ice40: Start work on the placement legaliser

Signed-off-by: David Shah <davey1576@gmail.com>

ice40/place_legaliser.cc

@@ -0,0 +1,78 @@
+/*
+ *  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 "place_legaliser.h"
+#include <algorithm>
+#include <vector>
+#include "cells.h"
+#include "design_utils.h"
+#include "log.h"
+#include "util.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+// Generic chain finder
+template <typename F1, typename F2, typename F3>
+std::vector<std::vector<CellInfo *>> 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<std::vector<CellInfo *>> chains;
+    for (auto cell : 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);
+            }
+            std::vector<CellInfo *> chain;
+            CellInfo *end = start;
+            while (end != nullptr) {
+                chain.push_back(end);
+                end = get_next(ctx, end);
+            }
+            if (chain.size() >= min_length) {
+                chains.push_back(chain);
+                for (auto c : chain)
+                    chained.insert(c->name);
+            }
+        }
+    }
+    return chains;
+};
+
+bool legalise_design(Context *ctx)
+{
+    std::vector<std::vector<CellInfo *>> carry_chains = find_chains(
+            ctx, is_lc,
+            [](const Context *ctx, const CellInfo *cell) {
+                return net_driven_by(ctx, cell->ports.at(ctx->id("CIN")).net, is_lc, ctx->id("COUT"));
+            },
+            [](const Context *ctx, const CellInfo *cell) {
+                return net_only_drives(ctx, cell->ports.at(ctx->id("COUT")).net, is_lc, ctx->id("CIN"), false);
+            });
+    // TODO
+    return true;
+}
+
+NEXTPNR_NAMESPACE_END

ice40/place_legaliser.h

@@ -0,0 +1,31 @@
+/*
+ *  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.
+ *
+ */
+
+#ifndef PLACE_LEGALISER_H
+#define PLACE_LEGALISER_H
+
+#include "nextpnr.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+bool legalise_design(Context *ctx);
+
+NEXTPNR_NAMESPACE_END
+
+#endif