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yosys/passes/techmap/muxcover.cc
Henner Zeller 3aa4484a3c Consistent use of 'override' for virtual methods in derived classes. 
o Not all derived methods were marked 'override', but it is a great
  feature of C++11 that we should make use of.
o While at it: touched header files got a -*- c++ -*- for emacs to
  provide support for that language.
o use YS_OVERRIDE for all override keywords (though we should probably
  use the plain keyword going forward now that C++11 is established)
2018-07-20 23:51:06 -07:00

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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"
USING_YOSYS_NAMESPACE
PRIVATE_NAMESPACE_BEGIN
#define COST_MUX2 100
#define COST_MUX4 220
#define COST_MUX8 460
#define COST_MUX16 940
struct MuxcoverWorker
{
Module *module;
SigMap sigmap;
struct newmux_t
{
int cost;
vector<SigBit> inputs, selects;
newmux_t() : cost(0) {}
};
struct tree_t
{
SigBit root;
dict<SigBit, Cell*> muxes;
dict<SigBit, newmux_t> newmuxes;
};
vector<tree_t> tree_list;
dict<tuple<SigBit, SigBit, SigBit>, tuple<SigBit, pool<SigBit>, bool>> decode_mux_cache;
dict<SigBit, tuple<SigBit, SigBit, SigBit>> decode_mux_reverse_cache;
int decode_mux_counter;
bool use_mux4;
bool use_mux8;
bool use_mux16;
bool nodecode;
MuxcoverWorker(Module *module) : module(module), sigmap(module)
{
use_mux4 = false;
use_mux8 = false;
use_mux16 = false;
nodecode = false;
decode_mux_counter = 0;
}
void treeify()
{
pool<SigBit> roots;
pool<SigBit> used_once;
dict<SigBit, Cell*> sig_to_mux;
for (auto wire : module->wires()) {
if (!wire->port_output)
continue;
for (auto bit : sigmap(wire))
roots.insert(bit);
}
for (auto cell : module->cells()) {
for (auto conn : cell->connections()) {
if (!cell->input(conn.first))
continue;
for (auto bit : sigmap(conn.second)) {
if (used_once.count(bit) || cell->type != "$_MUX_" || conn.first == "\\S")
roots.insert(bit);
used_once.insert(bit);
}
}
if (cell->type == "$_MUX_")
sig_to_mux[sigmap(cell->getPort("\\Y"))] = cell;
}
log(" Treeifying %d MUXes:\n", GetSize(sig_to_mux));
roots.sort();
for (auto rootsig : roots)
{
tree_t tree;
tree.root = rootsig;
pool<SigBit> wavefront;
wavefront.insert(rootsig);
while (!wavefront.empty()) {
SigBit bit = wavefront.pop();
if (sig_to_mux.count(bit) && (bit == rootsig || !roots.count(bit))) {
Cell *c = sig_to_mux.at(bit);
tree.muxes[bit] = c;
wavefront.insert(sigmap(c->getPort("\\A")));
wavefront.insert(sigmap(c->getPort("\\B")));
}
}
if (!tree.muxes.empty()) {
log(" Found tree with %d MUXes at root %s.\n", GetSize(tree.muxes), log_signal(tree.root));
tree_list.push_back(tree);
}
}
log(" Finished treeification: Found %d trees.\n", GetSize(tree_list));
}
bool follow_muxtree(SigBit &ret_bit, tree_t &tree, SigBit bit, const char *path)
{
if (*path) {
if (tree.muxes.count(bit) == 0)
return false;
char port_name[3] = {'\\', *path, 0};
return follow_muxtree(ret_bit, tree, sigmap(tree.muxes.at(bit)->getPort(port_name)), path+1);
} else {
ret_bit = bit;
return true;
}
}
int prepare_decode_mux(SigBit &A, SigBit B, SigBit sel, SigBit bit)
{
if (A == B)
return 0;
