From da6837659ff024da84b9fdcaf38f97ff1927128c Mon Sep 17 00:00:00 2001
From: Miodrag Milanovic <mmicko@gmail.com>
Date: Mon, 7 Jul 2025 16:33:00 +0200
Subject: [PATCH] Optimize CC_LUT1

---
 himbaechel/uarch/gatemate/pack.cc     | 58 ++++++++++++++++++++++++++-
 himbaechel/uarch/gatemate/pack.h      |  8 ++++
 himbaechel/uarch/gatemate/pack_cpe.cc |  2 +
 3 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/himbaechel/uarch/gatemate/pack.cc b/himbaechel/uarch/gatemate/pack.cc
index 66a81df1..e52741ae 100644
--- a/himbaechel/uarch/gatemate/pack.cc
+++ b/himbaechel/uarch/gatemate/pack.cc
@@ -260,6 +260,7 @@ void GateMatePacker::remove_not_used()
                 NetInfo *net = ci.getPort(p.first);
                 if (net && net->users.entries() == 0) {
                     ci.disconnectPort(p.first);
+                    count++;
                 }
             }
         }
@@ -283,6 +284,61 @@ void GateMatePacker::copy_constraint(NetInfo *in_net, NetInfo *out_net)
     }
 }
 
+void GateMatePacker::move_connections(NetInfo *from_net, NetInfo *to_net)
+{
+    for (const auto &usr : from_net->users) {
+        IdString port = usr.port;
+        usr.cell->disconnectPort(port);
+        usr.cell->connectPort(port, to_net);
+    }
+}
+
+void GateMatePacker::optimize_lut()
+{
+    for (auto &cell : ctx->cells) {
+        CellInfo &ci = *cell.second;
+        if (!ci.type.in(id_CC_LUT1))
+            continue;
+        uint8_t val = int_or_default(ci.params, id_INIT, 0);
+        NetInfo *o_net = ci.getPort(id_O);
+        if (!o_net) {
+            packed_cells.insert(ci.name);
+            count++;
+            continue;
+        }
+        switch (val) {
+        case 0: // constant 0
+            move_connections(o_net, gnd_net);
+            packed_cells.insert(ci.name);
+            count++;
+            break;
+        case 2: // propagate
+            move_connections(o_net, ci.getPort(id_I0));
+            packed_cells.insert(ci.name);
+            count++;
+            break;
+        case 3: // constant 1
+            move_connections(o_net, vcc_net);
+            packed_cells.insert(ci.name);
+            count++;
+            break;
+        default:
+            break;
+        }
+    }
+    flush_cells();
+}
+
+void GateMatePacker::cleanup()
+{
+    log_info("Running cleanups..\n");
+    do {
+        count = 0;
+        remove_not_used();
+        optimize_lut();
+    } while (count != 0);
+}
+
 void GateMateImpl::pack()
 {
     const ArchArgs &args = ctx->args;
@@ -292,7 +348,7 @@ void GateMateImpl::pack()
 
     GateMatePacker packer(ctx, this);
     packer.pack_constants();
-    packer.remove_not_used();
+    packer.cleanup();
     packer.pack_io();
     packer.insert_pll_bufg();
     packer.sort_bufg();
diff --git a/himbaechel/uarch/gatemate/pack.h b/himbaechel/uarch/gatemate/pack.h
index 0e870256..4a648312 100644
--- a/himbaechel/uarch/gatemate/pack.h
+++ b/himbaechel/uarch/gatemate/pack.h
@@ -66,12 +66,17 @@ struct GateMatePacker
     void remove_clocking();
     void remove_not_used();
 
+    void cleanup();
+
   private:
     void dff_to_cpe(CellInfo *dff);
     void insert_bufg(CellInfo *cell, IdString port);
     void disconnect_if_gnd(CellInfo *cell, IdString input);
     void pll_out(CellInfo *cell, IdString origPort, Loc fixed);
 
+    void optimize_lut();
+    void move_connections(NetInfo *from_net, NetInfo *to_net);
+
     PllCfgRecord get_pll_settings(double f_ref, double f_core, int mode, int low_jitter, bool pdiv0_mux, bool feedback);
 
     std::pair<CellInfo *, CellInfo *> move_ram_i(CellInfo *cell, IdString origPort, bool place = true,
@@ -101,6 +106,9 @@ struct GateMatePacker
     GateMateImpl *uarch;
 
     HimbaechelHelpers h;
+    NetInfo *vcc_net;
+    NetInfo *gnd_net;
+    int count;
 };
 
 NEXTPNR_NAMESPACE_END
diff --git a/himbaechel/uarch/gatemate/pack_cpe.cc b/himbaechel/uarch/gatemate/pack_cpe.cc
index bd360f43..bf8f7f8a 100644
--- a/himbaechel/uarch/gatemate/pack_cpe.cc
+++ b/himbaechel/uarch/gatemate/pack_cpe.cc
@@ -597,6 +597,8 @@ void GateMatePacker::pack_constants()
     const dict<IdString, Property> gnd_params = {{id_INIT_L10, Property(0b0000, 4)}};
 
     h.replace_constants(CellTypePort(id_CPE_L2T4, id_OUT), CellTypePort(id_CPE_L2T4, id_OUT), vcc_params, gnd_params);
+    vcc_net = ctx->nets.at(ctx->id("$PACKER_VCC")).get();
+    gnd_net = ctx->nets.at(ctx->id("$PACKER_GND")).get();
 }
 
 void GateMatePacker::remove_constants()