YM2413NukeYKT.hh

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/*
* Original copyright:
* -------------------------------------------------------------------
*    Copyright (C) 2019 Nuke.YKT
*
*    This program is free software; you can redistribute it and/or
*    modify it under the terms of the GNU General Public License
*    as published by the Free Software Foundation; either version 2
*    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 General Public License for more details.
*
*
*     Yamaha YM2413 emulator
*     Thanks:
*         siliconpr0n.org(digshadow, John McMaster):
*             VRC VII decap and die shot.
*
*     version: 0.9
* -------------------------------------------------------------------
*
* Heavily modified by Wouter Vermaelen for use in openMSX.
*
* The most important changes are:
* - Adapt to the openMSX API (the 'YM2413Core' base-class).
* - The original NukeYKT code is probably close to how the real hardware is
*   implemented, this is very useful while reverse engineering the YM2413. For
*   example it faithfully implements the YM2413 'pipeline' (how the sound
*   generation suboperations are spread over time). Though, for use in openMSX,
*   we're only interested in the final result. So as long as the generated
*   sound remains 100% identical, we're free to transform the code to a form
*   that's more suited for an efficient software implementation. Of course
*   large parts of this pipeline remain in the transformed code because it does
*   play an important role in for example the exact timing of when register
*   changes take effect. So all transformations have to be tested very
*   carefully.
* - The current code runs (on average) over 3x faster than the original, while
*   still generating identical output. This was measured/tested on a large set
*   of vgm files.
*  - TODO document better what kind of transformations were done.
*      * Emulate 18-steps at-a-time.
*      * Specialize for the common case that testmode==0 (but still have slower
*        fallback code).
*      * Move sub-operations in the pipeline (e.g. to eliminate temporary state)
*        when this doesn't have an observable effect.
*      * Lots of small tweak.
*      * ...
*
* TODO:
* - In openMSX the YM2413 is often silent for large periods of time (e.g. maybe
*   the emulated MSX program doesn't use the YM2413). Can we easily detect an
*   idle YM2413 and then bypass large parts of the emulation?
*/
 
#ifndef YM2413NUKEYKT_HH
#define YM2413NUKEYKT_HH
 
#include "YM2413Core.hh"
#include "inline.hh"
#include <array>
 
namespace openmsx::YM2413NukeYKT {
 
class YM2413 final : public YM2413Core
{
public:
        YM2413();
        void reset() override;
        void writePort(bool port, uint8_t value, int cycle_offset) override;
        void pokeReg(uint8_t reg, uint8_t value) override;
        [[nodiscard]] uint8_t peekReg(uint8_t reg) const override;
        void generateChannels(float* out[9 + 5], uint32_t n) override;
        [[nodiscard]] float getAmplificationFactor() const override;
 
        template<typename Archive>
        void serialize(Archive& ar, unsigned version);
 
        enum class EgState : uint8_t {
                attack,
                decay,
                sustain,
                release,
        };
 
private:
        using bool_2    = std::array<bool, 2>;
        using int8_t_2  = std::array<int8_t, 2>;
        using uint8_t_2 = std::array<uint8_t, 2>;
        struct Patch {
                constexpr Patch() = default;
                constexpr Patch(uint8_t tl_, uint8_t dcm_, uint8_t fb_,
                      bool_2 am_, bool_2 vib_, bool_2 et_, bool_2 ksr_, uint8_t_2 multi_,
                      uint8_t_2 ksl_, uint8_t_2 ar_, uint8_t_2 dr_, uint8_t_2 sl_, uint8_t_2 rr_)
                        : dcm(dcm_), vib(vib_), et(et_), sl(sl_) {
                        setTL(tl_);
                        setFB(fb_);
                        setAM(0, am_[0]);
                        setAM(1, am_[1]);
                        setKSR(0, ksr_[0]);
                        setKSR(1, ksr_[1]);
                        setMulti(0, multi_[0]);
                        setMulti(1, multi_[1]);
                        setKSL(0, ksl_[0]);
                        setKSL(1, ksl_[1]);
                        setAR(0, ar_[0]);
                        setAR(1, ar_[1]);
                        setDR(0, dr_[0]);
                        setDR(1, dr_[1]);
                        setRR(0, rr_[0]);
                        setRR(1, rr_[1]);
                }
 
