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Codify MOVE's status somewhat, avoid reading write-only operands.

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This commit is contained in:
Thomas Harte 2022-05-17 16:57:33 -04:00
parent f3d3e588fd
commit aa9e7eb7a2
2 changed files with 14 additions and 3 deletions
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11
Processors/68000Mk2/Implementation/68000Mk2Implementation.hpp
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@ -202,11 +202,14 @@ void Processor<BusHandler, dtack_is_implicit, permit_overrun, signal_will_perfor
//
// TODO: add MOVE special case, somewhere.
case State::FetchOperand:
switch(instruction_.mode(next_operand_)) {
case Mode::None:
// Check that this operand is meant to be fetched.
if(!(operand_flags_ & (1 << next_operand_))) {
state_ = perform_state_;
continue;
}
// Figure out how to fetch it.
switch(instruction_.mode(next_operand_)) {
case Mode::AddressRegisterDirect:
case Mode::DataRegisterDirect:
operand_[next_operand_] = registers_[instruction_.lreg(next_operand_)];
@ -295,6 +298,10 @@ void Processor<BusHandler, dtack_is_implicit, permit_overrun, signal_will_perfor
switch(instruction_.operation) {
BIND(NBCD, instruction_.mode(0) == Mode::DataRegisterDirect ? State::Perform_np_n : State::Perform_np);
// MOVEs are a special case for having an operand they write but did not read. So they segue into a
// specialised state for writing the result.
BIND(MOVEw, State::MOVEWrite);
default:
assert(false);
}

4
Processors/68000Mk2/Implementation/68000Mk2Storage.hpp
View File

@ -37,6 +37,10 @@ struct ProcessorBase: public InstructionSet::M68k::NullFlowController {
Perform_np = -6,
Perform_np_n = -7,
// MOVE has unique bus usage, so has a specialised state.
MOVEWrite = -8,
};
int state_ = State::Reset;