Add user control over implicit sensitivity list warnings.

This patch adds two new warning classes that can be enabled or
disabled via the -W command line option. The first controls
whether a warning is generated if a part select within an
always @* statement causes the entire vector to be added to
the implicit sensitivity list. The second controls whether a
warning is generated if a word select within an always @*
statement causes the entire array to be added to the implicit
sensitivity list. The first class is not automatically enabled
by -Wall, the second class is.
(cherry picked from commit fc49420cb5)

compiler.h

@@ -88,6 +88,11 @@ extern bool warn_ob_select;
 /* Warn about structures that may have infinite loops. */
 extern bool warn_inf_loop;
 
+/* Warn about always @* statements where a part or word select causes
+   sensitivity to an entire vector or array. */
+extern bool warn_sens_entire_vec;
+extern bool warn_sens_entire_arr;
+
 /* This is true if verbose output is requested. */
 extern bool verbose_flag;
 

driver/iverilog.man

@@ -254,8 +254,8 @@ after a \fB-Wall\fP argument to suppress isolated warning types.
 
 .TP 8
 .B all
-This enables the implicit, portbind, select-range and timescale warning
-categories.
+This enables the implicit, portbind, select-range, timescale, and
+sensitivity-entire-array warning categories.
 
 .TP 8
 .B implicit
@@ -298,6 +298,22 @@ verified. It is expected that many of the warnings will be false
 positives, since the code treats the value of all variables and signals
 as indeterminate.
 
+.TP 8
+.B sensitivity-entire-vector
+This enables warnings for when a part select within an "always @*"
+statement results in the entire vector being added to the implicit
+sensitivity list. Although this behaviour is prescribed by the IEEE
+standard, it is not what might be expected and can have performance
+implications if the vector is large.
+
+.TP 8
+.B sensitivity-entire-array
+This enables warnings for when a word select within an "always @*"
+statement results in the entire array being added to the implicit
+sensitivity list. Although this behaviour is prescribed by the IEEE
+standard, it is not what might be expected and can have performance
+implications if the array is large.
+
 .SH "SYSTEM FUNCTION TABLE FILES"
 If the source file name as a \fB.sft\fP suffix, then it is taken to be
 a system function table file. A System function table file is used to

driver/main.c

@@ -471,6 +471,7 @@ static void process_warning_switch(const char*name)
 	    process_warning_switch("portbind");
 	    process_warning_switch("select-range");
 	    process_warning_switch("timescale");
+	    process_warning_switch("sensitivity-entire-array");
       } else if (strcmp(name,"implicit") == 0) {
 	    if (! strchr(warning_flags, 'i'))
 		  strcat(warning_flags, "i");
@@ -488,6 +489,12 @@ static void process_warning_switch(const char*name)
       } else if (strcmp(name,"infloop") == 0) {
 	    if (! strchr(warning_flags, 'l'))
 		  strcat(warning_flags, "l");
+      } else if (strcmp(name,"sensitivity-entire-vector") == 0) {
+	    if (! strchr(warning_flags, 'v'))
+		  strcat(warning_flags, "v");
+      } else if (strcmp(name,"sensitivity-entire-array") == 0) {
+	    if (! strchr(warning_flags, 'a'))
+		  strcat(warning_flags, "a");
       } else if (strcmp(name,"no-implicit") == 0) {
 	    char*cp = strchr(warning_flags, 'i');
 	    if (cp) while (*cp) {
@@ -512,6 +519,18 @@ static void process_warning_switch(const char*name)
 		  cp[0] = cp[1];
 		  cp += 1;
 	    }
+      } else if (strcmp(name,"no-sensitivity-entire-vector") == 0) {
+	    char*cp = strchr(warning_flags, 'v');
+	    if (cp) while (*cp) {
+		  cp[0] = cp[1];
+		  cp += 1;
+	    }
+      } else if (strcmp(name,"no-sensitivity-entire-array") == 0) {
+	    char*cp = strchr(warning_flags, 'a');
+	    if (cp) while (*cp) {
+		  cp[0] = cp[1];
+		  cp += 1;
+	    }
       }
 }
 

main.cc

@@ -116,6 +116,8 @@ bool warn_timescale = false;
 bool warn_portbinding = false;
 bool warn_inf_loop = false;
 bool warn_ob_select = false;
+bool warn_sens_entire_vec = false;
+bool warn_sens_entire_arr = false;
 
 bool error_implicit = false;
 
@@ -501,6 +503,12 @@ static void read_iconfig_file(const char*ipath)
 		      case 't':
 			warn_timescale = true;
 			break;
+		      case 'v':
+			warn_sens_entire_vec = true;
+			break;
+		      case 'a':
+			warn_sens_entire_arr = true;
+			break;
 		      default:
 			break;
 		  }

net_nex_input.cc

@@ -23,6 +23,7 @@
 
 # include  <cassert>
 # include  <typeinfo>
+# include  "compiler.h"
 # include  "netlist.h"
 # include  "netmisc.h"
 
@@ -115,7 +116,7 @@ NexusSet* NetESelect::nex_input(bool rem_out)
       result->add(*tmp);
       delete tmp;
 	/* See the comment for NetESignal below. */
-      if (base_) {
+      if (base_ && warn_sens_entire_vec) {
 	    cerr << get_fileline() << ": warning: @* is sensitive to all "
 	            "bits in '" << *expr_ << "'." << endl;
       }
@@ -151,10 +152,12 @@ NexusSet* NetESignal::nex_input(bool rem_out)
 	    tmp = word_->nex_input(rem_out);
 	    result->add(*tmp);
 	    delete tmp;
+            if (warn_sens_entire_arr) {
                   cerr << get_fileline() << ": warning: @* is sensitive to all "
                        << net_->array_count() << " words in array '"
                        << name() << "'." << endl;
             }
+      }
       for (unsigned idx = 0 ;  idx < net_->pin_count() ;  idx += 1)
 	    result->add(net_->pin(idx).nexus());