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yosys/passes/sat/clk2fflogic.cc

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/*
* yosys -- Yosys Open SYnthesis Suite
*
* Copyright (C) 2012 Claire Xenia Wolf <claire@yosyshq.com>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
#include "kernel/yosys.h"
#include "kernel/sigtools.h"
#include "kernel/ffinit.h"
#include "kernel/ff.h"
#include "kernel/mem.h"
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
struct SampledSig {
SigSpec sampled, current;
SigSpec &operator[](bool get_current) { return get_current ? current : sampled; }
};
struct Clk2fflogicPass : public Pass {
Clk2fflogicPass() : Pass("clk2fflogic", "convert clocked FFs to generic $ff cells") { }
void help() override
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" clk2fflogic [options] [selection]\n");
log("\n");
log("This command replaces clocked flip-flops with generic $ff cells that use the\n");
log("implicit global clock. This is useful for formal verification of designs with\n");
log("multiple clocks.\n");
log("\n");
log("This pass assumes negative hold time for the async FF inputs. For example when\n");
log("a reset deasserts with the clock edge, then the FF output will still drive the\n");
log("reset value in the next cycle regardless of the data-in value at the time of\n");
log("the clock edge.\n");
log("\n");
log(" -nolower\n");
log(" Do not automatically run 'chformal -lower' to lower $check cells.\n");
log("\n");
}
// Active-high sampled and current value of a level-triggered control signal. Initial sampled values is low/non-asserted.
SampledSig sample_control(Module *module, SigSpec sig, bool polarity, bool is_fine) {
if (!polarity) {
if (is_fine)
sig = module->NotGate(NEW_ID, sig);
else
sig = module->Not(NEW_ID, sig);
}
std::string sig_str = log_signal(sig);
sig_str.erase(std::remove(sig_str.begin(), sig_str.end(), ' '), sig_str.end());
Wire *sampled_sig = module->addWire(NEW_ID_SUFFIX(stringf("%s#sampled", sig_str.c_str())), GetSize(sig));
sampled_sig->attributes[ID::init] = RTLIL::Const(State::S0, GetSize(sig));
if (is_fine)
module->addFfGate(NEW_ID, sig, sampled_sig);
else
module->addFf(NEW_ID, sig, sampled_sig);
return {sampled_sig, sig};
}
// Active-high trigger signal for an edge-triggered control signal. Initial values is low/non-edge.
SigSpec sample_control_edge(Module *module, SigSpec sig, bool polarity, bool is_fine) {
std::string sig_str = log_signal(sig);
sig_str.erase(std::remove(sig_str.begin(), sig_str.end(), ' '), sig_str.end());
Wire *sampled_sig = module->addWire(NEW_ID_SUFFIX(stringf("%s#sampled", sig_str.c_str())), GetSize(sig));
sampled_sig->attributes[ID::init] = RTLIL::Const(polarity ? State::S1 : State::S0, GetSize(sig));
if (is_fine)
module->addFfGate(NEW_ID, sig, sampled_sig);
else
module->addFf(NEW_ID, sig, sampled_sig);
return module->Eqx(NEW_ID, {sampled_sig, sig}, polarity ? SigSpec {State::S0, State::S1} : SigSpec {State::S1, State::S0});
}
// Sampled and current value of a data signal.
