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Added removing of always inactive cells to "share" pass

This commit is contained in:
Clifford Wolf 2014-07-20 11:41:57 +02:00
parent 8819493db4
commit 7b98e46ac3
1 changed files with 42 additions and 8 deletions
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50
passes/sat/share.cc
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@ -41,6 +41,8 @@ struct ShareWorker
CellTypes fwd_ct, cone_ct;
ModWalker modwalker;
std::set<RTLIL::Cell*> cells_to_remove;
// ------------------------------------------------------------------------------
// Find terminal bits -- i.e. bits that do not (exclusively) feed into a mux tree
@ -229,7 +231,7 @@ struct ShareWorker
std::map<RTLIL::Cell*, std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>>> activation_patterns_cache;
bool sort_check_pattern(std::pair<RTLIL::SigSpec, RTLIL::Const> &p)
bool sort_check_activation_pattern(std::pair<RTLIL::SigSpec, RTLIL::Const> &p)
{
std::map<RTLIL::SigBit, RTLIL::State> p_bits;
@ -253,7 +255,13 @@ struct ShareWorker
return true;
}
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &find_cell_activation_patterns(RTLIL::Cell *cell)
void optimize_activation_patterns(std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> & /* patterns */)
{
// TODO: Remove patterns that are contained in other patterns
// TODO: Consolidate pairs of patterns that only differ in the value for one signal bit
}
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &find_cell_activation_patterns(RTLIL::Cell *cell, const char *indent)
{
if (activation_patterns_cache.count(cell))
return activation_patterns_cache.at(cell);
@ -276,7 +284,7 @@ struct ShareWorker
for (auto c : driven_cells)
{
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &c_patterns = find_cell_activation_patterns(c);
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &c_patterns = find_cell_activation_patterns(c, indent);
if (c->type == "$mux" || c->type == "$pmux")
{
@ -300,14 +308,14 @@ struct ShareWorker
for (auto p : c_patterns) {
for (int i = 0; i < SIZE(sig_s); i++)
p.first.append_bit(sig_s[i]), p.second.bits.push_back(RTLIL::State::S0);
if (sort_check_pattern(p))
if (sort_check_activation_pattern(p))
activation_patterns_cache[cell].insert(p);
}
for (int idx : used_in_b_parts)
for (auto p : c_patterns) {
p.first.append_bit(sig_s[idx]), p.second.bits.push_back(RTLIL::State::S1);
if (sort_check_pattern(p))
if (sort_check_activation_pattern(p))
activation_patterns_cache[cell].insert(p);
}
}
@ -319,6 +327,12 @@ struct ShareWorker
}
}
optimize_activation_patterns(activation_patterns_cache[cell]);
if (activation_patterns_cache[cell].empty()) {
log("%sFound cell that is never activated: %s\n", indent, log_id(cell));
cells_to_remove.insert(cell);
}
return activation_patterns_cache[cell];
}
@ -375,9 +389,14 @@ struct ShareWorker
log(" Analyzing resource sharing options for %s:\n", log_id(cell));
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &cell_activation_patterns = find_cell_activation_patterns(cell);
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &cell_activation_patterns = find_cell_activation_patterns(cell, " ");
RTLIL::SigSpec cell_activation_signals = bits_from_activation_patterns(cell_activation_patterns);
if (cell_activation_patterns.empty()) {
log (" Cell is never active. Sharing is pointless, we simply remove it.\n");
continue;
}
if (cell_activation_patterns.count(std::pair<RTLIL::SigSpec, RTLIL::Const>())) {
log (" Cell is always active. Therefore no sharing is possible.\n");
continue;
@ -402,11 +421,17 @@ struct ShareWorker
{
log(" Analyzing resource sharing with %s:\n", log_id(other_cell));
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &other_cell_activation_patterns = find_cell_activation_patterns(other_cell);
const std::set<std::pair<RTLIL::SigSpec, RTLIL::Const>> &other_cell_activation_patterns = find_cell_activation_patterns(other_cell, " ");
RTLIL::SigSpec other_cell_activation_signals = bits_from_activation_patterns(other_cell_activation_patterns);
if (other_cell_activation_patterns.empty()) {
log (" Cell is never active. Sharing is pointless, we simply remove it.\n");
shareable_cells.erase(other_cell);
continue;
}
if (other_cell_activation_patterns.count(std::pair<RTLIL::SigSpec, RTLIL::Const>())) {
log (" Cell is always active. Therefore no sharing is possible.\n");
log (" Cell is always active. Therefore no sharing is possible.\n");
continue;
}
@ -484,6 +509,15 @@ struct ShareWorker
break;
}
}
if (!cells_to_remove.empty()) {
log("Removing %d cells in module %s:\n", SIZE(cells_to_remove), log_id(module));
for (auto c : cells_to_remove) {
log(" Removing cell %s (%s).\n", log_id(c), log_id(c->type));
module->cells.erase(c->name);
delete c;
}
}
}
};