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Add basic exceptions.

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This commit is contained in:
Thomas Harte 2022-05-02 21:27:58 -04:00
parent 25ab478461
commit 011506f00d
2 changed files with 45 additions and 6 deletions
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4
InstructionSets/M68k/Executor.hpp
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@ -44,7 +44,8 @@ template <Model model, typename BusHandler> class Executor {
void stop();
void set_pc(uint32_t);
void add_pc(uint32_t);
void decline_branch();
void decline_branch() {}
void did_update_status();
// TODO: ownership of this shouldn't be here.
struct Registers {
@ -79,6 +80,7 @@ template <Model model, typename BusHandler> class Executor {
CPU::SlicedInt32 data_[8], address_[8];
CPU::SlicedInt32 stack_pointers_[2];
uint32_t instruction_address_;
int active_stack_pointer_ = 0;
// A lookup table to ensure that A7 is adjusted by 2 rather than 1 in
// postincrement and predecrement mode.

47
InstructionSets/M68k/Implementation/ExecutorImplementation.hpp
View File

@ -24,6 +24,7 @@ template <Model model, typename BusHandler>
void Executor<model, BusHandler>::reset() {
// Establish: supervisor state, all interrupts blocked.
status_.set_status(0b0010'0011'1000'0000);
did_update_status();
// Seed stack pointer and program counter.
data_[7].l = bus_handler_.template read<uint32_t>(0);
@ -212,7 +213,23 @@ void Executor<model, BusHandler>::run_for_instructions(int count) {
const auto opcode = read_pc<uint16_t>();
const Preinstruction instruction = decoder_.decode(opcode);
// TODO: check privilege level.
if(!status_.is_supervisor_ && instruction.requires_supervisor()) {
raise_exception(8);
continue;
}
if(instruction.operation == Operation::Undefined) {
switch(opcode & 0xf000) {
default:
raise_exception(4);
continue;
case 0xa000:
raise_exception(10);
continue;
case 0xf000:
raise_exception(11);
continue;
}
}
// Temporary storage.
CPU::SlicedInt32 operand_[2];
@ -328,7 +345,30 @@ void Executor<model, BusHandler>::set_state(const Registers &state) {
// TODO: flow control, all below here.
template <Model model, typename BusHandler>
void Executor<model, BusHandler>::raise_exception(int) {}
void Executor<model, BusHandler>::raise_exception(int index) {
const uint32_t address = index << 2;
// Grab the status to store, then switch into supervisor mode.
const uint16_t status = status_.status();
status_.is_supervisor_ = 1;
did_update_status();
// Push status and the program counter at instruction start.
bus_handler_.template write<uint32_t>(address_[7].l - 4, instruction_address_);
bus_handler_.template write<uint16_t>(address_[7].l - 6, status);
address_[7].l -= 6;
// Fetch the new program counter.
program_counter_.l = bus_handler_.template read<uint32_t>(address);
}
template <Model model, typename BusHandler>
void Executor<model, BusHandler>::did_update_status() {
// Shuffle the stack pointers.
stack_pointers_[active_stack_pointer_] = address_[7];
address_[7] = stack_pointers_[status_.is_supervisor_];
active_stack_pointer_ = status_.is_supervisor_;
}
template <Model model, typename BusHandler>
void Executor<model, BusHandler>::stop() {}
@ -339,9 +379,6 @@ void Executor<model, BusHandler>::set_pc(uint32_t) {}
template <Model model, typename BusHandler>
void Executor<model, BusHandler>::add_pc(uint32_t) {}
template <Model model, typename BusHandler>
void Executor<model, BusHandler>::decline_branch() {}
}
}