/*
* nextpnr -- Next Generation Place and Route
*
* Copyright (C) 2018 gatecat <gatecat@ds0.me>
*
* 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 "chains.h"
#include <algorithm>
#include <vector>
#include "cells.h"
#include "chain_utils.h"
#include "design_utils.h"
#include "log.h"
#include "place_common.h"
#include "util.h"
NEXTPNR_NAMESPACE_BEGIN
class ChainConstrainer
{
private:
int feedio_lcs = 0;
Context *ctx;
// Split a carry chain into multiple legal chains
std::vector<CellChain> split_carry_chain(CellChain &carryc)
{
bool start_of_chain = true;
std::vector<CellChain> chains;
std::vector<const CellInfo *> tile;
const int max_length = (ctx->chip_info->height - 2) * 8 - 2;
auto curr_cell = carryc.cells.begin();
while (curr_cell != carryc.cells.end()) {
CellInfo *cell = *curr_cell;
if (ctx->debug)
log_info(" processing cell %s\n", ctx->nameOf(cell));
if (tile.size() >= 8) {
tile.clear();
}
if (start_of_chain) {
tile.clear();
chains.emplace_back();
start_of_chain = false;
if (cell->ports.at(id_CIN).net) {
// CIN is not constant and not part of a chain. Must feed in from fabric
CellInfo *feedin = make_carry_feed_in(cell, cell->ports.at(id_CIN));
chains.back().cells.push_back(feedin);
tile.push_back(feedin);
++feedio_lcs;
}
}
tile.push_back(cell);
chains.back().cells.push_back(cell);
bool split_chain = (!ctx->logic_cells_compatible(tile.data(), tile.size())) ||
(int(chains.back().cells.size()) > max_length);
if (split_chain) {
CellInfo *passout = make_carry_pass_out((*(curr_cell - 1))->ports.at(id_COUT));
tile.pop_back();
chains.back().cells.back() = passout;
start_of_chain = true;
} else {
NetInfo *carry_net = cell->ports.at(id_COUT).net;
bool at_end = (curr_cell == carryc.cells.end() - 1);
if (carry_net != nullptr && (carry_net->users.entries() > 1 || at_end)) {
if (carry_net->users.entries() > 2 ||
(net_only_drives(ctx, carry_net, is_lc, id_I3, false) !=
net_only_drives(ctx, carry_net, is_lc, id_CIN, false)) ||
(at_end && !net_only_drives(ctx, carry_net, is_lc, id_I3, true))) {
if (ctx->debug)
log_info(" inserting feed-%s\n", at_end ? "out" : "out-in");
CellInfo *passout;
if (!at_end) {
// See if we need to split chain anyway
tile.push_back(*(curr_cell + 1));
bool split_chain_next = (!ctx->logic_cells_compatible(tile.data(), tile.size())) ||
(int(chains.back().cells.size()) > max_length);
tile.pop_back();
if (split_chain_next)
start_of_chain = true;
passout = make_carry_pass_out(cell->ports.at(id_COUT),
split_chain_next ? nullptr : *(curr_cell + 1));
} else {
passout = make_carry_pass_out(cell->ports.at(id_COUT), nullptr);
}
chains.back().cells.push_back(passout);
tile.push_back(passout);
++feedio_lcs;
}
}
++curr_cell;
}
}
return chains;
}
// Insert a logic cell to legalise a COUT->fabric connection
CellInfo *make_carry_pass_out(PortInfo &cout_port, CellInfo *cin_cell = nullptr)
{
NPNR_ASSERT(cout_port.net != nullptr);
std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, id_ICESTORM_LC);
lc->params[id_LUT_INIT] = Property(65280, 16); // 0xff00: O = I3
lc->params[id_CARRY_ENABLE] = Property::State::S1;
lc->ports.at(id_O).net = cout_port.net;
NetInfo *co_i3_net = ctx->createNet(ctx->id(lc->name.str(ctx) + "$I3"));
co_i3_net->driver = cout_port.net->driver;
lc->connectPort(id_I3, co_i3_net);
PortRef o_r;
o_r.port = id_O;
o_r.cell = lc.get();
cout_port.net->driver = o_r;
cout_port.net = co_i3_net;
// If COUT also connects to a CIN; preserve the carry chain
if (cin_cell) {
NetInfo *co_cin_net = ctx->createNet(ctx->id(lc->name.str(ctx) + "$COUT"));
// Connect I1 to 1 to preserve carry chain
NetInfo *vcc = ctx->nets.at(ctx->id("$PACKER_VCC_NET")).get();
lc->connectPort(id_I1, vcc);
// Connect co_cin_net to the COUT of the LC
lc->connectPort(id_COUT, co_cin_net);
// Find the user corresponding to the next CIN
int replaced_ports = 0;
if (ctx->debug)
log_info("cell: %s\n", cin_cell->name.c_str(ctx));
for (auto port : {id_CIN, id_I3}) {
