Generate an RTLIL representation of bind constructs

This code now takes the AST nodes of type AST_BIND and generates a
representation in the RTLIL for them.

This is a little tricky, because a binding of the form:

    bind baz foo_t foo_i (.arg (1 + bar));

means "make an instance of foo_t called foo_i, instantiate it inside
baz and connect the port arg to the result of the expression 1+bar".
Of course, 1+bar needs a cell for the addition. Where should that cell
live?

With this patch, the Binding structure that represents the construct
is itself an AST::AstModule module. This lets us put the adder cell
inside it. We'll pull the contents out and plonk them into 'baz' when
we actually do the binding operation as part of the hierarchy pass.

Of course, we don't want RTLIL::Binding to contain an
AST::AstModule (since kernel code shouldn't depend on a frontend), so
we define RTLIL::Binding as an abstract base class and put the
AST-specific code into an AST::Binding subclass. This is analogous to
the AST::AstModule class.

1 files changed, 58 insertions, 0 deletions

diff --git a/frontends/ast/ast_binding.h b/frontends/ast/ast_binding.h
new file mode 100644
index 000000000..641497d52
--- /dev/null
+++ b/frontends/ast/ast_binding.h
@@ -0,0 +1,58 @@
+/* -*- c++ -*-
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Claire Xenia Wolf <claire@yosyshq.com>
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ *  ---
+ *
+ *  This header declares the AST::Binding class
+ *
+ *  This is used to support the bind directive and is to RTLIL::Binding as
+ *  AST::AstModule is to RTLIL::Module, holding a syntax-level representation of
+ *  cells until we get to a stage where they make sense. In the case of a bind
+ *  directive, this is when we elaborate the design in the hierarchy pass.
+ *
+ */
+
+#ifndef AST_BINDING_H
+#define AST_BINDING_H
+
+#include "kernel/rtlil.h"
+#include "kernel/binding.h"
+
+#include <memory>
+
+YOSYS_NAMESPACE_BEGIN
+
+namespace AST
+{
+	class Binding : public RTLIL::Binding
+	{
+	public:
+		Binding(RTLIL::IdString  target_type,
+		        RTLIL::IdString  target_name,
+		        const AstNode   &cell);
+
+		std::string describe() const override;
+
+	private:
+		// The syntax-level representation of the cell to be bound.
+		std::unique_ptr<AstNode> ast_node;
+	};
+}
+
+YOSYS_NAMESPACE_END
+
+#endif