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yosys/passes/opt/pmux2shiftx.cc
Emil J. Tywoniak d2b28d7a25 s/NEW_ID/NEWER_ID/g
2025-09-16 17:43:02 +02:00

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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/utils.h"
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
struct OnehotDatabase
{
Module *module;
const SigMap &sigmap;
bool verbose = false;
bool initialized = false;
FfInitVals initvals;
dict<SigSpec, pool<SigSpec>> sig_sources_db;
dict<SigSpec, bool> sig_onehot_cache;
pool<SigSpec> recursion_guard;
OnehotDatabase(Module *module, const SigMap &sigmap) : module(module), sigmap(sigmap)
{
}
void initialize()
{
log_assert(!initialized);
initialized = true;
initvals.set(&sigmap, module);
for (auto cell : module->cells())
{
vector<SigSpec> inputs;
SigSpec output;
if (cell->type.in(ID($adff), ID($adffe), ID($dff), ID($dffe), ID($sdff), ID($sdffe), ID($sdffce), ID($dlatch), ID($adlatch), ID($ff)))
{
output = cell->getPort(ID::Q);
if (cell->type.in(ID($adff), ID($adffe), ID($adlatch)))
inputs.push_back(cell->getParam(ID::ARST_VALUE));
if (cell->type.in(ID($sdff), ID($sdffe), ID($sdffce)))
inputs.push_back(cell->getParam(ID::SRST_VALUE));
inputs.push_back(cell->getPort(ID::D));
}
if (cell->type.in(ID($mux), ID($pmux)))
{
output = cell->getPort(ID::Y);
inputs.push_back(cell->getPort(ID::A));
SigSpec B = cell->getPort(ID::B);
for (int i = 0; i < GetSize(B); i += GetSize(output))
inputs.push_back(B.extract(i, GetSize(output)));
}
if (!output.empty())
{
output = sigmap(output);
auto &srcs = sig_sources_db[output];
for (auto src : inputs) {
while (!src.empty() && src[GetSize(src)-1] == State::S0)
src.remove(GetSize(src)-1);
srcs.insert(sigmap(src));
}
}
}
}
void query_worker(const SigSpec &sig, bool &retval, bool &cache, int indent)
{
if (verbose)
log("%*s %s\n", indent, "", log_signal(sig));
log_assert(retval);
if (recursion_guard.count(sig)) {
if (verbose)
log("%*s - recursion\n", indent, "");
cache = false;
return;
}
auto it = sig_onehot_cache.find(sig);
if (it != sig_onehot_cache.end()) {
if (verbose)
log("%*s - cached (%s)\n", indent, "", it->second ? "true" : "false");
if (!it->second)
retval = false;
return;
}
bool found_init_ones = false;
for (auto bit : sig) {
if (initvals(bit) == State::S1) {
if (found_init_ones) {
if (verbose)
log("%*s - non-onehot init value\n", indent, "");
retval = false;
break;
}
found_init_ones = true;
}
}
if (retval)
{
if (sig.is_fully_const())
{
bool found_ones = false;
for (auto bit : sig) {
if (bit == State::S1) {
if (found_ones) {
if (verbose)
log("%*s - non-onehot constant\n", indent, "");
retval = false;
break;
}
found_ones = true;
}
}
}
else
{
auto srcs = sig_sources_db.find(sig);
if (srcs == sig_sources_db.end()) {
if (verbose)
log("%*s - no sources for non-const signal\n", indent, "");
retval = false;
} else {
for (auto &src : srcs->second) {
bool child_cache = true;
recursion_guard.insert(sig);
query_worker(src, retval, child_cache, indent+4);
recursion_guard.erase(sig);
if (!child_cache)
cache = false;
if (!retval)
break;
}
}
}
}
// it is always safe to cache a negative result
if (cache || !retval)
sig_onehot_cache[sig] = retval;
}
bool query(const SigSpec &sig)
