Gowin: deal with active-low tristate (#2971)

* deal with active-low tristate

* remove empty port

* update sim models

* add expected lut1 to tests

3 files changed, 12 insertions, 5 deletions

diff --git a/techlibs/gowin/cells_map.v b/techlibs/gowin/cells_map.v
index 851ef20b2..90eb9b5a4 100644
--- a/techlibs/gowin/cells_map.v
+++ b/techlibs/gowin/cells_map.v
@@ -122,6 +122,13 @@ module	\$_DFFE_NP0P_ (input D, C, R, E, output Q);
 	wire _TECHMAP_REMOVEINIT_Q_ = 1;
 endmodule
 
+module \$__GW_IOBUF (input I, OE, output O, inout IO);
+	IOBUF _TECHMAP_REPLACE_ (.I(I), .O(O), .OEN(~OE), .IO(IO));
+endmodule
+
+module \$__GW_TBUF (input I, OE, output O);
+	TBUF _TECHMAP_REPLACE_ (.I(I), .OEN(~OE), .O(O));
+endmodule
 
 module \$lut (A, Y);
 	parameter WIDTH = 0;
diff --git a/techlibs/gowin/cells_sim.v b/techlibs/gowin/cells_sim.v
index 509bf3ef2..41398409d 100644
--- a/techlibs/gowin/cells_sim.v
+++ b/techlibs/gowin/cells_sim.v
@@ -573,14 +573,14 @@ endmodule
 module TBUF (O, I, OEN);
   input I, OEN;
   output O;
-  assign O = OEN ? I : 1'bz;
+  assign O = OEN ? 1'bz : I;
 endmodule
 
 module IOBUF (O, IO, I, OEN);
   input I,OEN;
   output O;
   inout IO;
-  assign IO = OEN ? I : 1'bz;
+  assign IO = OEN ? 1'bz : I;
   assign I = IO;
 endmodule
 
diff --git a/techlibs/gowin/synth_gowin.cc b/techlibs/gowin/synth_gowin.cc
index c97bd595c..087f6b8cf 100644
--- a/techlibs/gowin/synth_gowin.cc
+++ b/techlibs/gowin/synth_gowin.cc
@@ -241,6 +241,9 @@ struct SynthGowinPass : public ScriptPass
 			if (retime || help_mode)
 				run("abc -dff -D 1", "(only if -retime)");
 			run("splitnets");
+			if (!noiopads || help_mode)
+				run("iopadmap -bits -inpad IBUF O:I -outpad OBUF I:O "
+					"-toutpad $__GW_TBUF OE:I:O -tinoutpad $__GW_IOBUF OE:O:I:IO", "(unless -noiopads)");
 		}
 
 		if (check_label("map_ffs"))
@@ -277,9 +280,6 @@ struct SynthGowinPass : public ScriptPass
 			run("opt_lut_ins -tech gowin");
 			run("setundef -undriven -params -zero");
 			run("hilomap -singleton -hicell VCC V -locell GND G");
-			if (!noiopads || help_mode)
-				run("iopadmap -bits -inpad IBUF O:I -outpad OBUF I:O "
-					"-toutpad TBUF OEN:I:O -tinoutpad IOBUF OEN:O:I:IO", "(unless -noiopads)");
 			run("clean");
 			run("autoname");
 		}