SampledSig sample_data(Module *module, SigSpec sig, RTLIL::Const init, bool is_fine, bool set_attribute = false) {
std::string sig_str = log_signal(sig);
sig_str.erase(std::remove(sig_str.begin(), sig_str.end(), ' '), sig_str.end());
Wire *sampled_sig = module->addWire(NEW_ID_SUFFIX(stringf("%s#sampled", sig_str.c_str())), GetSize(sig));
sampled_sig->attributes[ID::init] = init;
Cell *cell;
if (is_fine)
cell = module->addFfGate(NEW_ID, sig, sampled_sig);
else
cell = module->addFf(NEW_ID, sig, sampled_sig);
if (set_attribute) {
for (auto &chunk : sig.chunks())
if (chunk.wire != nullptr)
chunk.wire->set_bool_attribute(ID::keep);
cell->set_bool_attribute(ID(clk2fflogic));
}
return {sampled_sig, sig};
}
SigSpec mux(Module *module, SigSpec a, SigSpec b, SigSpec s, bool is_fine) {
if (is_fine)
return module->MuxGate(NEW_ID, a, b, s);
else
return module->Mux(NEW_ID, a, b, s);
}
SigSpec bitwise_sr(Module *module, SigSpec a, SigSpec s, SigSpec r, bool is_fine) {
if (is_fine)
return module->AndGate(NEW_ID, module->OrGate(NEW_ID, a, s), module->NotGate(NEW_ID, r));
else
return module->And(NEW_ID, module->Or(NEW_ID, a, s), module->Not(NEW_ID, r));
}
void execute(std::vector<std::string> args, RTLIL::Design *design) override
{
bool flag_nolower = false;
log_header(design, "Executing CLK2FFLOGIC pass (convert clocked FFs to generic $ff cells).\n");
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++)
{
if (args[argidx] == "-nolower") {
flag_nolower = true;
continue;
}
break;
}
extra_args(args, argidx, design);
bool have_check_cells = false;
for (auto module : design->selected_modules())
{
SigMap sigmap(module);
FfInitVals initvals(&sigmap, module);
for (auto &mem : Mem::get_selected_memories(module))
{
for (int i = 0; i < GetSize(mem.rd_ports); i++) {
auto &port = mem.rd_ports[i];
if (port.clk_enable)
log_error("Read port %d of memory %s.%s is clocked. This is not supported by \"clk2fflogic\"! "
"Call \"memory\" with -nordff to avoid this error.\n", i, log_id(mem.memid), log_id(module));
}
for (int i = 0; i < GetSize(mem.wr_ports); i++)
{
auto &port = mem.wr_ports[i];
if (!port.clk_enable)
continue;
log("Modifying write port %d on memory %s.%s: CLK=%s, A=%s, D=%s\n",
i, log_id(module), log_id(mem.memid), log_signal(port.clk),
log_signal(port.addr), log_signal(port.data));
Wire *past_clk = module->addWire(NEW_ID_SUFFIX(stringf("%s#%d#past_clk#%s", log_id(mem.memid), i, log_signal(port.clk))));
past_clk->attributes[ID::init] = port.clk_polarity ? State::S1 : State::S0;
module->addFf(NEW_ID, port.clk, past_clk);
SigSpec clock_edge_pattern;
if (port.clk_polarity) {
clock_edge_pattern.append(State::S0);
clock_edge_pattern.append(State::S1);
} else {
clock_edge_pattern.append(State::S1);
clock_edge_pattern.append(State::S0);
}
SigSpec clock_edge = module->Eqx(NEW_ID, {port.clk, SigSpec(past_clk)}, clock_edge_pattern);
SigSpec en_q = module->addWire(NEW_ID_SUFFIX(stringf("%s#%d#en_q", log_id(mem.memid), i)), GetSize(port.en));
module->addFf(NEW_ID, port.en, en_q);
SigSpec addr_q = module->addWire(NEW_ID_SUFFIX(stringf("%s#%d#addr_q", log_id(mem.memid), i)), GetSize(port.addr));
module->addFf(NEW_ID, port.addr, addr_q);
SigSpec data_q = module->addWire(NEW_ID_SUFFIX(stringf("%s#%d#data_q", log_id(mem.memid), i)), GetSize(port.data));
module->addFf(NEW_ID, port.data, data_q);
port.clk = State::S0;
port.en = module->Mux(NEW_ID, Const(0, GetSize(en_q)), en_q, clock_edge);
port.addr = addr_q;
port.data = data_q;
port.clk_enable = false;
port.clk_polarity = false;
}
mem.emit();
}
SigBit initstate;
for (auto cell : vector<Cell*>(module->selected_cells()))
{
if (cell->type.in(ID($print), ID($check)))
{
if (cell->type == ID($check))
have_check_cells = true;
bool trg_enable = cell->getParam(ID(TRG_ENABLE)).as_bool();
if (!trg_enable)
continue;
int trg_width = cell->getParam(ID(TRG_WIDTH)).as_int();
if (trg_width == 0) {
if (initstate == State::S0)
initstate = module->Initstate(NEW_ID);
SigBit sig_en = cell->getPort(ID::EN);
cell->setPort(ID::EN, module->And(NEW_ID, sig_en, initstate));
} else {
SigBit sig_en = cell->getPort(ID::EN);
SigSpec sig_args = cell->getPort(ID::ARGS);
Const trg_polarity = cell->getParam(ID(TRG_POLARITY));
SigSpec sig_trg = cell->getPort(ID::TRG);
SigSpec sig_trg_sampled;
for (auto const &bit : sig_trg)
sig_trg_sampled.append(sample_control_edge(module, bit, trg_polarity[GetSize(sig_trg_sampled)] == State::S1, false));
SigSpec sig_args_sampled = sample_data(module, sig_args, Const(State::S0, GetSize(sig_args)), false, false).sampled;
SigBit sig_en_sampled = sample_data(module, sig_en, State::S0, false, false).sampled;
SigBit sig_trg_combined = module->ReduceOr(NEW_ID, sig_trg_sampled);
cell->setPort(ID::EN, module->And(NEW_ID, sig_en_sampled, sig_trg_combined));
cell->setPort(ID::ARGS, sig_args_sampled);
if (cell->type == ID($check)) {
SigBit sig_a = cell->getPort(ID::A);
SigBit sig_a_sampled = sample_data(module, sig_a, State::S1, false, false).sampled;
cell->setPort(ID::A, sig_a_sampled);
}
}
cell->setPort(ID::TRG, SigSpec());
cell->setParam(ID::TRG_ENABLE, false);
cell->setParam(ID::TRG_WIDTH, 0);
cell->setParam(ID::TRG_POLARITY, false);
cell->set_bool_attribute(ID(trg_on_gclk));
continue;
}
if (!RTLIL::builtin_ff_cell_types().count(cell->type))
continue;
FfData ff(&initvals, cell);
if (ff.has_gclk) {
// Already a $ff or $_FF_ cell.
