gatemate: Add LUT tree library script

Co-authored-by: Claire Xenia Wolf <claire@clairexen.net>
Signed-off-by: gatecat <gatecat@ds0.me>

6 files changed, 591 insertions, 6 deletions

diff --git a/techlibs/gatemate/.gitignore b/techlibs/gatemate/.gitignore
new file mode 100644
index 000000000..f260d6e9d
--- /dev/null
+++ b/techlibs/gatemate/.gitignore
@@ -0,0 +1,4 @@
+lut_tree_cells.genlib
+lut_tree_map.v
+lut_tree_lib.mk
+
diff --git a/techlibs/gatemate/Makefile.inc b/techlibs/gatemate/Makefile.inc
index d1341d7bb..aeb318cc9 100644
--- a/techlibs/gatemate/Makefile.inc
+++ b/techlibs/gatemate/Makefile.inc
@@ -1,5 +1,6 @@
 

 OBJS += techlibs/gatemate/synth_gatemate.o

+OBJS += techlibs/gatemate/gatemate_foldinv.o

 

 $(eval $(call add_share_file,share/gatemate,techlibs/gatemate/reg_map.v))

 $(eval $(call add_share_file,share/gatemate,techlibs/gatemate/mux_map.v))

@@ -12,3 +13,18 @@ $(eval $(call add_share_file,share/gatemate,techlibs/gatemate/brams_map.v))
 $(eval $(call add_share_file,share/gatemate,techlibs/gatemate/brams.txt))

 $(eval $(call add_share_file,share/gatemate,techlibs/gatemate/brams_init_20.vh))

 $(eval $(call add_share_file,share/gatemate,techlibs/gatemate/brams_init_40.vh))

+$(eval $(call add_share_file,share/gatemate,techlibs/gatemate/inv_map.v))

+

+EXTRA_OBJS += techlibs/gatemate/lut_tree_lib.mk

+.SECONDARY: techlibs/gatemate/lut_tree_lib.mk

+

+techlibs/gatemate/lut_tree_lib.mk: techlibs/gatemate/make_lut_tree_lib.py

+	$(Q) mkdir -p techlibs/gatemate

+	$(P) $(PYTHON_EXECUTABLE) $<

+	$(Q) touch $@

+

+techlibs/gatemate/lut_tree_cells.genlib: techlibs/gatemate/lut_tree_lib.mk

+techlibs/gatemate/lut_tree_map.v: techlibs/gatemate/lut_tree_lib.mk

+

+$(eval $(call add_gen_share_file,share/gatemate,techlibs/gatemate/lut_tree_cells.genlib))

+$(eval $(call add_gen_share_file,share/gatemate,techlibs/gatemate/lut_tree_map.v))

