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proc_dff: optimize repeated values at bit granularity

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This commit is contained in:
George Rennie 2024-11-28 17:49:52 +01:00
parent 480abc09c7
commit 2780875e8c
1 changed files with 16 additions and 2 deletions
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18
passes/proc/proc_dff.cc
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@ -154,10 +154,24 @@ public:
// Combine adjacent async rules that assign the same value into one rule // Combine adjacent async rules that assign the same value into one rule
// with a disjunction of triggers. The resulting trigger is optimized by // with a disjunction of triggers. The resulting trigger is optimized by
// constant evaluation. // constant evaluation. We apply all of these optimizations that can be
// done to the LSB and shrink the size of the signal we are considering if
// higher bits cannot be optimized in the same way.
void optimize_same_value(ConstEval& ce) { void optimize_same_value(ConstEval& ce) {
for (size_t i = 0; i + 1 < async_rules.size();) { for (size_t i = 0; i + 1 < async_rules.size();) {
if (async_rules[i].value != async_rules[i + 1].value) { const auto bit_optimizable = [&](const size_t bit) {
return async_rules[i].value[bit] == async_rules[i + 1].value[bit];
};
const bool lsb_optimizable = bit_optimizable(0);
size_t new_size;
for (new_size = 1; new_size < size(); new_size++)
if (bit_optimizable(new_size) != lsb_optimizable)
break;
resize(new_size);
if (!lsb_optimizable) {
i++; i++;
continue; continue;
} }