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diff --git a/frontends/ast/ast.h b/frontends/ast/ast.h
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+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2012  Clifford Wolf <clifford@clifford.at>
+ *  
+ *  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 is the AST frontend library.
+ *
+ *  The AST frontend library is not a frontend on it's own but provides a
+ *  generic abstract syntax tree (AST) abstraction for HDL code and can be
+ *  used by HDL frontends. See "ast.h" for an overview of the API and the
+ *  Verilog frontend for an usage example.
+ *
+ */
+
+#ifndef AST_H
+#define AST_H
+
+#include "kernel/rtlil.h"
+#include <stdint.h>
+#include <set>
+
+namespace AST
+{
+	// all node types, type2str() must be extended
+	// whenever a new node type is added here
+	enum AstNodeType
+	{
+		AST_NONE,
+		AST_DESIGN,
+		AST_MODULE,
+		AST_TASK,
+		AST_FUNCTION,
+
+		AST_WIRE,
+		AST_MEMORY,
+		AST_AUTOWIRE,
+		AST_PARAMETER,
+		AST_LOCALPARAM,
+		AST_PARASET,
+		AST_ARGUMENT,
+		AST_RANGE,
+		AST_CONSTANT,
+		AST_CELLTYPE,
+		AST_IDENTIFIER,
+
+		AST_FCALL,
+		AST_TO_SIGNED,
+		AST_TO_UNSIGNED,
+		AST_CONCAT,
+		AST_REPLICATE,
+		AST_BIT_NOT,
+		AST_BIT_AND,
+		AST_BIT_OR,
+		AST_BIT_XOR,
+		AST_BIT_XNOR,
+		AST_REDUCE_AND,
+		AST_REDUCE_OR,
+		AST_REDUCE_XOR,
+		AST_REDUCE_XNOR,
+		AST_REDUCE_BOOL,
+		AST_SHIFT_LEFT,
+		AST_SHIFT_RIGHT,
+		AST_SHIFT_SLEFT,
+		AST_SHIFT_SRIGHT,
+		AST_LT,
+		AST_LE,
+		AST_EQ,
+		AST_NE,
+		AST_GE,
+		AST_GT,
+		AST_ADD,
+		AST_SUB,
+		AST_MUL,
+		AST_DIV,
+		AST_MOD,
+		AST_POW,
+		AST_POS,
+		AST_NEG,
+		AST_LOGIC_AND,
+		AST_LOGIC_OR,
+		AST_LOGIC_NOT,
+		AST_TERNARY,
+		AST_MEMRD,
+		AST_MEMWR,
+
+		AST_TCALL,
+		AST_ASSIGN,
+		AST_CELL,
+		AST_PRIMITIVE,
+		AST_ALWAYS,
+		AST_BLOCK,
+		AST_ASSIGN_EQ,
+		AST_ASSIGN_LE,
+		AST_CASE,
+		AST_COND,
+		AST_DEFAULT,
+		AST_FOR,
+
+		AST_GENVAR,
+		AST_GENFOR,
+		AST_GENIF,
+		AST_GENBLOCK,
+
+		AST_POSEDGE,
+		AST_NEGEDGE,
+		AST_EDGE
+	};
+
+	// convert an node type to a string (e.g. for debug output)
+	std::string type2str(AstNodeType type);
+
+	// The AST is built using instances of this struct
+	struct AstNode
+	{
+		// this nodes type
+		AstNodeType type;
+
+		// the list of child nodes for this node
+		std::vector<AstNode*> children;
+
+		// the list of attributes assigned to this node
+		std::map<RTLIL::IdString, AstNode*> attributes;
+
+		// node content - most of it is unused in most node types
+		std::string str;
+		std::vector<RTLIL::State> bits;
+		bool is_input, is_output, is_reg, is_signed, range_valid;
+		int port_id, range_left, range_right;
+		uint32_t integer;
+
+		// this is set by simplify and used during RTLIL generation
+		AstNode *id2ast;
+
+		// this is the original sourcecode location that resulted in this AST node
+		// it is automatically set by the constructor using AST::current_filename and
+		// the AST::get_line_num() callback function.
