From 78028a3310b7539b23f5b389936628e973c13b8e Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Mon, 28 Jul 2008 12:59:10 +0100
Subject: [PATCH] Fully support ternary expressions

---
 tgt-vhdl/expr.cc    | 30 ++++++++++++++++++++++++++++--
 tgt-vhdl/support.cc | 31 ++++++++++++++++++++++++++++++-
 tgt-vhdl/support.hh |  7 ++++++-
 3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/tgt-vhdl/expr.cc b/tgt-vhdl/expr.cc
index 007abb203..0632e53f5 100644
--- a/tgt-vhdl/expr.cc
+++ b/tgt-vhdl/expr.cc
@@ -419,9 +419,35 @@ static vhdl_expr *translate_ufunc(ivl_expr_t e)
 
 static vhdl_expr *translate_ternary(ivl_expr_t e)
 {
-   error("Ternary expression only supported as RHS of assignment");
+   support_function_t sf;
+   int width = ivl_expr_width(e);
+   bool issigned = ivl_expr_signed(e) != 0;
+   if (width == 1)
+      sf = SF_TERNARY_LOGIC;
+   else if (issigned)
+      sf = SF_TERNARY_SIGNED;
+   else
+      sf = SF_TERNARY_UNSIGNED;
    
-   return NULL;
+   require_support_function(sf);
+
+   vhdl_expr *test = translate_expr(ivl_expr_oper1(e));
+   vhdl_expr *true_part = translate_expr(ivl_expr_oper2(e));
+   vhdl_expr *false_part = translate_expr(ivl_expr_oper3(e));
+   if (!test || !true_part || !false_part)
+      return NULL;
+
+   vhdl_type boolean(VHDL_TYPE_BOOLEAN);
+   test = test->cast(&boolean);
+   
+   vhdl_fcall *fcall =
+      new vhdl_fcall(support_function::function_name(sf),
+                     vhdl_type::type_for(width, issigned));
+   fcall->add_expr(test);
+   fcall->add_expr(true_part);
+   fcall->add_expr(false_part);
+   
+   return fcall;
 }
 
 static vhdl_expr *translate_concat(ivl_expr_t e)
diff --git a/tgt-vhdl/support.cc b/tgt-vhdl/support.cc
index 4c396407f..5e26f159a 100644
--- a/tgt-vhdl/support.cc
+++ b/tgt-vhdl/support.cc
@@ -46,6 +46,12 @@ const char *support_function::function_name(support_function_t type)
       return "Reduce_AND";
    case SF_REDUCE_XOR:
       return "Reduce_XOR";
+   case SF_TERNARY_LOGIC:
+      return "Ternary_Logic";
+   case SF_TERNARY_UNSIGNED:
+      return "Ternary_Unsigned";
+   case SF_TERNARY_SIGNED:
+      return "Ternary_Signed";
    default:
       assert(false);
    }
@@ -61,12 +67,20 @@ vhdl_type *support_function::function_type(support_function_t type)
    case SF_REDUCE_OR:
    case SF_REDUCE_AND:
    case SF_REDUCE_XOR:
+   case SF_TERNARY_LOGIC:
       return vhdl_type::std_logic();
    default:
       assert(false);
    }
 }
 
+void support_function::emit_ternary(std::ostream &of, int level) const
+{
+   of << "begin" << nl_string(indent(level))
+      << "if T then return X; else return Y; end if;"
+      << nl_string(level);
+}
+
 void support_function::emit(std::ostream &of, int level) const
 {
    of << "function " << function_name(type_);
@@ -80,7 +94,7 @@ void support_function::emit(std::ostream &of, int level) const
    case SF_SIGNED_TO_BOOLEAN:
       of << "(X : signed) return Boolean is" << nl_string(level)
          << "begin" << nl_string(indent(level))
-         << "return X /= To_Signed(0, X'Length);" << nl_string (level);
+         << "return X /= To_Signed(0, X'Length);" << nl_string(level);
       break;
    case SF_BOOLEAN_TO_LOGIC:
       of << "(B : Boolean) return std_logic is" << nl_string(level)
@@ -121,6 +135,21 @@ void support_function::emit(std::ostream &of, int level) const
          << "end loop;" << nl_string(indent(level))
          << "return R;" << nl_string(level);
       break;
+   case SF_TERNARY_LOGIC:
+      of << "(T : Boolean; X, Y : std_logic) return std_logic is"
+         << nl_string(level);
+      emit_ternary(of, level);
+      break;
+   case SF_TERNARY_SIGNED:
+      of << "(T : Boolean; X, Y : signed) return signed is"
+         << nl_string(level);
+      emit_ternary(of, level);
+      break;
+   case SF_TERNARY_UNSIGNED:
+      of << "(T : Boolean; X, Y : signed) return unsigned is"
+         << nl_string(level);
+      emit_ternary(of, level);
+      break;
    default:
       assert(false);
    }
diff --git a/tgt-vhdl/support.hh b/tgt-vhdl/support.hh
index a5e247c94..80d6cfaff 100644
--- a/tgt-vhdl/support.hh
+++ b/tgt-vhdl/support.hh
@@ -24,12 +24,15 @@
 #include "vhdl_syntax.hh"
 
 enum support_function_t {
-   SF_UNSIGNED_TO_BOOLEAN,
+   SF_UNSIGNED_TO_BOOLEAN = 0,
    SF_SIGNED_TO_BOOLEAN,
    SF_BOOLEAN_TO_LOGIC,
    SF_REDUCE_OR,
    SF_REDUCE_AND,
    SF_REDUCE_XOR,
+   SF_TERNARY_LOGIC,
+   SF_TERNARY_UNSIGNED,
+   SF_TERNARY_SIGNED,
 };
 
 class support_function : public vhdl_function {
@@ -42,6 +45,8 @@ public:
    static vhdl_type *function_type(support_function_t type);
 
 private:
+   void emit_ternary(std::ostream &of, int level) const;
+   
    support_function_t type_;
 };