{
bool retval = true;
bool cache = true;
if (verbose)
log("** ONEHOT QUERY START (%s)\n", log_signal(sig));
if (!initialized)
initialize();
query_worker(sig, retval, cache, 3);
if (verbose)
log("** ONEHOT QUERY RESULT = %s\n", retval ? "true" : "false");
// it is always safe to cache the root result of a query
if (!cache)
sig_onehot_cache[sig] = retval;
return retval;
}
};
struct Pmux2ShiftxPass : public Pass {
Pmux2ShiftxPass() : Pass("pmux2shiftx", "transform $pmux cells to $shiftx cells") { }
void help() override
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" pmux2shiftx [options] [selection]\n");
log("\n");
log("This pass transforms $pmux cells to $shiftx cells.\n");
log("\n");
log(" -v, -vv\n");
log(" verbose output\n");
log("\n");
log(" -min_density <percentage>\n");
log(" specifies the minimum density for the shifter\n");
log(" default: 50\n");
log("\n");
log(" -min_choices <int>\n");
log(" specified the minimum number of choices for a control signal\n");
log(" default: 3\n");
log("\n");
log(" -onehot ignore|pmux|shiftx\n");
log(" select strategy for one-hot encoded control signals\n");
log(" default: pmux\n");
log("\n");
log(" -norange\n");
log(" disable $sub inference for \"range decoders\"\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) override
{
int min_density = 50;
int min_choices = 3;
bool allow_onehot = false;
bool optimize_onehot = true;
bool verbose = false;
bool verbose_onehot = false;
bool norange = false;
log_header(design, "Executing PMUX2SHIFTX pass.\n");
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++) {
if (args[argidx] == "-min_density" && argidx+1 < args.size()) {
min_density = atoi(args[++argidx].c_str());
continue;
}
if (args[argidx] == "-min_choices" && argidx+1 < args.size()) {
min_choices = atoi(args[++argidx].c_str());
continue;
}
if (args[argidx] == "-onehot" && argidx+1 < args.size() && args[argidx+1] == "ignore") {
argidx++;
allow_onehot = false;
optimize_onehot = false;
continue;
}
if (args[argidx] == "-onehot" && argidx+1 < args.size() && args[argidx+1] == "pmux") {
argidx++;
allow_onehot = false;
optimize_onehot = true;
continue;
}
if (args[argidx] == "-onehot" && argidx+1 < args.size() && args[argidx+1] == "shiftx") {
argidx++;
allow_onehot = true;
optimize_onehot = false;
continue;
}
if (args[argidx] == "-v") {
verbose = true;
continue;
}
if (args[argidx] == "-vv") {
verbose = true;
verbose_onehot = true;
continue;
}
if (args[argidx] == "-norange") {
norange = true;
continue;
}
break;
}
extra_args(args, argidx, design);
for (auto module : design->selected_modules())
{
SigMap sigmap(module);
OnehotDatabase onehot_db(module, sigmap);
onehot_db.verbose = verbose_onehot;
dict<SigBit, pair<SigSpec, Const>> eqdb;
for (auto cell : module->cells())
{
if (cell->type == ID($eq))
{
dict<SigBit, State> bits;
SigSpec A = sigmap(cell->getPort(ID::A));
SigSpec B = sigmap(cell->getPort(ID::B));
int a_width = cell->getParam(ID::A_WIDTH).as_int();
int b_width = cell->getParam(ID::B_WIDTH).as_int();
if (a_width < b_width) {
bool a_signed = cell->getParam(ID::A_SIGNED).as_int();
A.extend_u0(b_width, a_signed);
}
if (b_width < a_width) {
bool b_signed = cell->getParam(ID::B_SIGNED).as_int();
B.extend_u0(a_width, b_signed);
