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yosys/passes/opt/opt_lut.cc
whitequark efa278e232 Fix typographical and grammatical errors and inconsistencies. 
The initial list of hits was generated with the codespell command
below, and each hit was evaluated and fixed manually while taking
context into consideration.

    DIRS="kernel/ frontends/ backends/ passes/ techlibs/"
    DIRS="${DIRS} libs/ezsat/ libs/subcircuit"
    codespell $DIRS -S *.o -L upto,iff,thru,synopsys,uint

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2019-01-02 13:12:17 +00:00

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/*
* yosys -- Yosys Open SYnthesis Suite
*
* Copyright (C) 2018 whitequark <whitequark@whitequark.org>
*
* 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/modtools.h"
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
struct OptLutWorker
{
dict<IdString, dict<int, IdString>> &dlogic;
RTLIL::Module *module;
ModIndex index;
SigMap sigmap;
pool<RTLIL::Cell*> luts;
dict<RTLIL::Cell*, int> luts_arity;
dict<RTLIL::Cell*, pool<RTLIL::Cell*>> luts_dlogics;
dict<RTLIL::Cell*, pool<int>> luts_dlogic_inputs;
int combined_count = 0;
bool evaluate_lut(RTLIL::Cell *lut, dict<SigBit, bool> inputs)
{
SigSpec lut_input = sigmap(lut->getPort("\\A"));
int lut_width = lut->getParam("\\WIDTH").as_int();
Const lut_table = lut->getParam("\\LUT");
int lut_index = 0;
for (int i = 0; i < lut_width; i++)
{
SigBit input = sigmap(lut_input[i]);
if (inputs.count(input))
{
lut_index |= inputs[input] << i;
}
else
{
lut_index |= SigSpec(lut_input[i]).as_bool() << i;
}
}
return lut_table.extract(lut_index).as_bool();
}
void show_stats_by_arity()
{
dict<int, int> arity_counts;
dict<IdString, int> dlogic_counts;
int max_arity = 0;
for (auto lut_arity : luts_arity)
{
max_arity = max(max_arity, lut_arity.second);
arity_counts[lut_arity.second]++;
}
for (auto &lut_dlogics : luts_dlogics)
{
for (auto &lut_dlogic : lut_dlogics.second)
{
dlogic_counts[lut_dlogic->type]++;
}
}
log("Number of LUTs: %8zu\n", luts.size());
for (int arity = 1; arity <= max_arity; arity++)
{
if (arity_counts[arity])
log(" %d-LUT %16d\n", arity, arity_counts[arity]);
}
for (auto &dlogic_count : dlogic_counts)
{
log(" with %-12s %4d\n", dlogic_count.first.c_str(), dlogic_count.second);
}
}
OptLutWorker(dict<IdString, dict<int, IdString>> &dlogic, RTLIL::Module *module, int limit) :
dlogic(dlogic), module(module), index(module), sigmap(module)
{
log("Discovering LUTs.\n");
for (auto cell : module->selected_cells())
{
if (cell->type == "$lut")
{
int lut_width = cell->getParam("\\WIDTH").as_int();
SigSpec lut_input = cell->getPort("\\A");
int lut_arity = 0;
log("Found $lut\\WIDTH=%d cell %s.%s.\n", lut_width, log_id(module), log_id(cell));
luts.insert(cell);
// First, find all dedicated logic we're connected to. This results in an overapproximation
// of such connections.
pool<RTLIL::Cell*> lut_all_dlogics;
for (int i = 0; i < lut_width; i++)
{
SigBit bit = lut_input[i];
for (auto &port : index.query_ports(bit))
{
if (dlogic.count(port.cell->type))
{
auto &dlogic_map = dlogic[port.cell->type];
if (dlogic_map.count(i))
{
if (port.port == dlogic_map[i])
{
lut_all_dlogics.insert(port.cell);
}
}
}
}
}
// Second, make sure that the connection to dedicated logic is legal. If it is not legal,
// it means one of the two things:
// * The connection is spurious. I.e. this is dedicated logic that will be packed
// with some other LUT, and it just happens to be connected to this LUT as well.
// * The connection is illegal.
