From 7a36728b2fd640e166188b05c901b1992ec2af6b Mon Sep 17 00:00:00 2001
From: =?utf8?q?Marcelina=20Ko=C5=9Bcielnicka?= <mwk@0x04.net>
Date: Tue, 14 Apr 2020 16:33:09 +0200
Subject: [PATCH] dffinit: Avoid setting init parameter to zero-length value.

Fixes #1704.
---
 passes/techmap/dffinit.cc |  8 +++++---
 tests/techmap/dffinit.ys  | 25 +++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)
 create mode 100644 tests/techmap/dffinit.ys

diff --git a/passes/techmap/dffinit.cc b/passes/techmap/dffinit.cc
index 0424ce434..35645582b 100644
--- a/passes/techmap/dffinit.cc
+++ b/passes/techmap/dffinit.cc
@@ -154,9 +154,11 @@ struct DffinitPass : public Pass {
 							value = Const(low_string);
 					}
 
-					log("Setting %s.%s.%s (port=%s, net=%s) to %s.\n", log_id(module), log_id(cell), log_id(it.second),
-							log_id(it.first), log_signal(sig), log_signal(value));
-					cell->setParam(it.second, value);
+					if (value.size() != 0) {
+						log("Setting %s.%s.%s (port=%s, net=%s) to %s.\n", log_id(module), log_id(cell), log_id(it.second),
+								log_id(it.first), log_signal(sig), log_signal(value));
+						cell->setParam(it.second, value);
+					}
 				}
 			}
 
diff --git a/tests/techmap/dffinit.ys b/tests/techmap/dffinit.ys
new file mode 100644
index 000000000..218d411f8
--- /dev/null
+++ b/tests/techmap/dffinit.ys
@@ -0,0 +1,25 @@
+read_verilog <<EOT
+
+module ff(...);
+input d;
+output q;
+
+endmodule
+
+module top(...);
+input d;
+output q1;
+(* init = 1'b1 *)
+output q2;
+
+ff my_ff1(.d(d), .q(q1));
+ff my_ff2(.d(d), .q(q2));
+
+endmodule
+
+EOT
+
+dffinit -ff ff q init
+select -assert-count 2 t:ff
+select -assert-count 1 t:ff r:init %i
+select -assert-count 1 t:ff r:init=1'b1 %i
-- 
2.30.2