tuple<SigBit, SigBit, SigBit> key(A, B, sel);
if (decode_mux_cache.count(key) == 0) {
auto &entry = decode_mux_cache[key];
std::get<0>(entry) = module->addWire(NEW_ID);
std::get<2>(entry) = false;
decode_mux_reverse_cache[std::get<0>(entry)] = key;
}
auto &entry = decode_mux_cache[key];
A = std::get<0>(entry);
std::get<1>(entry).insert(bit);
if (std::get<2>(entry))
return 0;
return COST_MUX2 / GetSize(std::get<1>(entry));
}
void implement_decode_mux(SigBit ctrl_bit)
{
if (decode_mux_reverse_cache.count(ctrl_bit) == 0)
return;
auto &key = decode_mux_reverse_cache.at(ctrl_bit);
auto &entry = decode_mux_cache[key];
if (std::get<2>(entry))
return;
implement_decode_mux(std::get<0>(key));
implement_decode_mux(std::get<1>(key));
module->addMuxGate(NEW_ID, std::get<0>(key), std::get<1>(key), std::get<2>(key), ctrl_bit);
std::get<2>(entry) = true;
decode_mux_counter++;
}
int find_best_cover(tree_t &tree, SigBit bit)
{
if (tree.newmuxes.count(bit)) {
return tree.newmuxes.at(bit).cost;
}
SigBit A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P;
SigBit S1, S2, S3, S4, S5, S6, S7, S8;
SigBit T1, T2, T3, T4;
SigBit U1, U2;
SigBit V1;
newmux_t best_mux;
bool ok = true;
// 2-Input MUX
ok = ok && follow_muxtree(A, tree, bit, "A");
ok = ok && follow_muxtree(B, tree, bit, "B");
ok = ok && follow_muxtree(S1, tree, bit, "S");
if (ok)
{
newmux_t mux;
mux.inputs.push_back(A);
mux.inputs.push_back(B);
mux.selects.push_back(S1);
mux.cost += COST_MUX2;
mux.cost += find_best_cover(tree, A);
mux.cost += find_best_cover(tree, B);
best_mux = mux;
}
// 4-Input MUX
if (use_mux4)
{
ok = ok && follow_muxtree(A, tree, bit, "AA");
ok = ok && follow_muxtree(B, tree, bit, "AB");
ok = ok && follow_muxtree(C, tree, bit, "BA");
ok = ok && follow_muxtree(D, tree, bit, "BB");
ok = ok && follow_muxtree(S1, tree, bit, "AS");
ok = ok && follow_muxtree(S2, tree, bit, "BS");
if (nodecode)
ok = ok && S1 == S2;
ok = ok && follow_muxtree(T1, tree, bit, "S");
if (ok)
{
newmux_t mux;
mux.inputs.push_back(A);
mux.inputs.push_back(B);
mux.inputs.push_back(C);
mux.inputs.push_back(D);
mux.cost += prepare_decode_mux(S1, S2, T1, bit);
mux.selects.push_back(S1);
mux.selects.push_back(T1);
mux.cost += COST_MUX4;
mux.cost += find_best_cover(tree, A);
mux.cost += find_best_cover(tree, B);
mux.cost += find_best_cover(tree, C);
mux.cost += find_best_cover(tree, D);
if (best_mux.cost > mux.cost)
best_mux = mux;
}
}
// 8-Input MUX
if (use_mux8)
{
ok = ok && follow_muxtree(A, tree, bit, "AAA");
ok = ok && follow_muxtree(B, tree, bit, "AAB");
ok = ok && follow_muxtree(C, tree, bit, "ABA");
ok = ok && follow_muxtree(D, tree, bit, "ABB");
ok = ok && follow_muxtree(E, tree, bit, "BAA");
ok = ok && follow_muxtree(F, tree, bit, "BAB");
ok = ok && follow_muxtree(G, tree, bit, "BBA");
ok = ok && follow_muxtree(H, tree, bit, "BBB");
ok = ok && follow_muxtree(S1, tree, bit, "AAS");
ok = ok && follow_muxtree(S2, tree, bit, "ABS");
ok = ok && follow_muxtree(S3, tree, bit, "BAS");
ok = ok && follow_muxtree(S4, tree, bit, "BBS");
if (nodecode)
ok = ok && S1 == S2 && S2 == S3 && S3 == S4;
ok = ok && follow_muxtree(T1, tree, bit, "AS");
ok = ok && follow_muxtree(T2, tree, bit, "BS");
