Add support for local genvar declaration in generate loops.

As requested in GitHub issue #304.

PGenerate.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2006-2019 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2006-2020 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -26,6 +26,7 @@ PGenerate::PGenerate(LexicalScope*parent, unsigned id)
 {
       direct_nested_ = false;
       scheme_type = GS_NONE;
+      local_index = false;
       loop_init = 0;
       loop_test = 0;
       loop_step = 0;

PGenerate.h

@@ -1,7 +1,7 @@
 #ifndef IVL_PGenerate_H
 #define IVL_PGenerate_H
 /*
- * Copyright (c) 2006-2019 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2006-2020 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -71,6 +71,9 @@ class PGenerate : public PNamedItem, public LexicalScope {
 
 	// generate loops have an index variable and three
 	// expressions: for (index = <init>; <test>; index=<step>)
+	// the index is local if it was declared in the init expression,
+	// e.g. for (genvar index = <init>; <test>; index=<step>)
+      bool local_index;
       perm_string loop_index;
       PExpr*loop_init;
       PExpr*loop_test;

elab_scope.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2019 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2020 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2013 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -899,17 +899,19 @@ bool PGenerate::generate_scope(Design*des, NetScope*container)
  */
 bool PGenerate::generate_scope_loop_(Design*des, NetScope*container)
 {
-	// Check that the loop_index variable was declared in a
-	// genvar statement.
-      NetScope*cscope = container;
-      while (cscope && !cscope->find_genvar(loop_index))
-            cscope = cscope->parent();
-      if (!cscope) {
-	    cerr << get_fileline() << ": error: genvar is missing for "
-	            "generate \"loop\" variable '" << loop_index << "'."
-	         << endl;
-	    des->errors += 1;
-	    return false;
+      if (!local_index) {
+	      // Check that the loop_index variable was declared in a
+	      // genvar statement.
+	    NetScope*cscope = container;
+	    while (cscope && !cscope->find_genvar(loop_index))
+		  cscope = cscope->parent();
+	    if (!cscope) {
+		  cerr << get_fileline() << ": error: genvar is missing for "
+			  "generate \"loop\" variable '" << loop_index << "'."
+		       << endl;
+		  des->errors += 1;
+		  return false;
+	    }
       }
 
 	// We're going to need a genvar...

parse.y

@@ -567,7 +567,7 @@ static void current_function_set_statement(const YYLTYPE&loc, vector<Statement*>
 %type <number>  number pos_neg_number
 %type <flag>    signing unsigned_signed_opt signed_unsigned_opt
 %type <flag>    import_export
-%type <flag>    K_packed_opt K_reg_opt K_static_opt K_virtual_opt
+%type <flag>    K_genvar_opt K_packed_opt K_reg_opt K_static_opt K_virtual_opt
 %type <flag>    udp_reg_opt edge_operator
 %type <drive>   drive_strength drive_strength_opt dr_strength0 dr_strength1
 %type <letter>  udp_input_sym udp_output_sym
@@ -5275,10 +5275,10 @@ module_item
   | K_genvar list_of_identifiers ';'
       { pform_genvars(@1, $2); }
 
-  | K_for '(' IDENTIFIER '=' expression ';'
+  | K_for '(' K_genvar_opt IDENTIFIER '=' expression ';'
               expression ';'
               genvar_iteration ')'
-      { pform_start_generate_for(@1, $3, $5, $7, $9.text, $9.expr); }
+      { pform_start_generate_for(@2, $3, $4, $6, $8, $10.text, $10.expr); }
     generate_block
       { pform_endgenerate(false); }
 
@@ -7341,6 +7341,7 @@ unique_priority
      presence is significant. This is a fairly common pattern so
      collect those rules here. */
 
+K_genvar_opt   : K_genvar    { $$ = true; } | { $$ = false; } ;
 K_packed_opt   : K_packed    { $$ = true; } | { $$ = false; } ;
 K_reg_opt      : K_reg       { $$ = true; } | { $$ = false; } ;
 K_static_opt   : K_static    { $$ = true; } | { $$ = false; } ;

pform.cc

@@ -1486,6 +1486,7 @@ void pform_genvars(const struct vlltype&li, list<perm_string>*names)
 }
 
 void pform_start_generate_for(const struct vlltype&li,
+			      bool local_index,
 			      char*ident1, PExpr*init,
 			      PExpr*test,
 			      char*ident2, PExpr*next)
@@ -1499,6 +1500,7 @@ void pform_start_generate_for(const struct vlltype&li,
 
       pform_cur_generate->scheme_type = PGenerate::GS_LOOP;
 
+      pform_cur_generate->local_index = local_index;
       pform_cur_generate->loop_index = lex_strings.make(ident1);
       pform_cur_generate->loop_init = init;
       pform_cur_generate->loop_test = test;

pform.h

@@ -292,6 +292,7 @@ extern verinum* pform_verinum_with_size(verinum*s, verinum*val,
 extern void pform_genvars(const struct vlltype&li, list<perm_string>*names);
 
 extern void pform_start_generate_for(const struct vlltype&li,
+				     bool local_index,
 				     char*ident1,
 				     PExpr*init,
 				     PExpr*test,

symbol_search.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003-2019 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2003-2020 Stephen Williams (steve@icarus.com)
  * Copyright CERN 2012 / Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
@@ -108,6 +108,9 @@ static bool symbol_search(const LineInfo*li, Design*des, NetScope*scope,
       }
 
       while (scope) {
+            if (scope->genvar_tmp.str() && path_tail.name == scope->genvar_tmp)
+                  return false;
+
 	    if (path_tail.name == "#") {
 		  cerr << li->get_fileline() << ": sorry: "
 		       << "Implicit class handle \"super\" not supported." << endl;