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yosys/passes/opt/wreduce.cc

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/*
* yosys -- Yosys Open SYnthesis Suite
*
* Copyright (C) 2012 Clifford Wolf <clifford@clifford.at>
*
* 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
using namespace RTLIL;
PRIVATE_NAMESPACE_BEGIN
struct WreduceConfig
{
pool<IdString> supported_cell_types;
WreduceConfig()
{
supported_cell_types = pool<IdString>({
"$not", "$pos", "$neg",
"$and", "$or", "$xor", "$xnor",
"$shl", "$shr", "$sshl", "$sshr", "$shift", "$shiftx",
"$lt", "$le", "$eq", "$ne", "$eqx", "$nex", "$ge", "$gt",
"$add", "$sub", "$mul", // "$div", "$mod", "$pow",
"$mux", "$pmux"
});
}
};
struct WreduceWorker
{
WreduceConfig *config;
Module *module;
ModIndex mi;
std::set<Cell*, IdString::compare_ptr_by_name<Cell>> work_queue_cells;
std::set<SigBit> work_queue_bits;
pool<SigBit> keep_bits;
WreduceWorker(WreduceConfig *config, Module *module) :
config(config), module(module), mi(module) { }
void run_cell_mux(Cell *cell)
{
// Reduce size of MUX if inputs agree on a value for a bit or a output bit is unused
SigSpec sig_a = mi.sigmap(cell->getPort("\\A"));
SigSpec sig_b = mi.sigmap(cell->getPort("\\B"));
SigSpec sig_s = mi.sigmap(cell->getPort("\\S"));
SigSpec sig_y = mi.sigmap(cell->getPort("\\Y"));
std::vector<SigBit> bits_removed;
if (sig_y.has_const())
return;
for (int i = GetSize(sig_y)-1; i >= 0; i--)
{
auto info = mi.query(sig_y[i]);
if (!info->is_output && GetSize(info->ports) <= 1 && !keep_bits.count(mi.sigmap(sig_y[i]))) {
bits_removed.push_back(Sx);
continue;
}
SigBit ref = sig_a[i];
for (int k = 0; k < GetSize(sig_s); k++) {
if (ref != Sx && sig_b[k*GetSize(sig_a) + i] != Sx && ref != sig_b[k*GetSize(sig_a) + i])
goto no_match_ab;
if (sig_b[k*GetSize(sig_a) + i] != Sx)
ref = sig_b[k*GetSize(sig_a) + i];
}
if (0)
no_match_ab:
break;
bits_removed.push_back(ref);
}
if (bits_removed.empty())
return;
SigSpec sig_removed;
for (int i = GetSize(bits_removed)-1; i >= 0; i--)
sig_removed.append_bit(bits_removed[i]);
if (GetSize(bits_removed) == GetSize(sig_y)) {
log("Removed cell %s.%s (%s).\n", log_id(module), log_id(cell), log_id(cell->type));
module->connect(sig_y, sig_removed);
module->remove(cell);
return;
}
log("Removed top %d bits (of %d) from mux cell %s.%s (%s).\n",
GetSize(sig_removed), GetSize(sig_y), log_id(module), log_id(cell), log_id(cell->type));
int n_removed = GetSize(sig_removed);
int n_kept = GetSize(sig_y) - GetSize(sig_removed);
SigSpec new_work_queue_bits;
new_work_queue_bits.append(sig_a.extract(n_kept, n_removed));
new_work_queue_bits.append(sig_y.extract(n_kept, n_removed));
SigSpec new_sig_a = sig_a.extract(0, n_kept);
SigSpec new_sig_y = sig_y.extract(0, n_kept);
SigSpec new_sig_b;
for (int k = 0; k < GetSize(sig_s); k++) {
new_sig_b.append(sig_b.extract(k*GetSize(sig_a), n_kept));
new_work_queue_bits.append(sig_b.extract(k*GetSize(sig_a) + n_kept, n_removed));
}
for (auto bit : new_work_queue_bits)
work_queue_bits.insert(bit);
cell->setPort("\\A", new_sig_a);
cell->setPort("\\B", new_sig_b);
cell->setPort("\\Y", new_sig_y);
cell->fixup_parameters();
module->connect(sig_y.extract(n_kept, n_removed), sig_removed);
}
void run_reduce_inport(Cell *cell, char port, int max_port_size, bool &port_signed, bool &did_something)
{
port_signed = cell->getParam(stringf("\\%c_SIGNED", port)).as_bool();
SigSpec sig = mi.sigmap(cell->getPort(stringf("\\%c", port)));
if (port == 'B' && cell->type.in("$shl", "$shr", "$sshl", "$sshr"))
port_signed = false;
int bits_removed = 0;
if (GetSize(sig) > max_port_size) {
