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opt_muxtree: dense knowledge

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This commit is contained in:
Emil J. Tywoniak 2026-04-24 10:33:36 +02:00
parent 4abaca273e
commit e0b833ac1a
1 changed files with 25 additions and 21 deletions
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46
passes/opt/opt_muxtree.cc
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@ -21,11 +21,9 @@
#include "kernel/sigtools.h"
#include "kernel/log.h"
#include "kernel/celltypes.h"
#include <cstddef>
#include <stdlib.h>
#include <stdio.h>
#include <unordered_map>
#include <unordered_set>
#include <set>
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
@ -128,7 +126,7 @@ struct OptMuxtreeWorker
// In case of $pmux, port B is multiple slices, concatenated, one per bit of port S
for (int i = 0; i < GetSize(sig_s); i++) {
RTLIL::SigSpec sig = sig_b.extract(i*GetSize(sig_a), GetSize(sig_a));
RTLIL::SigSpec ctrl_sig = assign_map(sig_s.extract(i, 1));
RTLIL::SigSpec ctrl_sig = assign_map(SigSpec{sig_s[i]});
portinfo_t portinfo = used_port_bit(sig, this_mux_idx);
portinfo.ctrl_sig = sig2bits(ctrl_sig, false).front();
portinfo.const_activated = ctrl_sig.is_fully_const() && ctrl_sig.as_bool();
@ -342,14 +340,21 @@ struct OptMuxtreeWorker
// The payload is a reference counter used to manage the list
// When it is non-zero, the signal in known to be inactive
// When it reaches zero, the map element is removed
std::unordered_map<int, int> known_inactive;
std::vector<int> known_inactive;
// database of known active signals
std::unordered_map<int, int> known_active;
std::vector<int> known_active;
// this is just used to keep track of visited muxes in order to prohibit
// endless recursion in mux loops
std::unordered_set<int> visited_muxes;
std::vector<bool> visited_muxes;
// Initialize with the maximum possible sizes
knowledge_t(int num_bits, int num_muxes) {
known_inactive.assign(num_bits, 0);
known_active.assign(num_bits, 0);
visited_muxes.assign(num_muxes, false);
}
};
static void activate_port(knowledge_t &knowledge, int port_idx, const muxinfo_t &muxinfo) {
@ -366,11 +371,10 @@ struct OptMuxtreeWorker
}
static void deactivate_port(knowledge_t &knowledge, int port_idx, const muxinfo_t &muxinfo) {
auto unlearn = [](std::unordered_map<int, int>& knowns, int i) {
auto it = knowns.find(i);
if (it != knowns.end())
if (--it->second == 0)
knowns.erase(it);
auto unlearn = [](std::vector<int>& knowns, int bit_idx) {
if (knowns[bit_idx] > 0) {
--knowns[bit_idx];
}
};
if (port_idx < GetSize(muxinfo.ports)-1 && !muxinfo.ports[port_idx].const_activated)
@ -418,9 +422,9 @@ struct OptMuxtreeWorker
vector<int> input_mux_queue;
for (int m : muxinfo.ports[port_idx].input_muxes) {
if (knowledge.visited_muxes.count(m))
if (knowledge.visited_muxes[m])
continue;
knowledge.visited_muxes.insert(m);
knowledge.visited_muxes[m] = true;
input_mux_queue.push_back(m);
}
for (int m : input_mux_queue) {
@ -453,7 +457,7 @@ struct OptMuxtreeWorker
// Allow revisiting input muxes, since evaluating other ports should
// revisit these input muxes with different activation assumptions
for (int m : input_mux_queue)
knowledge.visited_muxes.erase(m);
knowledge.visited_muxes[m] = false;
// Undo our assumptions that the port is active
deactivate_port(knowledge, port_idx, muxinfo);
@ -475,11 +479,11 @@ struct OptMuxtreeWorker
vector<int> bits = sig2bits(sig, false);
for (int i = 0; i < GetSize(bits); i++) {
if (bits[i] >= 0) {
if (knowledge.known_inactive.count(bits[i]) > 0) {
if (knowledge.known_inactive[bits[i]] > 0) {
sig[i] = State::S0;
did_something = true;
} else
if (knowledge.known_active.count(bits[i]) > 0) {
if (knowledge.known_active[bits[i]] > 0) {
sig[i] = State::S1;
did_something = true;
}
@ -552,7 +556,7 @@ struct OptMuxtreeWorker
portinfo_t &portinfo = muxinfo.ports[port_idx];
if (portinfo.const_deactivated)
continue;
if (knowledge.known_active.count(portinfo.ctrl_sig) > 0) {
if (knowledge.known_active[portinfo.ctrl_sig] > 0) {
eval_mux_port(knowledge, mux_idx, port_idx, limits);
return;
}
@ -566,7 +570,7 @@ struct OptMuxtreeWorker
if (portinfo.const_deactivated)
continue;
if (port_idx < GetSize(muxinfo.ports)-1)
if (knowledge.known_inactive.count(portinfo.ctrl_sig) > 0)
if (knowledge.known_inactive[portinfo.ctrl_sig] > 0)
continue;
eval_mux_port(knowledge, mux_idx, port_idx, limits);
@ -578,8 +582,8 @@ struct OptMuxtreeWorker
void eval_root_mux(int mux_idx)
{
log_assert(glob_evals_left > 0);
knowledge_t knowledge;
knowledge.visited_muxes.insert(mux_idx);
knowledge_t knowledge(GetSize(bit2info), GetSize(mux2info));
knowledge.visited_muxes[mux_idx] = true;
limits_t limits = {};
limits.do_mark_ports_observable = root_enable_muxes.at(mux_idx);
eval_mux(knowledge, mux_idx, limits);