continue;
}
if (ff.has_clk) {
log("Replacing %s.%s (%s): CLK=%s, D=%s, Q=%s\n",
log_id(module), log_id(cell), log_id(cell->type),
log_signal(ff.sig_clk), log_signal(ff.sig_d), log_signal(ff.sig_q));
} else if (ff.has_aload) {
log("Replacing %s.%s (%s): EN=%s, D=%s, Q=%s\n",
log_id(module), log_id(cell), log_id(cell->type),
log_signal(ff.sig_aload), log_signal(ff.sig_ad), log_signal(ff.sig_q));
} else {
// $sr.
log("Replacing %s.%s (%s): SET=%s, CLR=%s, Q=%s\n",
log_id(module), log_id(cell), log_id(cell->type),
log_signal(ff.sig_set), log_signal(ff.sig_clr), log_signal(ff.sig_q));
}
ff.remove();
if (ff.has_clk)
ff.unmap_ce_srst();
auto next_q = sample_data(module, ff.sig_q, ff.val_init, ff.is_fine, true).sampled;
if (ff.has_clk) {
// The init value for the sampled d is never used, so we can set it to fixed zero, reducing uninit'd FFs
auto sampled_d = sample_data(module, ff.sig_d, RTLIL::Const(State::S0, ff.width), ff.is_fine);
auto clk_edge = sample_control_edge(module, ff.sig_clk, ff.pol_clk, ff.is_fine);
next_q = mux(module, next_q, sampled_d.sampled, clk_edge, ff.is_fine);
}
SampledSig sampled_aload, sampled_ad, sampled_set, sampled_clr, sampled_arst;
// The check for a constant sig_aload is also done by opt_dff, but when using verific and running
// clk2fflogic before opt_dff (which does more and possibly unwanted optimizations) this check avoids
// generating a lot of extra logic.
bool has_nonconst_aload = ff.has_aload && ff.sig_aload != (ff.pol_aload ? State::S0 : State::S1);
if (has_nonconst_aload) {
sampled_aload = sample_control(module, ff.sig_aload, ff.pol_aload, ff.is_fine);
// The init value for the sampled ad is never used, so we can set it to fixed zero, reducing uninit'd FFs
sampled_ad = sample_data(module, ff.sig_ad, RTLIL::Const(State::S0, ff.width), ff.is_fine);
}
if (ff.has_sr) {
sampled_set = sample_control(module, ff.sig_set, ff.pol_set, ff.is_fine);
sampled_clr = sample_control(module, ff.sig_clr, ff.pol_clr, ff.is_fine);
}
if (ff.has_arst)
sampled_arst = sample_control(module, ff.sig_arst, ff.pol_arst, ff.is_fine);
// First perform updates using _only_ sampled values, then again using _only_ current values. Unlike the previous
// implementation, this approach correctly handles all the cases of multiple signals changing simultaneously.
for (int current = 0; current < 2; current++) {
if (has_nonconst_aload)
next_q = mux(module, next_q, sampled_ad[current], sampled_aload[current], ff.is_fine);
if (ff.has_sr)
next_q = bitwise_sr(module, next_q, sampled_set[current], sampled_clr[current], ff.is_fine);
if (ff.has_arst)
next_q = mux(module, next_q, ff.val_arst, sampled_arst[current], ff.is_fine);
}
module->connect(ff.sig_q, next_q);
}
}
if (have_check_cells && !flag_nolower) {
log_push();
Pass::call(design, "chformal -lower");
log_pop();
}
}
} Clk2fflogicPass;
PRIVATE_NAMESPACE_END
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