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Corrects MULS timing.

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Thomas Harte 2019-06-30 22:33:54 -04:00
parent d30e7504c2
commit 255f0d4b2a
1 changed files with 6 additions and 5 deletions
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11
Processors/68000/Implementation/68000Implementation.hpp
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@ -945,18 +945,19 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
zero_result_ = active_program_->destination->full; zero_result_ = active_program_->destination->full;
negative_flag_ = zero_result_ & 0x80000000; negative_flag_ = zero_result_ & 0x80000000;
// Find the number of 01 or 10 pairs in the 17-bit number
// formed by the source value with a 0 suffix.
// TODO: optimise the below? // TODO: optimise the below?
int number_of_pairs = 0; int number_of_pairs = 0;
int source = active_program_->source->halves.low.full; int source = active_program_->source->halves.low.full;
int bit = 0; source = (source ^ (source << 1)) & 0xffff;
while(source | bit) { while(source) {
number_of_pairs += (bit ^ source) & 1; if(source&1) ++number_of_pairs;
bit = source & 1;
source >>= 1; source >>= 1;
} }
// Time taken = 38 cycles + 2 cycles per 1 in the source. // Time taken = 38 cycles + 2 cycles per 1 in the source.
set_next_microcycle_length(HalfCycles(4 * number_of_pairs + 38*2)); set_next_microcycle_length(HalfCycles(4 * number_of_pairs + 34*2));
} break; } break;
/* /*