simplify.cc

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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.
 *
 */

#include "kernel/log.h"
#include "libs/sha1/sha1.h"
#include "frontends/verilog/verilog_frontend.h"
#include "ast.h"

#include <sstream>
#include <stdarg.h>
#include <stdlib.h>
#include <math.h>

YOSYS_NAMESPACE_BEGIN

using namespace AST;
using namespace AST_INTERNAL;

// convert the AST into a simpler AST that has all parameters subsitited by their
// values, unrolled for-loops, expanded generate blocks, etc. when this function
// is done with an AST it can be converted into RTLIL using genRTLIL().
//
// this function also does all name resolving and sets the id2ast member of all
// nodes that link to a different node using names and lexical scoping.
bool AstNode::simplify(bool const_fold, bool at_zero, bool in_lvalue, int stage, int width_hint, bool sign_hint, bool in_param)
{
    AstNode *newNode = NULL;
    bool did_something = false;

#if 0
    log("-------------\n");
    log("const_fold=%d, at_zero=%d, in_lvalue=%d, stage=%d, width_hint=%d, sign_hint=%d, in_param=%d\n",
            int(const_fold), int(at_zero), int(in_lvalue), int(stage), int(width_hint), int(sign_hint), int(in_param));
    dumpAst(NULL, "> ");
#endif

    if (stage == 0)
    {
        log_assert(type == AST_MODULE);

        while (simplify(const_fold, at_zero, in_lvalue, 1, width_hint, sign_hint, in_param)) { }

        if (!flag_nomem2reg && !get_bool_attribute("\\nomem2reg"))
        {
            std::map<AstNode*, std::set<std::string>> mem2reg_places;
            std::map<AstNode*, uint32_t> mem2reg_candidates, dummy_proc_flags;
            uint32_t flags = flag_mem2reg ? AstNode::MEM2REG_FL_ALL : 0;
            mem2reg_as_needed_pass1(mem2reg_places, mem2reg_candidates, dummy_proc_flags, flags);

            std::set<AstNode*> mem2reg_set;
            for (auto &it : mem2reg_candidates)
            {
                AstNode *mem = it.first;
                uint32_t memflags = it.second;
                log_assert((memflags & ~0x00ffff00) == 0);

                if (mem->get_bool_attribute("\\nomem2reg"))
                    continue;

                if (memflags & AstNode::MEM2REG_FL_FORCED)
                    goto silent_activate;

                if (memflags & AstNode::MEM2REG_FL_EQ2)
                    goto verbose_activate;

                if (memflags & AstNode::MEM2REG_FL_SET_ASYNC)
                    goto verbose_activate;

                if ((memflags & AstNode::MEM2REG_FL_SET_INIT) && (memflags & AstNode::MEM2REG_FL_SET_ELSE))
                    goto verbose_activate;

                if (memflags & AstNode::MEM2REG_FL_CMPLX_LHS)
                    goto verbose_activate;

                // log("Note: Not replacing memory %s with list of registers (flags=0x%08lx).\n", mem->str.c_str(), long(memflags));
                continue;

            verbose_activate:
                if (mem2reg_set.count(mem) == 0) {
                    log_warning("Replacing memory %s with list of registers.", mem->str.c_str());
                    bool first_element = true;
                    for (auto &place : mem2reg_places[it.first]) {
                        log("%s%s", first_element ? " See " : ", ", place.c_str());
                        first_element = false;
                    }
                    log("\n");
                }

            silent_activate:
                // log("Note: Replacing memory %s with list of registers (flags=0x%08lx).\n", mem->str.c_str(), long(memflags));
                mem2reg_set.insert(mem);
            }

            for (auto node : mem2reg_set)
            {
                int mem_width, mem_size, addr_bits;
                node->meminfo(mem_width, mem_size, addr_bits);

                for (int i = 0; i < mem_size; i++) {
                    AstNode *reg = new AstNode(AST_WIRE, new AstNode(AST_RANGE,
                            mkconst_int(mem_width-1, true), mkconst_int(0, true)));
                    reg->str = stringf("%s[%d]", node->str.c_str(), i);
                    reg->is_reg = true;
                    reg->is_signed = node->is_signed;
                    children.push_back(reg);
                    while (reg->simplify(true, false, false, 1, -1, false, false)) { }
                }
            }

            mem2reg_as_needed_pass2(mem2reg_set, this, NULL);

            for (size_t i = 0; i < children.size(); i++) {
                if (mem2reg_set.count(children[i]) > 0) {
                    delete children[i];
                    children.erase(children.begin() + (i--));
                }
            }
        }

        while (simplify(const_fold, at_zero, in_lvalue, 2, width_hint, sign_hint, in_param)) { }
        return false;
    }

    current_filename = filename;
    set_line_num(linenum);

