Add option -gno-strict-parameter-declaration

The standards requires that parameters must be declared
before they are used.  Using -gno-strict-parameter-declaration
will allow using a parameter before declaration, e.g., in a port
declaration, with the parameter declared in the body of the
module.  Prior to version 13 this was allowed, so there is a large body
of existing code depending on the pre version 13 behaviour.

Documentation/usage/command_line_flags.rst

@@ -131,6 +131,14 @@ These flags affect the general behavior of the compiler.
     containing an unsized constant number, and unsized constant numbers are
     not truncated to integer width.
 
+  * strict-parameter-declaration/no-strict-parameter-declaration
+
+    The standards requires that parameters must be declared lexically
+    before they are used.  Using -gno-strict-parameter-declaration
+    will allow using a parameter before declaration, e.g., in a port
+    declaration, with the parameter declared in the body of the
+    module.
+
   * shared-loop-index/no-shared-loop-index
 
     Enable or disable the exclusion of for-loop control variables from

compiler.h

@@ -210,6 +210,12 @@ extern bool gn_strict_expr_width_flag;
    loop. */
 extern bool gn_shared_loop_index_flag;
 
+/* If this flag is true (default), then parameters must be declared before
+   use.
+   use `-gno-strict-parameter-declaration` for pre version 13 behaviour.
+ */
+extern bool gn_strict_parameter_declaration;
+
 static inline bool gn_system_verilog(void)
 {
       if (generation_flag >= GN_VER2005_SV)

driver/iverilog.man.in

@@ -150,6 +150,12 @@ parameter assignment is evaluated as a lossless expression, as is any
 expression containing an unsized constant number, and unsized constant
 numbers are not truncated to integer width.
 .TP 8
+.B -gstrict-parameter-declaration\fI|\fP-gno-strict-parameter-declaration
+The standards requires that parameters must be declared lexically
+before they are used.  Using \fB\-gno\-strict\-parameter\-declaration\fP
+will allow using a parameter before declaration, e.g., in a port
+declaration, with the parameter declared in the body of the module.
+.TP 8
 .B -gshared-loop-index\fI|\fP-gno-shared-loop-index
 Enable (default) or disable the exclusion of for-loop control variables
 from implicit event_expression lists. When enabled, if a for-loop control

driver/main.c

@@ -134,6 +134,7 @@ const char*gen_strict_ca_eval = "no-strict-ca-eval";
 const char*gen_strict_expr_width = "no-strict-expr-width";
 const char*gen_shared_loop_index = "shared-loop-index";
 const char*gen_verilog_ams = "no-verilog-ams";
+const char*gen_strict_parameter_declaration = "strict-parameter-declaration";
 
 /* Boolean: true means use a default include dir, false means don't */
 int gen_std_include = 1;
@@ -815,6 +816,12 @@ static int process_generation(const char*name)
       else if (strcmp(name,"no-verilog-ams") == 0)
 	    gen_verilog_ams = "no-verilog-ams";
 
+      else if (strcmp(name,"strict-parameter-declaration") == 0)
+	    gen_strict_parameter_declaration = "strict-parameter-declaration";
+
+      else if (strcmp(name,"no-strict-parameter-declaration") == 0)
+	    gen_strict_parameter_declaration = "no-strict-parameter-declaration";
+
       else {
 	    fprintf(stderr, "Unknown/Unsupported Language generation "
 		    "%s\n\n", name);
@@ -837,7 +844,8 @@ static int process_generation(const char*name)
 		            "    io-range-error | no-io-range-error\n"
 		            "    strict-ca-eval | no-strict-ca-eval\n"
 		            "    strict-expr-width | no-strict-expr-width\n"
-		            "    shared-loop-index | no-shared-loop-index\n");
+		            "    shared-loop-index | no-shared-loop-index\n"
+		            "    strict-parameter-declaration | no-strict-parameter-declaration\n");
 
 	    return 1;
       }
@@ -1385,6 +1393,7 @@ int main(int argc, char **argv)
       fprintf(iconfig_file, "generation:%s\n", gen_strict_expr_width);
       fprintf(iconfig_file, "generation:%s\n", gen_shared_loop_index);
       fprintf(iconfig_file, "generation:%s\n", gen_verilog_ams);
+      fprintf(iconfig_file, "generation:%s\n", gen_strict_parameter_declaration);
       fprintf(iconfig_file, "generation:%s\n", gen_icarus);
       fprintf(iconfig_file, "warnings:%s\n", warning_flags);
       fprintf(iconfig_file, "ignore_missing_modules:%s\n", ignore_missing_modules ? "true" : "false");

main.cc

@@ -117,6 +117,7 @@ bool gn_strict_ca_eval_flag = false;
 bool gn_strict_expr_width_flag = false;
 bool gn_shared_loop_index_flag = true;
 bool gn_verilog_ams_flag = false;
+bool gn_strict_parameter_declaration = true;
 
 /*
  * For some generations we allow a system function to be called
@@ -386,6 +387,12 @@ static void process_generation_flag(const char*gen)
       } else if (strcmp(gen,"no-shared-loop-index") == 0) {
 	    gn_shared_loop_index_flag = false;
 
+      } else if (strcmp(gen,"strict-parameter-declaration") == 0) {
+	    gn_strict_parameter_declaration = true;
+
+      } else if (strcmp(gen,"no-strict-parameter-declaration") == 0) {
+	    gn_strict_parameter_declaration = false;
+
 	  } else {
       }
 }

symbol_search.cc

@@ -189,7 +189,8 @@ bool symbol_search(const LineInfo*li, Design*des, NetScope*scope,
 		  }
 
 		  if (const NetExpr*par = scope->get_parameter(des, path_tail.name, res->type)) {
-			if (prefix_scope || (scope->get_parameter_lexical_pos(path_tail.name) <= lexical_pos)) {
+			if (!gn_strict_parameter_declaration || prefix_scope
+			    || (scope->get_parameter_lexical_pos(path_tail.name) <= lexical_pos)) {
 			      path.push_back(path_tail);
 			      res->scope = scope;
 			      res->par_val = par;