diff --git a/techlibs/gatemate/gatemate_foldinv.cc b/techlibs/gatemate/gatemate_foldinv.cc
new file mode 100644
index 000000000..20fbbf8a3
--- /dev/null
+++ b/techlibs/gatemate/gatemate_foldinv.cc
@@ -0,0 +1,218 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2021  gatecat <gatecat@ds0.me>
+ *  Copyright (C) 2021  Cologne Chip AG <support@colognechip.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 "kernel/yosys.h"
+#include "kernel/sigtools.h"
+
+USING_YOSYS_NAMESPACE
+PRIVATE_NAMESPACE_BEGIN
+
+struct LUTPin {
+    int input_bit;
+    IdString init_param;
+};
+
+struct LUTType {
+    dict<IdString, LUTPin> inputs;
+    IdString output_param;
+};
+
+static const dict<IdString, LUTType> lut_types = {
+    {ID(CC_LUT2), {{
+            {ID(I0), {0, ID(INIT)}},
+            {ID(I1), {1, ID(INIT)}},
+        }, ID(INIT)}},
+    {ID(CC_L2T4), {{
+            {ID(I0), {0, ID(INIT_L00)}},
+            {ID(I1), {1, ID(INIT_L00)}},
+            {ID(I2), {0, ID(INIT_L01)}},
+            {ID(I3), {1, ID(INIT_L01)}},
+        }, ID(INIT_L10)}},
+    {ID(CC_L2T5), {{
+            {ID(I0), {0, ID(INIT_L02)}},
+            {ID(I1), {1, ID(INIT_L02)}},
+            {ID(I2), {0, ID(INIT_L03)}},
+            {ID(I3), {1, ID(INIT_L03)}},
+            {ID(I4), {0, ID(INIT_L20)}},
+        }, ID(INIT_L20)}},
+};
+
+struct FoldInvWorker {
+    FoldInvWorker(Module *module) : module(module), sigmap(module) {};
+    Module *module;
+    SigMap sigmap;
+
+    // Mapping from inverter output to inverter input
+    dict<SigBit, SigBit> inverted_bits;
+    // Mapping from inverter input to inverter
+    dict<SigBit, Cell*> inverter_input;
+
+    void find_inverted_bits()
+    {
+        for (auto cell : module->selected_cells()) {
+            if (cell->type != ID($__CC_NOT))
+                continue;
+            SigBit a = sigmap(cell->getPort(ID::A)[0]);
+            SigBit y = sigmap(cell->getPort(ID::Y)[0]);
+            inverted_bits[y] = a;
+            inverter_input[a] = cell;
+        }
+    }
+
+    Const invert_lut_input(Const lut, int bit)
+    {
+        Const result(State::S0, GetSize(lut));
+        for (int i = 0; i < GetSize(lut); i++) {
+            int j = i ^ (1 << bit);
+            result[j] = lut[i];
+        }
+        return result;
+    }
+
+    Const invert_lut_output(Const lut)
+    {
+        Const result(State::S0, GetSize(lut));
+        for (int i = 0; i < GetSize(lut); i++)
+            result[i] = (lut[i] == State::S1) ? State::S0 : State::S1;
+        return result;
+    }
+
+    void fold_input_inverters()
+    {
+        for (auto cell : module->selected_cells()) {
+            auto found_type = lut_types.find(cell->type);
+            if (found_type == lut_types.end())
+                continue;
+            const auto &type = found_type->second;
+            for (const auto &ipin : type.inputs) {
+                if (!cell->hasPort(ipin.first))
+                    continue;
+                auto sig = cell->getPort(ipin.first);
+                if (GetSize(sig) == 0)
+                    continue;
+                SigBit bit = sigmap(sig[0]);
+                auto inv = inverted_bits.find(bit);
+                if (inv == inverted_bits.end())
+                    continue; // not the output of an inverter
+                // Rewire to inverter input
+                cell->unsetPort(ipin.first);
+                cell->setPort(ipin.first, inv->second);
+                // Rewrite init
+                cell->setParam(ipin.second.init_param,
+                    invert_lut_input(cell->getParam(ipin.second.init_param), ipin.second.input_bit));
+            }
+        }
+    }
+
+    void fold_output_inverters()
+    {
+        pool<SigBit> used_bits;
+        // Find bits that are actually used
+        for (auto cell : module->selected_cells()) {
