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memory_share: Improve sat-based port sharing.

This commit is contained in:
Marcelina Kościelnicka 2020-10-26 03:20:57 +01:00
parent cbf6b719fe
commit 2d10caabbc
1 changed files with 157 additions and 123 deletions
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150
passes/memory/memory_share.cc
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@ -139,13 +139,9 @@ struct MemoryShareWorker
if (GetSize(mem.wr_ports) <= 1) if (GetSize(mem.wr_ports) <= 1)
return; return;
ezSatPtr ez; // Get a list of ports that have any chance of being mergeable.
SatGen satgen(ez.get(), &modwalker.sigmap);
// find list of considered ports and port pairs pool<int> eligible_ports;
std::set<int> considered_ports;
std::set<int> considered_port_pairs;
for (int i = 0; i < GetSize(mem.wr_ports); i++) { for (int i = 0; i < GetSize(mem.wr_ports); i++) {
auto &port = mem.wr_ports[i]; auto &port = mem.wr_ports[i];
@ -154,60 +150,90 @@ struct MemoryShareWorker
if (bit == RTLIL::State::S1) if (bit == RTLIL::State::S1)
goto port_is_always_active; goto port_is_always_active;
if (modwalker.has_drivers(bits)) if (modwalker.has_drivers(bits))
considered_ports.insert(i); eligible_ports.insert(i);
port_is_always_active:; port_is_always_active:;
} }
if (eligible_ports.size() <= 1)
return;
log("Consolidating write ports of memory %s.%s using sat-based resource sharing:\n", log_id(module), log_id(mem.memid)); log("Consolidating write ports of memory %s.%s using sat-based resource sharing:\n", log_id(module), log_id(mem.memid));
bool cache_clk_enable = false; // Group eligible ports by clock domain and width.
bool cache_clk_polarity = false;
RTLIL::SigSpec cache_clk;
int cache_wide_log2 = 0;
pool<int> checked_ports;
std::vector<std::vector<int>> groups;
for (int i = 0; i < GetSize(mem.wr_ports); i++) for (int i = 0; i < GetSize(mem.wr_ports); i++)
{ {
auto &port = mem.wr_ports[i]; auto &port1 = mem.wr_ports[i];
if (!eligible_ports.count(i))
continue;
if (checked_ports.count(i))
continue;
if (port.clk_enable != cache_clk_enable ||
port.wide_log2 != cache_wide_log2 || std::vector<int> group;
(cache_clk_enable && (sigmap(port.clk) != cache_clk || group.push_back(i);
port.clk_polarity != cache_clk_polarity)))
for (int j = i + 1; j < GetSize(mem.wr_ports); j++)
{ {
cache_clk_enable = port.clk_enable; auto &port2 = mem.wr_ports[j];
cache_clk_polarity = port.clk_polarity; if (!eligible_ports.count(j))
cache_clk = sigmap(port.clk); continue;
cache_wide_log2 = port.wide_log2; if (checked_ports.count(j))
continue;
if (port1.clk_enable != port2.clk_enable)
continue;
if (port1.clk_enable) {
if (port1.clk != port2.clk)
continue;
if (port1.clk_polarity != port2.clk_polarity)
continue;
} }
else if (i > 0 && considered_ports.count(i-1) && considered_ports.count(i)) if (port1.wide_log2 != port2.wide_log2)
considered_port_pairs.insert(i); continue;
group.push_back(j);
if (cache_clk_enable)
log(" Port %d on %s %s: %s\n", i,
cache_clk_polarity ? "posedge" : "negedge", log_signal(cache_clk),
considered_ports.count(i) ? "considered" : "not considered");
else
log(" Port %d unclocked: %s\n", i,
considered_ports.count(i) ? "considered" : "not considered");
} }
if (considered_port_pairs.size() < 1) { for (auto j : group)
log(" No two subsequent ports in same clock domain considered -> nothing to consolidate.\n"); checked_ports.insert(j);
return;
if (group.size() <= 1)
continue;
groups.push_back(group);
} }
bool changed = false;
for (auto &group : groups) {
auto &some_port = mem.wr_ports[group[0]];
string ports;
for (auto idx : group) {
if (idx != group[0])
ports += ", ";
ports += std::to_string(idx);
}
if (!some_port.clk_enable) {
log(" Checking unclocked group, width %d: ports %s.\n", mem.width << some_port.wide_log2, ports.c_str());
} else {
log(" Checking group clocked with %sedge %s, width %d: ports %s.\n", some_port.clk_polarity ? "pos" : "neg", log_signal(some_port.clk), mem.width << some_port.wide_log2, ports.c_str());
}
// Okay, time to actually run the SAT solver.
