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167 lines
5.7 KiB
C++
167 lines
5.7 KiB
C++
//
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// Executor.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 29/04/2022.
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// Copyright © 2022 Thomas Harte. All rights reserved.
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//
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#pragma once
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#include "Decoder.hpp"
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#include "Instruction.hpp"
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#include "Model.hpp"
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#include "Perform.hpp"
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#include "RegisterSet.hpp"
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#include "Status.hpp"
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namespace InstructionSet::M68k {
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/// Maps the 68k function codes such that bits 0, 1 and 2 represent
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/// FC0, FC1 and FC2 respectively.
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enum class FunctionCode {
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UserData = 0b001,
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UserProgram = 0b010,
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SupervisorData = 0b101,
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SupervisorProgram = 0b110,
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InterruptAcknowledge = 0b111,
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};
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/// The Executor is templated on a class that implements bus handling as defined below;
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/// the bus handler is responsible for all reads and writes, and will also receive resets and
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/// interrupt acknowledgements.
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///
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/// The executor will provide 32-bit addresses and act as if it had a 32-bit data bus, even
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/// if interpretting the original 68000 instruction set.
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struct BusHandler {
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/// Write @c value of type/size @c IntT to @c address with the processor signalling
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/// a FunctionCode of @c function. @c IntT will be one of @c uint8_t, @c uint16_t
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/// or @c uint32_t.
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template <typename IntT> void write(uint32_t address, IntT value, FunctionCode function);
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/// Read and return a value of type/size @c IntT from @c address with the processor signalling
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/// a FunctionCode of @c function. @c IntT will be one of @c uint8_t, @c uint16_t
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/// or @c uint32_t.
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template <typename IntT> IntT read(uint32_t address, FunctionCode function);
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/// React to the processor programmatically strobing its RESET output.
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void reset();
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/// Respond to an interrupt acknowledgement at @c interrupt_level from the processor.
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/// Should return @c -1 in order to trigger autovectoring, or the appropriate exception vector
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/// number otherwise.
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///
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/// It is undefined behaviour to return a number greater than 255.
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int acknowlege_interrupt(int interrupt_level);
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};
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/// Ties together the decoder, sequencer and performer to provide an executor for 680x0 instruction streams.
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/// As is standard for these executors, no bus- or cache-level fidelity to any real 680x0 is attempted. This is
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/// simply an executor of 680x0 code.
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template <Model model, typename BusHandler> class Executor {
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public:
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Executor(BusHandler &);
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/// Reset the processor, back to a state as if just externally reset.
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void reset();
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/// Executes the number of instructions specified;
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/// other events — such as initial reset or branching
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/// to exceptions — may be zero costed, and interrupts
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/// will not necessarily take effect immediately when signalled.
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void run_for_instructions(int);
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/// Call this at any time to interrupt processing with a bus error;
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/// the function code and address must be provided. Internally
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/// this will raise a C++ exception, and therefore doesn't return.
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[[noreturn]] void signal_bus_error(FunctionCode, uint32_t address);
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/// Sets the current input interrupt level.
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void set_interrupt_level(int);
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// State for the executor is just the register set.
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RegisterSet get_state();
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void set_state(const RegisterSet &);
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private:
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class State: public NullFlowController {
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public:
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State(BusHandler &handler) : bus_handler_(handler) {}
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void run(int &);
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bool stopped = false;
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void read(DataSize size, uint32_t address, CPU::SlicedInt32 &value);
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void write(DataSize size, uint32_t address, CPU::SlicedInt32 value);
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template <typename IntT> IntT read(uint32_t address, bool is_from_pc = false);
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template <typename IntT> void write(uint32_t address, IntT value);
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template <typename IntT> IntT read_pc();
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// Processor state.
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Status status;
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CPU::SlicedInt32 program_counter;
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CPU::SlicedInt32 registers[16]; // D0–D7 followed by A0–A7.
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CPU::SlicedInt32 stack_pointers[2];
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uint32_t instruction_address;
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uint16_t instruction_opcode;
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// Things that are ephemerally duplicative of Status.
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int active_stack_pointer = 0;
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Status::FlagT should_trace = 0;
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// Bus state.
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int interrupt_input = 0;
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// A lookup table to ensure that A7 is adjusted by 2 rather than 1 in
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// postincrement and predecrement mode.
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static constexpr uint32_t byte_increments[] = {
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1, 1, 1, 1, 1, 1, 1, 2
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};
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// Flow control; Cf. Perform.hpp.
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template <bool use_current_instruction_pc = true> void raise_exception(int);
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void did_update_status();
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template <typename IntT> void complete_bcc(bool matched_condition, IntT offset);
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void complete_dbcc(bool matched_condition, bool overflowed, int16_t offset);
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void bsr(uint32_t offset);
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void jmp(uint32_t);
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void jsr(uint32_t offset);
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void rtr();
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void rts();
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void rte();
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void stop();
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void reset();
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void link(Preinstruction instruction, uint32_t offset);
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void unlink(uint32_t &address);
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void pea(uint32_t address);
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void move_to_usp(uint32_t address);
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void move_from_usp(uint32_t &address);
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template <typename IntT> void movep(Preinstruction instruction, uint32_t source, uint32_t dest);
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template <typename IntT> void movem_toM(Preinstruction instruction, uint32_t source, uint32_t dest);
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template <typename IntT> void movem_toR(Preinstruction instruction, uint32_t source, uint32_t dest);
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void tas(Preinstruction instruction, uint32_t address);
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private:
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BusHandler &bus_handler_;
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Predecoder<model> decoder_;
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struct EffectiveAddress {
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CPU::SlicedInt32 value;
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bool requires_fetch;
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};
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EffectiveAddress calculate_effective_address(Preinstruction instruction, uint16_t opcode, int index);
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uint32_t index_8bitdisplacement(uint32_t);
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} state_;
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};
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}
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#include "Implementation/ExecutorImplementation.hpp"
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