From c9ff60e3923a5bdd88fe4e35981fd662500dc177 Mon Sep 17 00:00:00 2001
From: gatecat <gatecat@ds0.me>
Date: Tue, 10 Feb 2026 15:09:10 +0100
Subject: [PATCH] Support use of router2 for gowin

Signed-off-by: gatecat <gatecat@ds0.me>
---
 common/route/router2.cc         | 8 ++++++--
 himbaechel/uarch/gowin/gowin.cc | 7 +++++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/common/route/router2.cc b/common/route/router2.cc
index df1a7876..5097a62e 100644
--- a/common/route/router2.cc
+++ b/common/route/router2.cc
@@ -54,7 +54,7 @@ struct Router2
     {
         WireId sink_wire;
         BoundingBox bb;
-        bool routed = false;
+        bool routed = false, pre_routed = false;
     };
 
     // As we allow overlap at first; the nextpnr bind functions can't be used
@@ -358,6 +358,9 @@ struct Router2
             cursor = ctx->getPipSrcWire(pip);
         }
         ad.routed = false;
+        // Once we've ripped up the arc, the routing may no longer be the same as before...
+        // (this should only happen if it was not strongly bound)
+        ad.pre_routed = false;
     }
 
     float score_wire_for_arc(NetInfo *net, store_index<PortRef> user, size_t phys_pin, WireId wire, PipId pip,
@@ -419,6 +422,7 @@ struct Router2
         auto &nd = nets.at(net->udata);
         auto &ad = nd.arcs.at(usr.idx()).at(phys_pin);
         ad.routed = true;
+        ad.pre_routed = true;
 
         WireId src = nets.at(net->udata).src_wire;
         WireId cursor = ad.sink_wire;
@@ -1141,7 +1145,7 @@ struct Router2
                 if (bound_net == nullptr) {
                     to_bind.push_back(p);
                 }
-            } else {
+            } else if (!ad.pre_routed || ctx->getBoundPipNet(p) != net) { // allow pre routing to break normal validity checking rules
                 if (ctx->verbose) {
                     log_info("Failed to bind pip %s to net %s\n", ctx->nameOfPip(p), net->name.c_str(ctx));
                 }
diff --git a/himbaechel/uarch/gowin/gowin.cc b/himbaechel/uarch/gowin/gowin.cc
index 3ca0739f..c5e0d76b 100644
--- a/himbaechel/uarch/gowin/gowin.cc
+++ b/himbaechel/uarch/gowin/gowin.cc
@@ -45,6 +45,7 @@ struct GowinImpl : HimbaechelAPI
 
     // wires
     bool checkPipAvail(PipId pip) const override;
+    bool checkPipAvailForNet(PipId pip, const NetInfo *net) const override;
 
     // Cluster
     bool isClusterStrict(const CellInfo *cell) const override { return true; }
@@ -247,6 +248,12 @@ bool GowinImpl::checkPipAvail(PipId pip) const
            (!(gwu.is_global_pip(pip) || gwu.is_segment_pip(pip)));
 }
 
+bool GowinImpl::checkPipAvailForNet(PipId pip, const NetInfo *net) const
+{
+    return (net->constant_value == IdString() && ctx->getWireConstantValue(ctx->getPipSrcWire(pip)) != IdString()) ||
+           (!(gwu.is_global_pip(pip) || gwu.is_segment_pip(pip)));
+}
+
 void GowinImpl::pack()
 {
     if (ctx->settings.count(ctx->id("cst.filename"))) {