summaryrefslogtreecommitdiff
path: root/passes/opt/opt_muxtree.cc
diff options
context:
space:
mode:
Diffstat (limited to 'passes/opt/opt_muxtree.cc')
-rw-r--r--passes/opt/opt_muxtree.cc42
1 files changed, 38 insertions, 4 deletions
diff --git a/passes/opt/opt_muxtree.cc b/passes/opt/opt_muxtree.cc
index 7bdc54af..fa91d453 100644
--- a/passes/opt/opt_muxtree.cc
+++ b/passes/opt/opt_muxtree.cc
@@ -256,7 +256,7 @@ struct OptMuxtreeWorker
list.push_back(value);
}
- std::vector<int> sig2bits(RTLIL::SigSpec sig)
+ std::vector<int> sig2bits(RTLIL::SigSpec sig, bool skip_non_wires = true)
{
std::vector<int> results;
assign_map.apply(sig);
@@ -271,7 +271,8 @@ struct OptMuxtreeWorker
bit2num[info.bit] = info.num;
}
results.push_back(bit2num[bit]);
- }
+ } else if (!skip_non_wires)
+ results.push_back(-1);
return results;
}
@@ -285,7 +286,7 @@ struct OptMuxtreeWorker
// database of known active signals
// the 2nd dimension is the list of or-ed signals. so we know that
// for each i there is a j so that known_active[i][j] points to an
- // inactive control signal.
+ // active control signal.
std::vector<std::vector<int>> known_active;
// this is just used to keep track of visited muxes in order to prohibit
@@ -331,10 +332,43 @@ struct OptMuxtreeWorker
}
}
+ void replace_known(knowledge_t &knowledge, muxinfo_t &muxinfo, IdString portname)
+ {
+ SigSpec sig = muxinfo.cell->getPort(portname);
+ bool did_something = false;
+
+ std::vector<int> bits = sig2bits(sig, false);
+ for (int i = 0; i < GetSize(bits); i++) {
+ if (bits[i] < 0)
+ continue;
+ if (knowledge.known_inactive[bits[i]]) {
+ sig[i] = State::S0;
+ did_something = true;
+ } else {
+ for (auto &it : knowledge.known_active)
+ if (GetSize(it) == 1 && it.front() == bits[i]) {
+ sig[i] = State::S1;
+ did_something = true;
+ break;
+ }
+ }
+ }
+
+ if (did_something) {
+ log(" Replacing known input bits on port %s of cell %s: %s -> %s\n", log_id(portname),
+ log_id(muxinfo.cell), log_signal(muxinfo.cell->getPort(portname)), log_signal(sig));
+ muxinfo.cell->setPort(portname, sig);
+ }
+ }
+
void eval_mux(knowledge_t &knowledge, int mux_idx)
{
muxinfo_t &muxinfo = mux2info[mux_idx];
+ // set input ports to constants if we find known active or inactive signals
+ replace_known(knowledge, muxinfo, "\\A");
+ replace_known(knowledge, muxinfo, "\\B");
+
// if there is a constant activated port we just use it
for (size_t port_idx = 0; port_idx < muxinfo.ports.size()-1; port_idx++)
{
@@ -360,7 +394,7 @@ struct OptMuxtreeWorker
}
// compare ports with known_inactive and known_active signals. If all control
- // signals of the port are know_inactive or if the control signals of all other
+ // signals of the port are known_inactive or if the control signals of all other
// ports are known_active this port can't be activated. this loop includes the
// default port but no known_inactive match is performed on the default port.
for (size_t port_idx = 0; port_idx < muxinfo.ports.size(); port_idx++)