// In either of these cases, we don't need to concern ourselves with preserving the connection
// between this LUT and this dedicated logic cell.
pool<RTLIL::Cell*> lut_legal_dlogics;
pool<int> lut_dlogic_inputs;
for (auto lut_dlogic : lut_all_dlogics)
{
auto &dlogic_map = dlogic[lut_dlogic->type];
bool legal = true;
for (auto &dlogic_conn : dlogic_map)
{
if (lut_width <= dlogic_conn.first)
{
log(" LUT has illegal connection to %s cell %s.%s.\n", lut_dlogic->type.c_str(), log_id(module), log_id(lut_dlogic));
log(" LUT input A[%d] not present.\n", dlogic_conn.first);
legal = false;
break;
}
if (sigmap(lut_input[dlogic_conn.first]) != sigmap(lut_dlogic->getPort(dlogic_conn.second)))
{
log(" LUT has illegal connection to %s cell %s.%s.\n", lut_dlogic->type.c_str(), log_id(module), log_id(lut_dlogic));
log(" LUT input A[%d] (wire %s) not connected to %s port %s (wire %s).\n", dlogic_conn.first, log_signal(lut_input[dlogic_conn.first]), lut_dlogic->type.c_str(), dlogic_conn.second.c_str(), log_signal(lut_dlogic->getPort(dlogic_conn.second)));
legal = false;
break;
}
}
if (legal)
{
log(" LUT has legal connection to %s cell %s.%s.\n", lut_dlogic->type.c_str(), log_id(module), log_id(lut_dlogic));
lut_legal_dlogics.insert(lut_dlogic);
for (auto &dlogic_conn : dlogic_map)
lut_dlogic_inputs.insert(dlogic_conn.first);
}
}
// Third, determine LUT arity. An n-wide LUT that has k constant inputs and m inputs shared with dedicated
// logic implements an (n-k-m)-ary function.
for (int i = 0; i < lut_width; i++)
{
SigBit bit = lut_input[i];
if (bit.wire || lut_dlogic_inputs.count(i))
lut_arity++;
}
log(" Cell implements a %d-LUT.\n", lut_arity);
luts_arity[cell] = lut_arity;
luts_dlogics[cell] = lut_legal_dlogics;
luts_dlogic_inputs[cell] = lut_dlogic_inputs;
}
}
show_stats_by_arity();
log("\n");
log("Eliminating LUTs.\n");
for (auto lut : luts)
{
SigSpec lut_input = sigmap(lut->getPort("\\A"));
pool<int> &lut_dlogic_inputs = luts_dlogic_inputs[lut];
vector<SigBit> lut_inputs;
for (auto &bit : lut_input)
{
if (bit.wire)
lut_inputs.push_back(sigmap(bit));
}
bool const0_match = true;
bool const1_match = true;
vector<bool> input_matches;
for (size_t i = 0; i < lut_inputs.size(); i++)
input_matches.push_back(true);
for (int eval = 0; eval < 1 << lut_inputs.size(); eval++)
{
dict<SigBit, bool> eval_inputs;
for (size_t i = 0; i < lut_inputs.size(); i++)
eval_inputs[lut_inputs[i]] = (eval >> i) & 1;
bool value = evaluate_lut(lut, eval_inputs);
if (value != 0)
const0_match = false;
if (value != 1)
const1_match = false;
for (size_t i = 0; i < lut_inputs.size(); i++)
{
if (value != eval_inputs[lut_inputs[i]])
input_matches[i] = false;
}
}
int input_match = -1;
for (size_t i = 0; i < lut_inputs.size(); i++)
if (input_matches[i])
input_match = i;
if (const0_match || const1_match || input_match != -1)
{
log("Found redundant cell %s.%s.\n", log_id(module), log_id(lut));
SigBit value;
if (const0_match)
{
log(" Cell evaluates constant 0.\n");
value = State::S0;
}
if (const1_match)
{
log(" Cell evaluates constant 1.\n");
value = State::S1;
}
if (input_match != -1) {
log(" Cell evaluates signal %s.\n", log_signal(lut_inputs[input_match]));
value = lut_inputs[input_match];
}
if (lut_dlogic_inputs.size())
{
log(" Not eliminating cell (connected to dedicated logic).\n");
}
else
{
SigSpec lut_output = lut->getPort("\\Y");
module->connect(lut_output, value);
module->remove(lut);
luts.erase(lut);
luts_arity.erase(lut);
luts_dlogics.erase(lut);
luts_dlogic_inputs.erase(lut);
}
}
}
show_stats_by_arity();
log("\n");
log("Combining LUTs.\n");
pool<RTLIL::Cell*> worklist = luts;
while (worklist.size())
{
if (limit == 0)
{
log("Limit reached.\n");
break;
}
auto lutA = worklist.pop();
SigSpec lutA_input = sigmap(lutA->getPort("\\A"));
SigSpec lutA_output = sigmap(lutA->getPort("\\Y")[0]);
int lutA_width = lutA->getParam("\\WIDTH").as_int();
int lutA_arity = luts_arity[lutA];