NetInfo *out_net = lc->ports.at(id_O).net;
auto &cin_p = cin_cell->ports.at(port);
if (cin_p.net == out_net) {
cin_cell->disconnectPort(port);
cin_cell->connectPort(port, co_cin_net);
++replaced_ports;
}
}
NPNR_ASSERT(replaced_ports > 0);
}
IdString name = lc->name;
ctx->assignCellInfo(lc.get());
ctx->cells[lc->name] = std::move(lc);
return ctx->cells[name].get();
}
// Insert a logic cell to legalise a CIN->fabric connection
CellInfo *make_carry_feed_in(CellInfo *cin_cell, PortInfo &cin_port)
{
NPNR_ASSERT(cin_port.net != nullptr);
std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, id_ICESTORM_LC);
lc->params[id_CARRY_ENABLE] = Property::State::S1;
lc->params[id_CIN_CONST] = Property::State::S1;
lc->params[id_CIN_SET] = Property::State::S1;
lc->connectPort(id_I1, cin_port.net);
cin_port.net->users.remove(cin_port.user_idx);
NetInfo *out_net = ctx->createNet(ctx->id(lc->name.str(ctx) + "$O"));
lc->connectPort(id_COUT, out_net);
cin_port.net = nullptr;
cin_cell->connectPort(cin_port.name, out_net);
IdString name = lc->name;
ctx->assignCellInfo(lc.get());
ctx->cells[lc->name] = std::move(lc);
return ctx->cells[name].get();
}
void process_carries()
{
// Find carry roots
std::vector<CellChain> carry_chains;
pool<IdString> processed;
for (auto &cell : ctx->cells) {
CellInfo *ci = cell.second.get();
if (is_lc(ctx, ci) && bool_or_default(ci->params, id_CARRY_ENABLE)) {
// possibly a non-root if CIN or I3 driven by another cout
NetInfo *cin = ci->getPort(id_CIN);
if (cin && cin->driver.cell && is_lc(ctx, cin->driver.cell) && cin->driver.port == id_COUT) {
continue;
}
carry_chains.emplace_back();
auto &cc = carry_chains.back();
CellInfo *cursor = ci;
while (cursor) {
cc.cells.push_back(cursor);
processed.insert(cursor->name);
NetInfo *cout = cursor->getPort(id_COUT);
if (!cout)
break;
cursor = nullptr;
// look for CIN connectivity
for (auto &usr : cout->users) {
if (is_lc(ctx, usr.cell) && usr.port == id_CIN && !processed.count(usr.cell->name)) {
cursor = usr.cell;
break;
}
}
// look for I3 connectivity - only to a top cell with no further chaining
if (cursor)
continue;
for (auto &usr : cout->users) {
if (is_lc(ctx, usr.cell) && usr.port == id_I3 && !processed.count(usr.cell->name) &&
!usr.cell->getPort(id_COUT)) {
cursor = usr.cell;
break;
}
}
}
}
}
// anything left behind....
for (auto &cell : ctx->cells) {
CellInfo *ci = cell.second.get();
if (is_lc(ctx, ci) && bool_or_default(ci->params, id_CARRY_ENABLE) && !processed.count(ci->name)) {
carry_chains.emplace_back();
carry_chains.back().cells.push_back(ci);
processed.insert(ci->name);
}
}
std::vector<CellChain> all_chains;
// Chain splitting
for (auto &base_chain : carry_chains) {
if (ctx->verbose) {
log_info("Found carry chain: \n");
for (auto entry : base_chain.cells)
log_info(" %s\n", entry->name.c_str(ctx));
log_info("\n");
}
std::vector<CellChain> split_chains = split_carry_chain(base_chain);
for (auto &chain : split_chains) {
all_chains.push_back(chain);
}
}
// Actual chain placement
for (auto &chain : all_chains) {
if (ctx->verbose)
log_info("Placing carry chain starting at '%s'\n", chain.cells.front()->name.c_str(ctx));
// Place carry chain
chain.cells.at(0)->constr_abs_z = true;
chain.cells.at(0)->constr_z = 0;
chain.cells.at(0)->cluster = chain.cells.at(0)->name;
for (int i = 1; i < int(chain.cells.size()); i++) {
chain.cells.at(i)->constr_x = 0;
chain.cells.at(i)->constr_y = (i / 8);
chain.cells.at(i)->constr_z = i % 8;
chain.cells.at(i)->constr_abs_z = true;
chain.cells.at(i)->cluster = chain.cells.at(0)->name;
chain.cells.at(0)->constr_children.push_back(chain.cells.at(i));
}
}
log_info(" %4d LCs used to legalise carry chains.\n", feedio_lcs);
}
public:
ChainConstrainer(Context *ctx) : ctx(ctx){};
void constrain_chains() { process_carries(); }
};
void constrain_chains(Context *ctx)
{
log_info("Constraining chains...\n");
ChainConstrainer(ctx).constrain_chains();
}
NEXTPNR_NAMESPACE_END