From 724c14d1f7fe53c200060429ea328a031e4f6759 Mon Sep 17 00:00:00 2001
From: tangxifan <tangxifan@gmail.com>
Date: Thu, 4 Jul 2024 11:09:01 -0700
Subject: [PATCH] [core] fixed a bug on build top module connections on
 perimeter gsb when cbs occur

---
 openfpga/src/fabric/build_top_module_connection.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/openfpga/src/fabric/build_top_module_connection.cpp b/openfpga/src/fabric/build_top_module_connection.cpp
index e6a98cd46..38b0491a9 100644
--- a/openfpga/src/fabric/build_top_module_connection.cpp
+++ b/openfpga/src/fabric/build_top_module_connection.cpp
@@ -760,6 +760,12 @@ static void add_top_module_nets_connect_sb_and_cb(
     }
 
     if (RIGHT == side_manager.get_side() || BOTTOM == side_manager.get_side()) {
+      /* Only for the condition where cbs are on perimeter, the neighbour cb will be invalid
+       * Bypass in such case on finding neighbour cbs
+       */
+      if (instance_sb_coordinate.x() == device_rr_gsb.get_gsb_range().x() || instance_sb_coordinate.y() == 0) {
+        continue;
+      }
       const RRGSB& adjacent_gsb =
         device_rr_gsb.get_gsb(module_gsb_cb_coordinate);
       if (false == adjacent_gsb.is_cb_exist(cb_type)) {