Add PINCONNECTEMPTY warning.

Changes

@@ -11,6 +11,8 @@ indicates the contributor was also the author of the fix; Thanks!
 
 ***   Add assertions on 'unique if', bug725. [Jeff Bush] 
 
+***   Add PINCONNECTEMPTY warning. [Holger Waechtler]
+
 ****  Documentation fixes, bug723. [Glen Gibb]
 
 ****  Fix tracing of package variables and real arrays.

bin/verilator

@@ -1095,8 +1095,9 @@ Disable the specified warning message.
 Disable all lint related warning messages, and all style warnings.  This is
 equivalent to "-Wno-ALWCOMBORDER -Wno-CASEINCOMPLETE -Wno-CASEOVERLAP
 -Wno-CASEX -Wno-CASEWITHX -Wno-CMPCONST -Wno-ENDLABEL -Wno-IMPLICIT
--Wno-LITENDIAN -Wno-PINMISSING -Wno-SYNCASYNCNET -Wno-UNDRIVEN
--Wno-UNSIGNED -Wno-UNUSED -Wno-WIDTH" plus the list shown for Wno-style.
+-Wno-LITENDIAN -Wno-PINCONNECTEMPTY -Wno-PINMISSING -Wno-SYNCASYNCNET
+-Wno-UNDRIVEN -Wno-UNSIGNED -Wno-UNUSED -Wno-WIDTH" plus the list shown for
+Wno-style.
 
 It is strongly recommended you cleanup your code rather than using this
 option, it is only intended to be use when running test-cases of code
@@ -1106,8 +1107,8 @@ received from third parties.
 
 Disable all code style related warning messages (note by default they are
 already disabled).  This is equivalent to "-Wno-DECLFILENAME -Wno-DEFPARAM
--Wno-INCABSPATH -Wno-PINNOCONNECT -Wno-SYNCASYNCNET -Wno-UNDRIVEN
--Wno-UNUSED -Wno-VARHIDDEN".
+-Wno-INCABSPATH -Wno-PINCONNECTEMPTY -Wno-PINNOCONNECT -Wno-SYNCASYNCNET
+-Wno-UNDRIVEN -Wno-UNUSED -Wno-VARHIDDEN".
 
 =item -Wno-fatal
 
@@ -3009,11 +3010,21 @@ not really needed.  The best solution is to insure that each module is in a
 unique file by the same name.  Otherwise, make sure all library files are
 read in as libraries with -v, instead of automatically with -y.
 
+=item PINCONNECTEMPTY
+
+Warns that a cell instantiation has a pin which is connected to
+.pin_name(), e.g. not another signal, but with an explicit mention of the
+pin.  It may be desirable to disable PINCONNECTEMPTY, as this indicates
+intention to have a no-connect.
+
+Disabled by default as this is a code style warning; it will simulate
+correctly.
+
 =item PINMISSING
 
 Warns that a module has a pin which is not mentioned in a cell
 instantiation.  If a pin is not missing it should still be specified on the
-cell declaration with a empty connection,using "(.pin_name())".
+cell declaration with a empty connection, using "(.pin_name())".
 
 Ignoring this warning will only suppress the lint check, it will simulate
 correctly.

src/V3Error.h

@@ -84,6 +84,7 @@ public:
 	MULTIDRIVEN,	// Driven from multiple blocks
 	PINMISSING,	// Cell pin not specified
 	PINNOCONNECT,	// Cell pin not connected
+	PINCONNECTEMPTY,// Cell pin connected by name with empty reference: ".name()" (can be used to mark unused pins)
 	REALCVT,	// Real conversion
 	REDEFMACRO,	// Redefining existing define macro
 	SELRANGE,	// Selection index out of range
@@ -127,7 +128,7 @@ public:
 	    "INCABSPATH", "INITIALDLY",
 	    "LITENDIAN", "MODDUP",
 	    "MULTIDRIVEN",
-	    "PINMISSING", "PINNOCONNECT",
+	    "PINMISSING", "PINNOCONNECT", "PINCONNECTEMPTY",
 	    "REALCVT", "REDEFMACRO",
 	    "SELRANGE", "STMTDLY", "SYMRSVDWORD", "SYNCASYNCNET",
 	    "UNDRIVEN", "UNOPT", "UNOPTFLAT", "UNPACKED", "UNSIGNED", "UNUSED",
@@ -165,6 +166,7 @@ public:
 				       || m_e==DEFPARAM
 				       || m_e==DECLFILENAME
 				       || m_e==INCABSPATH
+				       || m_e==PINCONNECTEMPTY
 				       || m_e==PINNOCONNECT
 				       || m_e==SYNCASYNCNET
 				       || m_e==UNDRIVEN