    // we do not look inside a task or function
    // (but as soon as a task of function is instanciated we process the generated AST as usual)
    if (type == AST_FUNCTION || type == AST_TASK)
        return false;

    // deactivate all calls to non-synthesis system taks
    if ((type == AST_FCALL || type == AST_TCALL) && (str == "$display" || str == "$stop" || str == "$finish")) {
        delete_children();
        str = std::string();
    }

    // activate const folding if this is anything that must be evaluated statically (ranges, parameters, attributes, etc.)
    if (type == AST_WIRE || type == AST_PARAMETER || type == AST_LOCALPARAM || type == AST_DEFPARAM || type == AST_PARASET || type == AST_RANGE || type == AST_PREFIX)
        const_fold = true;
    if (type == AST_IDENTIFIER && current_scope.count(str) > 0 && (current_scope[str]->type == AST_PARAMETER || current_scope[str]->type == AST_LOCALPARAM))
        const_fold = true;

    // in certain cases a function must be evaluated constant. this is what in_param controls.
    if (type == AST_PARAMETER || type == AST_LOCALPARAM || type == AST_DEFPARAM || type == AST_PARASET || type == AST_PREFIX)
        in_param = true;

    std::map<std::string, AstNode*> backup_scope;

    // create name resolution entries for all objects with names
    // also merge multiple declarations for the same wire (e.g. "output foobar; reg foobar;")
    if (type == AST_MODULE) {
        current_scope.clear();
        std::map<std::string, AstNode*> this_wire_scope;
        for (size_t i = 0; i < children.size(); i++) {
            AstNode *node = children[i];
            if (node->type == AST_WIRE) {
                if (this_wire_scope.count(node->str) > 0) {
                    AstNode *first_node = this_wire_scope[node->str];
                    if (!node->is_input && !node->is_output && node->is_reg && node->children.size() == 0)
                        goto wires_are_compatible;
                    if (first_node->children.size() != node->children.size())
                        goto wires_are_incompatible;
                    for (size_t j = 0; j < node->children.size(); j++) {
                        AstNode *n1 = first_node->children[j], *n2 = node->children[j];
                        if (n1->type == AST_RANGE && n2->type == AST_RANGE && n1->range_valid && n2->range_valid) {
                            if (n1->range_left != n2->range_left)
                                goto wires_are_incompatible;
                            if (n1->range_right != n2->range_right)
                                goto wires_are_incompatible;
                        } else if (*n1 != *n2)
                            goto wires_are_incompatible;
                    }
                    if (first_node->range_left != node->range_left)
                        goto wires_are_incompatible;
                    if (first_node->range_right != node->range_right)
                        goto wires_are_incompatible;
                    if (first_node->port_id == 0 && (node->is_input || node->is_output))
                        goto wires_are_incompatible;
                wires_are_compatible:
                    if (node->is_input)
                        first_node->is_input = true;
                    if (node->is_output)
                        first_node->is_output = true;
                    if (node->is_reg)
                        first_node->is_reg = true;
                    if (node->is_signed)
                        first_node->is_signed = true;
                    for (auto &it : node->attributes) {
                        if (first_node->attributes.count(it.first) > 0)
                            delete first_node->attributes[it.first];
                        first_node->attributes[it.first] = it.second->clone();
                    }
                    children.erase(children.begin()+(i--));
                    did_something = true;
                    delete node;
                    continue;
                wires_are_incompatible:
                    if (stage > 1)
                        log_error("Incompatible re-declaration of wire %s at %s:%d.\n", node->str.c_str(), filename.c_str(), linenum);
                    continue;
                }
                this_wire_scope[node->str] = node;
            }
            if (node->type == AST_PARAMETER || node->type == AST_LOCALPARAM || node->type == AST_WIRE || node->type == AST_AUTOWIRE || node->type == AST_GENVAR ||
                    node->type == AST_MEMORY || node->type == AST_FUNCTION || node->type == AST_TASK || node->type == AST_DPI_FUNCTION || node->type == AST_CELL) {
                backup_scope[node->str] = current_scope[node->str];
                current_scope[node->str] = node;
            }
        }
        for (size_t i = 0; i < children.size(); i++) {
            AstNode *node = children[i];
            if (node->type == AST_PARAMETER || node->type == AST_LOCALPARAM || node->type == AST_WIRE || node->type == AST_AUTOWIRE)
                while (node->simplify(true, false, false, 1, -1, false, node->type == AST_PARAMETER || node->type == AST_LOCALPARAM))
                    did_something = true;
        }
    }