}
for (int i = 0; i < GetSize(A); i++) {
SigBit a_bit = A[i], b_bit = B[i];
if (b_bit.wire && !a_bit.wire) {
std::swap(a_bit, b_bit);
}
if (!a_bit.wire || b_bit.wire)
goto next_cell;
if (bits.count(a_bit))
goto next_cell;
bits[a_bit] = b_bit.data;
}
if (GetSize(bits) > 20)
goto next_cell;
bits.sort();
pair<SigSpec, Const> entry;
RTLIL::Const::Builder entry_bits_builder(GetSize(bits));
for (auto it : bits) {
entry.first.append(it.first);
entry_bits_builder.push_back(it.second);
}
entry.second = entry_bits_builder.build();
eqdb[sigmap(cell->getPort(ID::Y)[0])] = entry;
goto next_cell;
}
if (cell->type == ID($logic_not))
{
dict<SigBit, State> bits;
SigSpec A = sigmap(cell->getPort(ID::A));
for (int i = 0; i < GetSize(A); i++)
bits[A[i]] = State::S0;
bits.sort();
pair<SigSpec, Const> entry;
RTLIL::Const::Builder entry_bits_builder(GetSize(bits));
for (auto it : bits) {
entry.first.append(it.first);
entry_bits_builder.push_back(it.second);
}
entry.second = entry_bits_builder.build();
eqdb[sigmap(cell->getPort(ID::Y)[0])] = entry;
goto next_cell;
}
next_cell:;
}
for (auto cell : module->selected_cells())
{
if (cell->type != ID($pmux))
continue;
string src = cell->get_src_attribute();
int width = cell->getParam(ID::WIDTH).as_int();
int width_bits = ceil_log2(width);
int extwidth = width;
while (extwidth & (extwidth-1))
extwidth++;
dict<SigSpec, pool<int>> seldb;
SigSpec A = cell->getPort(ID::A);
SigSpec B = cell->getPort(ID::B);
SigSpec S = sigmap(cell->getPort(ID::S));
for (int i = 0; i < GetSize(S); i++)
{
if (!eqdb.count(S[i]))
continue;
auto &entry = eqdb.at(S[i]);
seldb[entry.first].insert(i);
}
if (seldb.empty())
continue;
bool printed_pmux_header = false;
if (verbose) {
printed_pmux_header = true;
log("Inspecting $pmux cell %s/%s.\n", log_id(module), log_id(cell));
log(" data width: %d (next power-of-2 = %d, log2 = %d)\n", width, extwidth, width_bits);
}
SigSpec updated_S = cell->getPort(ID::S);
SigSpec updated_B = cell->getPort(ID::B);
while (!seldb.empty())
{
// pick the largest entry in seldb
SigSpec sig = seldb.begin()->first;
for (auto &it : seldb) {
if (GetSize(sig) < GetSize(it.first))
sig = it.first;
else if (GetSize(seldb.at(sig)) < GetSize(it.second))
sig = it.first;
}
// find the relevant choices
bool is_onehot = GetSize(sig) > 2;
dict<Const, int> choices;
for (int i : seldb.at(sig)) {
Const val = eqdb.at(S[i]).second;
int onebits = 0;
for (auto b : val)
if (b == State::S1)
onebits++;
if (onebits > 1)
is_onehot = false;
choices[val] = i;
}
bool full_pmux = GetSize(choices) == GetSize(S);
// TBD: also find choices that are using signals that are subsets of the bits in "sig"
if (!verbose)
{
if (is_onehot && !allow_onehot && !optimize_onehot) {
seldb.erase(sig);
continue;
}
if (GetSize(choices) < min_choices) {
seldb.erase(sig);
continue;
}
}
if (!printed_pmux_header) {
printed_pmux_header = true;
log("Inspecting $pmux cell %s/%s.\n", log_id(module), log_id(cell));
log(" data width: %d (next power-of-2 = %d, log2 = %d)\n", width, extwidth, width_bits);
}
log(" checking ctrl signal %s\n", log_signal(sig));
auto print_choices = [&]() {
log(" table of choices:\n");
for (auto &it : choices)
log(" %3d: %s: %s\n", it.second, log_signal(it.first),
