CORDIC_Rotate_APFX/sources/CCordicRotateConstexpr/CCordicRotateConstexpr.hpp

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/*
*
* Copyright 2022 Camille "DrasLorus" Monière.
*
* This file is part of CORDIC_Rotate_APFX.
*
* This program is free software: you can redistribute it and/or modify it under the terms of the GNU
* Lesser General Public License as published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
* even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License along with this program.
* If not, see <https://www.gnu.org/licenses/>.
*
*/
#ifndef C_CORDIC_ROTATE_CONSTEXPR_HPP
#define C_CORDIC_ROTATE_CONSTEXPR_HPP
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#include <climits>
#include <cmath>
#include <cstdint>
#include <cstdlib>
#include <complex>
#include <ap_fixed.h>
#include <ap_int.h>
#include "RomGeneratorConst/RomGeneratorConst.hpp"
namespace rcr = rom_cordic_rotate;
template <unsigned TIn_W, unsigned TIn_I, unsigned Tnb_stages, unsigned Tq, unsigned divider = 2>
class CCordicRotateConstexpr {
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static_assert(TIn_W > 0, "Inputs can't be on zero bits.");
static_assert(Tnb_stages < 8, "7 stages of CORDIC is the maximum supported.");
static_assert(Tnb_stages > 1, "2 stages of CORDIC is the minimum.");
static_assert(rcr::is_pow_2<divider>(), "divider must be a power of 2.");
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public:
// ``` GNU Octave
// kn_values(X) = prod(1 ./ abs(1 + 1j * 2.^ (-(0:X))))
// ```
static constexpr double kn_values[7] = {
0.70710678118655, 0.632455532033680, 0.613571991077900,
0.608833912517750, 0.607648256256170, 0.607351770141300, 0.607277644093530};
static constexpr const CRomGeneratorConst<TIn_W, Tnb_stages, Tq, divider> & rom_cordic {};
static constexpr unsigned In_W = TIn_W;
static constexpr unsigned In_I = TIn_I;
static constexpr unsigned Out_W = In_W + 2;
static constexpr unsigned Out_I = In_I + 2;
static constexpr unsigned nb_stages = Tnb_stages;
static constexpr unsigned kn_i = unsigned(kn_values[nb_stages - 1] * double(1U << 4)); // 4 bits are enough
static constexpr unsigned in_scale_factor = unsigned(1U << (In_W - In_I));
static constexpr unsigned out_scale_factor = unsigned(1U << (Out_W - Out_I));
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static constexpr double rotation = CRomGeneratorConst<TIn_W, Tnb_stages, Tq, divider>::rotation;
static constexpr unsigned addr_length = CRomGeneratorConst<TIn_W, Tnb_stages, Tq, divider>::addr_length;
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static constexpr int64_t scale_cordic(int64_t in) {
return in * kn_i / 16U;
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}
static constexpr double scale_cordic(double in) {
return in * kn_values[nb_stages - 1];
}
#if !defined(__SYNTHESIS__) && defined(SOFTWARE)
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static constexpr std::complex<int64_t> cordic(std::complex<int64_t> x_in,
uint64_t counter) {
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int64_t A = x_in.real();
int64_t B = x_in.imag();
const uint8_t R = rom_cordic.rom[counter];
uint8_t mask = 0x01;
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if ((R & mask) == mask) {
A = -A;
B = -B;
}
for (uint8_t u = 1; u < nb_stages + 1; u++) {
mask = mask << 1;
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const int64_t Ri = (R & mask) == mask ? 1 : -1;
const int64_t I = A + Ri * (B / int64_t(1LU << (u - 1)));
B = B - Ri * (A / int64_t(1LU << (u - 1)));
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A = I;
