From 14e3a886bdb84a5e2bc888b9a2bdb965bc00340a Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Sun, 23 Mar 2008 17:52:48 -0700
Subject: [PATCH] Find implicit nets in expressions passed to ports.

It is questionable, but probably legal, for expressions passed as
arguments to input ports of various kinds of gates to implicitly
declare nets. This patch allows the scan through different types
of expressions for implicit nets.

The elaborate_sig handling here does not test for the legality of
having a non-trivial expression as argument to a port. For example,
it is definitely NOT legal to have r-value expressions passed to
output or inout ports. But that will be checked for later when the
instance is elaborated for real.
---
 PExpr.h     |  6 ++++++
 elab_sig.cc | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/PExpr.h b/PExpr.h
index 3481351aa..7f82b1c6b 100644
--- a/PExpr.h
+++ b/PExpr.h
@@ -474,6 +474,8 @@ class PEUnary : public PExpr {
 
       virtual void dump(ostream&out) const;
 
+      virtual bool elaborate_sig(Design*des, NetScope*scope) const;
+
       virtual NetNet* elaborate_net(Design*des, NetScope*scope,
 				    unsigned width,
 				    const NetExpr* rise,
@@ -533,6 +535,8 @@ class PEBinary : public PExpr {
 				  unsigned min, unsigned lval,
 				  bool&unsized_flag) const;
 
+      virtual bool elaborate_sig(Design*des, NetScope*scope) const;
+
       virtual NetNet* elaborate_net(Design*des, NetScope*scope,
 				    unsigned width,
 				    const NetExpr* rise,
@@ -648,6 +652,8 @@ class PETernary : public PExpr {
 				  unsigned min, unsigned lval,
 				  bool&unsized_flag) const;
 
+      virtual bool elaborate_sig(Design*des, NetScope*scope) const;
+
       virtual NetNet* elaborate_net(Design*des, NetScope*scope,
 				    unsigned width,
 				    const NetExpr* rise,
diff --git a/elab_sig.cc b/elab_sig.cc
index dbbda62a4..95a9fa032 100644
--- a/elab_sig.cc
+++ b/elab_sig.cc
@@ -267,6 +267,28 @@ bool PEIdent::elaborate_sig(Design*des, NetScope*scope) const
       return sig != 0;
 }
 
+bool PEBinary::elaborate_sig(Design*des, NetScope*scope) const
+{
+      bool flag = true;
+
+      flag = left_->elaborate_sig(des, scope)  && flag;
+      flag = right_->elaborate_sig(des, scope) && flag;
+      return flag;
+}
+
+bool PETernary::elaborate_sig(Design*des, NetScope*scope) const
+{
+      bool flag = true;
+      flag = tru_->elaborate_sig(des, scope)  && flag;
+      flag = fal_->elaborate_sig(des, scope)  && flag;
+      return flag;
+}
+
+bool PEUnary::elaborate_sig(Design*des, NetScope*scope) const
+{
+      return expr_->elaborate_sig(des, scope);
+}
+
 bool PGate::elaborate_sig(Design*des, NetScope*scope) const
 {
       return true;