+            for (auto conn : cell->connections()) {
+                if (cell->output(conn.first))
+                    continue;
+                for (auto bit : sigmap(conn.second))
+                    used_bits.insert(bit);
+            }
+        }
+        // Find LUTs driving inverters
+        // (create a vector to avoid iterate-and-modify issues)
+        std::vector<std::pair<Cell *, Cell*>> lut_inv;
+        for (auto cell : module->selected_cells()) {
+            auto found_type = lut_types.find(cell->type);
+            if (found_type == lut_types.end())
+                continue;
+            if (!cell->hasPort(ID::O))
+                continue;
+            auto o_sig = cell->getPort(ID::O);
+            if (GetSize(o_sig) == 0)
+                continue;
+            SigBit o = sigmap(o_sig[0]);
+            auto found_inv = inverter_input.find(o);
+            if (found_inv == inverter_input.end())
+                continue; // doesn't drive an inverter
+            lut_inv.emplace_back(cell, found_inv->second);
+        }
+        for (auto pair : lut_inv) {
+            Cell *orig_lut = pair.first;
+            Cell *inv = pair.second;
+            // Find the inverter output
+            SigBit inv_y = sigmap(inv->getPort(ID::Y)[0]);
+            // Inverter output might not actually be used; if all users were folded into inputs already
+            if (!used_bits.count(inv_y))
+                continue;
+            // Create a duplicate of the LUT with an inverted output
+            // (if the uninverted version becomes unused it will be swept away)
+            Cell *dup_lut = module->addCell(NEW_ID, orig_lut->type);
+            inv->unsetPort(ID::Y);
+            dup_lut->setPort(ID::O, inv_y);
+            for (auto conn : orig_lut->connections()) {
+                if (conn.first == ID::O)
+                    continue;
+                dup_lut->setPort(conn.first, conn.second);
+            }
+            for (auto param : orig_lut->parameters) {
+                if (param.first == lut_types.at(orig_lut->type).output_param)
+                    dup_lut->parameters[param.first] = invert_lut_output(param.second);
+                else
+                    dup_lut->parameters[param.first] = param.second;
+            }
+        }
+    }
+
+    void operator()()
+    {
+        find_inverted_bits();
+        fold_input_inverters();
+        fold_output_inverters();
+    }
+};
+
+struct GatemateFoldInvPass : public Pass {
+    GatemateFoldInvPass() : Pass("gatemate_foldinv", "fold inverters into Gatemate LUT trees") { }
+    void help() override
+    {
+        //   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
+        log("\n");
+        log("    gatemate_foldinv [selection]\n");
+        log("\n");
+        log("\n");
+        log("This pass searches for $__CC_NOT cells and folds them into CC_LUT2, CC_L2T4\n");
+        log("and CC_L2T5 cells as created by LUT tree mapping.\n");
+        log("\n");
+    }
+
+    void execute(std::vector<std::string> args, RTLIL::Design *design) override
+    {
+        log_header(design, "Executing GATEMATE_FOLDINV pass (folding LUT tree inverters).\n");
+
+        size_t argidx = 1;
+        extra_args(args, argidx, design);
+
+        for (Module *module : design->selected_modules()) {
+            FoldInvWorker worker(module);
+            worker();
+        }        
+    }
+} GatemateFoldInvPass;
+
+PRIVATE_NAMESPACE_END
+
diff --git a/techlibs/gatemate/inv_map.v b/techlibs/gatemate/inv_map.v
new file mode 100644
index 000000000..8a5051747
--- /dev/null
+++ b/techlibs/gatemate/inv_map.v
@@ -0,0 +1,4 @@
+// Any inverters not folded into LUTs are mapped to a LUT of their own
+module \$__CC_NOT (input A, output Y);
+	CC_LUT1 #(.INIT(2'b01)) _TECHMAP_REPLACE_ (.I0(A), .O(Y));
+endmodule
