in lib/cmsis/CMSIS/DSP_Lib/Source/TransformFunctions/arm_cfft_radix4_q15.c [163:1028]
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 */
}