if (nodecode)
ok = ok && T1 == T2;
ok = ok && follow_muxtree(U1, tree, bit, "S");
if (ok)
{
newmux_t mux;
mux.inputs.push_back(A);
mux.inputs.push_back(B);
mux.inputs.push_back(C);
mux.inputs.push_back(D);
mux.inputs.push_back(E);
mux.inputs.push_back(F);
mux.inputs.push_back(G);
mux.inputs.push_back(H);
mux.cost += prepare_decode_mux(S1, S2, T1, bit);
mux.cost += prepare_decode_mux(S3, S4, T2, bit);
mux.cost += prepare_decode_mux(S1, S3, U1, bit);
mux.cost += prepare_decode_mux(T1, T2, U1, bit);
mux.selects.push_back(S1);
mux.selects.push_back(T1);
mux.selects.push_back(U1);
mux.cost += COST_MUX8;
mux.cost += find_best_cover(tree, A);
mux.cost += find_best_cover(tree, B);
mux.cost += find_best_cover(tree, C);
mux.cost += find_best_cover(tree, D);
mux.cost += find_best_cover(tree, E);
mux.cost += find_best_cover(tree, F);
mux.cost += find_best_cover(tree, G);
mux.cost += find_best_cover(tree, H);
if (best_mux.cost > mux.cost)
best_mux = mux;
}
}
// 16-Input MUX
if (use_mux16)
{
ok = ok && follow_muxtree(A, tree, bit, "AAAA");
ok = ok && follow_muxtree(B, tree, bit, "AAAB");
ok = ok && follow_muxtree(C, tree, bit, "AABA");
ok = ok && follow_muxtree(D, tree, bit, "AABB");
ok = ok && follow_muxtree(E, tree, bit, "ABAA");
ok = ok && follow_muxtree(F, tree, bit, "ABAB");
ok = ok && follow_muxtree(G, tree, bit, "ABBA");
ok = ok && follow_muxtree(H, tree, bit, "ABBB");
ok = ok && follow_muxtree(I, tree, bit, "BAAA");
ok = ok && follow_muxtree(J, tree, bit, "BAAB");
ok = ok && follow_muxtree(K, tree, bit, "BABA");
ok = ok && follow_muxtree(L, tree, bit, "BABB");
ok = ok && follow_muxtree(M, tree, bit, "BBAA");
ok = ok && follow_muxtree(N, tree, bit, "BBAB");
ok = ok && follow_muxtree(O, tree, bit, "BBBA");
ok = ok && follow_muxtree(P, tree, bit, "BBBB");
ok = ok && follow_muxtree(S1, tree, bit, "AAAS");
ok = ok && follow_muxtree(S2, tree, bit, "AABS");
ok = ok && follow_muxtree(S3, tree, bit, "ABAS");
ok = ok && follow_muxtree(S4, tree, bit, "ABBS");
ok = ok && follow_muxtree(S5, tree, bit, "BAAS");
ok = ok && follow_muxtree(S6, tree, bit, "BABS");
ok = ok && follow_muxtree(S7, tree, bit, "BBAS");
ok = ok && follow_muxtree(S8, tree, bit, "BBBS");
if (nodecode)
ok = ok && S1 == S2 && S2 == S3 && S3 == S4 && S4 == S5 && S5 == S6 && S6 == S7 && S7 == S8;
ok = ok && follow_muxtree(T1, tree, bit, "AAS");
ok = ok && follow_muxtree(T2, tree, bit, "ABS");
ok = ok && follow_muxtree(T3, tree, bit, "BAS");
ok = ok && follow_muxtree(T4, tree, bit, "BBS");
if (nodecode)
ok = ok && T1 == T2 && T2 == T3 && T3 == T4;
ok = ok && follow_muxtree(U1, tree, bit, "AS");
ok = ok && follow_muxtree(U2, tree, bit, "BS");
if (nodecode)
ok = ok && U1 == U2;
ok = ok && follow_muxtree(V1, tree, bit, "S");
if (ok)
{
newmux_t mux;
mux.inputs.push_back(A);
mux.inputs.push_back(B);
mux.inputs.push_back(C);
mux.inputs.push_back(D);
mux.inputs.push_back(E);
mux.inputs.push_back(F);
mux.inputs.push_back(G);
mux.inputs.push_back(H);
mux.inputs.push_back(I);
mux.inputs.push_back(J);
mux.inputs.push_back(K);
mux.inputs.push_back(L);
mux.inputs.push_back(M);
mux.inputs.push_back(N);
mux.inputs.push_back(O);
mux.inputs.push_back(P);
