From acc4490370184923b34c5adce422ec546e310e82 Mon Sep 17 00:00:00 2001
From: Wilson Snyder <wsnyder@wsnyder.org>
Date: Wed, 29 Dec 2010 20:24:31 -0500
Subject: [PATCH] For UNUSED, skip primitive tables

---
 src/V3Inst.cpp                     |  1 +
 src/V3Undriven.cpp                 |  3 +++
 test_regress/t/t_lint_unused_bad.v | 19 +++++++++++++++++--
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/V3Inst.cpp b/src/V3Inst.cpp
index fd9932d36..2386dd7c3 100644
--- a/src/V3Inst.cpp
+++ b/src/V3Inst.cpp
@@ -123,6 +123,7 @@ private:
 
     virtual void visit(AstUdpTable* nodep, AstNUser*) {
 	if (!v3Global.opt.bboxUnsup()) {
+	    // If we support primitives, update V3Undriven to remove special case
 	    nodep->v3error("Unsupported: Verilog 1995 UDP Tables.  Use --bbox-unsup to ignore tables.");
 	}
     }
diff --git a/src/V3Undriven.cpp b/src/V3Undriven.cpp
index 0efd0d7fe..5a76e6668 100644
--- a/src/V3Undriven.cpp
+++ b/src/V3Undriven.cpp
@@ -256,6 +256,9 @@ private:
 	else entryp->usedWhole();
     }
 
+    // Until we support tables, primitives will have undriven and unused I/Os
+    virtual void visit(AstPrimitive* nodep, AstNUser*) {}
+
     // Coverage artifacts etc shouldn't count as a sink
     virtual void visit(AstCoverDecl* nodep, AstNUser*) {}
     virtual void visit(AstCoverInc* nodep, AstNUser*) {}
diff --git a/test_regress/t/t_lint_unused_bad.v b/test_regress/t/t_lint_unused_bad.v
index d1021f8e3..9464fa944 100644
--- a/test_regress/t/t_lint_unused_bad.v
+++ b/test_regress/t/t_lint_unused_bad.v
@@ -13,10 +13,11 @@ module t (/*AUTOARG*/
    input in;  // inputs don't get flagged as undriven
    output out;  // outputs don't get flagged as unused
 
-   wire  out = in;
-
    sub sub ();
 
+   // Check we don't warn about unused UDP signals
+   udp_mux2 udpsub (out, in, in, in);
+
 endmodule
 
 module sub;
@@ -46,3 +47,17 @@ module sub;
       if (0 && mixed[1:0] != 0) begin end
    end
 endmodule
+
+primitive udp_mux2 (q, a, b, s);
+   output q;
+   input  a, b, s;
+   table
+      //a b  s  :  out
+      1   ?  0  :  1 ;
+      0   ?  0  :  0 ;
+      ?   1  1  :  1 ;
+      ?   0  1  :  0 ;
+      0   0  x  :  0 ;
+      1   1  x  :  1 ;
+   endtable
+endprimitive