (ya + yc), (xa + xc)) */
R = __QADD16(T, S);
/* S = packed((ya - yc), (xa - xc)) */
S = __QSUB16(T, S);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T = _SIMD32_OFFSET(pSi1);
/* Read yd (real), xd(imag) input */
U = _SIMD32_OFFSET(pSi3);
/* T = packed( (yb + yd), (xb + xd)) */
T = __QADD16(T, U);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
out1 = __SHADD16(R, T);
out1 = __SHADD16(out1, 0);
_SIMD32_OFFSET(pSi0) = out1;
pSi0 += 2 * n1;
/* R = packed( (ya + yc) - (yb + yd), (xa + xc) - (xb + xd)) */
R = __SHSUB16(R, T);
#ifndef ARM_MATH_BIG_ENDIAN
/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */
out1 = __SMUSD(C2, R) >> 16u;
/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out2 = __SMUADX(C2, R);
#else
/* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
out1 = __SMUADX(R, C2) >> 16u;
/* (ya-yb+yc-yd)* (si2) + (xa-xb+xc-xd)* co2 */
out2 = __SMUSD(__QSUB16(0, C2), R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* Reading i0+3fftLen/4 */
/* Read yb (real), xb(imag) input */
T = _SIMD32_OFFSET(pSi1);
/* writing the butterfly processed i0 + fftLen/4 sample */
/* xc' = (xa-xb+xc-xd)* co2 + (ya-yb+yc-yd)* (si2) */
/* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
_SIMD32_OFFSET(pSi1) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi1 += 2 * n1;
/* Butterfly calculations */
/* Read yd (real), xd(imag) input */
U = _SIMD32_OFFSET(pSi3);
/* T = packed(yb-yd, xb-xd) */
T = __QSUB16(T, U);
#ifndef ARM_MATH_BIG_ENDIAN
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __SHSAX(S, T);
/* S = packed((ya-yc) - (xb- xd), (xa-xc) + (yb-yd)) */
S = __SHASX(S, T);
/* Butterfly process for the i0+fftLen/2 sample */
out1 = __SMUSD(C1, S) >> 16u;
out2 = __SMUADX(C1, S);
#else
/* R = packed((ya-yc) + (xb- xd) , (xa-xc) - (yb-yd)) */
R = __SHASX(S, T);
/* S = packed((ya-yc) - (xb- xd), (xa-xc) + (yb-yd)) */
S = __SHSAX(S, T);
/* Butterfly process for the i0+fftLen/2 sample */
out1 = __SMUADX(S, C1) >> 16u;
out2 = __SMUSD(__QSUB16(0, C1), S);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* xb' = (xa+yb-xc-yd)* co1 + (ya-xb-yc+xd)* (si1) */
/* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
_SIMD32_OFFSET(pSi2) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi2 += 2 * n1;
/* Butterfly process for the i0+3fftLen/4 sample */
#ifndef ARM_MATH_BIG_ENDIAN
out1 = __SMUSD(C3, R) >> 16u;
out2 = __SMUADX(C3, R);
#else
out1 = __SMUADX(C3, R) >> 16u;
out2 = __SMUSD(__QSUB16(0, C3), R);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
/* xd' = (xa-yb-xc+yd)* co3 + (ya+xb-yc-xd)* (si3) */
/* yd' = (ya+xb-yc-xd)* co3 - (xa-yb-xc+yd)* (si3) */
_SIMD32_OFFSET(pSi3) =
((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
pSi3 += 2 * n1;
}
}
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
}
/* end of middle stage process */
/* data is in 10.6(q6) format for the 1024 point */
/* data is in 8.8(q8) format for the 256 point */