bits_removed = GetSize(sig) - max_port_size;
for (auto bit : sig.extract(max_port_size, bits_removed))
work_queue_bits.insert(bit);
sig = sig.extract(0, max_port_size);
}
if (port_signed) {
while (GetSize(sig) > 1 && sig[GetSize(sig)-1] == sig[GetSize(sig)-2])
work_queue_bits.insert(sig[GetSize(sig)-1]), sig.remove(GetSize(sig)-1), bits_removed++;
} else {
while (GetSize(sig) > 1 && sig[GetSize(sig)-1] == S0)
work_queue_bits.insert(sig[GetSize(sig)-1]), sig.remove(GetSize(sig)-1), bits_removed++;
}
if (bits_removed) {
log("Removed top %d bits (of %d) from port %c of cell %s.%s (%s).\n",
bits_removed, GetSize(sig) + bits_removed, port, log_id(module), log_id(cell), log_id(cell->type));
cell->setPort(stringf("\\%c", port), sig);
did_something = true;
}
}
void run_cell(Cell *cell)
{
bool did_something = false;
if (!cell->type.in(config->supported_cell_types))
return;
if (cell->type.in("$mux", "$pmux"))
return run_cell_mux(cell);
SigSpec sig = mi.sigmap(cell->getPort("\\Y"));
if (sig.has_const())
return;
// Reduce size of ports A and B based on constant input bits and size of output port
int max_port_a_size = cell->hasPort("\\A") ? GetSize(cell->getPort("\\A")) : -1;
int max_port_b_size = cell->hasPort("\\B") ? GetSize(cell->getPort("\\B")) : -1;
if (cell->type.in("$not", "$pos", "$neg", "$and", "$or", "$xor", "$add", "$sub")) {
max_port_a_size = min(max_port_a_size, GetSize(sig));
max_port_b_size = min(max_port_b_size, GetSize(sig));
}
bool port_a_signed = false;
bool port_b_signed = false;
if (max_port_a_size >= 0 && cell->type != "$shiftx")
run_reduce_inport(cell, 'A', max_port_a_size, port_a_signed, did_something);
if (max_port_b_size >= 0)
run_reduce_inport(cell, 'B', max_port_b_size, port_b_signed, did_something);
if (cell->hasPort("\\A") && cell->hasPort("\\B") && port_a_signed && port_b_signed) {
SigSpec sig_a = mi.sigmap(cell->getPort("\\A")), sig_b = mi.sigmap(cell->getPort("\\B"));
if (GetSize(sig_a) > 0 && sig_a[GetSize(sig_a)-1] == State::S0 &&
GetSize(sig_b) > 0 && sig_b[GetSize(sig_b)-1] == State::S0) {
log("Converting cell %s.%s (%s) from signed to unsigned.\n",
log_id(module), log_id(cell), log_id(cell->type));
cell->setParam("\\A_SIGNED", 0);
cell->setParam("\\B_SIGNED", 0);
port_a_signed = false;
port_b_signed = false;
did_something = true;
}
}
if (cell->hasPort("\\A") && !cell->hasPort("\\B") && port_a_signed) {
SigSpec sig_a = mi.sigmap(cell->getPort("\\A"));
if (GetSize(sig_a) > 0 && sig_a[GetSize(sig_a)-1] == State::S0) {
log("Converting cell %s.%s (%s) from signed to unsigned.\n",
log_id(module), log_id(cell), log_id(cell->type));
cell->setParam("\\A_SIGNED", 0);
port_a_signed = false;
did_something = true;
}
}
// Reduce size of port Y based on sizes for A and B and unused bits in Y
int bits_removed = 0;
if (port_a_signed && cell->type == "$shr") {
// do not reduce size of output on $shr cells with signed A inputs
} else {
while (GetSize(sig) > 0)
{
auto info = mi.query(sig[GetSize(sig)-1]);
if (info->is_output || GetSize(info->ports) > 1)
break;
sig.remove(GetSize(sig)-1);
bits_removed++;
}
}
if (cell->type.in("$pos", "$add", "$mul", "$and", "$or", "$xor"))
{
bool is_signed = cell->getParam("\\A_SIGNED").as_bool();
int a_size = 0, b_size = 0;
if (cell->hasPort("\\A")) a_size = GetSize(cell->getPort("\\A"));
if (cell->hasPort("\\B")) b_size = GetSize(cell->getPort("\\B"));
int max_y_size = max(a_size, b_size);
if (cell->type == "$add")
max_y_size++;
if (cell->type == "$mul")
max_y_size = a_size + b_size;
while (GetSize(sig) > 1 && GetSize(sig) > max_y_size) {