diff --git a/techlibs/gatemate/make_lut_tree_lib.py b/techlibs/gatemate/make_lut_tree_lib.py
new file mode 100644
index 000000000..25ca88882
--- /dev/null
+++ b/techlibs/gatemate/make_lut_tree_lib.py
@@ -0,0 +1,323 @@
+#!/usr/bin/env python3
+
+class FNode:
+    def __init__(self, fun, *args):
+        self.fun = fun
+        self.args = args
+
+        if len(self.args) == 0:
+            assert fun not in ("BUF", "NOT", "AND", "OR", "XOR", "MUX")
+
+        if len(self.args) == 1:
+            assert fun in ("BUF", "NOT")
+
+        if len(self.args) == 2:
+            assert fun in ("AND", "OR", "XOR")
+
+        if len(self.args) == 3:
+            assert fun in ("MUX")
+
+    def __str__(self):
+        if len(self.args) == 0:
+            return self.fun
+        if self.fun == "NOT" and len(self.args[0].args) == 0:
+            return "!" + self.args[0].fun
+        return self.fun + "(" + ",".join([str(a) for a in self.args]) + ")"
+
+    def as_genlib_term(self):
+        if len(self.args) == 0:
+            return self.fun
+        if self.fun == "NOT":
+            assert len(self.args[0].args) == 0
+            return "!" + self.args[0].fun
+        if self.fun == "AND":
+            return "(" + self.args[0].as_genlib_term() + "*" + self.args[1].as_genlib_term() + ")"
+        if self.fun == "OR":
+            return "(" + self.args[0].as_genlib_term() + "+" + self.args[1].as_genlib_term() + ")"
+        assert False
+
+    def mapMux(self):
+        if self.fun == "MUX":
+            A, B, C = self.args
+            return OR(AND(A, NOT(C)), AND(B, C)).mapMux()
+        return FNode(self.fun, *[a.mapMux() for a in self.args])
+
+    def mapXor(self):
+        if self.fun == "XOR":
+            A, B = self.args
+            return OR(AND(A, NOT(B)), AND(NOT(A), B)).mapXor()
+        return FNode(self.fun, *[a.mapXor() for a in self.args])
+
+    def mapNot(self):
+        if self.fun == "BUF":
+            return self.arg1.mapNot()
+        if self.fun == "NOT":
+            if self.args[0].fun == "AND":
+                return OR(NOT(self.args[0].args[0]),NOT(self.args[0].args[1])).mapNot()
+            if self.args[0].fun == "OR":
+                return AND(NOT(self.args[0].args[0]),NOT(self.args[0].args[1])).mapNot()
+            if self.args[0].fun == "NOT":
+                return self.args[0].args[0].mapNot()
+        return FNode(self.fun, *[a.mapNot() for a in self.args])
+
+    def map(self):
+        n = self
+        n = n.mapMux()
+        n = n.mapXor()
+        n = n.mapNot()
+        return n
+
+    def isInv(self):
+        if len(self.args) == 0:
+            return False
+        if self.fun == "XOR":
+            return False
+        if self.fun == "NOT":
+            return self.args[0].isNonInv()
+        for a in self.args:
+            if not a.isInv():
+                return False
+        return True
+
+    def isNonInv(self):
+        if len(self.args) == 0:
+            return True
+        if self.fun == "XOR":
+            return False
+        if self.fun == "NOT":
+            return self.args[0].isInv()
+        for a in self.args:
+            if not a.isNonInv():
+                return False
+        return True
+
+A = FNode("A")
+B = FNode("B")
+C = FNode("C")
+D = FNode("D")
+E = FNode("E")
+
+def BUF(arg): return FNode("BUF", arg)
+def NOT(arg): return FNode("NOT", arg)
+def AND(arg1, arg2): return FNode("AND", arg1, arg2)
+def  OR(arg1, arg2): return FNode( "OR", arg1, arg2)
+def XOR(arg1, arg2): return FNode("XOR", arg1, arg2)
+def MUX(arg1, arg2, arg3): return FNode("MUX", arg1, arg2, arg3)
+
+# Genlib Format:
+#
+# GATE <cell-name> <cell-area> <cell-logic-function>
+#
+# PIN <pin-name> <phase> <input-load> <max-load>
+#     <rise-block-delay> <rise-fanout-delay>
+#     <fall-block-delay> <fall-fanout-delay>
+#
+# phase:
+#     INV, NONINV, or UNKNOWN
+#