src/V3LinkCells.cpp

@@ -308,7 +308,13 @@ private:
 	    set<string> ports;	// Symbol table of all connected port names
 	    for (AstPin* pinp = nodep->pinsp(); pinp; pinp=pinp->nextp()->castPin()) {
 		if (pinp->name()=="") pinp->v3error("Connect by position is illegal in .* connected cells");
-		if (!pinp->exprp()) pinp->v3warn(PINNOCONNECT,"Cell pin is not connected: "<<pinp->prettyName());
+		if (!pinp->exprp()) {
+		    if (pinp->name().substr(0, 11) == "__pinNumber") {
+			pinp->v3warn(PINNOCONNECT,"Cell pin is not connected: "<<pinp->prettyName());
+		    } else {
+			pinp->v3warn(PINCONNECTEMPTY,"Cell pin connected by name with empty reference: "<<pinp->prettyName());
+		    }
+		}
 		if (ports.find(pinp->name()) == ports.end()) {
 		    ports.insert(pinp->name());
 		}

test_regress/t/t_inst_missing.v

@@ -6,10 +6,12 @@
 module t (/*AUTOARG*/);
    wire ok = 1'b0;
    // verilator lint_off PINNOCONNECT
-   sub sub (.ok(ok), .nc());
+   // verilator lint_off PINCONNECTEMPTY
+   sub sub (.ok(ok), , .nc());
+   // verilator lint_on PINCONNECTEMPTY
    // verilator lint_on PINNOCONNECT
 endmodule
 
-module sub (input ok, input nc);
-   initial if (ok&&nc) begin end  // No unused warning
+module sub (input ok, input none, input nc);
+   initial if (ok && none && nc) begin end  // No unused warning
 endmodule

test_regress/t/t_inst_missing_bad.pl

@@ -11,9 +11,10 @@ compile (
 	 v_flags2 => ["--lint-only --Wall -Wno-DECLFILENAME"],
 	 fails=>1,
 	 expect=>
-q{%Warning-PINNOCONNECT: t/t_inst_missing_bad.v:\d+: Cell pin is not connected: nc
+q{%Warning-PINNOCONNECT: t/t_inst_missing_bad.v:8: Cell pin is not connected: __pinNumber2
 %Warning-PINNOCONNECT: Use .*
-%Warning-PINMISSING: t/t_inst_missing_bad.v:\d+: Cell has missing pin: missing
+%Warning-PINCONNECTEMPTY: t/t_inst_missing_bad.v:8: Cell pin connected by name with empty reference: nc
+%Warning-PINMISSING: t/t_inst_missing_bad.v:8: Cell has missing pin: missing
 %Error: Exiting due to.*},
 	 );
 

test_regress/t/t_inst_missing_bad.v

@@ -5,9 +5,9 @@
 
 module t (/*AUTOARG*/);
    wire ok = 1'b0;
-   sub sub (.ok(ok), .nc());
+   sub sub (.ok(ok), , .nc());
 endmodule
 
-module sub (input ok, input nc, input missing);
-   initial if (ok&&nc&&missing) begin end  // No unused warning
+module sub (input ok, input none, input nc, input missing);
+   initial if (ok && none && nc && missing) begin end  // No unused warning
 endmodule