ezSatPtr ez;
SatGen satgen(ez.get(), &modwalker.sigmap);
// create SAT representation of common input cone of all considered EN signals // create SAT representation of common input cone of all considered EN signals
pool<Wire*> one_hot_wires; pool<Wire*> one_hot_wires;
std::set<RTLIL::Cell*> sat_cells; std::set<RTLIL::Cell*> sat_cells;
std::set<RTLIL::SigBit> bits_queue; std::set<RTLIL::SigBit> bits_queue;
std::map<int, int> port_to_sat_variable; dict<int, int> port_to_sat_variable;
for (int i = 0; i < GetSize(mem.wr_ports); i++) for (auto idx : group) {
if (considered_port_pairs.count(i) || considered_port_pairs.count(i+1)) RTLIL::SigSpec sig = modwalker.sigmap(mem.wr_ports[idx].en);
{ port_to_sat_variable[idx] = ez->expression(ez->OpOr, satgen.importSigSpec(sig));
RTLIL::SigSpec sig = modwalker.sigmap(mem.wr_ports[i].en);
port_to_sat_variable[i] = ez->expression(ez->OpOr, satgen.importSigSpec(sig));
std::vector<RTLIL::SigBit> bits = sig; std::vector<RTLIL::SigBit> bits = sig;
bits_queue.insert(bits.begin(), bits.end()); bits_queue.insert(bits.begin(), bits.end());
@ -246,29 +272,35 @@ struct MemoryShareWorker
log(" Size of unconstrained SAT problem: %d variables, %d clauses\n", ez->numCnfVariables(), ez->numCnfClauses()); log(" Size of unconstrained SAT problem: %d variables, %d clauses\n", ez->numCnfVariables(), ez->numCnfClauses());
// merge subsequent ports if possible // now try merging the ports.
bool changed = false; for (int ii = 0; ii < GetSize(group); ii++) {
for (int i = 0; i < GetSize(mem.wr_ports); i++) int idx1 = group[ii];
{ auto &port1 = mem.wr_ports[idx1];
if (!considered_port_pairs.count(i)) if (port1.removed)
continue;
for (int jj = ii + 1; jj < GetSize(group); jj++) {
int idx2 = group[jj];
auto &port2 = mem.wr_ports[idx2];
if (port2.removed)
continue; continue;
if (ez->solve(port_to_sat_variable.at(i-1), port_to_sat_variable.at(i))) { if (ez->solve(port_to_sat_variable.at(idx1), port_to_sat_variable.at(idx2))) {
log(" According to SAT solver sharing of port %d with port %d is not possible.\n", i-1, i); log(" According to SAT solver sharing of port %d with port %d is not possible.\n", idx1, idx2);
continue; continue;
} }
log(" Merging port %d into port %d.\n", i-1, i); log(" Merging port %d into port %d.\n", idx2, idx1);
port_to_sat_variable.at(i) = ez->OR(port_to_sat_variable.at(i-1), port_to_sat_variable.at(i)); mem.prepare_wr_merge(idx1, idx2);
port_to_sat_variable.at(idx1) = ez->OR(port_to_sat_variable.at(idx1), port_to_sat_variable.at(idx2));
RTLIL::SigSpec last_addr = mem.wr_ports[i-1].addr; RTLIL::SigSpec last_addr = port1.addr;
RTLIL::SigSpec last_data = mem.wr_ports[i-1].data; RTLIL::SigSpec last_data = port1.data;
std::vector<RTLIL::SigBit> last_en = modwalker.sigmap(mem.wr_ports[i-1].en); std::vector<RTLIL::SigBit> last_en = modwalker.sigmap(port1.en);
RTLIL::SigSpec this_addr = mem.wr_ports[i].addr; RTLIL::SigSpec this_addr = port2.addr;
RTLIL::SigSpec this_data = mem.wr_ports[i].data; RTLIL::SigSpec this_data = port2.data;
std::vector<RTLIL::SigBit> this_en = modwalker.sigmap(mem.wr_ports[i].en); std::vector<RTLIL::SigBit> this_en = modwalker.sigmap(port2.en);
RTLIL::SigBit this_en_active = module->ReduceOr(NEW_ID, this_en); RTLIL::SigBit this_en_active = module->ReduceOr(NEW_ID, this_en);
@ -277,8 +309,8 @@ struct MemoryShareWorker
else else
this_addr.extend_u0(GetSize(last_addr)); this_addr.extend_u0(GetSize(last_addr));
mem.wr_ports[i].addr = module->Mux(NEW_ID, last_addr, this_addr, this_en_active); port1.addr = module->Mux(NEW_ID, last_addr, this_addr, this_en_active);
mem.wr_ports[i].data = module->Mux(NEW_ID, last_data, this_data, this_en_active); port1.data = module->Mux(NEW_ID, last_data, this_data, this_en_active);
std::map<std::pair<RTLIL::SigBit, RTLIL::SigBit>, int> groups_en; std::map<std::pair<RTLIL::SigBit, RTLIL::SigBit>, int> groups_en;
RTLIL::SigSpec grouped_last_en, grouped_this_en, en; RTLIL::SigSpec grouped_last_en, grouped_this_en, en;
@ -296,11 +328,13 @@ struct MemoryShareWorker
} }
module->addMux(NEW_ID, grouped_last_en, grouped_this_en, this_en_active, grouped_en); module->addMux(NEW_ID, grouped_last_en, grouped_this_en, this_en_active, grouped_en);
mem.wr_ports[i].en = en; port1.en = en;
mem.wr_ports[i-1].removed = true; port2.removed = true;
changed = true; changed = true;
} }
}
}
if (changed) if (changed)
mem.emit(); mem.emit();