    auto backup_current_block = current_block;
    auto backup_current_block_child = current_block_child;
    auto backup_current_top_block = current_top_block;

    int backup_width_hint = width_hint;
    bool backup_sign_hint = sign_hint;

    bool detect_width_simple = false;
    bool child_0_is_self_determined = false;
    bool child_1_is_self_determined = false;
    bool child_2_is_self_determined = false;
    bool children_are_self_determined = false;
    bool reset_width_after_children = false;

    switch (type)
    {
    case AST_ASSIGN_EQ:
    case AST_ASSIGN_LE:
    case AST_ASSIGN:
        while (!children[0]->basic_prep && children[0]->simplify(false, false, true, stage, -1, false, in_param) == true)
            did_something = true;
        while (!children[1]->basic_prep && children[1]->simplify(false, false, false, stage, -1, false, in_param) == true)
            did_something = true;
        children[0]->detectSignWidth(backup_width_hint, backup_sign_hint);
        children[1]->detectSignWidth(width_hint, sign_hint);
        width_hint = std::max(width_hint, backup_width_hint);
        child_0_is_self_determined = true;
        break;

    case AST_PARAMETER:
    case AST_LOCALPARAM:
        while (!children[0]->basic_prep && children[0]->simplify(false, false, false, stage, -1, false, true) == true)
            did_something = true;
        children[0]->detectSignWidth(width_hint, sign_hint);
        if (children.size() > 1 && children[1]->type == AST_RANGE) {
            while (!children[1]->basic_prep && children[1]->simplify(false, false, false, stage, -1, false, true) == true)
                did_something = true;
            if (!children[1]->range_valid)
                log_error("Non-constant width range on parameter decl at %s:%d.\n", filename.c_str(), linenum);
            width_hint = std::max(width_hint, children[1]->range_left - children[1]->range_right + 1);
        }
        break;

    case AST_TO_BITS:
    case AST_TO_SIGNED:
    case AST_TO_UNSIGNED:
    case AST_CONCAT:
    case AST_REPLICATE:
    case AST_REDUCE_AND:
    case AST_REDUCE_OR:
    case AST_REDUCE_XOR:
    case AST_REDUCE_XNOR:
    case AST_REDUCE_BOOL:
        detect_width_simple = true;
        children_are_self_determined = true;
        break;

    case AST_NEG:
    case AST_BIT_NOT:
    case AST_POS:
    case AST_BIT_AND:
    case AST_BIT_OR:
    case AST_BIT_XOR:
    case AST_BIT_XNOR:
    case AST_ADD:
    case AST_SUB:
    case AST_MUL:
    case AST_DIV:
    case AST_MOD:
        detect_width_simple = true;
        break;

    case AST_SHIFT_LEFT:
    case AST_SHIFT_RIGHT:
    case AST_SHIFT_SLEFT:
    case AST_SHIFT_SRIGHT:
    case AST_POW:
        detect_width_simple = true;
        child_1_is_self_determined = true;
        break;

    case AST_LT:
    case AST_LE:
    case AST_EQ:
    case AST_NE:
    case AST_EQX:
    case AST_NEX:
    case AST_GE:
    case AST_GT:
        width_hint = -1;
        sign_hint = true;
        for (auto child : children) {
            while (!child->basic_prep && child->simplify(false, false, in_lvalue, stage, -1, false, in_param) == true)
                did_something = true;
            child->detectSignWidthWorker(width_hint, sign_hint);
        }
        reset_width_after_children = true;
        break;

    case AST_LOGIC_AND:
    case AST_LOGIC_OR:
    case AST_LOGIC_NOT:
        detect_width_simple = true;
        children_are_self_determined = true;
        break;

    case AST_TERNARY:
        detect_width_simple = true;
        child_0_is_self_determined = true;
        break;
    