+		std::string filename;
+		int linenum;
+
+		// creating and deleting nodes
+		AstNode(AstNodeType type = AST_NONE, AstNode *child1 = NULL, AstNode *child2 = NULL);
+		AstNode *clone();
+		void cloneInto(AstNode *other);
+		void delete_children();
+		~AstNode();
+
+		// simplify() creates a simpler AST by unrolling for-loops, expanding generate blocks, etc.
+		// it also sets the id2ast pointers so that identifier lookups are fast in genRTLIL()
+		bool simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage);
+		void expand_genblock(std::string index_var, std::string prefix, std::map<std::string, std::string> &name_map);
+		void replace_ids(std::map<std::string, std::string> &rules);
+		void mem2reg_as_needed_pass1(std::set<AstNode*> &mem2reg_set, std::set<AstNode*> &mem2reg_candidates, bool sync_proc, bool async_proc);
+		void mem2reg_as_needed_pass2(std::set<AstNode*> &mem2reg_set, AstNode *mod, AstNode *block);
+		void meminfo(int &mem_width, int &mem_size, int &addr_bits);
+
+		// create a human-readable text representation of the AST (for debugging)
+		void dumpAst(FILE *f, std::string indent, AstNode *other = NULL);
+		void dumpVlog(FILE *f, std::string indent);
+
+		// create RTLIL code for this AST node
+		// for expressions the resulting signal vector is returned
+		// all generated cell instances, etc. are written to the RTLIL::Module pointed to by AST_INTERNAL::current_module
+		RTLIL::SigSpec genRTLIL(int width_hint = -1);
+		RTLIL::SigSpec genWidthRTLIL(int width, RTLIL::SigSpec *subst_from = NULL,  RTLIL::SigSpec *subst_to = NULL);
+
+		// compare AST nodes
+		bool operator==(const AstNode &other) const;
+		bool operator!=(const AstNode &other) const;
+		bool contains(const AstNode *other) const;
+
+		// helper functions for creating AST nodes for constants
+		static AstNode *mkconst_int(uint32_t v, bool is_signed, int width = 32);
+		static AstNode *mkconst_bits(const std::vector<RTLIL::State> &v, bool is_signed);
+	};
+
+	// process an AST tree (ast must point to an AST_DESIGN node) and generate RTLIL code
+	void process(RTLIL::Design *design, AstNode *ast, bool dump_ast = false, bool dump_ast_diff = false, bool dump_vlog = false, bool nolatches = false, bool nomem2reg = false);
+
+	// parametric modules are supported directly by the AST library
+	// therfore we need our own derivate of RTLIL::Module with overloaded virtual functions
+	struct AstModule : RTLIL::Module {
+		AstNode *ast;
+		bool nolatches, nomem2reg;
+		virtual ~AstModule();
+		virtual RTLIL::IdString derive(RTLIL::Design *design, std::map<RTLIL::IdString, RTLIL::Const> parameters);
+		virtual void update_auto_wires(std::map<RTLIL::IdString, int> auto_sizes);
+	};
+
+	// this must be set by the language frontend before parsing the sources
+	// the AstNode constructor then uses current_filename and get_line_num()
+	// to initialize the filename and linenum properties of new nodes
+	extern std::string current_filename;
+	extern void (*set_line_num)(int);
+	extern int (*get_line_num)();
+
+	// set set_line_num and get_line_num to internal dummy functions
+	// (done by simplify(), AstModule::derive and AstModule::update_auto_wires to control
+	// the filename and linenum properties of new nodes not generated by a frontend parser)
+	void use_internal_line_num();
+}
+
+namespace AST_INTERNAL
+{
+	// internal state variables
+	extern bool flag_dump_ast, flag_dump_ast_diff, flag_nolatches, flag_nomem2reg;
+	extern AST::AstNode *current_ast, *current_ast_mod;
+	extern std::map<std::string, AST::AstNode*> current_scope;
+	extern RTLIL::SigSpec *genRTLIL_subst_from, *genRTLIL_subst_to;
+	extern AST::AstNode *current_top_block, *current_block, *current_block_child;
+	extern AST::AstModule *current_module;
+	struct ProcessGenerator;
+}
+
+#endif