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+/*
+ * nextpnr -- Next Generation Place and Route
+ *
+ * Copyright (C) 2018 David Shah <david@symbioticeda.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 "chains.h"
+#include <algorithm>
+#include <vector>
+#include "cells.h"
+#include "design_utils.h"
+#include "log.h"
+#include "place_common.h"
+#include "util.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+struct CellChain
+{
+ std::vector<CellInfo *> cells;
+};
+
+// Generic chain finder
+template <typename F1, typename F2, typename F3>
+std::vector<CellChain> find_chains(const Context *ctx, F1 cell_type_predicate, F2 get_previous, F3 get_next,
+ size_t min_length = 2)
+{
+ std::set<IdString> chained;
+ std::vector<CellChain> chains;
+ for (auto cell : sorted(ctx->cells)) {
+ if (chained.find(cell.first) != chained.end())
+ continue;
+ CellInfo *ci = cell.second;
+ if (cell_type_predicate(ctx, ci)) {
+ CellInfo *start = ci;
+ CellInfo *prev_start = ci;
+ while (prev_start != nullptr) {
+ start = prev_start;
+ prev_start = get_previous(ctx, start);
+ }
+ CellChain chain;
+ CellInfo *end = start;
+ while (end != nullptr) {
+ chain.cells.push_back(end);
+ end = get_next(ctx, end);
+ }
+ if (chain.cells.size() >= min_length) {
+ chains.push_back(chain);
+ for (auto c : chain.cells)
+ chained.insert(c->name);
+ }
+ }
+ }
+ return chains;
+}
+
+class ChainConstrainer
+{
+ private:
+ 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 (tile.size() >= 8) {
+ tile.clear();
+ }
+ if (start_of_chain) {
+ tile.clear();
+ chains.emplace_back();
+ start_of_chain = false;
+ if (cell->ports.at(ctx->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(ctx->id("CIN")));
+ chains.back().cells.push_back(feedin);
+ tile.push_back(feedin);
+ }
+ }
+ tile.push_back(cell);
+ chains.back().cells.push_back(cell);
+ bool split_chain = (!ctx->logicCellsCompatible(tile)) || (int(chains.back().cells.size()) > max_length);
+ if (split_chain) {
+ CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
+ tile.pop_back();
+ chains.back().cells.back() = passout;
+ start_of_chain = true;
+ } else {
+ NetInfo *carry_net = cell->ports.at(ctx->id("COUT")).net;
+ bool at_end = (curr_cell == carryc.cells.end() - 1);
+ if (carry_net != nullptr && (carry_net->users.size() > 1 || at_end)) {
+ if (carry_net->users.size() > 2 ||
+ (net_only_drives(ctx, carry_net, is_lc, ctx->id("I3"), false) !=
+ net_only_drives(ctx, carry_net, is_lc, ctx->id("CIN"), false)) ||
+ (at_end && !net_only_drives(ctx, carry_net, is_lc, ctx->id("I3"), true))) {
+ CellInfo *passout = make_carry_pass_out(cell->ports.at(ctx->id("COUT")));
+ chains.back().cells.push_back(passout);
+ tile.push_back(passout);
+ start_of_chain = true;
+ }
+ }
+ ++curr_cell;
+ }
+ }
+ return chains;
+ }
+
+ // Insert a logic cell to legalise a COUT->fabric connection
+ CellInfo *make_carry_pass_out(PortInfo &cout_port)
+ {
+ NPNR_ASSERT(cout_port.net != nullptr);
+ std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
+ lc->params[ctx->id("LUT_INIT")] = "65280"; // 0xff00: O = I3
+ lc->params[ctx->id("CARRY_ENABLE")] = "1";
+ lc->ports.at(ctx->id("O")).net = cout_port.net;
+ std::unique_ptr<NetInfo> co_i3_net(new NetInfo());
+ co_i3_net->name = ctx->id(lc->name.str(ctx) + "$I3");
+ co_i3_net->driver = cout_port.net->driver;
+ PortRef i3_r;
+ i3_r.port = ctx->id("I3");
+ i3_r.cell = lc.get();
+ co_i3_net->users.push_back(i3_r);
+ PortRef o_r;
+ o_r.port = ctx->id("O");
+ o_r.cell = lc.get();
+ cout_port.net->driver = o_r;
+ lc->ports.at(ctx->id("I3")).net = co_i3_net.get();
+ cout_port.net = co_i3_net.get();
