Fix for br1000 - avoid infinite loop when processes share a for-loop index.

compiler.h

@@ -1,7 +1,7 @@
 #ifndef IVL_compiler_H
 #define IVL_compiler_H
 /*
- * Copyright (c) 1999-2014 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 1999-2016 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
@@ -189,6 +189,11 @@ extern bool gn_strict_ca_eval_flag;
    standard expression width rules. */
 extern bool gn_strict_expr_width_flag;
 
+/* If this flag is true, then don't add a for-loop control variable
+   to an implicit event_expression list if it is only used inside the
+   loop. */
+extern bool gn_shared_loop_index_flag;
+
 /* If variables can be converted to uwires by a continuous assignment
    (assuming no procedural assign, then return true. This will be true
    for SystemVerilog */

driver/iverilog.man.in

@@ -1,4 +1,4 @@
-.TH iverilog 1 "Aug 7th, 2015" "" "Version %M.%n%E"
+.TH iverilog 1 "Mar 5th, 2016" "" "Version %M.%n%E"
 .SH NAME
 iverilog - Icarus Verilog compiler
 
@@ -133,6 +133,17 @@ 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 -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
+variable (loop index) is only used inside the for-loop statement, the
+compiler will not include it in an implicit event_expression list it
+calculates for that statement or any enclosing statement. This allows
+the same control variable to be used in multiple processes without risk
+of entering an infinite loop caused by each process triggering all other
+processes that use the same varaible. For strict compliance with the
+standards, this behaviour should be disabled.
+.TP 8
 .B -I\fIincludedir\fP
 Append directory \fIincludedir\fP to list of directories searched
 for Verilog include files. The \fB\-I\fP switch may be used many times
@@ -537,7 +548,7 @@ Tips on using, debugging, and developing the compiler can be found at
 
 .SH COPYRIGHT
 .nf
-Copyright \(co  2002\-2015 Stephen Williams
+Copyright \(co  2002\-2016 Stephen Williams
 
 This document can be freely redistributed according to the terms of the
 GNU General Public License version 2.0

driver/main.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2015 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2016 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
@@ -128,6 +128,7 @@ const char*gen_icarus = "icarus-misc";
 const char*gen_io_range_error = "io-range-error";
 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";
 
 /* Boolean: true means use a default include dir, false means don't */
@@ -739,6 +740,12 @@ static int process_generation(const char*name)
       else if (strcmp(name,"no-strict-expr-width") == 0)
 	    gen_strict_expr_width = "no-strict-expr-width";
 
+      else if (strcmp(name,"shared-loop-index") == 0)
+	    gen_shared_loop_index = "shared-loop-index";
+
+      else if (strcmp(name,"no-shared-loop-index") == 0)
+	    gen_shared_loop_index = "no-shared-loop-index";
+
       else if (strcmp(name,"verilog-ams") == 0)
 	    gen_verilog_ams = "verilog-ams";
 
@@ -764,7 +771,8 @@ static int process_generation(const char*name)
 		            "    icarus-misc | no-icarus-misc\n"
 		            "    io-range-error | no-io-range-error\n"
 		            "    strict-ca-eval | no-strict-ca-eval\n"
-		            "    strict-expr-width | no-strict-expr-width\n");
+		            "    strict-expr-width | no-strict-expr-width\n"
+		            "    shared-loop-index | no-shared-loop-index\n");
 
 	    return 1;
       }
@@ -1118,6 +1126,7 @@ int main(int argc, char **argv)
       fprintf(iconfig_file, "generation:%s\n", gen_io_range_error);
       fprintf(iconfig_file, "generation:%s\n", gen_strict_ca_eval);
       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_icarus);
       fprintf(iconfig_file, "warnings:%s\n", warning_flags);

main.cc

@@ -108,6 +108,7 @@ bool gn_assertions_flag = true;
 bool gn_io_range_error_flag = true;
 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;
 
 /*
@@ -347,6 +348,12 @@ static void process_generation_flag(const char*gen)
       } else if (strcmp(gen,"no-strict-expr-width") == 0) {
 	    gn_strict_expr_width_flag = false;
 
+      } else if (strcmp(gen,"shared-loop-index") == 0) {
+	    gn_shared_loop_index_flag = true;
+
+      } else if (strcmp(gen,"no-shared-loop-index") == 0) {
+	    gn_shared_loop_index_flag = false;
+
 	  } else {
       }
 }

net_nex_input.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002-2013 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2002-2016 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
@@ -427,6 +427,15 @@ NexusSet* NetForLoop::nex_input(bool rem_out)
       result->add(*tmp);
       delete tmp;
 
+      if (gn_shared_loop_index_flag) {
+	    tmp = new NexusSet();
+	    for (unsigned idx = 0 ; idx < index_->pin_count() ; idx += 1)
+		tmp->add(index_->pin(idx).nexus(), 0, index_->vector_width());
+
+	    result->rem(*tmp);
+	    delete tmp;
+      }
+
       return result;
 }