}
return {(A), (B)};
}
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static constexpr std::complex<double> cordic(std::complex<double> x_in,
uint64_t counter) {
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const std::complex<int64_t> fx_x_in(int64_t(x_in.real() * double(in_scale_factor)),
int64_t(x_in.imag() * double(in_scale_factor)));
const std::complex<int64_t> fx_out = cordic(fx_x_in, counter);
return {scale_cordic(double(fx_out.real())) / double(out_scale_factor), scale_cordic(double(fx_out.imag())) / double(out_scale_factor)};
}
#endif
static ap_int<Out_W> scale_cordic(const ap_int<Out_W> & in) {
const ap_int<Out_W + 4> tmp = in * ap_uint<4>(kn_i);
return ap_int<Out_W>(tmp >> 4);
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}
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static void cordic(const ap_int<In_W> & re_in, const ap_int<In_W> & im_in,
const ap_uint<addr_length> & counter,
ap_int<Out_W> & re_out, ap_int<Out_W> & im_out) {
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const ap_uint<nb_stages + 1> R = rom_cordic.rom[counter];
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ap_int<Out_W> A = bool(R[0]) ? ap_int<In_W>(-re_in) : re_in;
ap_int<Out_W> B = bool(R[0]) ? ap_int<In_W>(-im_in) : im_in;
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for (uint8_t u = 1; u < nb_stages + 1; u++) { // nb_stages stages
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const bool Ri = bool(R[u]);
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// Results in (X / 2^(u - 1)), meaning only the
// Out_W - u LSBs are meaninfull in shifted_X
// Can't use range access since 11111111 (-1) would become 00001111 (15).
// Would be possible if the loop is manually unrolled, to predict bitsize,
// thus directly put 1111 into 4 bits (so still -1).
const ap_int<Out_W> shifted_A = A >> (u - 1); // A(Out_W - 1, u - 1);
const ap_int<Out_W> shifted_B = B >> (u - 1); // B(Out_W - 1, u - 1);
const ap_int<Out_W> arc_step_A
= Ri
? ap_int<Out_W>(-shifted_A)
: shifted_A;
const ap_int<Out_W> arc_step_B
= Ri
? shifted_B
: ap_int<Out_W>(-shifted_B);
const ap_int<Out_W + 1> I = A + arc_step_B;
B = B + arc_step_A;
A = I;
}
re_out = A;
im_out = B;
}
constexpr CCordicRotateConstexpr() = default;
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};
#if 0
template <>
inline void CCordicRotateConstexpr<16, 4, 6, 64>::cordic(
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const ap_int<16> & re_in, const ap_int<16> & im_in,
const ap_uint<8> & counter,
ap_int<Out_W> & re_out, ap_int<Out_W> & im_out) const {
const ap_uint<6 + 1> R = (rom_cordic.rom[counter.to_uint()] >> (7 - 6));
ap_int<Out_W> A = bool(R[6]) ? ap_int<16>(-re_in) : re_in;
ap_int<Out_W> B = bool(R[6]) ? ap_int<16>(-im_in) : im_in;
for (uint8_t u = 1; u < 6 + 1; u++) { // 6 stages
const bool Ri = bool(R[6 - u]);
// Results in (X / 2^(u - 1)), meaning only the
// Out_W - u LSBs are meaninfull in shifted_X
// Can't use range access since 11111111 (-1) would become 00001111 (15).
// Would be possible if the loop is manually unrolled, to predict bitsize,
// thus directly put 1111 into 4 bits (so still -1).
const ap_int<Out_W> shifted_A = A >> (u - 1); // A(Out_W - 1, u - 1);
const ap_int<Out_W> shifted_B = B >> (u - 1); // B(Out_W - 1, u - 1);
const ap_int<Out_W> arc_step_A
= Ri
? ap_int<Out_W>(-shifted_A)
: shifted_A;
const ap_int<Out_W> arc_step_B
= Ri
? shifted_B
: ap_int<Out_W>(-shifted_B);
const auto I = A + arc_step_B;
B = B + arc_step_A;
A = I;
}
re_out = A;
im_out = B;
}
#endif
#endif // C_CORDIC_ROTATE_CONSTEXPR_HPP