    case AST_MEMRD:
        detect_width_simple = true;
        children_are_self_determined = true;
        break;

    default:
        width_hint = -1;
        sign_hint = false;
    }

    if (detect_width_simple && width_hint < 0) {
        if (type == AST_REPLICATE)
            while (children[0]->simplify(true, false, in_lvalue, stage, -1, false, true) == true)
                did_something = true;
        for (auto child : children)
            while (!child->basic_prep && child->simplify(false, false, in_lvalue, stage, -1, false, in_param) == true)
                did_something = true;
        detectSignWidth(width_hint, sign_hint);
    }

    if (type == AST_TERNARY) {
        int width_hint_left, width_hint_right;
        bool sign_hint_left, sign_hint_right;
        bool found_real_left, found_real_right;
        children[1]->detectSignWidth(width_hint_left, sign_hint_left, &found_real_left);
        children[2]->detectSignWidth(width_hint_right, sign_hint_right, &found_real_right);
        if (found_real_left || found_real_right) {
            child_1_is_self_determined = true;
            child_2_is_self_determined = true;
        }
    }

    if (const_fold && type == AST_CASE)
    {
        while (children[0]->simplify(const_fold, at_zero, in_lvalue, stage, width_hint, sign_hint, in_param)) { }
        if (children[0]->type == AST_CONSTANT && children[0]->bits_only_01()) {
            std::vector<AstNode*> new_children;
            new_children.push_back(children[0]);
            for (int i = 1; i < GetSize(children); i++) {
                AstNode *child = children[i];
                log_assert(child->type == AST_COND);
                for (auto v : child->children) {
                    if (v->type == AST_DEFAULT)
                        goto keep_const_cond;
                    if (v->type == AST_BLOCK)
                        continue;
                    while (v->simplify(const_fold, at_zero, in_lvalue, stage, width_hint, sign_hint, in_param)) { }
                    if (v->type == AST_CONSTANT && v->bits_only_01()) {
                        if (v->bits == children[0]->bits) {
                            while (i+1 < GetSize(children))
                                delete children[++i];
                            goto keep_const_cond;
                        }
                        continue;
                    }
                    goto keep_const_cond;
                }
                if (0)
            keep_const_cond:
                    new_children.push_back(child);
                else
                    delete child;
            }
            new_children.swap(children);
        }
    }

    // simplify all children first
    // (iterate by index as e.g. auto wires can add new children in the process)
    for (size_t i = 0; i < children.size(); i++) {
        bool did_something_here = true;
        if ((type == AST_GENFOR || type == AST_FOR) && i >= 3)
            break;
        if ((type == AST_GENIF || type == AST_GENCASE) && i >= 1)
            break;
        if (type == AST_GENBLOCK)
            break;
        if (type == AST_BLOCK && !str.empty())
            break;
        if (type == AST_PREFIX && i >= 1)
            break;
        while (did_something_here && i < children.size()) {
            bool const_fold_here = const_fold, in_lvalue_here = in_lvalue;
            int width_hint_here = width_hint;
            bool sign_hint_here = sign_hint;
            bool in_param_here = in_param;
            if (i == 0 && (type == AST_REPLICATE || type == AST_WIRE))
                const_fold_here = true, in_param_here = true;
            if (type == AST_PARAMETER || type == AST_LOCALPARAM)
                const_fold_here = true;
            if (i == 0 && (type == AST_ASSIGN || type == AST_ASSIGN_EQ || type == AST_ASSIGN_LE))
                in_lvalue_here = true;
            if (type == AST_BLOCK) {
                current_block = this;
                current_block_child = children[i];
            }
            if ((type == AST_ALWAYS || type == AST_INITIAL) && children[i]->type == AST_BLOCK)
                current_top_block = children[i];
            if (i == 0 && child_0_is_self_determined)
                width_hint_here = -1, sign_hint_here = false;
            if (i == 1 && child_1_is_self_determined)
                width_hint_here = -1, sign_hint_here = false;
            if (i == 2 && child_2_is_self_determined)
                width_hint_here = -1, sign_hint_here = false;
            if (children_are_self_determined)
                width_hint_here = -1, sign_hint_here = false;
            did_something_here = children[i]->simplify(const_fold_here, at_zero, in_lvalue_here, stage, width_hint_here, sign_hint_here, in_param_here);
            if (did_something_here)
                did_something = true;
        }
        if (stage == 2 && children[i]->type == AST_INITIAL && current_ast_mod != this) {
            current_ast_mod->children.push_back(children[i]);
            children.erase(children.begin() + (i--));
            did_something = true;
        }
    }
    for (auto &attr : attributes) {
        while (attr.second->simplify(true, false, false, stage, -1, false, true))
            did_something = true;
    }

