From 3b5d56e087cbd0d4d351b531b67333a1d33fa2e1 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Mon, 9 Jun 2008 14:53:50 +0100
Subject: [PATCH] Allow n-ary expressions

---
 tgt-vhdl/scope.cc       |  4 ++++
 tgt-vhdl/vhdl_syntax.cc | 42 +++++++++++++++++++++++++++++------------
 tgt-vhdl/vhdl_syntax.hh | 14 +++++++++++---
 3 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/tgt-vhdl/scope.cc b/tgt-vhdl/scope.cc
index 1ff2f5031..18c3a7679 100644
--- a/tgt-vhdl/scope.cc
+++ b/tgt-vhdl/scope.cc
@@ -53,6 +53,10 @@ static vhdl_var_ref *nexus_to_var_ref(vhdl_arch *arch, ivl_nexus_t nexus)
    assert(false);
 }
 
+/*
+ * Convert the inputs of a logic gate to a binary expression.
+ */
+
 /*
  * Translate all the primitive logic gates into concurrent
  * signal assignments.
diff --git a/tgt-vhdl/vhdl_syntax.cc b/tgt-vhdl/vhdl_syntax.cc
index bcd1751b9..572667f74 100644
--- a/tgt-vhdl/vhdl_syntax.cc
+++ b/tgt-vhdl/vhdl_syntax.cc
@@ -471,29 +471,47 @@ void vhdl_unaryop_expr::emit(std::ofstream &of, int level) const
    operand_->emit(of, level);
 }
 
+vhdl_binop_expr::vhdl_binop_expr(vhdl_expr *left, vhdl_binop_t op,
+                                 vhdl_expr *right, vhdl_type *type)
+   : vhdl_expr(type), op_(op)
+{
+   add_expr(left);
+   add_expr(right);
+}
+
 vhdl_binop_expr::~vhdl_binop_expr()
 {
-   delete left_;
-   delete right_;
+   delete_children<vhdl_expr>(operands_);
+}
+
+void vhdl_binop_expr::add_expr(vhdl_expr *e)
+{
+   operands_.push_back(e);
 }
 
 void vhdl_binop_expr::emit(std::ofstream &of, int level) const
 {
    // Expressions are fully parenthesized to remove any
    // ambiguity in the output
+
    of << "(";
-   right_->emit(of, level);
 
-   switch (op_) {
-   case VHDL_BINOP_AND:
-      of << " and ";
-      break;
-   case VHDL_BINOP_OR:
-      of << " or ";
-      break;
-   }
+   assert(operands_.size() > 0);   
+   std::list<vhdl_expr*>::const_iterator it = operands_.begin();
+
+   do {
+      (*it)->emit(of, level);
+      
+      switch (op_) {
+      case VHDL_BINOP_AND:
+         of << " and ";
+         break;
+      case VHDL_BINOP_OR:
+         of << " or ";
+         break;
+      }
+   } while (++it != operands_.end());      
 
-   right_->emit(of, level);
    of << ")";
 }
 
diff --git a/tgt-vhdl/vhdl_syntax.hh b/tgt-vhdl/vhdl_syntax.hh
index 9b9c9a9cc..12f14cfff 100644
--- a/tgt-vhdl/vhdl_syntax.hh
+++ b/tgt-vhdl/vhdl_syntax.hh
@@ -58,16 +58,24 @@ enum vhdl_binop_t {
    VHDL_BINOP_OR,
 };
 
+/*
+ * A binary expression contains a list of operands rather
+ * than just two: this is to model n-input gates and the
+ * like. A second constructor is provided to handle the
+ * common case of a true binary expression.
+ */
 class vhdl_binop_expr : public vhdl_expr {
 public:
+   vhdl_binop_expr(vhdl_binop_t op, vhdl_type *type)
+      : vhdl_expr(type), op_(op) {}
    vhdl_binop_expr(vhdl_expr *left, vhdl_binop_t op,
-                   vhdl_expr *right, vhdl_type *type)
-      : vhdl_expr(type), left_(left), right_(right), op_(op) {}
+                   vhdl_expr *right, vhdl_type *type);
    ~vhdl_binop_expr();
 
+   void add_expr(vhdl_expr *e);
    void emit(std::ofstream &of, int level) const;
 private:
-   vhdl_expr *left_, *right_;
+   std::list<vhdl_expr*> operands_;
    vhdl_binop_t op_;
 };