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yosys/passes/opt/opt_lut_ins.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"
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
struct OptLutInsPass : public Pass {
OptLutInsPass() : Pass("opt_lut_ins", "discard unused LUT inputs") { }
void help() override
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" opt_lut_ins [options] [selection]\n");
log("\n");
log("This pass removes unused inputs from LUT cells (that is, inputs that can not\n");
log("influence the output signal given this LUT's value). While such LUTs cannot\n");
log("be directly emitted by ABC, they can be a result of various post-ABC\n");
log("transformations, such as mapping wide LUTs (not all sub-LUTs will use the\n");
log("full set of inputs) or optimizations such as xilinx_dffopt.\n");
log("\n");
log(" -tech <technology>\n");
log(" Instead of generic $lut cells, operate on LUT cells specific\n");
log(" to the given technology. Valid values are: xilinx, lattice, gowin.\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) override
{
log_header(design, "Executing OPT_LUT_INS pass (discard unused LUT inputs).\n");
string techname;
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++)
{
if (args[argidx] == "-tech" && argidx+1 < args.size()) {
techname = args[++argidx];
continue;
}
break;
}
extra_args(args, argidx, design);
if (techname != "" && techname != "xilinx" && techname != "lattice" && techname != "ecp5" && techname != "gowin")
log_cmd_error("Unsupported technology: '%s'\n", techname.c_str());
for (auto module : design->selected_modules())
{
log("Optimizing LUTs in %s.\n", log_id(module));
std::vector<Cell *> remove_cells;
// Gather LUTs.
for (auto cell : module->selected_cells())
{
if (cell->get_bool_attribute(ID::keep))
continue;
Const lut;
std::vector<SigBit> inputs;
std::vector<SigBit> output;
bool ignore_const = false;
if (techname == "") {
if (cell->type != ID($lut))
continue;
inputs = cell->getPort(ID::A).bits();
output = cell->getPort(ID::Y);
lut = cell->getParam(ID::LUT);
} else if (techname == "xilinx" || techname == "gowin") {
if (cell->type == ID(LUT1)) {
inputs = {
cell->getPort(ID(I0)),
};
} else if (cell->type == ID(LUT2)) {
inputs = {
cell->getPort(ID(I0)),
cell->getPort(ID(I1)),
};
} else if (cell->type == ID(LUT3)) {
inputs = {
cell->getPort(ID(I0)),
cell->getPort(ID(I1)),
cell->getPort(ID(I2)),
};
} else if (cell->type == ID(LUT4)) {
inputs = {
cell->getPort(ID(I0)),
cell->getPort(ID(I1)),
cell->getPort(ID(I2)),
cell->getPort(ID(I3)),
};
} else if (cell->type == ID(LUT5)) {
inputs = {
cell->getPort(ID(I0)),
cell->getPort(ID(I1)),
cell->getPort(ID(I2)),
cell->getPort(ID(I3)),
cell->getPort(ID(I4)),
};
} else if (cell->type == ID(LUT6)) {
inputs = {
cell->getPort(ID(I0)),
cell->getPort(ID(I1)),
cell->getPort(ID(I2)),
cell->getPort(ID(I3)),
cell->getPort(ID(I4)),
cell->getPort(ID(I5)),
};
} else {
// Not a LUT.
continue;
}
lut = cell->getParam(ID::INIT);
if (techname == "xilinx")
output = cell->getPort(ID::O);
else
output = cell->getPort(ID::F);
} else if (techname == "lattice" || techname == "ecp5") {
if (cell->type == ID(LUT4)) {
inputs = {
cell->getPort(ID::A),
cell->getPort(ID::B),
cell->getPort(ID::C),
cell->getPort(ID::D),
};
lut = cell->getParam(ID::INIT);
output = cell->getPort(ID(Z));
ignore_const = true;
} else {
// Not a LUT.
continue;
}
}
std::vector<int> swizzle;
std::vector<SigBit> new_inputs;
bool doit = false;
for (int i = 0; i < GetSize(inputs); i++) {
SigBit input = inputs[i];
if (!input.wire) {
if (input.data == State::S1)
swizzle.push_back(-2);
else
swizzle.push_back(-1);
// For ECP5, smaller LUTs are
// implemented as LUT4s with
// extra const inputs. Do not
// consider that to be a reason
// to redo a LUT.
