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Makes a failed attempt to implement MOVEM to registers.

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This commit is contained in:
Thomas Harte 2022-05-05 20:32:21 -04:00
parent d7d0a5c15e
commit f7991e18de
1 changed files with 31 additions and 8 deletions
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39
InstructionSets/M68k/Implementation/ExecutorImplementation.hpp
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@ -440,13 +440,6 @@ void Executor<model, BusHandler>::movep(Preinstruction instruction, uint32_t sou
template <Model model, typename BusHandler>
template <typename IntT>
void Executor<model, BusHandler>::movem(Preinstruction instruction, uint32_t source, uint32_t dest) {
// NB:
//
// "For the MC68020, MC68030, MC68040, and CPU32, if the addressing register is also
// moved to memory, the value written is the initial register value decremented by the
// size of the operation. The MC68000 and MC68010 write the initial register value
// (not decremented)."
if(instruction.mode<0>() == AddressingMode::ImmediateData) {
// Move registers to memory. This is the only permitted use of the predecrement mode,
// which reverses output order.
@ -456,7 +449,12 @@ void Executor<model, BusHandler>::movem(Preinstruction instruction, uint32_t sou
// reaching here, and it'll have been by two bytes per the operand size
// rather than according to the instruction size. That's not wanted, so undo it.
//
// (TODO: with the caveat that the 68020+ have different behaviour.).
// TODO: with the caveat that the 68020+ have different behaviour:
//
// "For the MC68020, MC68030, MC68040, and CPU32, if the addressing register is also
// moved to memory, the value written is the initial register value decremented by the
// size of the operation. The MC68000 and MC68010 write the initial register value
// (not decremented)."
registers_[8 + instruction.reg<1>()].l += 2;
uint32_t reg = registers_[8 + instruction.reg<1>()].l;
@ -487,6 +485,31 @@ void Executor<model, BusHandler>::movem(Preinstruction instruction, uint32_t sou
} else {
// Move memory to registers.
if(instruction.mode<0>() == AddressingMode::AddressRegisterIndirectWithPostincrement) {
// If the effective address is specified by the postincrement mode ...
// [i]f the addressing register is also loaded from memory, the memory value is
// ignored and the register is written with the postincremented effective address.
source -= 2;
}
int index = 0;
while(dest) {
if(dest & 1) {
if constexpr (sizeof(IntT) == 2) {
registers_[index].l = int16_t(bus_handler_.template read<uint16_t>(source));
} else {
registers_[index].l = bus_handler_.template read<uint32_t>(source);
}
source += sizeof(IntT);
}
++index;
dest >>= 1;
}
if(instruction.mode<0>() == AddressingMode::AddressRegisterIndirectWithPostincrement) {
registers_[8 + instruction.reg<0>()].l = source;
}
}
}