mux.cost += prepare_decode_mux(S1, S2, T1, bit);
mux.cost += prepare_decode_mux(S3, S4, T2, bit);
mux.cost += prepare_decode_mux(S5, S6, T3, bit);
mux.cost += prepare_decode_mux(S7, S8, T4, bit);
mux.cost += prepare_decode_mux(S1, S3, U1, bit);
mux.cost += prepare_decode_mux(S5, S7, U2, bit);
mux.cost += prepare_decode_mux(S1, S5, V1, bit);
mux.cost += prepare_decode_mux(T1, T2, U1, bit);
mux.cost += prepare_decode_mux(T3, T4, U2, bit);
mux.cost += prepare_decode_mux(T1, T3, V1, bit);
mux.cost += prepare_decode_mux(U1, U2, V1, bit);
mux.selects.push_back(S1);
mux.selects.push_back(T1);
mux.selects.push_back(U1);
mux.selects.push_back(V1);
mux.cost += COST_MUX16;
mux.cost += find_best_cover(tree, A);
mux.cost += find_best_cover(tree, B);
mux.cost += find_best_cover(tree, C);
mux.cost += find_best_cover(tree, D);
mux.cost += find_best_cover(tree, E);
mux.cost += find_best_cover(tree, F);
mux.cost += find_best_cover(tree, G);
mux.cost += find_best_cover(tree, H);
mux.cost += find_best_cover(tree, I);
mux.cost += find_best_cover(tree, J);
mux.cost += find_best_cover(tree, K);
mux.cost += find_best_cover(tree, L);
mux.cost += find_best_cover(tree, M);
mux.cost += find_best_cover(tree, N);
mux.cost += find_best_cover(tree, O);
mux.cost += find_best_cover(tree, P);
if (best_mux.cost > mux.cost)
best_mux = mux;
}
}
tree.newmuxes[bit] = best_mux;
return best_mux.cost;
}
void implement_best_cover(tree_t &tree, SigBit bit, int count_muxes_by_type[4])
{
newmux_t mux = tree.newmuxes.at(bit);
for (auto inbit : mux.inputs)
implement_best_cover(tree, inbit, count_muxes_by_type);
for (auto selbit : mux.selects)
implement_decode_mux(selbit);
if (GetSize(mux.inputs) == 0)
return;
if (GetSize(mux.inputs) == 2) {
count_muxes_by_type[0]++;
Cell *cell = module->addCell(NEW_ID, "$_MUX_");
cell->setPort("\\A", mux.inputs[0]);
cell->setPort("\\B", mux.inputs[1]);
cell->setPort("\\S", mux.selects[0]);
cell->setPort("\\Y", bit);
return;
}
if (GetSize(mux.inputs) == 4) {
count_muxes_by_type[1]++;
Cell *cell = module->addCell(NEW_ID, "$_MUX4_");
cell->setPort("\\A", mux.inputs[0]);
cell->setPort("\\B", mux.inputs[1]);
cell->setPort("\\C", mux.inputs[2]);
cell->setPort("\\D", mux.inputs[3]);
cell->setPort("\\S", mux.selects[0]);
cell->setPort("\\T", mux.selects[1]);
cell->setPort("\\Y", bit);
return;
}
if (GetSize(mux.inputs) == 8) {
count_muxes_by_type[2]++;
Cell *cell = module->addCell(NEW_ID, "$_MUX8_");
cell->setPort("\\A", mux.inputs[0]);
cell->setPort("\\B", mux.inputs[1]);
cell->setPort("\\C", mux.inputs[2]);
cell->setPort("\\D", mux.inputs[3]);
cell->setPort("\\E", mux.inputs[4]);
cell->setPort("\\F", mux.inputs[5]);
cell->setPort("\\G", mux.inputs[6]);
cell->setPort("\\H", mux.inputs[7]);
cell->setPort("\\S", mux.selects[0]);
cell->setPort("\\T", mux.selects[1]);
cell->setPort("\\U", mux.selects[2]);
cell->setPort("\\Y", bit);
return;
}
if (GetSize(mux.inputs) == 16) {
count_muxes_by_type[3]++;
Cell *cell = module->addCell(NEW_ID, "$_MUX16_");
cell->setPort("\\A", mux.inputs[0]);
cell->setPort("\\B", mux.inputs[1]);
cell->setPort("\\C", mux.inputs[2]);
cell->setPort("\\D", mux.inputs[3]);
cell->setPort("\\E", mux.inputs[4]);