    if (reset_width_after_children) {
        width_hint = backup_width_hint;
        sign_hint = backup_sign_hint;
        if (width_hint < 0)
            detectSignWidth(width_hint, sign_hint);
    }

    current_block = backup_current_block;
    current_block_child = backup_current_block_child;
    current_top_block = backup_current_top_block;

    for (auto it = backup_scope.begin(); it != backup_scope.end(); it++) {
        if (it->second == NULL)
            current_scope.erase(it->first);
        else
            current_scope[it->first] = it->second;
    }

    current_filename = filename;
    set_line_num(linenum);

    if (type == AST_MODULE)
        current_scope.clear();

    // convert defparam nodes to cell parameters
    if (type == AST_DEFPARAM && !str.empty()) {
        size_t pos = str.rfind('.');
        if (pos == std::string::npos)
            log_error("Defparam `%s' does not contain a dot (module/parameter separator) at %s:%d!\n",
                    RTLIL::unescape_id(str).c_str(), filename.c_str(), linenum);
        std::string modname = str.substr(0, pos), paraname = "\\" + str.substr(pos+1);
        if (current_scope.count(modname) == 0 || current_scope.at(modname)->type != AST_CELL)
            log_error("Can't find cell for defparam `%s . %s` at %s:%d!\n", RTLIL::unescape_id(modname).c_str(), RTLIL::unescape_id(paraname).c_str(), filename.c_str(), linenum);
        AstNode *cell = current_scope.at(modname), *paraset = clone();
        cell->children.insert(cell->children.begin() + 1, paraset);
        paraset->type = AST_PARASET;
        paraset->str = paraname;
        str.clear();
    }

    // resolve constant prefixes
    if (type == AST_PREFIX) {
        if (children[0]->type != AST_CONSTANT) {
            // dumpAst(NULL, ">   ");
            log_error("Index in generate block prefix syntax at %s:%d is not constant!\n", filename.c_str(), linenum);
        }
        log_assert(children[1]->type == AST_IDENTIFIER);
        newNode = children[1]->clone();
        const char *second_part = children[1]->str.c_str();
        if (second_part[0] == '\\')
            second_part++;
        newNode->str = stringf("%s[%d].%s", str.c_str(), children[0]->integer, second_part);
        goto apply_newNode;
    }

    // evaluate TO_BITS nodes
    if (type == AST_TO_BITS) {
        if (children[0]->type != AST_CONSTANT)
            log_error("Left operand of to_bits expression is not constant at %s:%d!\n", filename.c_str(), linenum);
        if (children[1]->type != AST_CONSTANT)
            log_error("Right operand of to_bits expression is not constant at %s:%d!\n", filename.c_str(), linenum);
        RTLIL::Const new_value = children[1]->bitsAsConst(children[0]->bitsAsConst().as_int(), children[1]->is_signed);
        newNode = mkconst_bits(new_value.bits, children[1]->is_signed);
        goto apply_newNode;
    }

    // annotate constant ranges
    if (type == AST_RANGE) {
        bool old_range_valid = range_valid;
        range_valid = false;
        range_swapped = false;
        range_left = -1;
        range_right = 0;
        log_assert(children.size() >= 1);
        if (children[0]->type == AST_CONSTANT) {
            range_valid = true;
            range_left = children[0]->integer;
            if (children.size() == 1)
                range_right = range_left;
        }
        if (children.size() >= 2) {
            if (children[1]->type == AST_CONSTANT)
                range_right = children[1]->integer;
            else
                range_valid = false;
        }
        if (old_range_valid != range_valid)
            did_something = true;
        if (range_valid && range_left >= 0 && range_right > range_left) {
            int tmp = range_right;
            range_right = range_left;
            range_left = tmp;
            range_swapped = true;
        }
    }

