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Implements MULU and MULS.

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This commit is contained in:
Thomas Harte
2019-04-16 22:16:43 -04:00
parent be722143e1
commit 8f77d1831b
3 changed files with 102 additions and 6 deletions
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40
Processors/68000/Implementation/68000Implementation.hpp
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@@ -477,6 +477,46 @@ template <class T, bool dtack_is_implicit> void Processor<T, dtack_is_implicit>:
set_ccr(active_program_->source->full);
break;
case Operation::MULU: {
active_program_->destination->full =
active_program_->destination->halves.low.full * active_program_->source->halves.low.full;
carry_flag_ = overflow_flag_ = 0;
zero_result_ = active_program_->destination->full;
negative_flag_ = zero_result_ & 0x80000000;
// TODO: optimise the below?
int number_of_ones = 0;
auto source = active_program_->source->halves.low.full;
while(source) {
source >>= 1;
++number_of_ones;
}
// Time taken = 38 cycles + 2 cycles per 1 in the source.
active_step_->microcycle.length = HalfCycles(4 * number_of_ones + 38*2);
} break;
case Operation::MULS: {
active_program_->destination->full =
int16_t(active_program_->destination->halves.low.full) * int16_t(active_program_->source->halves.low.full);
carry_flag_ = overflow_flag_ = 0;
zero_result_ = active_program_->destination->full;
negative_flag_ = zero_result_ & 0x80000000;
// TODO: optimise the below?
int number_of_pairs = 0;
int source = active_program_->source->halves.low.full;
int bit = 0;
while(source | bit) {
number_of_pairs += (bit ^ source) & 1;
bit = source & 1;
source >>= 1;
}
// Time taken = 38 cycles + 2 cycles per 1 in the source.
active_step_->microcycle.length = HalfCycles(4 * number_of_pairs + 38*2);
} break;
/*
MOVEM: multi-word moves.
*/