From 0fcd2d9db69433f71b9d5855b50cec6e5b43600e Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Wed, 5 Jun 2013 20:39:04 -0700
Subject: [PATCH] Handle rising_edge and falling_edge functions.

---
 vhdlpp/architec_elaborate.cc | 49 ++++++++++++++++++++++++++++++++++--
 vhdlpp/expression.h          |  4 +++
 vhdlpp/expression_emit.cc    | 10 ++++++++
 3 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/vhdlpp/architec_elaborate.cc b/vhdlpp/architec_elaborate.cc
index e7308f96e..3ffc8c6da 100644
--- a/vhdlpp/architec_elaborate.cc
+++ b/vhdlpp/architec_elaborate.cc
@@ -174,9 +174,54 @@ int ProcessStatement::rewrite_as_always_edge_(Entity*, Architecture*)
 	    return -1;
 
       const Expression*ce_raw = stmt->peek_condition();
+	// Now we have matched this pattern:
+	//   process(<expr>) begin if <ce_raw>...
+	// The <ce_raw> is the condition.
 
-	// We expect the condition to be <name>'event AND <name>='1'.
-	// If it's not a logical AND, I give up.
+      if (const ExpFunc*ce_func = dynamic_cast<const ExpFunc*>(ce_raw)) {
+	    if (ce_func->func_args() != 1)
+		  return -1;
+	    if (ce_func->func_name()!="rising_edge" && ce_func->func_name()!="falling_edge")
+		  return -1;
+
+	    if (! se->symbolic_compare(ce_func->func_arg(0)))
+		return -1;
+
+	      // We've matched this pattern:
+	      //  process(<se>) if (rising_edge(<se>)) then ...
+	      // and we can convert it to:
+	      //  always @(posedge <se>) ...
+
+	    ExpEdge::fun_t use_edge;
+	    if (ce_func->func_name()=="rising_edge")
+		  use_edge = ExpEdge::POSEDGE;
+	    else if (ce_func->func_name()=="falling_edge")
+		  use_edge = ExpEdge::NEGEDGE;
+	    else
+		  use_edge = ExpEdge::ANYEDGE;
+
+	      // Replace the sensitivity expression with an edge
+	      // expression. The ExpEdge expression signals that this
+	      // is an always-@(edge) statement.
+	    ExpEdge*edge = new ExpEdge(use_edge, se);
+	    assert(sensitivity_list_.size() == 1);
+	    sensitivity_list_.pop_front();
+	    sensitivity_list_.push_front(edge);
+
+	      // Replace the statement with the body of the always
+	      // statement, which is the true clause of the top "if"
+	      // statement. There should be no "else" clause.
+	    assert(statements_list_.size() == 1);
+	    statements_list_.pop_front();
+	    stmt->extract_true(statements_list_);
+
+	    delete stmt;
+	    return 0;
+      }
+
+	// Here we expect the condition to be
+	//    <name>'event AND <name>='1'.
+	// So if ce_raw is not a logical AND, I give up.
       const ExpLogical*ce = dynamic_cast<const ExpLogical*> (ce_raw);
       if (ce == 0)
 	    return -1;
diff --git a/vhdlpp/expression.h b/vhdlpp/expression.h
index 6d24335f0..d779e484a 100644
--- a/vhdlpp/expression.h
+++ b/vhdlpp/expression.h
@@ -461,6 +461,10 @@ class ExpFunc : public Expression {
       ExpFunc(perm_string nn, std::list<Expression*>*args);
       ~ExpFunc();
 
+      inline perm_string func_name() const { return name_; }
+      inline size_t func_args() const { return argv_.size(); }
+      inline const Expression*func_arg(size_t idx) const { return argv_[idx]; }
+
     public: // Base methods
       int elaborate_expr(Entity*ent, Architecture*arc, const VType*ltype);
       void write_to_stream(std::ostream&fd);
diff --git a/vhdlpp/expression_emit.cc b/vhdlpp/expression_emit.cc
index d4fa884e1..63c1f6eb5 100644
--- a/vhdlpp/expression_emit.cc
+++ b/vhdlpp/expression_emit.cc
@@ -554,6 +554,16 @@ int ExpFunc::emit(ostream&out, Entity*ent, Architecture*arc)
 	    errors += argv_[0]->emit(out, ent, arc);
 	    out << ")";
 
+      } else if (name_ == "rising_edge" && argv_.size()==1) {
+	    out << "$ivlh_rising_edge(";
+	    errors += argv_[0]->emit(out, ent, arc);
+	    out << ")";
+
+      } else if (name_ == "falling_edge" && argv_.size()==1) {
+	    out << "$ivlh_falling_edge(";
+	    errors += argv_[0]->emit(out, ent, arc);
+	    out << ")";
+
       } else {
 	    out << "\\" << name_ << " (";
 	    for (size_t idx = 0; idx < argv_.size() ; idx += 1) {