/* data is in 6.10(q10) format for the 64 point */
/* data is in 4.12(q12) format for the 16 point */
/* Initializations for the last stage */
j = fftLen >> 2;
ptr1 = &pSrc16[0];
/* start of last stage process */
/* Butterfly implementation */
do
{
/* Read xa (real), ya(imag) input */
xaya = *__SIMD32(ptr1)++;
/* Read xb (real), yb(imag) input */
xbyb = *__SIMD32(ptr1)++;
/* Read xc (real), yc(imag) input */
xcyc = *__SIMD32(ptr1)++;
/* Read xd (real), yd(imag) input */
xdyd = *__SIMD32(ptr1)++;
/* R = packed((ya + yc), (xa + xc)) */
R = __QADD16(xaya, xcyc);
/* T = packed((yb + yd), (xb + xd)) */
T = __QADD16(xbyb, xdyd);
/* pointer updation for writing */
ptr1 = ptr1 - 8u;
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
*__SIMD32(ptr1)++ = __SHADD16(R, T);
/* T = packed((yb + yd), (xb + xd)) */
T = __QADD16(xbyb, xdyd);
/* xc' = (xa-xb+xc-xd) */
/* yc' = (ya-yb+yc-yd) */
*__SIMD32(ptr1)++ = __SHSUB16(R, T);
/* S = packed((ya - yc), (xa - xc)) */
S = __QSUB16(xaya, xcyc);
/* Read yd (real), xd(imag) input */
/* T = packed( (yb - yd), (xb - xd)) */
U = __QSUB16(xbyb, xdyd);
#ifndef ARM_MATH_BIG_ENDIAN
/* xb' = (xa+yb-xc-yd) */
/* yb' = (ya-xb-yc+xd) */
*__SIMD32(ptr1)++ = __SHASX(S, U);
/* xd' = (xa-yb-xc+yd) */
/* yd' = (ya+xb-yc-xd) */
*__SIMD32(ptr1)++ = __SHSAX(S, U);
#else
/* xb' = (xa+yb-xc-yd) */
/* yb' = (ya-xb-yc+xd) */
*__SIMD32(ptr1)++ = __SHSAX(S, U);
/* xd' = (xa-yb-xc+yd) */
/* yd' = (ya+xb-yc-xd) */
*__SIMD32(ptr1)++ = __SHASX(S, U);
#endif /* #ifndef ARM_MATH_BIG_ENDIAN */
} while(--j);
/* end of last stage process */
/* output is in 11.5(q5) format for the 1024 point */
/* output is in 9.7(q7) format for the 256 point */
/* output is in 7.9(q9) format for the 64 point */
/* output is in 5.11(q11) format for the 16 point */
#else
/* Run the below code for Cortex-M0 */
q15_t R0, R1, S0, S1, T0, T1, U0, U1;
q15_t Co1, Si1, Co2, Si2, Co3, Si3, out1, out2;
uint32_t n1, n2, ic, i0, i1, i2, i3, j, k;
/* Total process is divided into three stages */
/* process first stage, middle stages, & last stage */
/* Initializations for the first stage */
n2 = fftLen;
n1 = n2;
/* n2 = fftLen/4 */
n2 >>= 2u;
/* Index for twiddle coefficient */
ic = 0u;
/* Index for input read and output write */
i0 = 0u;
j = n2;
/* Input is in 1.15(q15) format */
/* Start of first stage process */
do
{
/* Butterfly implementation */
/* index calculation for the input as, */
/* pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Reading i0, i0+fftLen/2 inputs */
/* input is down scale by 4 to avoid overflow */
/* Read ya (real), xa(imag) input */
T0 = pSrc16[i0 * 2u] >> 2u;
T1 = pSrc16[(i0 * 2u) + 1u] >> 2u;
/* input is down scale by 4 to avoid overflow */
/* Read yc (real), xc(imag) input */
S0 = pSrc16[i2 * 2u] >> 2u;
S1 = pSrc16[(i2 * 2u) + 1u] >> 2u;
/* R0 = (ya + yc), R1 = (xa + xc) */
R0 = __SSAT(T0 + S0, 16u);
R1 = __SSAT(T1 + S1, 16u);
/* S0 = (ya - yc), S1 = (xa - xc) */
S0 = __SSAT(T0 - S0, 16u);
