ice40: Adding a placement validity checker

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

5 files changed, 148 insertions, 6 deletions

diff --git a/ice40/arch_place.cc b/ice40/arch_place.cc
new file mode 100644
index 00000000..2367d981
--- /dev/null
+++ b/ice40/arch_place.cc
@@ -0,0 +1,89 @@
+/*
+ *  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.
+ *
+ */
+
+#include "arch_place.h"
+
+static bool logicCellsCompatible(const std::vector<const CellInfo *> &cells)
+{
+    bool dffs_exist = false, dffs_neg = false;
+    const NetInfo *cen = nullptr, *clk = nullptr, *sr = nullptr;
+    std::unordered_set<const NetInfo *> locals;
+
+    for (auto cell : cells) {
+        if (std::stoi(cell->params.at("DFF_ENABLE"))) {
+            if (!dffs_exist) {
+                dffs_exist = true;
+                cen = cell->ports.at("CEN").net;
+                clk = cell->ports.at("CLK").net;
+                sr = cell->ports.at("SR").net;
+
+                locals.insert(cen);
+                locals.insert(clk);
+                locals.insert(sr);
+
+                if (std::stoi(cell->params.at("NEG_CLK"))) {
+                    dffs_neg = true;
+                }
+            } else {
+                if (cen != cell->ports.at("CEN").net)
+                    return false;
+                if (clk == cell->ports.at("CLK").net)
+                    return false;
+                if (sr != cell->ports.at("SR").net)
+                    return false;
+                if (dffs_neg != bool(std::stoi(cell->params.at("NEG_CLK"))))
+                    return false;
+            }
+        }
+
+        locals.insert(cell->ports.at("I0").net);
+        locals.insert(cell->ports.at("I1").net);
+        locals.insert(cell->ports.at("I2").net);
+        locals.insert(cell->ports.at("I3").net);
+    }
+
+    locals.erase(nullptr); // disconnected signals don't use local tracks
+
+    return locals.size() <= 32;
+}
+
+bool isValidBelForCell(Design *design, CellInfo *cell, BelId bel)
+{
+    const Chip &chip = design->chip;
+    if (cell->type == "ICESTORM_LC") {
+        assert(chip.getBelType(bel) == TYPE_ICESTORM_LC);
+
+        std::vector<const CellInfo *> cells;
+
+        for (auto bel_other : chip.getBelsAtSameTile(bel)) {
+            IdString cell_other = chip.getBelCell(bel_other, false);
+            if (cell_other != IdString()) {
+                const CellInfo *ci_other = design->cells[cell_other];
+                cells.push_back(ci_other);
+            }
+        }
+
+        cells.push_back(cell);
+        return logicCellsCompatible(cells);
+
+    } else {
+        // TODO: IO cell clock checks
+        return true;
+    }
+}
diff --git a/ice40/arch_place.h b/ice40/arch_place.h
new file mode 100644
index 00000000..19b0635f
--- /dev/null
+++ b/ice40/arch_place.h
@@ -0,0 +1,31 @@
+/*
+ *  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 ICE40_ARCH_PLACE_H
+#define ICE40_ARCH_PLACE_H
+
+#include "nextpnr.h"
+// Architecure-specific placement functions
+
+// Whether or not a given cell can be placed at a given Bel
+// This is not intended for Bel type checks, but finer-grained constraints
+// such as conflicting set/reset signals, etc
+bool isValidBelForCell(Chip *chip, CellInfo *cell, BelId bel);
+
+#endif
diff --git a/ice40/chip.cc b/ice40/chip.cc
index 42252fa0..21beb648 100644
--- a/ice40/chip.cc
+++ b/ice40/chip.cc
@@ -151,6 +151,26 @@ BelId Chip::getBelByName(IdString name) const
     return ret;
 }
 
+BelRange Chip::getBelsAtSameTile(BelId bel) const
+{
+    BelRange br;
+    assert(bel != BelId());
+    // This requires Bels at the same tile are consecutive
+    int x = chip_info.bel_data[bel.index].x;
+    int y = chip_info.bel_data[bel.index].y;
+    int start = bel.index, end = bel.index;
+    while (start >= 0 && chip_info.bel_data[start].x == x &&
+           chip_info.bel_data[start].y == y)
+        start--;
+    start++;
+    br.b.cursor = start;
+    while (end < chip_info.num_bels && chip_info.bel_data[end].x == x &&
+           chip_info.bel_data[end].y == y)
+        end++;
+    br.e.cursor = end;
+    return br;
+}
+
 WireId Chip::getWireBelPin(BelId bel, PortPin pin) const
 {
     WireId ret;
diff --git a/ice40/chip.h b/ice40/chip.h
index 451be9ce..097fb286 100644
--- a/ice40/chip.h
+++ b/ice40/chip.h
@@ -479,6 +479,8 @@ struct Chip
         return range;
     }
 
+    BelRange getBelsAtSameTile(BelId bel) const;
+
     BelType getBelType(BelId bel) const
     {
         assert(bel != BelId());
diff --git a/ice40/pack.cc b/ice40/pack.cc
index eb783f2f..ff421c17 100644
--- a/ice40/pack.cc
+++ b/ice40/pack.cc
@@ -90,13 +90,12 @@ static void pack_nonlut_ffs(Design *design)
 }
 
 // Pack constants (simple implementation)
-static void pack_constants(Design *design) {
-    CellInfo *gnd_cell = create_ice_cell(design, "ICESTORM_LC",
-                                       "$PACKER_GND");
+static void pack_constants(Design *design)
+{
+    CellInfo *gnd_cell = create_ice_cell(design, "ICESTORM_LC", "$PACKER_GND");
     gnd_cell->attrs["LUT_INIT"] = "0";
 
-    CellInfo *vcc_cell = create_ice_cell(design, "ICESTORM_LC",
-                                         "$PACKER_VCC");
+    CellInfo *vcc_cell = create_ice_cell(design, "ICESTORM_LC", "$PACKER_VCC");
     vcc_cell->attrs["LUT_INIT"] = "1";
 
     for (auto net : design->nets) {
@@ -105,7 +104,8 @@ static void pack_constants(Design *design) {
             ni->driver.cell = gnd_cell;
             ni->driver.port = "O";
             design->cells[gnd_cell->name] = gnd_cell;
-        } else if (ni->driver.cell != nullptr && ni->driver.cell->type == "VCC") {
+        } else if (ni->driver.cell != nullptr &&
+                   ni->driver.cell->type == "VCC") {
             ni->driver.cell = vcc_cell;
             ni->driver.port = "O";
             design->cells[vcc_cell->name] = vcc_cell;