    // annotate wires with their ranges
    if (type == AST_WIRE) {
        if (children.size() > 0) {
            if (children[0]->range_valid) {
                if (!range_valid)
                    did_something = true;
                range_valid = true;
                range_swapped = children[0]->range_swapped;
                range_left = children[0]->range_left;
                range_right = children[0]->range_right;
            }
        } else {
            if (!range_valid)
                did_something = true;
            range_valid = true;
            range_swapped = false;
            range_left = 0;
            range_right = 0;
        }
    }

    // resolve multiranges on memory decl
    if (type == AST_MEMORY && children.size() > 1 && children[1]->type == AST_MULTIRANGE)
    {
        int total_size = 1;
        multirange_dimensions.clear();
        for (auto range : children[1]->children) {
            if (!range->range_valid)
                log_error("Non-constant range on memory decl at %s:%d.\n", filename.c_str(), linenum);
            multirange_dimensions.push_back(std::min(range->range_left, range->range_right));
            multirange_dimensions.push_back(std::max(range->range_left, range->range_right) - std::min(range->range_left, range->range_right) + 1);
            total_size *= multirange_dimensions.back();
        }
        delete children[1];
        children[1] = new AstNode(AST_RANGE, AstNode::mkconst_int(0, true), AstNode::mkconst_int(total_size-1, true));
        did_something = true;
    }

    // resolve multiranges on memory access
    if (type == AST_IDENTIFIER && id2ast && id2ast->type == AST_MEMORY && children.size() > 0 && children[0]->type == AST_MULTIRANGE)
    {
        AstNode *index_expr = nullptr;

        for (int i = 0; 2*i < GetSize(id2ast->multirange_dimensions); i++)
        {
            if (GetSize(children[0]->children) < i)
                log_error("Insufficient number of array indices for %s at %s:%d.\n", log_id(str), filename.c_str(), linenum);

            AstNode *new_index_expr = children[0]->children[i]->children.at(0)->clone();

            if (id2ast->multirange_dimensions[2*i])
                new_index_expr = new AstNode(AST_SUB, new_index_expr, AstNode::mkconst_int(id2ast->multirange_dimensions[2*i], true));

            if (i == 0)
                index_expr = new_index_expr;
            else
                index_expr = new AstNode(AST_ADD, new AstNode(AST_MUL, index_expr, AstNode::mkconst_int(id2ast->multirange_dimensions[2*i-1], true)), new_index_expr);
        }

        for (int i = GetSize(id2ast->multirange_dimensions)/1; i < GetSize(children[0]->children); i++)
            children.push_back(children[0]->children[i]->clone());

        delete children[0];
        if (index_expr == nullptr)
            children.erase(children.begin());
        else
            children[0] = new AstNode(AST_RANGE, index_expr);

        did_something = true;
    }

    // trim/extend parameters
    if (type == AST_PARAMETER || type == AST_LOCALPARAM) {
        if (children.size() > 1 && children[1]->type == AST_RANGE) {
            if (!children[1]->range_valid)
                log_error("Non-constant width range on parameter decl at %s:%d.\n", filename.c_str(), linenum);
            int width = children[1]->range_left - children[1]->range_right + 1;
            if (children[0]->type == AST_REALVALUE) {
                RTLIL::Const constvalue = children[0]->realAsConst(width);
                log_warning("converting real value %e to binary %s at %s:%d.\n",
                        children[0]->realvalue, log_signal(constvalue), filename.c_str(), linenum);
                delete children[0];
                children[0] = mkconst_bits(constvalue.bits, sign_hint);
                did_something = true;
            }
            if (children[0]->type == AST_CONSTANT) {
                if (width != int(children[0]->bits.size())) {
                    RTLIL::SigSpec sig(children[0]->bits);
                    sig.extend_u0(width, children[0]->is_signed);
                    AstNode *old_child_0 = children[0];
                    children[0] = mkconst_bits(sig.as_const().bits, children[0]->is_signed);
                    delete old_child_0;
                }
                children[0]->is_signed = is_signed;
            }
            range_valid = true;
            range_swapped = children[1]->range_swapped;
            range_left = children[1]->range_left;
            range_right = children[1]->range_right;
        } else
        if (children.size() > 1 && children[1]->type == AST_REALVALUE && children[0]->type == AST_CONSTANT) {
            double as_realvalue = children[0]->asReal(sign_hint);
            delete children[0];
            children[0] = new AstNode(AST_REALVALUE);
            children[0]->realvalue = as_realvalue;
            did_something = true;
        }
    }

