ice40: Start working on a packer, currently not tested

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

common/design_utils.h

@@ -37,6 +37,8 @@ template <typename F1>
 CellInfo *net_only_drives(NetInfo *net, F1 cell_pred, IdString port,
                           bool exclusive = false)
 {
+    if (net == nullptr)
+        return nullptr;
     if (exclusive && (net->users.size() != 1)) {
         return nullptr;
     } else {
@@ -54,6 +56,8 @@ CellInfo *net_only_drives(NetInfo *net, F1 cell_pred, IdString port,
 template <typename F1>
 CellInfo *net_driven_by(NetInfo *net, F1 cell_pred, IdString port)
 {
+    if (net == nullptr)
+        return nullptr;
     if (cell_pred(net->driver.cell) && net->driver.port == port) {
         return net->driver.cell;
     } else {

ice40/cells.cc

@@ -64,6 +64,19 @@ CellInfo *create_ice_cell(Design *design, IdString type, IdString name)
     return new_cell;
 }
 
+void lut_to_lc(CellInfo *lut, CellInfo *lc, bool no_dff)
+{
+    lc->params["LUT_INIT"] = lut->params["LUT_INIT"];
+    replace_port(lut, "I0", lc, "I0");
+    replace_port(lut, "I1", lc, "I1");
+    replace_port(lut, "I2", lc, "I2");
+    replace_port(lut, "I3", lc, "I3");
+    if (no_dff) {
+        replace_port(lut, "O", lc, "O");
+        lc->params["DFF_ENABLE"] = "0";
+    }
+}
+
 void dff_to_lc(CellInfo *dff, CellInfo *lc, bool pass_thru_lut)
 {
     lc->params["DFF_ENABLE"] = "1";

ice40/cells.h

@@ -45,6 +45,11 @@ inline bool is_ff(const CellInfo *cell)
            cell->type == "SB_DFFNESS" || cell->type == "SB_DFFNES";
 }
 
+// Convert a SB_LUT primitive to (part of) an ICESTORM_LC, swapping ports
+// as needed. Set no_dff if a DFF is not being used, so that the output
+// can be reconnected
+void lut_to_lc(CellInfo *lut, CellInfo *lc, bool no_dff = true);
+
 // Convert a SB_DFFx primitive to (part of) an ICESTORM_LC, setting parameters
 // and reconnecting signals as necessary. If pass_thru_lut is True, the LUT will
 // be configured as pass through and D connected to I0, otherwise D will be

ice40/pack.cc

@@ -0,0 +1,79 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018  Clifford Wolf <clifford@clifford.at>
+ *  Copyright (C) 2018  David Shah <dave@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 "pack.h"
+#include "cells.h"
+#include "design_utils.h"
+#include "log.h"
+
+#include <unordered_set>
+
+// Pack LUTs and LUT-FF pairs
+static void pack_lut_lutffs(Design *design)
+{
+    std::unordered_set<IdString> packed_cells;
+    for (auto cell : design->cells) {
+        CellInfo *ci = cell.second;
+        if (is_lut(ci)) {
+            CellInfo *packed = create_ice_cell(design, "ICESTORM_LC",
+                                               std::string(ci->name) + "_LC");
+            packed_cells.insert(ci->name);
+            // See if we can pack into a DFF
+            // TODO: LUT cascade
+            NetInfo *o = ci->ports.at("O").net;
+            CellInfo *dff = net_only_drives(o, is_ff, "D", true);
+            if (dff) {
+                lut_to_lc(ci, packed, false);
+                dff_to_lc(dff, packed, false);
+                packed_cells.insert(dff->name);
+            } else {
+                lut_to_lc(ci, packed, true);
+            }
+        }
+    }
+    for (auto pcell : packed_cells) {
+        design->cells.erase(pcell);
+    }
+}
+
+// Pack FFs not packed as LUTFFs
+static void pack_nonlut_ffs(Design *design)
+{
+    std::unordered_set<IdString> packed_cells;
+    for (auto cell : design->cells) {
+        CellInfo *ci = cell.second;
+        if (is_ff(ci)) {
+            CellInfo *packed = create_ice_cell(design, "ICESTORM_LC",
+                                               std::string(ci->name) + "_LC");
+            packed_cells.insert(ci->name);
+            dff_to_lc(ci, packed, true);
+        }
+    }
+    for (auto pcell : packed_cells) {
+        design->cells.erase(pcell);
+    }
+}
+
+// Main pack function
+void pack_design(Design *design)
+{
+    pack_lut_lutffs(design);
+    pack_nonlut_ffs(design);
+}

ice40/pack.h

@@ -0,0 +1,27 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2018  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.
+ *
+ */
+
+#ifndef PACK_H
+#define PACK_H
+
+#include "nextpnr.h"
+
+void pack_design(Design *design);
+
+#endif // ROUTE_H