From 8e0bf3ebff3027a53274c87978893982985c30f7 Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Sun, 10 Aug 2008 11:22:23 +0100
Subject: [PATCH] Add conversion from std_logic to (un)signed types

Implemented using the expression (0 => X, others => '0')
---
 tgt-vhdl/cast.cc        |  9 +++++++++
 tgt-vhdl/vhdl_syntax.cc | 31 +++++++++++++++++++++++++++++++
 tgt-vhdl/vhdl_syntax.hh | 21 +++++++++++++++++++++
 3 files changed, 61 insertions(+)

diff --git a/tgt-vhdl/cast.cc b/tgt-vhdl/cast.cc
index 167efc4d2..43fcf6aaf 100644
--- a/tgt-vhdl/cast.cc
+++ b/tgt-vhdl/cast.cc
@@ -83,6 +83,15 @@ vhdl_expr *vhdl_expr::cast(const vhdl_type *to)
 
       return conv;
    }
+   else if ((to->get_name() == VHDL_TYPE_UNSIGNED
+             || to->get_name() == VHDL_TYPE_SIGNED) &&
+            type_->get_name() == VHDL_TYPE_STD_LOGIC) {
+      vhdl_bit_spec_expr *bs =
+         new vhdl_bit_spec_expr(new vhdl_type(*to), new vhdl_const_bit('0'));
+      bs->add_bit(0, this);
+
+      return bs;
+   }
    else if (to->get_name() == VHDL_TYPE_STD_LOGIC &&
             type_->get_name() == VHDL_TYPE_BOOLEAN) {
       require_support_function(SF_BOOLEAN_TO_LOGIC);
diff --git a/tgt-vhdl/vhdl_syntax.cc b/tgt-vhdl/vhdl_syntax.cc
index 4cb29c66e..c96ca6ffa 100644
--- a/tgt-vhdl/vhdl_syntax.cc
+++ b/tgt-vhdl/vhdl_syntax.cc
@@ -735,6 +735,37 @@ void vhdl_binop_expr::emit(std::ostream &of, int level) const
    of << ")";
 }
 
+vhdl_bit_spec_expr::~vhdl_bit_spec_expr()
+{
+   delete others_;
+
+   std::list<bit_map>::iterator it;
+   for (it = bits_.begin(); it != bits_.end(); ++it)
+      delete (*it).e;
+}
+
+void vhdl_bit_spec_expr::add_bit(int bit, vhdl_expr *e)
+{
+   bit_map bm = { bit, e };
+   bits_.push_back(bm);
+}
+
+void vhdl_bit_spec_expr::emit(std::ostream &of, int level) const
+{
+   of << "(";
+   
+   std::list<bit_map>::const_iterator it;
+   for (it = bits_.begin(); it != bits_.end(); ++it) {
+      of << (*it).bit << " => ";
+      (*it).e->emit(of, level);
+      of << ", ";
+   }
+
+   of << "others => ";
+   others_->emit(of, level);
+   of << ")";
+}
+
 vhdl_case_branch::~vhdl_case_branch()
 {
    delete when_;
diff --git a/tgt-vhdl/vhdl_syntax.hh b/tgt-vhdl/vhdl_syntax.hh
index a9fd93024..855173ab6 100644
--- a/tgt-vhdl/vhdl_syntax.hh
+++ b/tgt-vhdl/vhdl_syntax.hh
@@ -129,6 +129,27 @@ private:
 };
 
 
+/*
+ * An expression like (0 => '1', 2 => '0', others => 'Z')
+ */
+class vhdl_bit_spec_expr : public vhdl_expr {
+public:
+   vhdl_bit_spec_expr(vhdl_type *type, vhdl_expr *others)
+      : vhdl_expr(type), others_(others) {}
+   ~vhdl_bit_spec_expr();
+
+   void add_bit(int bit, vhdl_expr *e);
+   void emit(std::ostream &of, int level) const;
+private:
+   vhdl_expr *others_;
+   struct bit_map {
+      int bit;
+      vhdl_expr *e;
+   };
+   std::list<bit_map> bits_;
+};
+
+
 class vhdl_const_string : public vhdl_expr {
 public:
    vhdl_const_string(const char *value)