    // annotate identifiers using scope resolution and create auto-wires as needed
    if (type == AST_IDENTIFIER) {
        if (current_scope.count(str) == 0) {
            for (auto node : current_ast_mod->children) {
                if ((node->type == AST_PARAMETER || node->type == AST_LOCALPARAM || node->type == AST_WIRE || node->type == AST_AUTOWIRE || node->type == AST_GENVAR ||
                        node->type == AST_MEMORY || node->type == AST_FUNCTION || node->type == AST_TASK || node->type == AST_DPI_FUNCTION) && str == node->str) {
                    current_scope[node->str] = node;
                    break;
                }
            }
        }
        if (current_scope.count(str) == 0) {
            // log_warning("Creating auto-wire `%s' in module `%s'.\n", str.c_str(), current_ast_mod->str.c_str());
            AstNode *auto_wire = new AstNode(AST_AUTOWIRE);
            auto_wire->str = str;
            current_ast_mod->children.push_back(auto_wire);
            current_scope[str] = auto_wire;
            did_something = true;
        }
        if (id2ast != current_scope[str]) {
            id2ast = current_scope[str];
            did_something = true;
        }
    }

    // split memory access with bit select to individual statements
    if (type == AST_IDENTIFIER && children.size() == 2 && children[0]->type == AST_RANGE && children[1]->type == AST_RANGE && !in_lvalue)
    {
        if (id2ast == NULL || id2ast->type != AST_MEMORY || children[0]->children.size() != 1)
            log_error("Invalid bit-select on memory access at %s:%d!\n", filename.c_str(), linenum);

        int mem_width, mem_size, addr_bits;
        id2ast->meminfo(mem_width, mem_size, addr_bits);

        std::stringstream sstr;
        sstr << "$mem2bits$" << children[0]->str << "$" << filename << ":" << linenum << "$" << (autoidx++);
        std::string wire_id = sstr.str();

        AstNode *wire = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(mem_width-1, true), mkconst_int(0, true)));
        wire->str = wire_id;
        if (current_block)
            wire->attributes["\\nosync"] = AstNode::mkconst_int(1, false);
        current_ast_mod->children.push_back(wire);
        while (wire->simplify(true, false, false, 1, -1, false, false)) { }

        AstNode *data = clone();
        delete data->children[1];
        data->children.pop_back();

        AstNode *assign = new AstNode(AST_ASSIGN_EQ, new AstNode(AST_IDENTIFIER), data);
        assign->children[0]->str = wire_id;

        if (current_block)
        {
            size_t assign_idx = 0;
            while (assign_idx < current_block->children.size() && current_block->children[assign_idx] != current_block_child)
                assign_idx++;
            log_assert(assign_idx < current_block->children.size());
            current_block->children.insert(current_block->children.begin()+assign_idx, assign);
            wire->is_reg = true;
        }
        else
        {
            AstNode *proc = new AstNode(AST_ALWAYS, new AstNode(AST_BLOCK));
            proc->children[0]->children.push_back(assign);
            current_ast_mod->children.push_back(proc);
        }

        newNode = new AstNode(AST_IDENTIFIER, children[1]->clone());
        newNode->str = wire_id;
        newNode->id2ast = wire;
        goto apply_newNode;
    }

    if (type == AST_WHILE)
        log_error("While loops are only allowed in constant functions at %s:%d!\n", filename.c_str(), linenum);

    if (type == AST_REPEAT)
        log_error("Repeat loops are only allowed in constant functions at %s:%d!\n", filename.c_str(), linenum);

    // unroll for loops and generate-for blocks
    if ((type == AST_GENFOR || type == AST_FOR) && children.size() != 0)
    {
        AstNode *init_ast = children[0];
        AstNode *while_ast = children[1];
        AstNode *next_ast = children[2];
        AstNode *body_ast = children[3];

        while (body_ast->type == AST_GENBLOCK && body_ast->str.empty() &&
                body_ast->children.size() == 1 && body_ast->children.at(0)->type == AST_GENBLOCK)
            body_ast = body_ast->children.at(0);

        if (init_ast->type != AST_ASSIGN_EQ)
            log_error("Unsupported 1st expression of generate for-loop at %s:%d!\n", filename.c_str(), linenum);
        if (next_ast->type != AST_ASSIGN_EQ)
            log_error("Unsupported 3rd expression of generate for-loop at %s:%d!\n", filename.c_str(), linenum);

