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Add time calculation for MULU and MULS.

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This commit is contained in:
Thomas Harte 2022-05-27 14:41:42 -04:00
parent 7601dab464
commit f599a78cad
1 changed files with 19 additions and 4 deletions
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23
Processors/68000Mk2/Implementation/68000Mk2Implementation.hpp
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@ -2565,14 +2565,29 @@ template <bool did_overflow> void ProcessorBase::did_divs(int32_t, int32_t) {
// TODO: calculate cost. // TODO: calculate cost.
} }
template <typename IntT> void ProcessorBase::did_mulu(IntT) { #define convert_to_bit_count_16(x) \
// TODO: calculate cost. x = ((x & 0xaaaa) >> 1) + (x & 0x5555); \
x = ((x & 0xcccc) >> 2) + (x & 0x3333); \
x = ((x & 0xf0f0) >> 4) + (x & 0x0f0f); \
x = ((x & 0xff00) >> 8) + (x & 0x00ff);
template <typename IntT> void ProcessorBase::did_mulu(IntT multiplier) {
// Count number of bits set.
convert_to_bit_count_16(multiplier);
dynamic_instruction_length_ = multiplier;
} }
template <typename IntT> void ProcessorBase::did_muls(IntT) { template <typename IntT> void ProcessorBase::did_muls(IntT multiplier) {
// TODO: calculate cost. // Count number of transitions from 0 to 1 or from 1 to 0 — i.e. the
// number of times that a bit is not equal to the one to its right.
// Treat the bit to the right of b0 as 0.
int number_of_pairs = (multiplier ^ (multiplier << 1)) & 0xffff;
convert_to_bit_count_16(number_of_pairs);
dynamic_instruction_length_ = number_of_pairs;
} }
#undef convert_to_bit_count_16
void ProcessorBase::did_shift(int bits_shifted) { void ProcessorBase::did_shift(int bits_shifted) {
dynamic_instruction_length_ = bits_shifted; dynamic_instruction_length_ = bits_shifted;
} }