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Generalise CBW.

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This commit is contained in:
Thomas Harte 2023-10-09 15:00:04 -04:00
parent 08aed3bac5
commit fe6e2eb0a1
1 changed files with 18 additions and 4 deletions
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22
InstructionSets/x86/Implementation/PerformImplementation.hpp
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@ -493,12 +493,20 @@ void call_far(InstructionT &instruction,
flow_controller.call(segment, offset);
}
inline void cbw(CPU::RegisterPair16 &ax) {
ax.halves.high = (ax.halves.low & 0x80) ? 0xff : 0x00;
template <typename IntT>
void cbw(IntT &ax) {
constexpr IntT test_bit = 1 << (sizeof(IntT) * 4 - 1);
constexpr IntT low_half = (1 << (sizeof(IntT) * 4)) - 1;
if(ax & test_bit) {
ax |= ~low_half;
} else {
ax &= low_half;
}
}
template <typename IntT>
inline void cwd(IntT &dx, IntT ax) {
void cwd(IntT &dx, IntT ax) {
dx = ax & top_bit<IntT>() ? IntT(~0) : IntT(0);
}
@ -567,7 +575,13 @@ template <
case Operation::DAA: Primitive::daa(registers.al(), status); return;
case Operation::DAS: Primitive::das(registers.al(), status); return;
case Operation::CBW: Primitive::cbw(registers.axp()); return;
case Operation::CBW:
if constexpr (data_size == DataSize::Word) {
Primitive::cbw(registers.ax());
} else if constexpr (is_32bit(model) && data_size == DataSize::DWord) {
Primitive::cbw(registers.eax());
}
return;
case Operation::CWD:
if constexpr (data_size == DataSize::Word) {
Primitive::cwd(registers.dx(), registers.ax());