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Unify subtractions.

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This commit is contained in:
Thomas Harte 2024-03-11 14:52:48 -04:00
parent e7457461ba
commit 971bfb2ecb
1 changed files with 22 additions and 29 deletions
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51
InstructionSets/ARM/Executor.hpp
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@ -113,8 +113,27 @@ struct Executor {
operand2 = decode_shift<true, shift_sets_carry>(fields, rotate_carry, shift_by_register ? 8 : 4); operand2 = decode_shift<true, shift_sets_carry>(fields, rotate_carry, shift_by_register ? 8 : 4);
} }
// Perform the data processing operation.
uint32_t conditions = 0; uint32_t conditions = 0;
const auto sub = [&](uint32_t lhs, uint32_t rhs) {
conditions = lhs - rhs;
if constexpr (flags.operation() == DataProcessingOperation::SBC || flags.operation() == DataProcessingOperation::RSC) {
conditions += registers_.c() - 1;
}
if constexpr (flags.set_condition_codes()) {
// "For a subtraction, including the comparison instruction CMP, C is set to 0 if
// the subtraction produced a borrow (that is, an unsigned underflow), and to 1 otherwise."
registers_.set_c(!Numeric::carried_out<false, 31>(lhs, rhs, conditions));
registers_.set_v(Numeric::overflow<false>(lhs, rhs, conditions));
}
if constexpr (!is_comparison(flags.operation())) {
destination = conditions;
}
};
// Perform the data processing operation.
switch(flags.operation()) { switch(flags.operation()) {
// Logical operations. // Logical operations.
case DataProcessingOperation::AND: conditions = destination = operand1 & operand2; break; case DataProcessingOperation::AND: conditions = destination = operand1 & operand2; break;
@ -150,38 +169,12 @@ struct Executor {
case DataProcessingOperation::SUB: case DataProcessingOperation::SUB:
case DataProcessingOperation::SBC: case DataProcessingOperation::SBC:
case DataProcessingOperation::CMP: case DataProcessingOperation::CMP:
conditions = operand1 - operand2; sub(operand1, operand2);
if constexpr (flags.operation() == DataProcessingOperation::SBC) {
conditions += registers_.c() - 1;
}
if constexpr (flags.set_condition_codes()) {
// "For a subtraction, including the comparison instruction CMP, C is set to 0 if
// the subtraction produced a borrow (that is, an unsigned underflow), and to 1 otherwise."
registers_.set_c(!Numeric::carried_out<false, 31>(operand1, operand2, conditions));
registers_.set_v(Numeric::overflow<false>(operand1, operand2, conditions));
}
if constexpr (!is_comparison(flags.operation())) {
destination = conditions;
}
break; break;
case DataProcessingOperation::RSB: case DataProcessingOperation::RSB:
case DataProcessingOperation::RSC: case DataProcessingOperation::RSC:
conditions = operand2 - operand1; sub(operand2, operand1);
if constexpr (flags.operation() == DataProcessingOperation::RSC) {
conditions += registers_.c() - 1;
}
if constexpr (flags.set_condition_codes()) {
registers_.set_c(!Numeric::carried_out<false, 31>(operand2, operand1, conditions));
registers_.set_v(Numeric::overflow<false>(operand2, operand1, conditions));
}
destination = conditions;
break; break;
} }