Michele Riccio
mbed-os 6.10 versione
Diff: cmsis_dsp/TransformFunctions/arm_cfft_radix4_q15.c
- Revision:
- 1:fdd22bb7aa52
- Child:
- 2:da51fb522205
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/cmsis_dsp/TransformFunctions/arm_cfft_radix4_q15.c Wed Nov 28 12:30:09 2012 +0000
@@ -0,0 +1,1896 @@
+/* ----------------------------------------------------------------------
+* Copyright (C) 2010 ARM Limited. All rights reserved.
+*
+* $Date: 15. February 2012
+* $Revision: V1.1.0
+*
+* 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
+*
+* Version 1.1.0 2012/02/15
+* Updated with more optimizations, bug fixes and minor API changes.
+*
+* Version 1.0.10 2011/7/15
+* Big Endian support added and Merged M0 and M3/M4 Source code.
+*
+* Version 1.0.3 2010/11/29
+* Re-organized the CMSIS folders and updated documentation.
+*
+* Version 1.0.2 2010/11/11
+* Documentation updated.
+*
+* Version 1.0.1 2010/10/05
+* Production release and review comments incorporated.
+*
+* Version 1.0.0 2010/09/20
+* Production release and review comments incorporated.
+*
+* Version 0.0.5 2010/04/26
+* incorporated review comments and updated with latest CMSIS layer
+*
+* Version 0.0.3 2010/03/10
+* Initial version
+* -------------------------------------------------------------------- */
+
+#include "arm_math.h"
+
+/**
+ * @ingroup groupTransforms
+ */
+
+/**
+ * @addtogroup Radix4_CFFT_CIFFT
+ * @{
+ */
+
+
+/**
+ * @details
+ * @brief Processing function for the Q15 CFFT/CIFFT.
+ * @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 Radix4_CFFT_CIFFT 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
+
+ /* 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, i1, i2, i3, j, k;
+ q15_t in;
+
+ q15_t *ptr1;
+
+
+
+ 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 */
+ 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 */
+ /* Read ya (real), xa(imag) input */
+ T = _SIMD32_OFFSET(pSrc16 + (2u * i0));
+ in = ((int16_t) (T & 0xFFFF)) >> 2;
+ T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* Read yc (real), xc(imag) input */
+ S = _SIMD32_OFFSET(pSrc16 + (2u * i2));
+ in = ((int16_t) (S & 0xFFFF)) >> 2;
+ S = ((S >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* 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(pSrc16 + (2u * i1));
+ in = ((int16_t) (T & 0xFFFF)) >> 2;
+ T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* Read yd (real), xd(imag) input */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+ in = ((int16_t) (U & 0xFFFF)) >> 2;
+ U = ((U >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* 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(pSrc16 + (2u * i0)) = __SHADD16(R, T);
+
+ /* 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(pSrc16 + (2u * i1));
+ in = ((int16_t) (T & 0xFFFF)) >> 2;
+ T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* writing the butterfly processed i0 + fftLen/4 sample */
+ /* writing output(xc', yc') in little endian format */
+ _SIMD32_OFFSET(pSrc16 + (2u * i1)) =
+ (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* Butterfly calculations */
+ /* U = packed(yd, xd) */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+ in = ((int16_t) (U & 0xFFFF)) >> 2;
+ U = ((U >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* 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(pSrc16 + (2u * i2)) =
+ ((out2) & 0xFFFF0000) | ((out1) & 0x0000FFFF);
+
+
+ /* 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(pSrc16 + (2u * i3)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* 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 */
+ 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;
+
+ /* 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 */
+ T = _SIMD32_OFFSET(pSrc16 + (2u * i0));
+
+ /* Read yc (real), xc(imag) input */
+ S = _SIMD32_OFFSET(pSrc16 + (2u * i2));
+
+ /* 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(pSrc16 + (2u * i1));
+
+ /* Read yd (real), xd(imag) input */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+
+ /* 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);
+ in = ((int16_t) (out1 & 0xFFFF)) >> 1;
+ out1 = ((out1 >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+ _SIMD32_OFFSET(pSrc16 + (2u * i0)) = out1;
+
+ /* 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(pSrc16 + (2u * i1));
+
+ /* 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(pSrc16 + (2u * i1)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* Butterfly calculations */
+
+ /* Read yd (real), xd(imag) input */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+
+ /* 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(pSrc16 + (2u * i2)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* 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(pSrc16 + (2u * i3)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+ }
+ }
+ /* 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 = (short) ((Co2 * R0 + Si2 * R1) >> 16u);
+ /* yc' = (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
+ out2 = (short) ((-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 = (short) __SSAT((q31_t) (S0 - T1), 16);
+ R1 = (short) __SSAT((q31_t) (S1 + T0), 16);
+
+ /* S1 = (ya-yc) - (xb- xd), S0 = (xa-xc) + (yb-yd)) */
+ S0 = (short) __SSAT(((q31_t) S0 + T1), 16u);