log_signal(B.extract(it.second*width, width)));
};
if (verbose)
{
if (is_onehot && !allow_onehot && !optimize_onehot) {
print_choices();
log(" ignoring one-hot encoding.\n");
seldb.erase(sig);
continue;
}
if (GetSize(choices) < min_choices) {
print_choices();
log(" insufficient choices.\n");
seldb.erase(sig);
continue;
}
}
if (is_onehot && optimize_onehot)
{
print_choices();
if (!onehot_db.query(sig))
{
log(" failed to detect onehot driver. do not optimize.\n");
}
else
{
log(" optimizing one-hot encoding.\n");
for (auto &it : choices)
{
const Const &val = it.first;
int index = -1;
for (int i = 0; i < GetSize(val); i++)
if (val[i] == State::S1) {
log_assert(index < 0);
index = i;
}
if (index < 0) {
log(" %3d: zero encoding.\n", it.second);
continue;
}
SigBit new_ctrl = sig[index];
log(" %3d: new crtl signal is %s.\n", it.second, log_signal(new_ctrl));
updated_S[it.second] = new_ctrl;
}
}
seldb.erase(sig);
continue;
}
// find the best permutation
vector<int> perm_new_from_old(GetSize(sig));
Const perm_xormask(State::S0, GetSize(sig));
{
vector<int> values(GetSize(choices));
vector<bool> used_src_columns(GetSize(sig));
vector<vector<bool>> columns(GetSize(sig), vector<bool>(GetSize(values)));
for (int i = 0; i < GetSize(choices); i++) {
Const val = choices.element(i)->first;
for (int k = 0; k < GetSize(val); k++)
if (val[k] == State::S1)
columns[k][i] = true;
}
for (int dst_col = GetSize(sig)-1; dst_col >= 0; dst_col--)
{
int best_src_col = -1;
bool best_inv = false;
int best_maxval = 0;
int best_delta = 0;
// find best src column for this dst column
for (int src_col = 0; src_col < GetSize(sig); src_col++)
{
if (used_src_columns[src_col])
continue;
int this_maxval = 0;
int this_minval = 1 << 30;
int this_inv_maxval = 0;
int this_inv_minval = 1 << 30;
for (int i = 0; i < GetSize(values); i++)
{
int val = values[i];
int inv_val = val;
if (columns[src_col][i])
val |= 1 << dst_col;
else
inv_val |= 1 << dst_col;
this_maxval = std::max(this_maxval, val);
this_minval = std::min(this_minval, val);
this_inv_maxval = std::max(this_inv_maxval, inv_val);
this_inv_minval = std::min(this_inv_minval, inv_val);
}
int this_delta = this_maxval - this_minval;
int this_inv_delta = this_maxval - this_minval;
bool this_inv = false;
if (!norange && this_delta != this_inv_delta)
this_inv = this_inv_delta < this_delta;
else if (this_maxval != this_inv_maxval)
this_inv = this_inv_maxval < this_maxval;
if (this_inv) {
this_delta = this_inv_delta;
this_maxval = this_inv_maxval;
this_minval = this_inv_minval;
}
bool this_is_better = false;
if (best_src_col < 0)
this_is_better = true;
else if (!norange && this_delta != best_delta)
this_is_better = this_delta < best_delta;
else if (this_maxval != best_maxval)
this_is_better = this_maxval < best_maxval;
else
this_is_better = sig[best_src_col] < sig[src_col];
if (this_is_better) {
best_src_col = src_col;
best_inv = this_inv;
best_maxval = this_maxval;
best_delta = this_delta;
}
}
used_src_columns[best_src_col] = true;
perm_new_from_old[dst_col] = best_src_col;
perm_xormask.set(dst_col, best_inv ? State::S1 : State::S0);
}
}
// permutated sig
SigSpec perm_sig(State::S0, GetSize(sig));
for (int i = 0; i < GetSize(sig); i++)