cell->setPort("\\F", mux.inputs[5]);
cell->setPort("\\G", mux.inputs[6]);
cell->setPort("\\H", mux.inputs[7]);
cell->setPort("\\I", mux.inputs[8]);
cell->setPort("\\J", mux.inputs[9]);
cell->setPort("\\K", mux.inputs[10]);
cell->setPort("\\L", mux.inputs[11]);
cell->setPort("\\M", mux.inputs[12]);
cell->setPort("\\N", mux.inputs[13]);
cell->setPort("\\O", mux.inputs[14]);
cell->setPort("\\P", mux.inputs[15]);
cell->setPort("\\S", mux.selects[0]);
cell->setPort("\\T", mux.selects[1]);
cell->setPort("\\U", mux.selects[2]);
cell->setPort("\\V", mux.selects[3]);
cell->setPort("\\Y", bit);
return;
}
log_abort();
}
void treecover(tree_t &tree)
{
int count_muxes_by_type[4] = {0, 0, 0, 0};
find_best_cover(tree, tree.root);
implement_best_cover(tree, tree.root, count_muxes_by_type);
log(" Replaced tree at %s: %d MUX2, %d MUX4, %d MUX8, %d MUX16\n", log_signal(tree.root),
count_muxes_by_type[0], count_muxes_by_type[1], count_muxes_by_type[2], count_muxes_by_type[3]);
for (auto &it : tree.muxes)
module->remove(it.second);
}
void run()
{
log("Covering MUX trees in module %s..\n", log_id(module));
treeify();
log(" Covering trees:\n");
// pre-fill cache of decoder muxes
if (!nodecode)
for (auto &tree : tree_list) {
find_best_cover(tree, tree.root);
tree.newmuxes.clear();
}
for (auto &tree : tree_list)
treecover(tree);
if (!nodecode)
log(" Added a total of %d decoder MUXes.\n", decode_mux_counter);
}
};
struct MuxcoverPass : public Pass {
MuxcoverPass() : Pass("muxcover", "cover trees of MUX cells with wider MUXes") { }
void help() YS_OVERRIDE
{
// |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
log("\n");
log(" muxcover [options] [selection]\n");
log("\n");
log("Cover trees of $_MUX_ cells with $_MUX{4,8,16}_ cells\n");
log("\n");
log(" -mux4, -mux8, -mux16\n");
log(" Use the specified types of MUXes. If none of those options are used,\n");
log(" the effect is the same as if all of them where used.\n");
log("\n");
log(" -nodecode\n");
log(" Do not insert decoder logic. This reduces the number of possible\n");
log(" substitutions, but guarantees that the resulting circuit is not\n");
log(" less efficient than the original circuit.\n");
log("\n");
}
void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
{
log_header(design, "Executing MUXCOVER pass (mapping to wider MUXes).\n");
bool use_mux4 = false;
bool use_mux8 = false;
bool use_mux16 = false;
bool nodecode = false;
size_t argidx;
for (argidx = 1; argidx < args.size(); argidx++)
{
if (args[argidx] == "-mux4") {
use_mux4 = true;
continue;
}
if (args[argidx] == "-mux8") {
use_mux8 = true;
continue;
}
if (args[argidx] == "-mux16") {
use_mux16 = true;
continue;
}
if (args[argidx] == "-nodecode") {
nodecode = true;
continue;
}
break;
}
extra_args(args, argidx, design);
if (!use_mux4 && !use_mux8 && !use_mux16) {
use_mux4 = true;
use_mux8 = true;
use_mux16 = true;
}
for (auto module : design->selected_modules())
{
MuxcoverWorker worker(module);
worker.use_mux4 = use_mux4;
worker.use_mux8 = use_mux8;
worker.use_mux16 = use_mux16;
worker.nodecode = nodecode;
worker.run();
}
}
} MuxcoverPass;
PRIVATE_NAMESPACE_END
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