+ S1 = (short) __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 = (short) ((Si1 * S1 + Co1 * S0) >> 16);
+ /* yb' = (ya-xb-yc+xd)* co1 - (xa+yb-xc-yd)* (si1) */
+ out2 = (short) ((-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 = (short) ((Si3 * R1 + Co3 * R0) >> 16u);
+ /* yd' = (ya+xb-yc-xd)* Co3 - (xa-yb-xc+yd)* (si3) */
+ out2 = (short) ((-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 = (short) ((Co2 * R0 + Si2 * R1) >> 16u);
+
+ /* (ya-yb+yc-yd)* co2 - (xa-xb+xc-xd)* (si2) */
+ out2 = (short) ((-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 = (short) ((Co1 * S0 + Si1 * S1) >> 16u);
+
+ out2 = (short) ((-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 = (short) ((Si3 * R1 + Co3 * R0) >> 16u);
+
+ out2 = (short) ((-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 */
+
+}
+
+
+/**
+ * @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
+
+ /* 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, i1, i2, i3, j, k;
+ q15_t in;
+
+ q15_t *ptr1;
+
+
+
+ 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 */
+ 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 */
+ /* Read ya (real), xa(imag) input */
+ T = _SIMD32_OFFSET(pSrc16 + (2u * i0));
+ in = ((int16_t) (T & 0xFFFF)) >> 2;
+ T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* Read yc (real), xc(imag) input */
+ S = _SIMD32_OFFSET(pSrc16 + (2u * i2));
+ in = ((int16_t) (S & 0xFFFF)) >> 2;
+ S = ((S >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* 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(pSrc16 + (2u * i1));
+ in = ((int16_t) (T & 0xFFFF)) >> 2;
+ T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* Read yd (real), xd(imag) input */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+ in = ((int16_t) (U & 0xFFFF)) >> 2;
+ U = ((U >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* 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(pSrc16 + (2u * i0)) = __SHADD16(R, T);
+
+ /* 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(pSrc16 + (2u * i1));
+ in = ((int16_t) (T & 0xFFFF)) >> 2;
+ T = ((T >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* writing the butterfly processed i0 + fftLen/4 sample */
+ /* writing output(xc', yc') in little endian format */
+ _SIMD32_OFFSET(pSrc16 + (2u * i1)) =
+ (q31_t) ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* Butterfly calculations */
+ /* U = packed(yd, xd) */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+ in = ((int16_t) (U & 0xFFFF)) >> 2;
+ U = ((U >> 2) & 0xFFFF0000) | (in & 0xFFFF);
+
+ /* 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(pSrc16 + (2u * i2)) =
+ ((out2) & 0xFFFF0000) | ((out1) & 0x0000FFFF);
+
+
+ /* 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(pSrc16 + (2u * i3)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* 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 */
+ 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;
+
+ /* 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 */
+ T = _SIMD32_OFFSET(pSrc16 + (2u * i0));
+
+ /* Read yc (real), xc(imag) input */
+ S = _SIMD32_OFFSET(pSrc16 + (2u * i2));
+
+ /* 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(pSrc16 + (2u * i1));
+
+ /* Read yd (real), xd(imag) input */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+
+ /* 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);
+ in = ((int16_t) (out1 & 0xFFFF)) >> 1;
+ out1 = ((out1 >> 1) & 0xFFFF0000) | (in & 0xFFFF);
+ _SIMD32_OFFSET(pSrc16 + (2u * i0)) = out1;
+
+ /* 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(pSrc16 + (2u * i1));
+
+ /* 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(pSrc16 + (2u * i1)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* Butterfly calculations */
+
+ /* Read yd (real), xd(imag) input */
+ U = _SIMD32_OFFSET(pSrc16 + (2u * i3));
+
+ /* 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(pSrc16 + (2u * i2)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+
+ /* 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(pSrc16 + (2u * i3)) =
+ ((out2) & 0xFFFF0000) | (out1 & 0x0000FFFF);
+ }
+ }
+ /* 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 = (short) ((Co2 * R0 - Si2 * R1) >> 16u);
+ /* yc' = (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */
+ out2 = (short) ((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 = (short) __SSAT((q31_t) (S0 + T1), 16);
+ R1 = (short) __SSAT((q31_t) (S1 - T0), 16);
+ /* S = (ya-yc) + (xb- xd), S1 = (xa-xc) - (yb-yd) */
+ S0 = (short) __SSAT((q31_t) (S0 - T1), 16);
+ S1 = (short) __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 = (short) ((Co1 * S0 - Si1 * S1) >> 16u);
+ /* yb' = (ya+xb-yc-xd)* co1 + (xa-yb-xc+yd)* (si1) */
+ out2 = (short) ((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 = (short) ((Co3 * R0 - Si3 * R1) >> 16u);
+ /* yd' = (ya-xb-yc+xd)* Co3 + (xa+yb-xc-yd)* (si3) */
+ out2 = (short) ((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 = (short) ((Co2 * R0 - Si2 * R1) >> 16);
+ /* (ya-yb+yc-yd)* co2 + (xa-xb+xc-xd)* (si2) */
+ out2 = (short) ((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 = (short) ((Co1 * S0 - Si1 * S1) >> 16u);
+ out2 = (short) ((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 = (short) ((Co3 * R0 - Si3 * R1) >> 16u);
+
+ out2 = (short) ((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 */
+
+}