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Eliminate 64-bit work.

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This commit is contained in:
Thomas Harte 2022-10-11 10:33:28 -04:00
parent 58396f0c52
commit ec5d57fefe
1 changed files with 9 additions and 10 deletions
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19
InstructionSets/M68k/Implementation/PerformImplementation.hpp
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@ -67,26 +67,25 @@ static Status::FlagT overflow(IntT source, IntT destination, IntT result) {
template <bool is_add, bool is_extend, typename IntT> template <bool is_add, bool is_extend, typename IntT>
static void add_sub(IntT source, IntT &destination, Status &status) { static void add_sub(IntT source, IntT &destination, Status &status) {
static_assert(!std::numeric_limits<IntT>::is_signed); static_assert(!std::numeric_limits<IntT>::is_signed);
using BigIntT = typename BiggerInt<IntT>::type;
const BigIntT extend = (is_extend && status.extend_flag) ? 1 : 0; const IntT extend = (is_extend && status.extend_flag) ? 1 : 0;
const BigIntT result = is_add ? const IntT result = is_add ?
(BigIntT(destination) + BigIntT(source) + extend) : (destination + source + extend) :
(BigIntT(destination) - BigIntT(source) - extend); (destination - source - extend);
// Extend operations can reset the zero flag only; non-extend operations // Extend operations can reset the zero flag only; non-extend operations
// can either set it or reset it. Which in the reverse-logic world of // can either set it or reset it. Which in the reverse-logic world of
// zero_result means ORing or storing. // zero_result means ORing or storing.
if constexpr (is_extend) { if constexpr (is_extend) {
status.zero_result |= IntT(result); status.zero_result |= Status::FlagT(result);
} else { } else {
status.zero_result = IntT(result); status.zero_result = Status::FlagT(result);
} }
status.extend_flag = status.extend_flag =
status.carry_flag = Status::FlagT(result >> bit_count<IntT>()); status.carry_flag = is_add ? result < destination : result > destination;
status.negative_flag = Status::FlagT(result & top_bit<IntT>()); status.negative_flag = Status::FlagT(result & top_bit<IntT>());
status.overflow_flag = overflow<is_add>(source, destination, IntT(result)); status.overflow_flag = overflow<is_add>(source, destination, result);
destination = IntT(result); destination = result;
} }
} }