+# cell-logic-function:
+#     <output> = <term with *(AND), +(OR), !(NOT)>
+
+
+cells = [
+    ["$__CC_BUF", 5, A],
+    ["$__CC_NOT", 0, NOT(A)],
+    ["$__CC_MUX", 5, MUX(A, B, C)],
+]
+
+base_cells = [
+    ["$__CC2_A", AND(A, B)],
+    ["$__CC2_O",  OR(A, B)],
+    ["$__CC2_X", XOR(A, B)],
+
+    ["$__CC3_AA", AND(AND(A, B), C)],
+    ["$__CC3_OO",  OR( OR(A, B), C)],
+    ["$__CC3_XX", XOR(XOR(A, B), C)],
+    ["$__CC3_AO",  OR(AND(A, B), C)],
+    ["$__CC3_OA", AND( OR(A, B), C)],
+    ["$__CC3_AX", XOR(AND(A, B), C)],
+    ["$__CC3_XA", AND(XOR(A, B), C)],
+
+#   ["$__CC3_AAA", AND(AND(A,B),AND(A,C))],
+#   ["$__CC3_AXA", XOR(AND(A,B),AND(A,C))],
+#   ["$__CC3_XAX", AND(XOR(A,B),XOR(A,C))],
+#   ["$__CC3_AAX", AND(AND(A,B),XOR(A,C))],
+#   ["$__CC3_AXX", XOR(AND(A,B),XOR(A,C))],
+#   ["$__CC3_XXX", XOR(XOR(A,B),XOR(A,C))],
+#   ["$__CC3_AAO", AND(AND(A,B), OR(A,C))],
+#   ["$__CC3_AOA",  OR(AND(A,B),AND(A,C))],
+#   ["$__CC3_AOX",  OR(AND(A,B),XOR(A,C))],
+
+#   ["$__CC3_AAA_N", AND(AND(A,B),AND(NOT(A),C))],
+#   ["$__CC3_AXA_N", XOR(AND(A,B),AND(NOT(A),C))],
+#   ["$__CC3_XAX_N", AND(XOR(A,B),XOR(NOT(A),C))],
+#   ["$__CC3_AAX_N", AND(AND(A,B),XOR(NOT(A),C))],
+#   ["$__CC3_AXX_N", XOR(AND(A,B),XOR(NOT(A),C))],
+#   ["$__CC3_XXX_N", XOR(XOR(A,B),XOR(NOT(A),C))],
+#   ["$__CC3_AAO_N", AND(AND(A,B), OR(NOT(A),C))],
+#   ["$__CC3_AOA_N",  OR(AND(A,B),AND(NOT(A),C))],
+#   ["$__CC3_AOX_N",  OR(AND(A,B),XOR(NOT(A),C))],
+
+    ["$__CC4_AAA", AND(AND(A,B),AND(C,D))],
+    ["$__CC4_AXA", XOR(AND(A,B),AND(C,D))],
+    ["$__CC4_XAX", AND(XOR(A,B),XOR(C,D))],
+    ["$__CC4_AAX", AND(AND(A,B),XOR(C,D))],
+    ["$__CC4_AXX", XOR(AND(A,B),XOR(C,D))],
+    ["$__CC4_XXX", XOR(XOR(A,B),XOR(C,D))],
+    ["$__CC4_AAO", AND(AND(A,B), OR(C,D))],
+    ["$__CC4_AOA",  OR(AND(A,B),AND(C,D))],
+    ["$__CC4_AOX",  OR(AND(A,B),XOR(C,D))],
+]
+
+for name, expr in base_cells:
+    cells.append([name, 10, expr])
+
+    name = (name
+        .replace("$__CC4_", "$__CC5_")
+        .replace("$__CC3_", "$__CC4_")
+        .replace("$__CC2_", "$__CC3_"))
+
+    # Cells such as $__CC4_AA_A are redundant, as $__CC4_AAA is equivalent
+    if name not in ("$__CC4_AA", "$__CC3_A"):
+        cells.append([name + "_A", 12, AND(E, expr)])
+    if name not in ("$__CC4_OO", "$__CC3_O"):
+        cells.append([name + "_O", 12,  OR(E, expr)])
+    if name not in ("$__CC4_XX", "$__CC3_X"):
+        cells.append([name + "_X", 12, XOR(E, expr)])
+
+with open("techlibs/gatemate/lut_tree_cells.genlib", "w") as glf:
+    def mkGate(name, cost, expr, max_load=9999, block_delay = 10, fanout_delay = 5):
+        name = name.replace(" ", "")
+        expr = expr.map()
+
+        phase = "UNKNOWN"
+        if expr.isInv(): phase = "INV"
+        if expr.isNonInv(): phase = "NONINV"
+
+        print("", file=glf)
+        print("GATE %s %d Y=%s;" % (name, cost, expr.as_genlib_term()), file=glf)
+        print("PIN * %s 1 %d %d %d %d %d" % (phase, max_load, block_delay, fanout_delay, block_delay, fanout_delay), file=glf)
+    print("GATE $__ZERO 0 Y=CONST0;", file=glf)
+    print("GATE $__ONE 0 Y=CONST1;", file=glf)
+    for name, cost, expr in cells:
+        mkGate(name, cost, expr)
+
+class LUTTreeNode:
+    def __init__(self, name, width, inputs=None):
+        self.name = name
+        self.width = width
+        self.inputs = inputs
+    def is_input(self):
+        return self.width == 0
+    def map(self, expr, params, ports):
+        if self.is_input():
+            # Input to LUT tree
+            if expr is None:
+                ports[self.name] = "" # disconnected input
+            else:
+                assert(len(expr.args) == 0)
+                ports[self.name] = expr.fun
+            return
+        if expr is None:
+            # Unused part of tree
+            params[self.name] = "4'b0000"
+            for i in self.inputs:
+                i.map(None, params, ports)
+            return
+        elif len(expr.args) == 0:
+            # Input to the expression; but not LUT tree
+            # Insert a route through
+            params[self.name] = "4'b1010"
+            self.inputs[0].map(expr, params, ports)
+            for i in self.inputs[1:]:
+                i.map(None, params, ports)
+            return
+        # Map uphill LUTs; uninverting arguments and keeping track of that if needed
+        arg_inv = []
+        for (i, arg) in zip(self.inputs, expr.args):
+            if arg.fun == "NOT":
+                i.map(arg.args[0], params, ports)
+                arg_inv.append(True)
+            else:
+                i.map(arg, params, ports)
+                arg_inv.append(False)
+        # Determine base init value
+        assert self.width == 2
+        if expr.fun == "AND":
+            init = 0b1000
+        elif expr.fun == "OR":
+            init = 0b1110
+        elif expr.fun == "XOR":
+            init = 0b0110
+        else:
+            assert False, expr.fun
+        # Swap bits if init inverted
+        swapped_init = 0b0000
+        for b in range(4):
+            if ((init >> b) & 0x1) == 0: continue
+            for i in range(2):
+                if arg_inv[i]:
+                    b ^= (1 << i)
+            swapped_init |= (1 << b)
+        # Set init param
+        params[self.name] = "4'b{:04b}".format(swapped_init)
+
+def LUT2(name, i0, i1): return LUTTreeNode(name, 2, [i0, i1])
+def I(name): return LUTTreeNode(name, 0)
+
+lut_prims = {
+    "CC_LUT2": LUT2("INIT", I("I0"), I("I1")),
+    "CC_L2T4": LUT2(
+        "INIT_L10",
+        LUT2("INIT_L00", I("I0"), I("I1")),
+        LUT2("INIT_L01", I("I2"), I("I3")),
+    ),
+    "CC_L2T5": LUT2(
+        "INIT_L20", I("I4"), LUT2("INIT_L11",
+            LUT2("INIT_L02", I("I0"), I("I1")),
+            LUT2("INIT_L03", I("I2"), I("I3")),
+        )
+    )
+}
+
+with open("techlibs/gatemate/lut_tree_map.v", "w") as vf:
+    # Non-automatic rules
+    print("""
+module \\$__ZERO (output Y); assign Y = 1'b0; endmodule
+module \\$__ONE (output Y); assign Y = 1'b1; endmodule
+
+module \\$__CC_BUF (input A, output Y); assign Y = A; endmodule
+
+module \\$__CC_MUX (input A, B, C, output Y);
+    CC_MX2 _TECHMAP_REPLACE_ (
+        .D0(A), .D1(B), .S0(C),
+        .Y(Y)
+    );
+endmodule
+""", file=vf)
+    for name, cost, expr in cells:
+        expr = expr.mapMux().mapNot() # Don't map XOR
+        if name in ("$__CC_BUF", "$__CC_NOT", "$__CC_MUX"):
+            # Special cases
+            continue
+        if name.startswith("$__CC2_"):
+            prim = "CC_LUT2"
+        elif name.startswith("$__CC5_") or (name.startswith("$__CC4_") and cost == 12):
+            prim = "CC_L2T5"
+        else:
+            prim = "CC_L2T4"
+        ports = {}
+        params = {}
+        lut_prims[prim].map(expr, params, ports)
+        print("", file=vf)
+        print("module \\%s (input %s, output Y);" % (name,
+            ", ".join(sorted(set(x for x in ports.values() if x)))), file=vf)
+        print("    %s #(" % prim, file=vf)
+        for k, v in sorted(params.items(), key=lambda x: x[0]):
+            print("        .%s(%s)," % (k, v), file=vf)
+        print("    ) _TECHMAP_REPLACE_ (", file=vf)
+        print("         %s," % ", ".join(".%s(%s)" % (k, v) for k, v in sorted(ports.items(), key=lambda x:x[0])),
+            file=vf)
+        print("         .O(Y)", file=vf)
+        print("    );", file=vf)
+        print("endmodule", file=vf)
diff --git a/techlibs/gatemate/synth_gatemate.cc b/techlibs/gatemate/synth_gatemate.cc
index 93b16b2e0..dd4fde643 100644
--- a/techlibs/gatemate/synth_gatemate.cc
+++ b/techlibs/gatemate/synth_gatemate.cc
@@ -67,7 +67,10 @@ struct SynthGateMatePass : public ScriptPass
 		log("\n");

