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97 lines
2.4 KiB
C++
97 lines
2.4 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 16/1/21.
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// Copyright © 2021 Thomas Harte. All rights reserved.
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//
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#include "Executor.hpp"
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#include <cassert>
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using namespace InstructionSet::M50740;
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Executor::Executor() {
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// Cut down the list of all generated performers to those the processor actually uses, and install that
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// for future referencing by action_for.
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Decoder decoder;
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for(size_t c = 0; c < 256; c++) {
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const auto instruction = decoder.instrucion_for_opcode(uint8_t(c));
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performers_[c] = performer_lookup_.performer(instruction.operation, instruction.addressing_mode);
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}
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}
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template <Operation operation, AddressingMode addressing_mode> void Executor::perform() {
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// Deal with all modes that don't access memory up here;
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// those that access memory will go through a slightly longer
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// sequence below that wraps the address and checks whether
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// a write is valid [if required].
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int address;
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#define next8() memory_[(program_counter_ + 1) & 0x1fff]
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#define next16() (memory_[(program_counter_ + 1) & 0x1fff] | (memory_[(program_counter_ + 2) & 0x1fff] << 8))
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switch(addressing_mode) {
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// Addressing modes with no further memory access.
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case AddressingMode::Implied:
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perform<operation>(nullptr);
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++program_counter_;
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return;
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case AddressingMode::Accumulator:
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perform<operation>(&a_);
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++program_counter_;
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return;
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case AddressingMode::Immediate:
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perform<operation>(&next8());
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program_counter_ += 2;
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return;
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// Addressing modes with a memory access.
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case AddressingMode::Absolute:
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address = next16();
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program_counter_ += 3;
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break;
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case AddressingMode::AbsoluteX:
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address = next16() + x_;
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program_counter_ += 3;
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break;
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case AddressingMode::AbsoluteY:
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address = next16() + y_;
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program_counter_ += 3;
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break;
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/* TODO: the rest. */
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default:
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assert(false);
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}
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#undef next16
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#undef next8
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assert(access_type(operation) != AccessType::None);
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if constexpr(access_type(operation) == AccessType::Read) {
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perform<operation>(&memory_[address & 0x1fff]);
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return;
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}
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uint8_t value = memory_[address & 0x1fff];
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perform<operation>(&value);
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// TODO: full writing logic here; only the first 96 bytes are RAM,
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// there are also timers and IO ports to handle.
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memory_[address & 0x1fff] = value;
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}
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template <Operation operation> void Executor::perform(uint8_t *operand [[maybe_unused]]) {
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}
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