                constexpr void setTL(uint8_t tl) { tl2 = 2 * tl; }
                constexpr void setFB(uint8_t fb) { fb_t = fb ? (8 - fb) : 31; }
                constexpr void setAM(int i, bool am) { am_t[i] = am ? -1 : 0; }
                constexpr void setKSR(int i, bool ksr) { ksr_t[i] = ksr ? 0 : 2; }
                constexpr void setMulti(int i, uint8_t multi) {
                        constexpr uint8_t PG_MULTI[16] = {
                                1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 20, 24, 24, 30, 30
                        };
                        multi_t[i] = PG_MULTI[multi];
                }
                constexpr void setKSL(int i, uint8_t ksl) { ksl_t[i] = ksl ? (3 - ksl) : 31; }
                constexpr void setAR (int i, uint8_t ar)  { ar4[i] = 4 * ar; }
                constexpr void setDR (int i, uint8_t dr)  { dr4[i] = 4 * dr; }
                constexpr void setRR (int i, uint8_t rr)  { rr4[i] = 4 * rr; }
 
                uint8_t   tl2 = 0; // multiplied by 2
                uint8_t   dcm = 0;
                uint8_t   fb_t = 31; // 0->31, 1->7, 2->6, .., 6->2, 7->1
                int8_t_2  am_t = {0, 0}; // false->0, true->-1
                bool_2    vib = {false, false};
                bool_2    et  = {false, false};
                uint8_t_2 ksr_t = {2, 2}; // 0->2, 1->0
                uint8_t_2 multi_t = {1, 1}; // transformed via PG_MULTI[]
                uint8_t_2 ksl_t = {31, 31}; // 0->31, 1->2, 2->1, 3->0
                uint8_t_2 ar4 = {0, 0}; // multiplied by 4
                uint8_t_2 dr4 = {0, 0}; // multiplied by 4
                uint8_t_2 sl  = {0, 0};
                uint8_t_2 rr4 = {0, 0}; // multiplied by 4
        };
        struct Locals {
                float** out;
                uint8_t rm_hh_bits;
                bool use_rm_patches;
                bool lfo_am_car;
                bool eg_timer_carry;
        };
        struct Write {
                uint8_t port;
                uint8_t value;
 
                template<typename Archive>
                void serialize(Archive& ar, unsigned version);
        };
 
private:
        template<bool TEST_MODE> NEVER_INLINE void step18(float* out[9 + 5]);
        template<uint32_t CYCLES, bool TEST_MODE> ALWAYS_INLINE void step(Locals& l);
 
        template<uint32_t CYCLES>                 ALWAYS_INLINE uint32_t phaseCalcIncrement(const Patch& patch1) const;
        template<uint32_t CYCLES>                 ALWAYS_INLINE void channelOutput(float* out[9 + 5], int32_t ch_out);
        template<uint32_t CYCLES>                 ALWAYS_INLINE const Patch& preparePatch1(bool use_rm_patches) const;
        template<uint32_t CYCLES, bool TEST_MODE> ALWAYS_INLINE uint32_t getPhase(uint8_t& rm_hh_bits);
        template<uint32_t CYCLES>                 ALWAYS_INLINE bool keyOnEvent() const;
        template<uint32_t CYCLES, bool TEST_MODE> ALWAYS_INLINE void incrementPhase(uint32_t phase_incr, bool prev_rhythm);
        template<uint32_t CYCLES>                 ALWAYS_INLINE uint32_t getPhaseMod(uint8_t fb_t);
        template<uint32_t CYCLES>                 ALWAYS_INLINE void doOperator(float* out[9 + 5], bool eg_silent);
        template<uint32_t CYCLES, bool TEST_MODE> ALWAYS_INLINE uint8_t envelopeOutput(uint32_t ksltl, int8_t am_t) const;
        template<uint32_t CYCLES>                 ALWAYS_INLINE uint32_t envelopeKSLTL(const Patch& patch1, bool use_rm_patches) const;
        template<uint32_t CYCLES>                 ALWAYS_INLINE void envelopeTimer1();
        template<uint32_t CYCLES, bool TEST_MODE> ALWAYS_INLINE void envelopeTimer2(bool& eg_timer_carry);
        template<uint32_t CYCLES>                 ALWAYS_INLINE bool envelopeGenerate1();
        template<uint32_t CYCLES>                 ALWAYS_INLINE void envelopeGenerate2(const Patch& patch1, bool use_rm_patches);
        template<uint32_t CYCLES, bool TEST_MODE> ALWAYS_INLINE void doLFO(bool& lfo_am_car);
        template<uint32_t CYCLES, bool TEST_MODE> ALWAYS_INLINE void doRhythm();
        template<uint32_t CYCLES>                 ALWAYS_INLINE void doRegWrite();
        template<uint32_t CYCLES>                 ALWAYS_INLINE void doIO();
 