 		log("    -nomx8, -nomx4\n");

 		log("        do not use CC_MX{8,4} multiplexer cells in output netlist.\n");

-		log("\n");;

+		log("\n");

+		log("    -luttree\n");

+		log("        use new LUT tree mapping approach (EXPERIMENTAL).\n");

+		log("\n");

 		log("    -dff\n");

 		log("        run 'abc' with -dff option\n");

 		log("\n");

@@ -87,7 +90,7 @@ struct SynthGateMatePass : public ScriptPass
 	}

 

 	string top_opt, vlog_file, json_file;

-	bool noflatten, nobram, noaddf, nomult, nomx4, nomx8, dff, retime, noiopad, noclkbuf;

+	bool noflatten, nobram, noaddf, nomult, nomx4, nomx8, luttree, dff, retime, noiopad, noclkbuf;

 

 	void clear_flags() override

 	{

@@ -100,6 +103,7 @@ struct SynthGateMatePass : public ScriptPass
 		nomult = false;

 		nomx4 = false;

 		nomx8 = false;

+		luttree = false;

 		dff = false;

 		retime = false;

 		noiopad = false;

@@ -158,6 +162,10 @@ struct SynthGateMatePass : public ScriptPass
 				nomx8 = true;

 				continue;

 			}

+			if (args[argidx] == "-luttree") {

+				luttree = true;

+				continue;

+			}

 			if (args[argidx] == "-dff") {

 				dff = true;

 				continue;

@@ -298,11 +306,23 @@ struct SynthGateMatePass : public ScriptPass
 

 		if (check_label("map_luts"))

 		{

-			std::string abc_args = " -dress -lut 4";

-			if (dff) {

-				abc_args += " -dff";

+			if (luttree || help_mode) {

+				std::string abc_args = " -genlib +/gatemate/lut_tree_cells.genlib";

+				if (dff) {

+					abc_args += " -dff";

+				}

+				run("abc " + abc_args, "(with -luttree)");

+				run("techmap -map +/gatemate/lut_tree_map.v", "(with -luttree)");

+				run("gatemate_foldinv", "(with -luttree)");

+				run("techmap -map +/gatemate/inv_map.v", "(with -luttree)");

+			}

+			if (!luttree || help_mode) {

+				std::string abc_args = " -dress -lut 4";

+				if (dff) {

+					abc_args += " -dff";

+				}

+				run("abc " + abc_args, "(without -luttree)");

 			}

-			run("abc " + abc_args);

 			run("clean");

 		}