verilog: indirect AST_CONCAT and AST_TO_UNSIGNED port connections

- AST_CONCAT and AST_TO_UNSIGNED are always unsigned, but may generate
  RTLIL that exclusively reference a signed wire.
- AST_CONCAT may also contain a memory write.

CHANGELOG

@@ -5,6 +5,12 @@ List of major changes and improvements between releases
 Yosys 0.40 .. Yosys 0.41-dev
 --------------------------
 
+ * Verilog
+    - Fixed an issue that prevented using `{<expr>}` or `$unsigned(<expr>)` for
+      certain signed expressions in port connections
+    - Fixed an issue that prevented writing to a memory word via a concatenation
+      in an output port connection
+
 Yosys 0.39 .. Yosys 0.40
 --------------------------
  * New commands and options

frontends/ast/genrtlil.cc

@@ -2124,11 +2124,9 @@ RTLIL::SigSpec AstNode::genRTLIL(int width_hint, bool sign_hint)
 						if (sig.is_wire()) {
 							// if the resulting SigSpec is a wire, its
 							// signedness should match that of the AstNode
-							if (arg->type == AST_IDENTIFIER && arg->id2ast && arg->id2ast->is_signed && !arg->is_signed)
-								// fully-sliced signed wire will be resolved
-								// once the module becomes available
-								log_assert(attributes.count(ID::reprocess_after));
-							else
+							// unless this instantiation depends on module
+							// information that isn't available yet
+							if (!attributes.count(ID::reprocess_after))
 								log_assert(arg->is_signed == sig.as_wire()->is_signed);
 						} else if (arg->is_signed) {
 							// non-trivial signed nodes are indirected through

frontends/ast/simplify.cc

@@ -1292,6 +1292,12 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 				else if (contains_unbased_unsized(value))
 					// unbased unsized literals extend to width of the context
 					lookup_suggested = true;
+				else if (value->type == AST_TO_UNSIGNED)
+					// inner expression may be signed by default
+					lookup_suggested = true;
+				else if (value->type == AST_CONCAT && value->children.size() == 1)
+					// concat of a single expression is equivalent to $unsigned
+					lookup_suggested = true;
 			}
 		}
 

tests/simple/memwr_port_connection.sv

@@ -5,9 +5,11 @@ module producer(
 endmodule
 
 module top(
-    output logic [3:0] out
+    output logic [3:0] out0, out1
 );
-    logic [3:0] v[0:0];
-    producer p(v[0]);
-    assign out = v[0];
+    logic [3:0] v[1:0];
+    producer p0(v[0]);
+    producer p1({v[1]});
+    assign out0 = v[0];
+    assign out1 = v[1];
 endmodule

tests/verilog/signed_concat.v

@@ -0,0 +1,45 @@
+`define OUTPUTS(mode) \
+    o``mode``0, \
+    o``mode``1, \
+    o``mode``2, \
+    o``mode``3, \
+    o``mode``4
+
+module gate(
+    input [1:0] iu,
+    input signed [1:0] is,
+    output [2:0] `OUTPUTS(u),
+    output signed [2:0] `OUTPUTS(s)
+);
+`define INSTANCES(mode) \
+    mod m``mode``0({i``mode}, {o``mode``0}); \
+    mod m``mode``1($unsigned(i``mode), o``mode``1); \
+    mod m``mode``2({i``mode[1:0]}, o``mode``2); \
+    mod m``mode``3({$signed(i``mode)}, o``mode``3); \
+    mod m``mode``4($unsigned({i``mode}), o``mode``4);
+`INSTANCES(u)
+`INSTANCES(s)
+`undef INSTANCES
+endmodule
+
+module gold(
+    input [1:0] iu, is,
+    output [2:0] `OUTPUTS(u), `OUTPUTS(s)
+);
+`define INSTANCES(mode) \
+    assign o``mode``0 = i``mode; \
+    assign o``mode``1 = i``mode; \
+    assign o``mode``2 = i``mode; \
+    assign o``mode``3 = i``mode; \
+    assign o``mode``4 = i``mode;
+`INSTANCES(u)
+`INSTANCES(s)
+`undef INSTANCES
+endmodule
+
+module mod(
+    input [2:0] inp,
+    output [2:0] out
+);
+    assign out = inp;
+endmodule

tests/verilog/signed_concat.ys

@@ -0,0 +1,7 @@
+read_verilog signed_concat.v
+hierarchy
+proc
+flatten gate
+equiv_make gold gate equiv
+equiv_simple
+equiv_status -assert