        NEVER_INLINE void doRegWrite(uint32_t channel);
                     void doRegWrite(uint8_t block, uint8_t channel, uint8_t data);
        NEVER_INLINE void doIO(uint32_t cycles_plus_1, Write& write);
 
        void doModeWrite(uint8_t address, uint8_t value);
        void changeFnumBlock(uint32_t ch);
 
private:
        static const Patch m_patches[15];
        static const Patch r_patches[ 6];
 
        // IO
        Write writes[18];
        uint8_t write_data;
        uint8_t fm_data;
        uint8_t write_address;
        uint8_t write_fm_cycle;
        bool fast_fm_rewrite;
        bool test_mode_active;
 
        // Envelope generator
        const uint8_t* attackPtr;  // redundant: calculate from eg_timer_shift_lock, eg_timer_lock
        const uint8_t* releasePtr; // redundant: calculate from eg_timer_shift_lock, eg_timer_lock, eg_counter_state
        uint32_t eg_timer;
        uint8_t eg_sl[2];
        uint8_t eg_out[2];
        uint8_t eg_counter_state; // 0..3
        uint8_t eg_timer_shift;
        uint8_t eg_timer_shift_lock;
        uint8_t eg_timer_lock;
        EgState eg_state[18];
        uint8_t eg_level[18];
        uint8_t eg_rate[2];
        bool eg_dokon[18];
        bool eg_kon[2];
        bool eg_off[2];
        bool eg_timer_shift_stop;
 
        // Phase generator
        uint32_t pg_phase[18];
 
        // Operator
        int16_t op_fb1[9];
        int16_t op_fb2[9];
        int16_t op_mod;
        uint16_t op_phase[2];
 
        // LFO
        uint16_t lfo_counter;
        uint16_t lfo_am_counter;
        uint8_t lfo_vib_counter;
        int8_t lfo_vib; // redundant: equal to VIB_TAB[lfo_vib_counter]
        uint8_t lfo_am_out;
        bool lfo_am_step;
        bool lfo_am_dir;
 
        // Register set
        uint16_t fnum[9];
        uint8_t block[9];
        uint8_t p_ksl[9];      // redundant: calculate from fnum[] and block[]
        uint16_t p_incr[9];    // redundant: calculate from fnum[] and block[]
        uint8_t p_ksr_freq[9]; // redundant: calculate from fnum[] and block[]
        uint8_t sk_on[9];
        uint8_t vol8[9]; // multiplied by 8
        uint8_t inst[9];
        const Patch* p_inst[9]; // redundant: &patches[inst[]]
        uint8_t rhythm;
        uint8_t testmode;
        Patch patches[1 + 15]; // user patch (modifyable) + 15 ROM patches
        uint8_t c_dcm[3];
 
        // Rhythm mode
        uint32_t rm_noise;
        uint8_t rm_tc_bits;
 
        int delay6;
        int delay7;
        int delay10;
        int delay11;
        int delay12;
 
        // only used for peekReg();
        uint8_t regs[64];
        uint8_t latch;
 
        int allowed_offset = 0; // Hack: see comments in writePort()
};
 
} // namespace openmsx::NukeYKT
 
#endif