pool<int> &lutA_dlogic_inputs = luts_dlogic_inputs[lutA];
auto lutA_output_ports = index.query_ports(lutA->getPort("\\Y"));
if (lutA_output_ports.size() != 2)
continue;
for (auto &port : lutA_output_ports)
{
if (port.cell == lutA)
continue;
if (luts.count(port.cell))
{
auto lutB = port.cell;
SigSpec lutB_input = sigmap(lutB->getPort("\\A"));
SigSpec lutB_output = sigmap(lutB->getPort("\\Y")[0]);
int lutB_width = lutB->getParam("\\WIDTH").as_int();
int lutB_arity = luts_arity[lutB];
pool<int> &lutB_dlogic_inputs = luts_dlogic_inputs[lutB];
log("Found %s.%s (cell A) feeding %s.%s (cell B).\n", log_id(module), log_id(lutA), log_id(module), log_id(lutB));
if (index.query_is_output(lutA->getPort("\\Y")))
{
log(" Not combining LUTs (cascade connection feeds module output).\n");
continue;
}
pool<SigBit> lutA_inputs;
pool<SigBit> lutB_inputs;
for (auto &bit : lutA_input)
{
if (bit.wire)
lutA_inputs.insert(sigmap(bit));
}
for (auto &bit : lutB_input)
{
if (bit.wire)
lutB_inputs.insert(sigmap(bit));
}
pool<SigBit> common_inputs;
for (auto &bit : lutA_inputs)
{
if (lutB_inputs.count(bit))
common_inputs.insert(bit);
}
int lutM_arity = lutA_arity + lutB_arity - 1 - common_inputs.size();
if (lutA_dlogic_inputs.size())
log(" Cell A is a %d-LUT with %zu dedicated connections. ", lutA_arity, lutA_dlogic_inputs.size());
else
log(" Cell A is a %d-LUT. ", lutA_arity);
if (lutB_dlogic_inputs.size())
log("Cell B is a %d-LUT with %zu dedicated connections.\n", lutB_arity, lutB_dlogic_inputs.size());
else
log("Cell B is a %d-LUT.\n", lutB_arity);
log(" Cells share %zu input(s) and can be merged into one %d-LUT.\n", common_inputs.size(), lutM_arity);
const int COMBINE_A = 1, COMBINE_B = 2, COMBINE_EITHER = COMBINE_A | COMBINE_B;
int combine_mask = 0;
if (lutM_arity > lutA_width)
{
log(" Not combining LUTs into cell A (combined LUT wider than cell A).\n");
}
else if (lutB_dlogic_inputs.size() > 0)
{
log(" Not combining LUTs into cell A (cell B is connected to dedicated logic).\n");
}
else if (lutB->get_bool_attribute("\\lut_keep"))
{
log(" Not combining LUTs into cell A (cell B has attribute \\lut_keep).\n");
}
else
{
combine_mask |= COMBINE_A;
}
if (lutM_arity > lutB_width)
{
log(" Not combining LUTs into cell B (combined LUT wider than cell B).\n");
}
else if (lutA_dlogic_inputs.size() > 0)
{
log(" Not combining LUTs into cell B (cell A is connected to dedicated logic).\n");
}
else if (lutA->get_bool_attribute("\\lut_keep"))
{
log(" Not combining LUTs into cell B (cell A has attribute \\lut_keep).\n");
}
else
{
combine_mask |= COMBINE_B;
}
int combine = combine_mask;
if (combine == COMBINE_EITHER)
{
log(" Can combine into either cell.\n");
if (lutA_arity == 1)
{
log(" Cell A is a buffer or inverter, combining into cell B.\n");
combine = COMBINE_B;
}
else if (lutB_arity == 1)
{
log(" Cell B is a buffer or inverter, combining into cell A.\n");
combine = COMBINE_A;
}
else
{
log(" Arbitrarily combining into cell A.\n");
combine = COMBINE_A;
}
}
RTLIL::Cell *lutM, *lutR;
pool<SigBit> lutM_inputs, lutR_inputs;
pool<int> lutM_dlogic_inputs;
if (combine == COMBINE_A)
{
log(" Combining LUTs into cell A.\n");
lutM = lutA;
lutM_inputs = lutA_inputs;
lutM_dlogic_inputs = lutA_dlogic_inputs;
lutR = lutB;
lutR_inputs = lutB_inputs;
}
else if (combine == COMBINE_B)
{
log(" Combining LUTs into cell B.\n");
lutM = lutB;
lutM_inputs = lutB_inputs;
lutM_dlogic_inputs = lutB_dlogic_inputs;
lutR = lutA;
lutR_inputs = lutA_inputs;
}
else
{
log(" Cannot combine LUTs.\n");
continue;
}
pool<SigBit> lutR_unique;
for (auto &bit : lutR_inputs)
{
if (!common_inputs.count(bit) && bit != lutA_output)
lutR_unique.insert(bit);
}
int lutM_width = lutM->getParam("\\WIDTH").as_int();
SigSpec lutM_input = sigmap(lutM->getPort("\\A"));
std::vector<SigBit> lutM_new_inputs;
for (int i = 0; i < lutM_width; i++)
{
bool input_unused = false;
if (sigmap(lutM_input[i]) == lutA_output)
input_unused = true;
