From 2d3753d730c99ab2c0253be119b04cec413e10ba Mon Sep 17 00:00:00 2001
From: =?utf8?q?Marcin=20Ko=C5=9Bcielnicki?= <mwk@0x04.net>
Date: Mon, 30 Mar 2020 15:35:31 +0200
Subject: [PATCH] iopadmap: Fix z assignment to inout port

Fixes #1841.
---
 passes/techmap/iopadmap.cc | 16 +++++++++++++++-
 tests/techmap/iopadmap.ys  | 10 +++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/passes/techmap/iopadmap.cc b/passes/techmap/iopadmap.cc
index 8b1862237..f754aecb8 100644
--- a/passes/techmap/iopadmap.cc
+++ b/passes/techmap/iopadmap.cc
@@ -229,11 +229,13 @@ struct IopadmapPass : public Pass {
 		for (auto module : design->selected_modules())
 		{
 			dict<Wire *, dict<int, pair<Cell *, IdString>>> rewrite_bits;
+			pool<SigSig> remove_conns;
 
 			if (!toutpad_celltype.empty() || !tinoutpad_celltype.empty())
 			{
 				dict<SigBit, Cell *> tbuf_bits;
 				pool<SigBit> driven_bits;
+				dict<SigBit, SigSig> z_conns;
 
 				// Gather tristate buffers and always-on drivers.
 				for (auto cell : module->cells())
@@ -252,8 +254,10 @@ struct IopadmapPass : public Pass {
 					for (int i = 0; i < GetSize(conn.first); i++) {
 						SigBit dstbit = conn.first[i];
 						SigBit srcbit = conn.second[i];
-						if (!srcbit.wire && srcbit.data == State::Sz)
+						if (!srcbit.wire && srcbit.data == State::Sz) {
+							z_conns[dstbit] = conn;
 							continue;
+						}
 						driven_bits.insert(dstbit);
 					}
 
@@ -302,6 +306,8 @@ struct IopadmapPass : public Pass {
 							// enable.
 							en_sig = SigBit(State::S0);
 							data_sig = SigBit(State::Sx);
+							if (z_conns.count(wire_bit))
+								remove_conns.insert(z_conns[wire_bit]);
 						}
 
 						if (wire->port_input)
@@ -454,6 +460,14 @@ struct IopadmapPass : public Pass {
 				}
 			}
 
+			if (!remove_conns.empty()) {
+				std::vector<SigSig> new_conns;
+				for (auto &conn : module->connections())
+					if (!remove_conns.count(conn))
+						new_conns.push_back(conn);
+				module->new_connections(new_conns);
+			}
+
 			for (auto &it : rewrite_bits) {
 				RTLIL::Wire *wire = it.first;
 				RTLIL::Wire *new_wire = module->addWire(
diff --git a/tests/techmap/iopadmap.ys b/tests/techmap/iopadmap.ys
index 25ea94dfc..df029b3a0 100644
--- a/tests/techmap/iopadmap.ys
+++ b/tests/techmap/iopadmap.ys
@@ -55,13 +55,19 @@ obuf b (.i(i), .o(tmp));
 assign o = tmp;
 endmodule
 
+module k(inout o, o2);
+assign o = 1'bz;
+endmodule
+
 EOT
 
 opt_clean
 tribuf
 simplemap
-iopadmap -bits -inpad ibuf o:i -outpad obuf i:o -toutpad obuft oe:i:o -tinoutpad iobuf oe:o:i:io a b c d e f g h i j
+iopadmap -bits -inpad ibuf o:i -outpad obuf i:o -toutpad obuft oe:i:o -tinoutpad iobuf oe:o:i:io a b c d e f g h i j k
 opt_clean
+hierarchy -check
+check
 
 select -assert-count 1 a/t:ibuf
 select -assert-count 1 a/t:obuf
@@ -140,6 +146,8 @@ select -assert-count 0 i/t:obuf
 select -assert-count 1 j/t:ibuf
 select -assert-count 1 j/t:obuf
 
+select -assert-count 2 k/t:iobuf
+
 
 # Check that \init attributes get moved from output buffer
 #   to buffer input
-- 
2.30.2