Optionally suppress output from display system tasks in read_verilog

frontends/ast/ast.cc

@@ -45,7 +45,7 @@ namespace AST {
 
 // instantiate global variables (private API)
 namespace AST_INTERNAL {
-	bool flag_dump_ast1, flag_dump_ast2, flag_no_dump_ptr, flag_dump_vlog1, flag_dump_vlog2, flag_dump_rtlil, flag_nolatches, flag_nomeminit;
+	bool flag_nodisplay, flag_dump_ast1, flag_dump_ast2, flag_no_dump_ptr, flag_dump_vlog1, flag_dump_vlog2, flag_dump_rtlil, flag_nolatches, flag_nomeminit;
 	bool flag_nomem2reg, flag_mem2reg, flag_noblackbox, flag_lib, flag_nowb, flag_noopt, flag_icells, flag_pwires, flag_autowire;
 	AstNode *current_ast, *current_ast_mod;
 	std::map<std::string, AstNode*> current_scope;
@@ -1320,11 +1320,12 @@ static void rename_in_package_stmts(AstNode *pkg)
 }
 
 // create AstModule instances for all modules in the AST tree and add them to 'design'
-void AST::process(RTLIL::Design *design, AstNode *ast, bool dump_ast1, bool dump_ast2, bool no_dump_ptr, bool dump_vlog1, bool dump_vlog2, bool dump_rtlil,
+void AST::process(RTLIL::Design *design, AstNode *ast, bool nodisplay, bool dump_ast1, bool dump_ast2, bool no_dump_ptr, bool dump_vlog1, bool dump_vlog2, bool dump_rtlil,
 		bool nolatches, bool nomeminit, bool nomem2reg, bool mem2reg, bool noblackbox, bool lib, bool nowb, bool noopt, bool icells, bool pwires, bool nooverwrite, bool overwrite, bool defer, bool autowire)
 {
 	current_ast = ast;
 	current_ast_mod = nullptr;
+	flag_nodisplay = nodisplay;
 	flag_dump_ast1 = dump_ast1;
 	flag_dump_ast2 = dump_ast2;
 	flag_no_dump_ptr = no_dump_ptr;

frontends/ast/ast.h

@@ -376,7 +376,7 @@ namespace AST
 	};
 
 	// process an AST tree (ast must point to an AST_DESIGN node) and generate RTLIL code
-	void process(RTLIL::Design *design, AstNode *ast, bool dump_ast1, bool dump_ast2, bool no_dump_ptr, bool dump_vlog1, bool dump_vlog2, bool dump_rtlil, bool nolatches, bool nomeminit,
+	void process(RTLIL::Design *design, AstNode *ast, bool nodisplay, bool dump_ast1, bool dump_ast2, bool no_dump_ptr, bool dump_vlog1, bool dump_vlog2, bool dump_rtlil, bool nolatches, bool nomeminit,
 			bool nomem2reg, bool mem2reg, bool noblackbox, bool lib, bool nowb, bool noopt, bool icells, bool pwires, bool nooverwrite, bool overwrite, bool defer, bool autowire);
 
 	// parametric modules are supported directly by the AST library
@@ -432,7 +432,7 @@ namespace AST
 namespace AST_INTERNAL
 {
 	// internal state variables
-	extern bool flag_dump_ast1, flag_dump_ast2, flag_no_dump_ptr, flag_dump_rtlil, flag_nolatches, flag_nomeminit;
+	extern bool flag_nodisplay, flag_dump_ast1, flag_dump_ast2, flag_no_dump_ptr, flag_dump_rtlil, flag_nolatches, flag_nomeminit;
 	extern bool flag_nomem2reg, flag_mem2reg, flag_lib, flag_noopt, flag_icells, flag_pwires, flag_autowire;
 	extern AST::AstNode *current_ast, *current_ast_mod;
 	extern std::map<std::string, AST::AstNode*> current_scope;

frontends/ast/simplify.cc

@@ -1058,7 +1058,14 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 	{
 		if (!current_always) {
 			log_file_warning(filename, location.first_line, "System task `%s' outside initial or always block is unsupported.\n", str.c_str());
-		} else if (current_always->type == AST_INITIAL) {
+			delete_children();
+			str = std::string();
+		} else {
+			// simplify the expressions and convert them to a special cell later in genrtlil
+			for (auto node : children)
+				while (node->simplify(true, stage, -1, false)) {}
+
+			if (current_always->type == AST_INITIAL && !flag_nodisplay && stage == 2) {
 				int default_base = 10;
 				if (str.back() == 'b')
 					default_base = 2;
@@ -1072,19 +1079,10 @@ bool AstNode::simplify(bool const_fold, int stage, int width_hint, bool sign_hin
 				if (str.substr(0, 8) == "$display")
 					fmt.append_string("\n");
 				log("%s", fmt.render().c_str());
-			for (auto node : children)
-				while (node->simplify(true, stage, -1, false)) {}
-			return false;
-		} else {
-			// when $display()/$write() functions are used in an always block, simplify the expressions and
-			// convert them to a special cell later in genrtlil
-			for (auto node : children)
-				while (node->simplify(true, stage, -1, false)) {}
-			return false;
 			}
 
-		delete_children();
-		str = std::string();
+			return false;
+		}
 	}
 
 	// activate const folding if this is anything that must be evaluated statically (ranges, parameters, attributes, etc.)

frontends/verilog/verilog_frontend.cc

@@ -100,6 +100,10 @@ struct VerilogFrontend : public Frontend {
 		log("    -assert-assumes\n");
 		log("        treat all assume() statements like assert() statements\n");
 		log("\n");
+		log("    -nodisplay\n");
+		log("        suppress output from display system tasks ($display et. al).\n");
+		log("        This does not affect the output from a later 'sim' command.\n");
+		log("\n");
 		log("    -debug\n");
 		log("        alias for -dump_ast1 -dump_ast2 -dump_vlog1 -dump_vlog2 -yydebug\n");
 		log("\n");
@@ -235,6 +239,7 @@ struct VerilogFrontend : public Frontend {
 	}
 	void execute(std::istream *&f, std::string filename, std::vector<std::string> args, RTLIL::Design *design) override
 	{
+		bool flag_nodisplay = false;
 		bool flag_dump_ast1 = false;
 		bool flag_dump_ast2 = false;
 		bool flag_no_dump_ptr = false;
@@ -308,6 +313,10 @@ struct VerilogFrontend : public Frontend {
 				assert_assumes_mode = true;
 				continue;
 			}
+			if (arg == "-nodisplay") {
+				flag_nodisplay = true;
+				continue;
+			}
 			if (arg == "-debug") {
 				flag_dump_ast1 = true;
 				flag_dump_ast2 = true;
@@ -510,7 +519,7 @@ struct VerilogFrontend : public Frontend {
 		if (flag_nodpi)
 			error_on_dpi_function(current_ast);
 
-		AST::process(design, current_ast, flag_dump_ast1, flag_dump_ast2, flag_no_dump_ptr, flag_dump_vlog1, flag_dump_vlog2, flag_dump_rtlil, flag_nolatches,
+		AST::process(design, current_ast, flag_nodisplay, flag_dump_ast1, flag_dump_ast2, flag_no_dump_ptr, flag_dump_vlog1, flag_dump_vlog2, flag_dump_rtlil, flag_nolatches,
 				flag_nomeminit, flag_nomem2reg, flag_mem2reg, flag_noblackbox, lib_mode, flag_nowb, flag_noopt, flag_icells, flag_pwires, flag_nooverwrite, flag_overwrite, flag_defer, default_nettype_wire);