+
+ IdString co_i3_name = co_i3_net->name;
+ NPNR_ASSERT(ctx->nets.find(co_i3_name) == ctx->nets.end());
+ ctx->nets[co_i3_name] = std::move(co_i3_net);
+ IdString name = lc->name;
+ ctx->assignCellInfo(lc.get());
+ ctx->cells[lc->name] = std::move(lc);
+ return ctx->cells[name].get();
+ }
+
+ // Insert a logic cell to legalise a CIN->fabric connection
+ CellInfo *make_carry_feed_in(CellInfo *cin_cell, PortInfo &cin_port)
+ {
+ NPNR_ASSERT(cin_port.net != nullptr);
+ std::unique_ptr<CellInfo> lc = create_ice_cell(ctx, ctx->id("ICESTORM_LC"));
+ lc->params[ctx->id("CARRY_ENABLE")] = "1";
+ lc->params[ctx->id("CIN_CONST")] = "1";
+ lc->params[ctx->id("CIN_SET")] = "1";
+ lc->ports.at(ctx->id("I1")).net = cin_port.net;
+ cin_port.net->users.erase(std::remove_if(cin_port.net->users.begin(), cin_port.net->users.end(),
+ [cin_cell, cin_port](const PortRef &usr) {
+ return usr.cell == cin_cell && usr.port == cin_port.name;
+ }));
+
+ PortRef i1_ref;
+ i1_ref.cell = lc.get();
+ i1_ref.port = ctx->id("I1");
+ lc->ports.at(ctx->id("I1")).net->users.push_back(i1_ref);
+
+ std::unique_ptr<NetInfo> out_net(new NetInfo());
+ out_net->name = ctx->id(lc->name.str(ctx) + "$O");
+
+ PortRef drv_ref;
+ drv_ref.port = ctx->id("COUT");
+ drv_ref.cell = lc.get();
+ out_net->driver = drv_ref;
+ lc->ports.at(ctx->id("COUT")).net = out_net.get();
+
+ PortRef usr_ref;
+ usr_ref.port = cin_port.name;
+ usr_ref.cell = cin_cell;
+ out_net->users.push_back(usr_ref);
+ cin_cell->ports.at(cin_port.name).net = out_net.get();
+
+ IdString out_net_name = out_net->name;
+ NPNR_ASSERT(ctx->nets.find(out_net_name) == ctx->nets.end());
+ ctx->nets[out_net_name] = std::move(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()
+ {
+ std::vector<CellChain> carry_chains =
+ find_chains(ctx, [](const Context *ctx, const CellInfo *cell) { return is_lc(ctx, cell); },
+ [](const Context *ctx, const
+
+ CellInfo *cell) {
+ CellInfo *carry_prev =
+ net_driven_by(ctx, cell->ports.at(ctx->id("CIN")).net, is_lc, ctx->id("COUT"));
+ if (carry_prev != nullptr)
+ return carry_prev;
+ /*CellInfo *i3_prev = net_driven_by(ctx, cell->ports.at(ctx->id("I3")).net, is_lc,
+ ctx->id("COUT")); if (i3_prev != nullptr) return i3_prev;*/
+ return (CellInfo *)nullptr;
+ },
+ [](const Context *ctx, const CellInfo *cell) {
+ CellInfo *carry_next = net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc,
+ ctx->id("CIN"), false);
+ if (carry_next != nullptr)
+ return carry_next;
+ /*CellInfo *i3_next =
+ net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc, ctx->id("I3"),
+ false); if (i3_next != nullptr) return i3_next;*/
+ return (CellInfo *)nullptr;
+ });
+ std::unordered_set<IdString> chained;
+ for (auto &base_chain : carry_chains) {
+ for (auto c : base_chain.cells)
+ chained.insert(c->name);
+ }
+ // Any cells not in chains, but with carry enabled, must also be put in a single-carry chain
+ // for correct processing
+ for (auto cell : sorted(ctx->cells)) {
+ CellInfo *ci = cell.second;
+ if (chained.find(cell.first) == chained.end() && is_lc(ctx, ci) &&
+ bool_or_default(ci->params, ctx->id("CARRY_ENABLE"))) {
+ CellChain sChain;
+ sChain.cells.push_back(ci);
+ chained.insert(cell.first);
+ carry_chains.push_back(sChain);
+ }
+ }
+ 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;
+ 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)->constr_parent = chain.cells.at(0);
+ chain.cells.at(0)->constr_children.push_back(chain.cells.at(i));
+ }
+ }
+ }
+
+ 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
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