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Decode logic for muxpack

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This commit is contained in:
Alain Dargelas 2024-12-27 15:23:25 -08:00
parent 33b3d933de
commit 8d6a542a5d
1 changed files with 75 additions and 8 deletions
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83
passes/opt/muxpack.cc
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@ -31,9 +31,9 @@ struct ExclusiveDatabase
dict<SigBit, std::pair<SigSpec,std::vector<Const>>> sig_cmp_prev;
ExclusiveDatabase(Module *module, const SigMap &sigmap, bool assume_excl) : module(module), sigmap(sigmap)
ExclusiveDatabase(Module *module, const SigMap &sigmap, bool assume_excl, bool make_excl) : module(module), sigmap(sigmap)
{
if (assume_excl) return;
if (assume_excl || make_excl) return;
SigSpec const_sig, nonconst_sig;
SigBit y_port;
pool<Cell*> reduce_or;
@ -243,7 +243,7 @@ struct MuxpackWorker
return chain;
}
void process_chain(vector<Cell*> &chain)
void process_chain(vector<Cell*> &chain, bool make_excl)
{
if (GetSize(chain) < 2)
return;
@ -289,8 +289,66 @@ struct MuxpackWorker
remove_cells.insert(cursor_cell);
}
if (make_excl) {
/* We create the following one-hot select line decoder
S0 S1 S2 S3 ...
| | | |
+--------+ +----------+ +-------------+ |
| _|_ | _|_ | _|_ |
| \_/ | \_/ | \_/ |
| o | o | o |
| | | | | __ | |
| +---------\ | | / \ | |
| | | |___| | / |___| |
| |___| \ & / / / \ & / / ...
| \ & / \_/ / / \_/ / /
| \_/ | | / | | /
| | +------/ +-------/
| | | | | |
| | |___| |___|
| | \ & / \ & /
| | \_/ \_/
| | | |
S0 S0'S1 S0'S1'S2 S0'S1'S2'S3 ...
*/
SigSpec decodedSelect;
Cell *cell = last_cell;
std::vector<RTLIL::SigBit> select_bits = s_sig.bits();
RTLIL::SigBit prevSigNot = RTLIL::State::S1;
RTLIL::SigBit prevSigAnd = RTLIL::State::S1;
for (int i = (int) (select_bits.size() -1); i >= 0; i--) {
Yosys::RTLIL::SigBit sigbit = select_bits[i];
if (i == (int) (select_bits.size() -1)) {
decodedSelect.append(sigbit);
Wire *not_y = module->addWire(NEW_ID, 1);
module->addNot(NEW_ID2_SUFFIX("not"), sigbit, not_y, false, last_cell->get_src_attribute());
prevSigNot = not_y;
} else if (i == (int) (select_bits.size() -2)) {
Wire *and_y = module->addWire(NEW_ID, 1);
module->addAndGate(NEW_ID2_SUFFIX("sel"), sigbit, prevSigNot, and_y, last_cell->get_src_attribute());
decodedSelect.append(and_y);
Wire *not_y = module->addWire(NEW_ID, 1);
module->addNot(NEW_ID2_SUFFIX("not"), sigbit, not_y, false, last_cell->get_src_attribute());
prevSigAnd = prevSigNot;
prevSigNot = not_y;
} else {
Wire *and_y1 = module->addWire(NEW_ID, 1);
module->addAndGate(NEW_ID2_SUFFIX("sel"), prevSigAnd, prevSigNot, and_y1, last_cell->get_src_attribute());
Wire *and_y2 = module->addWire(NEW_ID, 1);
module->addAndGate(NEW_ID2_SUFFIX("sel"), sigbit, and_y1, and_y2, last_cell->get_src_attribute());
decodedSelect.append(and_y2);
Wire *not_y = module->addWire(NEW_ID, 1);
module->addNot(NEW_ID2_SUFFIX("not"), sigbit, not_y, false, last_cell->get_src_attribute());
prevSigAnd = and_y1;
prevSigNot = not_y;
}
}
decodedSelect.reverse();
first_cell->setPort(ID::S, decodedSelect);
} else {
first_cell->setPort(ID::S, s_sig);
}
first_cell->setPort(ID::B, b_sig);
first_cell->setPort(ID::S, s_sig);
first_cell->setParam(ID::S_WIDTH, GetSize(s_sig));
first_cell->setPort(ID::Y, last_cell->getPort(ID::Y));
@ -310,15 +368,15 @@ struct MuxpackWorker
candidate_cells.clear();
}
MuxpackWorker(Module *module, bool assume_excl) :
module(module), sigmap(module), mux_count(0), pmux_count(0), excl_db(module, sigmap, assume_excl)
MuxpackWorker(Module *module, bool assume_excl, bool make_excl) :
module(module), sigmap(module), mux_count(0), pmux_count(0), excl_db(module, sigmap, assume_excl, make_excl)
{
make_sig_chain_next_prev();
find_chain_start_cells(assume_excl);
for (auto c : chain_start_cells) {
vector<Cell*> chain = create_chain(c);
process_chain(chain);
process_chain(chain, make_excl);
}
cleanup();
@ -346,12 +404,16 @@ struct MuxpackPass : public Pass {
log("\n");
log(" -assume_excl\n");
log(" assume mutually exclusive constraint when packing (may result in inequivalence)\n");
log(" -make_excl\n");
log(" Adds a one-hot decoder on the control signals\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) override
{
bool splitfanout = false;
bool assume_excl = false;
bool make_excl = false;
log_header(design, "Executing MUXPACK pass ($mux cell cascades to $pmux).\n");
@ -366,6 +428,11 @@ struct MuxpackPass : public Pass {
assume_excl = true;
continue;
}
if (args[argidx] == "-make_excl") {
make_excl = true;
assume_excl = true;
continue;
}
break;
}
extra_args(args, argidx, design);
@ -377,7 +444,7 @@ struct MuxpackPass : public Pass {
int pmux_count = 0;
for (auto module : design->selected_modules()) {
MuxpackWorker worker(module, assume_excl);
MuxpackWorker worker(module, assume_excl, make_excl);
mux_count += worker.mux_count;
pmux_count += worker.pmux_count;
}