S1 = __SSAT(T1 - S1, 16u);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* input is down scale by 4 to avoid overflow */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u] >> 2u;
T1 = pSrc16[(i1 * 2u) + 1u] >> 2u;
/* Read yd (real), xd(imag) input */
/* input is down scale by 4 to avoid overflow */
U0 = pSrc16[i3 * 2u] >> 2u;
U1 = pSrc16[(i3 * 2u) + 1u] >> 2u;
/* T0 = (yb + yd), T1 = (xb + xd) */
T0 = __SSAT(T0 + U0, 16u);
T1 = __SSAT(T1 + U1, 16u);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
pSrc16[i0 * 2u] = (R0 >> 1u) + (T0 >> 1u);
pSrc16[(i0 * 2u) + 1u] = (R1 >> 1u) + (T1 >> 1u);
/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc)- (xb + xd) */
R0 = __SSAT(R0 - T0, 16u);
R1 = __SSAT(R1 - T1, 16u);
/* co2 & si2 are read from Coefficient pointer */
Co2 = pCoef16[2u * ic * 2u];
Si2 = pCoef16[(2u * ic * 2u) + 1u];
/* xc' = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) */
out1 = (q15_t) ((Co2 * R0 - Si2 * R1) >> 16u);
/* yc' = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */
out2 = (q15_t) ((Si2 * R0 + Co2 * R1) >> 16u);
/* Reading i0+fftLen/4 */
/* input is down scale by 4 to avoid overflow */
/* T0 = yb, T1 = xb */
T0 = pSrc16[i1 * 2u] >> 2u;
T1 = pSrc16[(i1 * 2u) + 1u] >> 2u;
/* writing the butterfly processed i0 + fftLen/4 sample */
/* writing output(xc', yc') in little endian format */
pSrc16[i1 * 2u] = out1;
pSrc16[(i1 * 2u) + 1u] = out2;
/* Butterfly calculations */
/* input is down scale by 4 to avoid overflow */
/* U0 = yd, U1 = xd) */
U0 = pSrc16[i3 * 2u] >> 2u;
U1 = pSrc16[(i3 * 2u) + 1u] >> 2u;
/* T0 = yb-yd, T1 = xb-xd) */
T0 = __SSAT(T0 - U0, 16u);
T1 = __SSAT(T1 - U1, 16u);
/* R0 = (ya-yc) - (xb- xd) , R1 = (xa-xc) + (yb-yd) */
R0 = (q15_t) __SSAT((q31_t) (S0 + T1), 16);
R1 = (q15_t) __SSAT((q31_t) (S1 - T0), 16);
/* S = (ya-yc) + (xb- xd), S1 = (xa-xc) - (yb-yd) */
S0 = (q15_t) __SSAT((q31_t) (S0 - T1), 16);
S1 = (q15_t) __SSAT((q31_t) (S1 + T0), 16);
/* co1 & si1 are read from Coefficient pointer */
Co1 = pCoef16[ic * 2u];
Si1 = pCoef16[(ic * 2u) + 1u];
/* Butterfly process for the i0+fftLen/2 sample */
/* xb' = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) */
out1 = (q15_t) ((Co1 * S0 - Si1 * S1) >> 16u);
/* yb' = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */
out2 = (q15_t) ((Si1 * S0 + Co1 * S1) >> 16u);
/* writing output(xb', yb') in little endian format */
pSrc16[i2 * 2u] = out1;
pSrc16[(i2 * 2u) + 1u] = out2;
/* Co3 & si3 are read from Coefficient pointer */
Co3 = pCoef16[3u * ic * 2u];
Si3 = pCoef16[(3u * ic * 2u) + 1u];
/* Butterfly process for the i0+3fftLen/4 sample */
/* xd' = (xa+yb-xc-yd)* Co3 - (ya-xb-yc+xd)* (si3) */
out1 = (q15_t) ((Co3 * R0 - Si3 * R1) >> 16u);
/* yd' = (ya-xb-yc+xd)* Co3 + (xa+yb-xc-yd)* (si3) */
out2 = (q15_t) ((Si3 * R0 + Co3 * R1) >> 16u);
/* writing output(xd', yd') in little endian format */
pSrc16[i3 * 2u] = out1;
pSrc16[(i3 * 2u) + 1u] = out2;
