From 74c4fa67510d4438b72b59897b750dd9bbf4ac5a Mon Sep 17 00:00:00 2001
From: David Shah <dave@ds0.me>
Date: Sun, 27 Dec 2020 20:11:08 +0000
Subject: ice40: Nicer error for unconstrained SB_GB_IO

Signed-off-by: David Shah <dave@ds0.me>
---
 ice40/pack.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/ice40/pack.cc b/ice40/pack.cc
index 7b03939a..9eb7d7c1 100644
--- a/ice40/pack.cc
+++ b/ice40/pack.cc
@@ -433,6 +433,8 @@ static std::unique_ptr<CellInfo> create_padin_gbuf(Context *ctx, CellInfo *cell,
                                                    std::string gbuf_name)
 {
     // Find the matching SB_GB BEL connected to the same global network
+    if (!cell->attrs.count(ctx->id("BEL")))
+        log_error("Unconstrained SB_GB_IO %s is not supported.\n", ctx->nameOf(cell));
     BelId bel = ctx->getBelByName(ctx->id(cell->attrs[ctx->id("BEL")].as_string()));
     BelId gb_bel = find_padin_gbuf(ctx, bel, port_name);
     NPNR_ASSERT(gb_bel != BelId());
-- 
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