add option -gno-strict-declaration

The new option allows parameter, net and events to be used before
declaration.  With variants

 -gno-strict-net-declaration for nets and events,
 -gno-strict-parameter-declaration for parameters.

Documentation/usage/command_line_flags.rst

@@ -131,12 +131,18 @@ 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-declaration/no-strict-declaration
+
+  * strict-net-declaration/no-net-strict-declaration
+
   * 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, with a
-    warning. The warning can be suppressed with -Wno-declaration-after-use.
+    The standards requires that nets and parameters must be declared
+    lexically before they are used.  Using -gno-strict-declaration
+    will allow using a net or parameter before declaration, with a
+    warning. The warning can be suppressed with
+    -Wno-declaration-after-use.  The option can be applied for nets
+    and parameters separately.
 
   * shared-loop-index/no-shared-loop-index
 

compiler.h

@@ -214,12 +214,19 @@ extern bool gn_strict_expr_width_flag;
 extern bool gn_shared_loop_index_flag;
 
 /* If this flag is true (default), then parameters must be declared before
-   use. `-gno-strict-parameter-declaration` allows to use parameters before
+   use. `-gno-strict[-parameter]-declaration` allows to use parameters before
    declaration, as prior to version 13.
-   A warning is emited with -Wanachronisms (default).
+   A warning is emited with -Wdeclaration-after-use (default).
  */
 extern bool gn_strict_parameter_declaration;
 
+/* If this flag is true (default), then nets must be declared before
+   use. `-gno-strict[-net]-declaration` allows to use nets before
+   declaration, as prior to version 13.
+   A warning is emited with -Wdeclaration-after-use (default).
+ */
+extern bool gn_strict_net_declaration;
+
 static inline bool gn_system_verilog(void)
 {
       if (generation_flag >= GN_VER2005_SV)

driver/iverilog.man.in

@@ -150,11 +150,16 @@ 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-declaration\fI|\fP-gno-strict-declaration
+.TP 8
+.B -gstrict-net-declaration\fI|\fP-gno-strict-net-declaration
+.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
+The standards requires that nets and parameters must be declared lexically
+before they are used.  Using \fB\-gno\-strict\-declaration\fP
 will allow using a parameter before declaration, with a warning.
-The warning can be suppressed with -Wno-declaration-after-use.
+The warning can be suppressed with -Wno-declaration-after-use. The
+option can be applied for nets and parameters separately. 
 .TP 8
 .B -gshared-loop-index\fI|\fP-gno-shared-loop-index
 Enable (default) or disable the exclusion of for-loop control variables

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_net_declaration = "strict-net-declaration";
 const char*gen_strict_parameter_declaration = "strict-parameter-declaration";
 
 /* Boolean: true means use a default include dir, false means don't */
@@ -826,6 +827,20 @@ 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-declaration") == 0) {
+	    gen_strict_net_declaration = "strict-net-declaration";
+	    gen_strict_parameter_declaration = "strict-parameter-declaration";
+      }
+      else if (strcmp(name,"no-strict-declaration") == 0) {
+	    gen_strict_net_declaration = "no-strict-net-declaration";
+	    gen_strict_parameter_declaration = "no-strict-parameter-declaration";
+      }
+      else if (strcmp(name,"strict-net-declaration") == 0)
+	    gen_strict_net_declaration = "strict-net-declaration";
+
+      else if (strcmp(name,"no-strict-net-declaration") == 0)
+	    gen_strict_net_declaration = "no-strict-net-declaration";
+
       else if (strcmp(name,"strict-parameter-declaration") == 0)
 	    gen_strict_parameter_declaration = "strict-parameter-declaration";
 
@@ -855,7 +870,8 @@ static int process_generation(const char*name)
 		            "    strict-ca-eval | no-strict-ca-eval\n"
 		            "    strict-expr-width | no-strict-expr-width\n"
 		            "    shared-loop-index | no-shared-loop-index\n"
-		            "    strict-parameter-declaration | no-strict-parameter-declaration\n");
+		            "    strict-declaration | no-strict-declaration\n"
+		            "    [no-]strict-[net|parameter]-declaration\n");
 
 	    return 1;
       }
@@ -1403,6 +1419,7 @@ 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_net_declaration);
       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);

main.cc

@@ -118,6 +118,7 @@ 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;
+bool gn_strict_net_declaration = true;
 
 /*
  * For some generations we allow a system function to be called
@@ -394,6 +395,12 @@ static void process_generation_flag(const char*gen)
       } else if (strcmp(gen,"no-strict-parameter-declaration") == 0) {
 	    gn_strict_parameter_declaration = false;
 
+      } else if (strcmp(gen,"strict-net-declaration") == 0) {
+	    gn_strict_net_declaration = true;
+
+      } else if (strcmp(gen,"no-strict-net-declaration") == 0) {
+	    gn_strict_net_declaration = false;
+
 	  } else {
       }
 }

symbol_search.cc

@@ -164,12 +164,18 @@ bool symbol_search(const LineInfo*li, Design*des, NetScope*scope,
 		  }
 
 		  if (NetNet*net = scope->find_signal(path_tail.name)) {
-			if (prefix_scope || (net->lexical_pos() <= lexical_pos)) {
+			bool decl_after_use = !prefix_scope && !(net->lexical_pos() <= lexical_pos);
+			if (!gn_strict_net_declaration || !decl_after_use) {
 			      path.push_back(path_tail);
 			      res->scope = scope;
 			      res->net = net;
 			      res->type = net->net_type();
 			      res->path_head = path;
+			      if (warn_decl_after_use && decl_after_use) {
+				    cerr << li->get_fileline()
+					 << ": warning: net `" << path_tail.name
+					 << "` used before declaration." << endl;
+			      }
 			      return true;
 			} else if (!res->decl_after_use) {
 			      res->decl_after_use = net;
@@ -177,11 +183,17 @@ bool symbol_search(const LineInfo*li, Design*des, NetScope*scope,
 		  }
 
 		  if (NetEvent*eve = scope->find_event(path_tail.name)) {
-			if (prefix_scope || (eve->lexical_pos() <= lexical_pos)) {
+			bool decl_after_use = !prefix_scope && !(eve->lexical_pos() <= lexical_pos);
+			if (!gn_strict_net_declaration || !decl_after_use) {
 			      path.push_back(path_tail);
 			      res->scope = scope;
 			      res->eve = eve;
 			      res->path_head = path;
+			      if (warn_decl_after_use && decl_after_use) {
+				    cerr << li->get_fileline()
+					 << ": warning: event `" << path_tail.name
+					 << "` used before declaration." << endl;
+			      }
 			      return true;
 			} else if (!res->decl_after_use) {
 			      res->decl_after_use = eve;