if (!ignore_const)
doit = true;
} else {
bool redundant = true;
for (int j = 0; j < GetSize(lut); j++) {
if (lut[j] != lut[j ^ 1 << i])
redundant = false;
}
if (redundant) {
swizzle.push_back(-1);
doit = true;
} else {
swizzle.push_back(GetSize(new_inputs));
new_inputs.push_back(input);
}
}
}
if (!doit)
continue;
log(" Optimizing lut %s (%d -> %d)\n", log_id(cell), GetSize(inputs), GetSize(new_inputs));
if (techname == "lattice" || techname == "ecp5") {
// Pad the LUT to 4 inputs, adding consts from the front.
int extra = 4 - GetSize(new_inputs);
log_assert(extra >= 0);
if (extra) {
for (int i = 0; i < extra; i++)
new_inputs.insert(new_inputs.begin(), State::S0);
for (auto &swz : swizzle)
if (swz >= 0)
swz += extra;
}
}
if (techname == "gowin") {
// Pad the LUT to 1 input, adding consts from the front.
if (new_inputs.empty()) {
new_inputs.insert(new_inputs.begin(), State::S0);
}
}
Const new_lut(0, 1 << GetSize(new_inputs));
for (int i = 0; i < GetSize(new_lut); i++) {
int lidx = 0;
for (int j = 0; j < GetSize(inputs); j++) {
int val;
if (swizzle[j] == -2) {
val = 1;
} else if (swizzle[j] == -1) {
val = 0;
} else {
val = (i >> swizzle[j]) & 1;
}
lidx |= val << j;
}
new_lut[i] = lut[lidx];
}
// For lattice, and gowin do not replace with a const driver — the nextpnr
// packer requires a complete set of LUTs for wide LUT muxes.
if (new_inputs.empty() && techname != "lattice" && techname != "ecp5" && techname != "gowin") {
// const driver.
remove_cells.push_back(cell);
module->connect(output, new_lut[0]);
} else {
if (techname == "") {
cell->setParam(ID::LUT, new_lut);
cell->setParam(ID::WIDTH, GetSize(new_inputs));
cell->setPort(ID::A, new_inputs);
} else if (techname == "lattice" || techname == "ecp5") {
log_assert(GetSize(new_inputs) == 4);
cell->setParam(ID::INIT, new_lut);
cell->setPort(ID::A, new_inputs[0]);
cell->setPort(ID::B, new_inputs[1]);
cell->setPort(ID::C, new_inputs[2]);
cell->setPort(ID::D, new_inputs[3]);
} else {
// xilinx, gowin
cell->setParam(ID::INIT, new_lut);
if (techname == "xilinx")
log_assert(GetSize(new_inputs) <= 6);
else
log_assert(GetSize(new_inputs) <= 4);
if (GetSize(new_inputs) == 1)
cell->type = ID(LUT1);
else if (GetSize(new_inputs) == 2)
cell->type = ID(LUT2);
else if (GetSize(new_inputs) == 3)
cell->type = ID(LUT3);
else if (GetSize(new_inputs) == 4)
cell->type = ID(LUT4);
else if (GetSize(new_inputs) == 5)
cell->type = ID(LUT5);
else if (GetSize(new_inputs) == 6)
cell->type = ID(LUT6);
else
log_assert(0);
cell->unsetPort(ID(I0));
cell->unsetPort(ID(I1));
cell->unsetPort(ID(I2));
cell->unsetPort(ID(I3));
cell->unsetPort(ID(I4));
cell->unsetPort(ID(I5));
cell->setPort(ID(I0), new_inputs[0]);
if (GetSize(new_inputs) >= 2)
cell->setPort(ID(I1), new_inputs[1]);
if (GetSize(new_inputs) >= 3)
cell->setPort(ID(I2), new_inputs[2]);
if (GetSize(new_inputs) >= 4)
cell->setPort(ID(I3), new_inputs[3]);
if (GetSize(new_inputs) >= 5)
cell->setPort(ID(I4), new_inputs[4]);
if (GetSize(new_inputs) >= 6)
cell->setPort(ID(I5), new_inputs[5]);
}
}
}
for (auto cell : remove_cells)
module->remove(cell);
}
}
} OptLutInsPass;
PRIVATE_NAMESPACE_END
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