perm_sig[i] = sig[perm_new_from_old[i]];
log(" best permutation: %s\n", log_signal(perm_sig));
log(" best xor mask: %s\n", log_signal(perm_xormask));
// permutated choices
int min_choice = 1 << 30;
int max_choice = -1;
dict<Const, int> perm_choices;
for (auto &it : choices)
{
Const &old_c = it.first;
Const new_c(State::S0, GetSize(old_c));
for (int i = 0; i < GetSize(old_c); i++)
new_c.set(i, old_c[perm_new_from_old[i]]);
Const new_c_before_xor = new_c;
new_c = const_xor(new_c, perm_xormask, false, false, GetSize(new_c));
perm_choices[new_c] = it.second;
min_choice = std::min(min_choice, new_c.as_int());
max_choice = std::max(max_choice, new_c.as_int());
log(" %3d: %s -> %s -> %s: %s\n", it.second, log_signal(old_c), log_signal(new_c_before_xor),
log_signal(new_c), log_signal(B.extract(it.second*width, width)));
}
int range_density = 100*GetSize(choices) / (max_choice-min_choice+1);
int absolute_density = 100*GetSize(choices) / (max_choice+1);
log(" choices: %d\n", GetSize(choices));
log(" min choice: %d\n", min_choice);
log(" max choice: %d\n", max_choice);
log(" range density: %d%%\n", range_density);
log(" absolute density: %d%%\n", absolute_density);
if (full_pmux) {
int full_density = 100*GetSize(choices) / (1 << GetSize(sig));
log(" full density: %d%%\n", full_density);
if (full_density < min_density) {
full_pmux = false;
} else {
min_choice = 0;
max_choice = (1 << GetSize(sig))-1;
log(" update to full case.\n");
log(" new min choice: %d\n", min_choice);
log(" new max choice: %d\n", max_choice);
}
}
bool full_case = (min_choice == 0) && (max_choice == (1 << GetSize(sig))-1) && (full_pmux || max_choice+1 == GetSize(choices));
log(" full case: %s\n", full_case ? "true" : "false");
// check density percentages
Const offset(State::S0, GetSize(sig));
if (!norange && absolute_density < min_density && range_density >= min_density)
{
offset = Const(min_choice, GetSize(sig));
log(" offset: %s\n", log_signal(offset));
min_choice -= offset.as_int();
max_choice -= offset.as_int();
dict<Const, int> new_perm_choices;
for (auto &it : perm_choices)
new_perm_choices[const_sub(it.first, offset, false, false, GetSize(sig))] = it.second;
perm_choices.swap(new_perm_choices);
} else
if (absolute_density < min_density) {
log(" insufficient density.\n");
seldb.erase(sig);
continue;
}
// creat cmp signal
SigSpec cmp = perm_sig;
if (perm_xormask.as_bool())
cmp = module->Xor(NEWER_ID, cmp, perm_xormask, false, src);
if (offset.as_bool())
cmp = module->Sub(NEWER_ID, cmp, offset, false, src);
// create enable signal
SigBit en = State::S1;
if (!full_case) {
Const enable_mask(State::S0, max_choice+1);
for (auto &it : perm_choices)
enable_mask.set(it.first.as_int(), State::S1);
en = module->addWire(NEWER_ID);
module->addShift(NEWER_ID, enable_mask, cmp, en, false, src);
}
// create data signal
SigSpec data(State::Sx, (max_choice+1)*extwidth);
if (full_pmux) {
for (int i = 0; i <= max_choice; i++)
data.replace(i*extwidth, A);
}
for (auto &it : perm_choices) {
int position = it.first.as_int()*extwidth;
int data_index = it.second;
data.replace(position, B.extract(data_index*width, width));
updated_S[data_index] = State::S0;
updated_B.replace(data_index*width, SigSpec(State::Sx, width));
}
