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read_liberty: support loopy retention cells

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This commit is contained in:
Emil J. Tywoniak 2025-11-20 13:21:17 +01:00
parent 302643330c
commit d5c1cd8fc0
1 changed files with 23 additions and 6 deletions
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29
frontends/liberty/liberty.cc
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@ -191,11 +191,23 @@ static RTLIL::SigSpec create_tristate(RTLIL::Module *module, RTLIL::SigSpec func
return cell->getPort(ID::Y);
}
static void create_latch_ff_wires(RTLIL::Module *module, const LibertyAst *node)
{
module->addWire(RTLIL::escape_id(node->args.at(0)));
module->addWire(RTLIL::escape_id(node->args.at(1)));
}
static std::pair<RTLIL::SigSpec, RTLIL::SigSpec> find_latch_ff_wires(RTLIL::Module *module, const LibertyAst *node)
{
auto* iq_wire = module->wire(RTLIL::escape_id(node->args.at(0)));
auto* iqn_wire = module->wire(RTLIL::escape_id(node->args.at(1)));
log_assert(iq_wire && iqn_wire);
return std::make_pair(iq_wire, iqn_wire);
}
static void create_ff(RTLIL::Module *module, const LibertyAst *node)
{
RTLIL::SigSpec iq_sig(module->addWire(RTLIL::escape_id(node->args.at(0))));
RTLIL::SigSpec iqn_sig(module->addWire(RTLIL::escape_id(node->args.at(1))));
auto [iq_sig, iqn_sig] = find_latch_ff_wires(module, node);
RTLIL::SigSpec clk_sig, data_sig, clear_sig, preset_sig;
bool clk_polarity = true, clear_polarity = true, preset_polarity = true;
@ -270,9 +282,7 @@ static void create_ff(RTLIL::Module *module, const LibertyAst *node)
static bool create_latch(RTLIL::Module *module, const LibertyAst *node, bool flag_ignore_miss_data_latch)
{
RTLIL::SigSpec iq_sig(module->addWire(RTLIL::escape_id(node->args.at(0))));
RTLIL::SigSpec iqn_sig(module->addWire(RTLIL::escape_id(node->args.at(1))));
auto [iq_sig, iqn_sig] = find_latch_ff_wires(module, node);
RTLIL::SigSpec enable_sig, data_sig, clear_sig, preset_sig;
bool enable_polarity = true, clear_polarity = true, preset_polarity = true;
@ -646,6 +656,13 @@ struct LibertyFrontend : public Frontend {
{
// some liberty files do not put ff/latch at the beginning of a cell
// try to find "ff" or "latch" and create FF/latch _before_ processing all other nodes
// but first, in case of balloon retention cells, we need all ff/latch output wires
// defined before we add ff/latch cells
for (auto node : cell->children)
{
if ((node->id == "ff" && node->args.size() == 2) || (node->id == "latch" && node->args.size() == 2))
create_latch_ff_wires(module, node);
}
for (auto node : cell->children)
{
if (node->id == "ff" && node->args.size() == 2)