From 2a8bab976d04745355800e9f23db6a7d208ce81c Mon Sep 17 00:00:00 2001
From: myrtle <gatecat@ds0.me>
Date: Tue, 10 Feb 2026 20:54:09 +0100
Subject: [PATCH] gowin: Perfomance improvements round 1 (#1632)

* gowin: Configure HeAP

Signed-off-by: gatecat <gatecat@ds0.me>

* gowin: Use fast constant value routing

Signed-off-by: gatecat <gatecat@ds0.me>

---------

Signed-off-by: gatecat <gatecat@ds0.me>
---
 himbaechel/uarch/gowin/gowin.cc          | 26 ++++++++++++++++++++++++
 himbaechel/uarch/gowin/gowin_arch_gen.py |  4 ----
 himbaechel/uarch/gowin/pack.cc           |  1 +
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/himbaechel/uarch/gowin/gowin.cc b/himbaechel/uarch/gowin/gowin.cc
index 39a1a3e1..c9362876 100644
--- a/himbaechel/uarch/gowin/gowin.cc
+++ b/himbaechel/uarch/gowin/gowin.cc
@@ -16,6 +16,8 @@
 #include "gowin_utils.h"
 #include "pack.h"
 
+#include "placer_heap.h"
+
 NEXTPNR_NAMESPACE_BEGIN
 
 namespace {
@@ -49,6 +51,9 @@ struct GowinImpl : HimbaechelAPI
     bool getClusterPlacement(ClusterId cluster, BelId root_bel,
                              std::vector<std::pair<CellInfo *, BelId>> &placement) const override;
 
+
+    void configurePlacerHeap(PlacerHeapCfg &cfg) override;
+
   private:
     HimbaechelHelpers h;
     GowinUtils gwu;
@@ -1270,6 +1275,27 @@ void GowinImpl::notifyBelChange(BelId bel, CellInfo *cell)
     }
 }
 
+void GowinImpl::configurePlacerHeap(PlacerHeapCfg &cfg)
+{
+    // SLICE types are closely associated with each other
+    cfg.cellGroups.emplace_back();
+    cfg.cellGroups.back().insert(id_LUT4);
+    cfg.cellGroups.back().insert(id_DFF);
+    cfg.cellGroups.back().insert(id_ALU);
+    cfg.cellGroups.back().insert(id_MUX2_LUT5);
+    cfg.cellGroups.back().insert(id_MUX2_LUT6);
+    cfg.cellGroups.back().insert(id_MUX2_LUT7);
+    cfg.cellGroups.back().insert(id_MUX2_LUT8);
+    cfg.cellGroups.back().insert(id_RAM16SDP4);
+
+    // Treat control and constants like IO buffers, because they have only one possible location
+    cfg.ioBufTypes.insert(id_GOWIN_VCC);
+    cfg.ioBufTypes.insert(id_GOWIN_GND);
+    cfg.ioBufTypes.insert(id_PINCFG);
+    cfg.ioBufTypes.insert(id_GSR);
+}
+
+
 } // namespace
 
 NEXTPNR_NAMESPACE_END
diff --git a/himbaechel/uarch/gowin/gowin_arch_gen.py b/himbaechel/uarch/gowin/gowin_arch_gen.py
index 4cb8c095..cced755b 100644
--- a/himbaechel/uarch/gowin/gowin_arch_gen.py
+++ b/himbaechel/uarch/gowin/gowin_arch_gen.py
@@ -509,10 +509,6 @@ def create_nodes(chip: Chip, db: chipdb):
             for node in nodes:
                 chip.add_node(node)
 
-            # VCC and VSS sources in the all tiles
-            global_nodes.setdefault('GND', []).append(NodeWire(x, y, 'VSS'))
-            global_nodes.setdefault('VCC', []).append(NodeWire(x, y, 'VCC'))
-
     # add nodes from the apicula db
     for node_name, node_hdr in db.nodes.items():
         wire_type, node = node_hdr
diff --git a/himbaechel/uarch/gowin/pack.cc b/himbaechel/uarch/gowin/pack.cc
index 47b7c26e..fd82e126 100644
--- a/himbaechel/uarch/gowin/pack.cc
+++ b/himbaechel/uarch/gowin/pack.cc
@@ -1740,6 +1740,7 @@ struct GowinPacker
                 continue;
             }
             NetInfo *constnet = net->second.get();
+            constnet->constant_value = (constnet->name == ctx->id("$PACKER_GND")) ? id_VSS : id_VCC;
             for (auto user : constnet->users) {
                 CellInfo *uc = user.cell;
                 if (is_lut(uc) && (user.port.str(ctx).at(0) == 'I')) {