if (!lutM_input[i].wire && !lutM_dlogic_inputs.count(i))
input_unused = true;
if (input_unused && lutR_unique.size())
{
SigBit new_input = lutR_unique.pop();
log(" Connecting input %d as %s.\n", i, log_signal(new_input));
lutM_new_inputs.push_back(new_input);
}
else if (sigmap(lutM_input[i]) == lutA_output)
{
log(" Disconnecting cascade input %d.\n", i);
lutM_new_inputs.push_back(SigBit());
}
else
{
log(" Leaving input %d as %s.\n", i, log_signal(lutM_input[i]));
lutM_new_inputs.push_back(lutM_input[i]);
}
}
log_assert(lutR_unique.size() == 0);
RTLIL::Const lutM_new_table(State::Sx, 1 << lutM_width);
for (int eval = 0; eval < 1 << lutM_width; eval++)
{
dict<SigBit, bool> eval_inputs;
for (size_t i = 0; i < lutM_new_inputs.size(); i++)
{
eval_inputs[lutM_new_inputs[i]] = (eval >> i) & 1;
}
eval_inputs[lutA_output] = evaluate_lut(lutA, eval_inputs);
lutM_new_table[eval] = (RTLIL::State) evaluate_lut(lutB, eval_inputs);
}
log(" Cell A truth table: %s.\n", lutA->getParam("\\LUT").as_string().c_str());
log(" Cell B truth table: %s.\n", lutB->getParam("\\LUT").as_string().c_str());
log(" Merged truth table: %s.\n", lutM_new_table.as_string().c_str());
lutM->setParam("\\LUT", lutM_new_table);
lutM->setPort("\\A", lutM_new_inputs);
lutM->setPort("\\Y", lutB_output);
luts_arity[lutM] = lutM_arity;
luts.erase(lutR);
luts_arity.erase(lutR);
lutR->module->remove(lutR);
worklist.insert(lutM);
worklist.erase(lutR);
combined_count++;
if (limit > 0)
limit--;
}
}
}
show_stats_by_arity();
}
};
static void split(std::vector<std::string> &tokens, const std::string &text, char sep)
{
size_t start = 0, end = 0;
while ((end = text.find(sep, start)) != std::string::npos) {
tokens.push_back(text.substr(start, end - start));
start = end + 1;
}
tokens.push_back(text.substr(start));
}
struct OptLutPass : public Pass {
OptLutPass() : Pass("opt_lut", "optimize LUT cells") { }
void help() YS_OVERRIDE
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" opt_lut [options] [selection]\n");
log("\n");
log("This pass combines cascaded $lut cells with unused inputs.\n");
log("\n");
log(" -dlogic <type>:<cell-port>=<LUT-input>[:<cell-port>=<LUT-input>...]\n");
log(" preserve connections to dedicated logic cell <type> that has ports\n");
log(" <cell-port> connected to LUT inputs <LUT-input>. this includes\n");
log(" the case where both LUT and dedicated logic input are connected to\n");
log(" the same constant.\n");
log("\n");
log(" -limit N\n");
log(" only perform the first N combines, then stop. useful for debugging.\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
{
log_header(design, "Executing OPT_LUT pass (optimize LUTs).\n");
dict<IdString, dict<int, IdString>> dlogic;
int limit = -1;
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++)
{
if (args[argidx] == "-dlogic" && argidx+1 < args.size())
{
std::vector<std::string> tokens;
split(tokens, args[++argidx], ':');
if (tokens.size() < 2)
log_cmd_error("The -dlogic option requires at least one connection.\n");
IdString type = "\\" + tokens[0];
for (auto it = tokens.begin() + 1; it != tokens.end(); ++it) {
std::vector<std::string> conn_tokens;
split(conn_tokens, *it, '=');
if (conn_tokens.size() != 2)
log_cmd_error("Invalid format of -dlogic signal mapping.\n");
IdString logic_port = "\\" + conn_tokens[0];
int lut_input = atoi(conn_tokens[1].c_str());
dlogic[type][lut_input] = logic_port;
}
continue;
}
if (args[argidx] == "-limit" && argidx + 1 < args.size())
{
limit = atoi(args[++argidx].c_str());
continue;
}
break;
}
extra_args(args, argidx, design);
int total_count = 0;
for (auto module : design->selected_modules())
{
OptLutWorker worker(dlogic, module, limit - total_count);
total_count += worker.combined_count;
}
if (total_count)
design->scratchpad_set_bool("opt.did_something", true);
log("\n");
log("Combined %d LUTs.\n", total_count);
}
} OptLutPass;
PRIVATE_NAMESPACE_END
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