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diff --git a/frontends/verilog/const2ast.cc b/frontends/verilog/const2ast.cc
new file mode 100644
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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.
+ *
+ *  ---
+ *
+ *  The Verilog frontend.
+ *
+ *  This frontend is using the AST frontend library (see frontends/ast/).
+ *  Thus this frontend does not generate RTLIL code directly but creates an
+ *  AST directly from the Verilog parse tree and then passes this AST to
+ *  the AST frontend library.
+ *
+ *  ---
+ *
+ *  This file contains an ad-hoc parser for Verilog constants. The Verilog
+ *  lexer does only recognize a constant but does not actually split it to its
+ *  components. I.e. it just passes the Verilog code for the constant to the
+ *  bison parser. The parser then uses the function const2ast() from this file
+ *  to create an AST node for the constant.
+ *
+ */
+
+#include "verilog_frontend.h"
+#include "kernel/log.h"
+#include <assert.h>
+#include <string.h>
+#include <math.h>
+
+using namespace AST;
+
+// divide an arbitrary length decimal number by two and return the rest
+static int my_decimal_div_by_two(std::vector<uint8_t> &digits)
+{
+	int carry = 0;
+	for (size_t i = 0; i < digits.size(); i++) {
+		assert(digits[i] < 10);
+		digits[i] += carry * 10;
+		carry = digits[i] % 2;
+		digits[i] /= 2;
+	}
+	return carry;
+}
+
+// find the number of significant bits in a binary number (not including the sign bit)
+static int my_ilog2(int x)
+{
+	int ret = 0;
+	while (x != 0 && x != -1) {
+		x = x >> 1;
+		ret++;
+	}
+	return ret;
+}
+
+// parse a binary, decimal, hexadecimal or octal number with support for special bits ('x', 'z' and '?')
+static void my_strtobin(std::vector<RTLIL::State> &data, const char *str, int len_in_bits, int base, char case_type)
+{
+	// all digits in string (MSB at index 0)
+	std::vector<uint8_t> digits;
+
+	while (*str) {
+		if ('0' <= *str && *str <= '9')
+			digits.push_back(*str - '0');
+		else if ('a' <= *str && *str <= 'f')
+			digits.push_back(10 + *str - 'a');
+		else if ('A' <= *str && *str <= 'F')
+			digits.push_back(10 + *str - 'A');
+		else if (*str == 'x' || *str == 'X')
+			digits.push_back(0xf0);
+		else if (*str == 'z' || *str == 'Z')
+			digits.push_back(0xf1);
+		else if (*str == '?')
+			digits.push_back(0xf2);
+		str++;
+	}
+
+	if (base == 10) {
+		data.clear();
+		if (len_in_bits < 0)
+			len_in_bits = ceil(digits.size()/log10(2));
+		for (int i = 0; i < len_in_bits; i++)
+			data.push_back(my_decimal_div_by_two(digits) ? RTLIL::S1 : RTLIL::S0);
+		return;
+	}
+
+	int bits_per_digit = my_ilog2(base-1);
+	if (len_in_bits < 0)
+		len_in_bits = digits.size() * bits_per_digit;
+
+	data.clear();
+	data.resize(len_in_bits);
+
+	for (int i = 0; i < len_in_bits; i++) {
+		int bitmask = 1 << (i % bits_per_digit);
+		int digitidx = digits.size() - (i / bits_per_digit) - 1;
+		if (digitidx < 0) {
+			if (i > 0 && (data[i-1] == RTLIL::Sz || data[i-1] == RTLIL::Sx || data[i-1] == RTLIL::Sa))
+				data[i] = data[i-1];
+			else
+				data[i] = RTLIL::S0;
+		} else if (digits[digitidx] == 0xf0)
+			data[i] = case_type == 'x' ? RTLIL::Sa : RTLIL::Sx;
+		else if (digits[digitidx] == 0xf1)
+			data[i] = case_type == 'x' || case_type == 'z' ? RTLIL::Sa : RTLIL::Sz;
+		else if (digits[digitidx] == 0xf2)
+			data[i] = RTLIL::Sa;
+		else
+			data[i] = (digits[digitidx] & bitmask) ? RTLIL::S1 : RTLIL::S0;
+	}
+}
+
+// convert the verilog code for a constant to an AST node
+AstNode *VERILOG_FRONTEND::const2ast(std::string code, char case_type)
+{
+	const char *str = code.c_str();
+
+	// Strings
+	if (*str == '"') {
+		int len = strlen(str) - 2;
+		std::vector<RTLIL::State> data;
+		data.reserve(len * 8);
+		for (int i = 0; i < len; i++) {
+			unsigned char ch = str[len - i];
+			for (int j = 0; j < 8; j++) {
+				data.push_back((ch & 1) ? RTLIL::S1 : RTLIL::S0);
+				ch = ch >> 1;
+			}
+		}
+		AstNode *ast = AstNode::mkconst_bits(data, false);
+		ast->str = code;
+		return ast;
+	}
+
+	for (size_t i = 0; i < code.size(); i++)
+		if (code[i] == '_' || code[i] == ' ' || code[i] == '\t' || code[i] == '\r' || code[i] == '\n')
+			code.erase(code.begin()+(i--));
+	str = code.c_str();
+
+	char *endptr;
+	long intval = strtol(str, &endptr, 10);
+
+	// Simple 32 bit integer
+	if (*endptr == 0)
+		return AstNode::mkconst_int(intval, true);
+	
+	// variable length constant
+	if (str == endptr)
+		intval = -1;
+
+	// The "<bits>'[bodh]<digits>" syntax
+	if (*endptr == '\'')
+	{
+		int len_in_bits = intval;
+		std::vector<RTLIL::State> data;
+		bool is_signed = false;
+		if (*(endptr+1) == 's') {
+			is_signed = true;
+			endptr++;
+		}
+		switch (*(endptr+1))
+		{
+		case 'b':
+			my_strtobin(data, endptr+2, len_in_bits, 2, case_type);
+			break;
+		case 'o':
+			my_strtobin(data, endptr+2, len_in_bits, 8, case_type);
+			break;
+		case 'd':
+			my_strtobin(data, endptr+2, len_in_bits, 10, case_type);
+			break;
+		case 'h':
+			my_strtobin(data, endptr+2, len_in_bits, 16, case_type);
+			break;
+		default:
+			goto error;
+		}
+		return AstNode::mkconst_bits(data, is_signed);
+	}
+
+error:
+	log_error("Value conversion failed: `%s'\n", code.c_str());
+}
+