// create shiftx cell
SigSpec shifted_cmp = {cmp, SigSpec(State::S0, width_bits)};
SigSpec outsig = module->addWire(NEWER_ID, width);
Cell *c = module->addShiftx(NEWER_ID, data, shifted_cmp, outsig, false, src);
updated_S.append(en);
updated_B.append(outsig);
log(" created $shiftx cell %s.\n", log_id(c));
// remove this sig and continue with the next block
seldb.erase(sig);
}
// update $pmux cell
cell->setPort(ID::S, updated_S);
cell->setPort(ID::B, updated_B);
cell->setParam(ID::S_WIDTH, GetSize(updated_S));
}
}
}
} Pmux2ShiftxPass;
struct OnehotPass : public Pass {
OnehotPass() : Pass("onehot", "optimize $eq cells for onehot signals") { }
void help() override
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" onehot [options] [selection]\n");
log("\n");
log("This pass optimizes $eq cells that compare one-hot signals against constants\n");
log("\n");
log(" -v, -vv\n");
log(" verbose output\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) override
{
bool verbose = false;
bool verbose_onehot = false;
log_header(design, "Executing ONEHOT pass.\n");
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++) {
if (args[argidx] == "-v") {
verbose = true;
continue;
}
if (args[argidx] == "-vv") {
verbose = true;
verbose_onehot = true;
continue;
}
break;
}
extra_args(args, argidx, design);
for (auto module : design->selected_modules())
{
SigMap sigmap(module);
OnehotDatabase onehot_db(module, sigmap);
onehot_db.verbose = verbose_onehot;
for (auto cell : module->selected_cells())
{
if (cell->type != ID($eq))
continue;
SigSpec A = sigmap(cell->getPort(ID::A));
SigSpec B = sigmap(cell->getPort(ID::B));
int a_width = cell->getParam(ID::A_WIDTH).as_int();
int b_width = cell->getParam(ID::B_WIDTH).as_int();
if (a_width < b_width) {
bool a_signed = cell->getParam(ID::A_SIGNED).as_int();
A.extend_u0(b_width, a_signed);
}
if (b_width < a_width) {
bool b_signed = cell->getParam(ID::B_SIGNED).as_int();
B.extend_u0(a_width, b_signed);
}
if (A.is_fully_const())
std::swap(A, B);
if (!B.is_fully_const())
continue;
if (verbose)
log("Checking $eq(%s, %s) cell %s/%s.\n", log_signal(A), log_signal(B), log_id(module), log_id(cell));
if (!onehot_db.query(A)) {
if (verbose)
log(" onehot driver test on %s failed.\n", log_signal(A));
continue;
}
int index = -1;
bool not_onehot = false;
for (int i = 0; i < GetSize(B); i++) {
if (B[i] != State::S1)
continue;
if (index >= 0)
not_onehot = true;
index = i;
}
if (index < 0) {
if (verbose)
log(" not optimizing the zero pattern.\n");
continue;
}
SigSpec Y = cell->getPort(ID::Y);
if (not_onehot)
{
if (verbose)
log(" replacing with constant 0 driver.\n");
else
log("Replacing one-hot $eq(%s, %s) cell %s/%s with constant 0 driver.\n", log_signal(A), log_signal(B), log_id(module), log_id(cell));
module->connect(Y, SigSpec(1, GetSize(Y)));
}
else
{
SigSpec sig = A[index];
if (verbose)
log(" replacing with signal %s.\n", log_signal(sig));
else
log("Replacing one-hot $eq(%s, %s) cell %s/%s with signal %s.\n",log_signal(A), log_signal(B), log_id(module), log_id(cell), log_signal(sig));
sig.extend_u0(GetSize(Y));
module->connect(Y, sig);
}
module->remove(cell);
}
}
}
} OnehotPass;
PRIVATE_NAMESPACE_END
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