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
/* Updating input index */
i0 = i0 + 1u;
} while(--j);
/* End of first stage process */
/* data is in 4.11(q11) format */
/* Start of Middle stage process */
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
/* Calculation of Middle stage */
for (k = fftLen / 4u; k > 4u; k >>= 2u)
{
/* Initializations for the middle stage */
n1 = n2;
n2 >>= 2u;
ic = 0u;
for (j = 0u; j <= (n2 - 1u); j++)
{
/* index calculation for the coefficients */
Co1 = pCoef16[ic * 2u];
Si1 = pCoef16[(ic * 2u) + 1u];
Co2 = pCoef16[2u * ic * 2u];
Si2 = pCoef16[2u * ic * 2u + 1u];
Co3 = pCoef16[3u * ic * 2u];
Si3 = pCoef16[(3u * ic * 2u) + 1u];
/* Twiddle coefficients index modifier */
ic = ic + twidCoefModifier;
/* Butterfly implementation */
for (i0 = j; i0 < fftLen; i0 += n1)
{
/* index calculation for the input as, */
/* pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T0 = pSrc16[i0 * 2u];
T1 = pSrc16[(i0 * 2u) + 1u];
/* Read yc (real), xc(imag) input */
S0 = pSrc16[i2 * 2u];
S1 = pSrc16[(i2 * 2u) + 1u];
/* R0 = (ya + yc), R1 = (xa + xc) */
R0 = __SSAT(T0 + S0, 16u);
R1 = __SSAT(T1 + S1, 16u);
/* S0 = (ya - yc), S1 = (xa - xc) */
S0 = __SSAT(T0 - S0, 16u);
S1 = __SSAT(T1 - S1, 16u);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = (yb + yd), T1 = (xb + xd) */
T0 = __SSAT(T0 + U0, 16u);
T1 = __SSAT(T1 + U1, 16u);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
pSrc16[i0 * 2u] = ((R0 >> 1u) + (T0 >> 1u)) >> 1u;
pSrc16[(i0 * 2u) + 1u] = ((R1 >> 1u) + (T1 >> 1u)) >> 1u;
/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */
R0 = (R0 >> 1u) - (T0 >> 1u);
R1 = (R1 >> 1u) - (T1 >> 1u);
/* (ya-yb+yc-yd)* (si2) - (xa-xb+xc-xd)* co2 */
out1 = (q15_t) ((Co2 * R0 - Si2 * R1) >> 16);
/* (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */
out2 = (q15_t) ((Si2 * R0 + Co2 * R1) >> 16);
/* Reading i0+3fftLen/4 */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* writing the butterfly processed i0 + fftLen/4 sample */
/* xc' = (xa-xb+xc-xd)* co2 - (ya-yb+yc-yd)* (si2) */
/* yc' = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */
pSrc16[i1 * 2u] = out1;
pSrc16[(i1 * 2u) + 1u] = out2;
/* Butterfly calculations */
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = yb-yd, T1 = xb-xd) */
T0 = __SSAT(T0 - U0, 16u);
T1 = __SSAT(T1 - U1, 16u);
/* R0 = (ya-yc) - (xb- xd) , R1 = (xa-xc) + (yb-yd) */
R0 = (S0 >> 1u) + (T1 >> 1u);
R1 = (S1 >> 1u) - (T0 >> 1u);
/* S1 = (ya-yc) + (xb- xd), S1 = (xa-xc) - (yb-yd) */
S0 = (S0 >> 1u) - (T1 >> 1u);
S1 = (S1 >> 1u) + (T0 >> 1u);
/* Butterfly process for the i0+fftLen/2 sample */
out1 = (q15_t) ((Co1 * S0 - Si1 * S1) >> 16u);
out2 = (q15_t) ((Si1 * S0 + Co1 * S1) >> 16u);
/* xb' = (xa-yb-xc+yd)* co1 - (ya+xb-yc-xd)* (si1) */
/* yb' = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */
pSrc16[i2 * 2u] = out1;
pSrc16[(i2 * 2u) + 1u] = out2;
/* Butterfly process for the i0+3fftLen/4 sample */
