From bd0af4052c434b1cf3ed8522360b5acc78bd17a2 Mon Sep 17 00:00:00 2001
From: YRabbit <rabbit@yrabbit.cyou>
Date: Thu, 9 Jun 2022 08:20:29 +1000
Subject: [PATCH] gowin: Use local aliases

In the Gowin chips, the tiles are connected to each other by a one-hop
wire, among others. There are 4 one-hop wires, of which 2 are shared
between north/south and east/west, have three names: e.g. SN10 and N110
and S110.

But only one of them, the first, occurs as a sink for PIP, that is, you
can not get a route that would pass through the S110 for example.

This commit corrects the names to SN?0 and EW?0 at the wire creation
stage to avoid dead wires.

In addition, the SN?0 and EW?0 are among the few sinks for global clock
wires and now there is the possibility of a more optimal clock routing.

Signed-off-by: YRabbit <rabbit@yrabbit.cyou>
---
 gowin/arch.cc | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/gowin/arch.cc b/gowin/arch.cc
index a991879e..82f5018b 100644
--- a/gowin/arch.cc
+++ b/gowin/arch.cc
@@ -34,6 +34,8 @@
 
 NEXTPNR_NAMESPACE_BEGIN
 
+const PairPOD *pairLookup(const PairPOD *list, const size_t len, const int dest);
+
 // GUI
 void Arch::fixClockSpineDecals(void)
 {
@@ -627,7 +629,15 @@ IdString Arch::wireToGlobal(int &row, int &col, const DatabasePOD *db, IdString
     }
     snprintf(buf, 32, "%c%d0", direction, num);
     wire = id(buf);
-    snprintf(buf, 32, "R%dC%d_%c%d", row + 1, col + 1, direction, num);
+    // local aliases
+    const TilePOD *tile = db->grid[row * db->cols + col].get();
+    auto local_alias = pairLookup(tile->aliases.get(), tile->num_aliases, wire.index);
+    if (local_alias != nullptr) {
+        wire = IdString(local_alias->src_id);
+        snprintf(buf, 32, "R%dC%d_%s", row + 1, col + 1, wire.c_str(this));
+    } else {
+        snprintf(buf, 32, "R%dC%d_%c%d", row + 1, col + 1, direction, num);
+    }
     return id(buf);
 }
 
@@ -1491,12 +1501,6 @@ Arch::Arch(ArchArgs args) : args(args)
                 snprintf(buf, 32, "R%dC%d_%s_%s", row + 1, col + 1, srcid.c_str(this), destid.c_str(this));
                 IdString pipname = id(buf);
                 DelayQuad delay = getWireTypeDelay(destid);
-                // local alias
-                auto local_alias = pairLookup(tile->aliases.get(), tile->num_aliases, srcid.index);
-                if (local_alias != nullptr) {
-                    srcid = IdString(local_alias->src_id);
-                    gsrcname = wireToGlobal(srcrow, srccol, db, srcid);
-                }
                 // global alias
                 srcid = IdString(pip.src_id);
                 GlobalAliasPOD alias;