module->connect(sig[GetSize(sig)-1], is_signed ? sig[GetSize(sig)-2] : S0);
sig.remove(GetSize(sig)-1);
bits_removed++;
}
}
if (GetSize(sig) == 0) {
log("Removed cell %s.%s (%s).\n", log_id(module), log_id(cell), log_id(cell->type));
module->remove(cell);
return;
}
if (bits_removed) {
log("Removed top %d bits (of %d) from port Y of cell %s.%s (%s).\n",
bits_removed, GetSize(sig) + bits_removed, log_id(module), log_id(cell), log_id(cell->type));
cell->setPort("\\Y", sig);
did_something = true;
}
if (did_something) {
cell->fixup_parameters();
run_cell(cell);
}
}
static int count_nontrivial_wire_attrs(RTLIL::Wire *w)
{
int count = w->attributes.size();
count -= w->attributes.count("\\src");
count -= w->attributes.count("\\unused_bits");
return count;
}
void run()
{
for (auto w : module->wires())
if (w->get_bool_attribute("\\keep"))
for (auto bit : mi.sigmap(w))
keep_bits.insert(bit);
for (auto c : module->selected_cells())
work_queue_cells.insert(c);
while (!work_queue_cells.empty())
{
work_queue_bits.clear();
for (auto c : work_queue_cells)
run_cell(c);
work_queue_cells.clear();
for (auto bit : work_queue_bits)
for (auto port : mi.query_ports(bit))
if (module->selected(port.cell))
work_queue_cells.insert(port.cell);
}
pool<SigSpec> complete_wires;
for (auto w : module->wires())
complete_wires.insert(mi.sigmap(w));
for (auto w : module->selected_wires())
{
int unused_top_bits = 0;
if (w->port_id > 0 || count_nontrivial_wire_attrs(w) > 0)
continue;
for (int i = GetSize(w)-1; i >= 0; i--) {
SigBit bit(w, i);
auto info = mi.query(bit);
if (info && (info->is_input || info->is_output || GetSize(info->ports) > 0))
break;
unused_top_bits++;
}
if (unused_top_bits == 0 || unused_top_bits == GetSize(w))
continue;
if (complete_wires[mi.sigmap(w).extract(0, GetSize(w) - unused_top_bits)])
continue;
log("Removed top %d bits (of %d) from wire %s.%s.\n", unused_top_bits, GetSize(w), log_id(module), log_id(w));
Wire *nw = module->addWire(NEW_ID, GetSize(w) - unused_top_bits);
module->connect(nw, SigSpec(w).extract(0, GetSize(nw)));
module->swap_names(w, nw);
}
}
};
struct WreducePass : public Pass {
WreducePass() : Pass("wreduce", "reduce the word size of operations if possible") { }
virtual void help()
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" wreduce [options] [selection]\n");
log("\n");
log("This command reduces the word size of operations. For example it will replace\n");
log("the 32 bit adders in the following code with adders of more appropriate widths:\n");
log("\n");
log(" module test(input [3:0] a, b, c, output [7:0] y);\n");
log(" assign y = a + b + c + 1;\n");
log(" endmodule\n");
log("\n");
}
virtual void execute(std::vector<std::string> args, Design *design)
{
WreduceConfig config;
log_header(design, "Executing WREDUCE pass (reducing word size of cells).\n");
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++) {
break;
}
extra_args(args, argidx, design);
for (auto module : design->selected_modules())
{
if (module->has_processes_warn())
continue;
for (auto c : module->selected_cells())
if (c->type.in("$reduce_and", "$reduce_or", "$reduce_xor", "$reduce_xnor", "$reduce_bool",
"$lt", "$le", "$eq", "$ne", "$eqx", "$nex", "$ge", "$gt",
"$logic_not", "$logic_and", "$logic_or") && GetSize(c->getPort("\\Y")) > 1) {
SigSpec sig = c->getPort("\\Y");
if (!sig.has_const()) {
c->setPort("\\Y", sig[0]);
c->setParam("\\Y_WIDTH", 1);
sig.remove(0);
module->connect(sig, Const(0, GetSize(sig)));
}
}
WreduceWorker worker(&config, module);
worker.run();
}
}
} WreducePass;
PRIVATE_NAMESPACE_END
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