out1 = (q15_t) ((Co3 * R0 - Si3 * R1) >> 16u);
out2 = (q15_t) ((Si3 * R0 + Co3 * R1) >> 16u);
/* xd' = (xa+yb-xc-yd)* Co3 - (ya-xb-yc+xd)* (si3) */
/* yd' = (ya-xb-yc+xd)* Co3 + (xa+yb-xc-yd)* (si3) */
pSrc16[i3 * 2u] = out1;
pSrc16[(i3 * 2u) + 1u] = out2;
}
}
/* Twiddle coefficients index modifier */
twidCoefModifier <<= 2u;
}
/* End of Middle stages process */
/* data is in 10.6(q6) format for the 1024 point */
/* data is in 8.8(q8) format for the 256 point */
/* data is in 6.10(q10) format for the 64 point */
/* data is in 4.12(q12) format for the 16 point */
/* start of last stage process */
/* Initializations for the last stage */
n1 = n2;
n2 >>= 2u;
/* Butterfly implementation */
for (i0 = 0u; i0 <= (fftLen - n1); i0 += n1)
{
/* index calculation for the input as, */
/* pSrc16[i0 + 0], pSrc16[i0 + fftLen/4], pSrc16[i0 + fftLen/2], pSrc16[i0 + 3fftLen/4] */
i1 = i0 + n2;
i2 = i1 + n2;
i3 = i2 + n2;
/* Reading i0, i0+fftLen/2 inputs */
/* Read ya (real), xa(imag) input */
T0 = pSrc16[i0 * 2u];
T1 = pSrc16[(i0 * 2u) + 1u];
/* Read yc (real), xc(imag) input */
S0 = pSrc16[i2 * 2u];
S1 = pSrc16[(i2 * 2u) + 1u];
/* R0 = (ya + yc), R1 = (xa + xc) */
R0 = __SSAT(T0 + S0, 16u);
R1 = __SSAT(T1 + S1, 16u);
/* S0 = (ya - yc), S1 = (xa - xc) */
S0 = __SSAT(T0 - S0, 16u);
S1 = __SSAT(T1 - S1, 16u);
/* Reading i0+fftLen/4 , i0+3fftLen/4 inputs */
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = (yb + yd), T1 = (xb + xd) */
T0 = __SSAT(T0 + U0, 16u);
T1 = __SSAT(T1 + U1, 16u);
/* writing the butterfly processed i0 sample */
/* xa' = xa + xb + xc + xd */
/* ya' = ya + yb + yc + yd */
pSrc16[i0 * 2u] = (R0 >> 1u) + (T0 >> 1u);
pSrc16[(i0 * 2u) + 1u] = (R1 >> 1u) + (T1 >> 1u);
/* R0 = (ya + yc) - (yb + yd), R1 = (xa + xc) - (xb + xd) */
R0 = (R0 >> 1u) - (T0 >> 1u);
R1 = (R1 >> 1u) - (T1 >> 1u);
/* Read yb (real), xb(imag) input */
T0 = pSrc16[i1 * 2u];
T1 = pSrc16[(i1 * 2u) + 1u];
/* writing the butterfly processed i0 + fftLen/4 sample */
/* xc' = (xa-xb+xc-xd) */
/* yc' = (ya-yb+yc-yd) */
pSrc16[i1 * 2u] = R0;
pSrc16[(i1 * 2u) + 1u] = R1;
/* Read yd (real), xd(imag) input */
U0 = pSrc16[i3 * 2u];
U1 = pSrc16[(i3 * 2u) + 1u];
/* T0 = (yb - yd), T1 = (xb - xd) */
T0 = __SSAT(T0 - U0, 16u);
T1 = __SSAT(T1 - U1, 16u);
/* writing the butterfly processed i0 + fftLen/2 sample */
/* xb' = (xa-yb-xc+yd) */
/* yb' = (ya+xb-yc-xd) */
pSrc16[i2 * 2u] = (S0 >> 1u) - (T1 >> 1u);
pSrc16[(i2 * 2u) + 1u] = (S1 >> 1u) + (T0 >> 1u);
/* writing the butterfly processed i0 + 3fftLen/4 sample */
/* xd' = (xa+yb-xc-yd) */
/* yd' = (ya-xb-yc+xd) */
pSrc16[i3 * 2u] = (S0 >> 1u) + (T1 >> 1u);
pSrc16[(i3 * 2u) + 1u] = (S1 >> 1u) - (T0 >> 1u);
}
/* end of last stage process */
/* output is in 11.5(q5) format for the 1024 point */
/* output is in 9.7(q7) format for the 256 point */
/* output is in 7.9(q9) format for the 64 point */
/* output is in 5.11(q11) format for the 16 point */
#endif /* #ifndef ARM_MATH_CM0_FAMILY */
}