        if (type == AST_GENFOR) {
            if (init_ast->children[0]->id2ast == NULL || init_ast->children[0]->id2ast->type != AST_GENVAR)
                log_error("Left hand side of 1st expression of generate for-loop at %s:%d is not a gen var!\n", filename.c_str(), linenum);
            if (next_ast->children[0]->id2ast == NULL || next_ast->children[0]->id2ast->type != AST_GENVAR)
                log_error("Left hand side of 3rd expression of generate for-loop at %s:%d is not a gen var!\n", filename.c_str(), linenum);
        } else {
            if (init_ast->children[0]->id2ast == NULL || init_ast->children[0]->id2ast->type != AST_WIRE)
                log_error("Left hand side of 1st expression of generate for-loop at %s:%d is not a register!\n", filename.c_str(), linenum);
            if (next_ast->children[0]->id2ast == NULL || next_ast->children[0]->id2ast->type != AST_WIRE)
                log_error("Left hand side of 3rd expression of generate for-loop at %s:%d is not a register!\n", filename.c_str(), linenum);
        }

        if (init_ast->children[0]->id2ast != next_ast->children[0]->id2ast)
            log_error("Incompatible left-hand sides in 1st and 3rd expression of generate for-loop at %s:%d!\n", filename.c_str(), linenum);

        // eval 1st expression
        AstNode *varbuf = init_ast->children[1]->clone();
        while (varbuf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }

        if (varbuf->type != AST_CONSTANT)
            log_error("Right hand side of 1st expression of generate for-loop at %s:%d is not constant!\n", filename.c_str(), linenum);

        varbuf = new AstNode(AST_LOCALPARAM, varbuf);
        varbuf->str = init_ast->children[0]->str;

        AstNode *backup_scope_varbuf = current_scope[varbuf->str];
        current_scope[varbuf->str] = varbuf;

        size_t current_block_idx = 0;
        if (type == AST_FOR) {
            while (current_block_idx < current_block->children.size() &&
                    current_block->children[current_block_idx] != current_block_child)
                current_block_idx++;
        }

        while (1)
        {
            // eval 2nd expression
            AstNode *buf = while_ast->clone();
            while (buf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }

            if (buf->type != AST_CONSTANT)
                log_error("2nd expression of generate for-loop at %s:%d is not constant!\n", filename.c_str(), linenum);

            if (buf->integer == 0) {
                delete buf;
                break;
            }
            delete buf;

            // expand body
            int index = varbuf->children[0]->integer;
            if (body_ast->type == AST_GENBLOCK)
                buf = body_ast->clone();
            else
                buf = new AstNode(AST_GENBLOCK, body_ast->clone());
            if (buf->str.empty()) {
                std::stringstream sstr;
                sstr << "$genblock$" << filename << ":" << linenum << "$" << (autoidx++);
                buf->str = sstr.str();
            }
            std::map<std::string, std::string> name_map;
            std::stringstream sstr;
            sstr << buf->str << "[" << index << "].";
            buf->expand_genblock(varbuf->str, sstr.str(), name_map);

            if (type == AST_GENFOR) {
                for (size_t i = 0; i < buf->children.size(); i++) {
                    buf->children[i]->simplify(false, false, false, stage, -1, false, false);
                    current_ast_mod->children.push_back(buf->children[i]);
                }
            } else {
                for (size_t i = 0; i < buf->children.size(); i++)
                    current_block->children.insert(current_block->children.begin() + current_block_idx++, buf->children[i]);
            }
            buf->children.clear();
            delete buf;

            // eval 3rd expression
            buf = next_ast->children[1]->clone();
            while (buf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }

            if (buf->type != AST_CONSTANT)
                log_error("Right hand side of 3rd expression of generate for-loop at %s:%d is not constant!\n", filename.c_str(), linenum);

            delete varbuf->children[0];
            varbuf->children[0] = buf;
        }

        current_scope[varbuf->str] = backup_scope_varbuf;
        delete varbuf;
        delete_children();
        did_something = true;
    }

    // transform block with name
    if (type == AST_BLOCK && !str.empty())
    {
        std::map<std::string, std::string> name_map;
        expand_genblock(std::string(), str + ".", name_map);

        std::vector<AstNode*> new_children;
        for (size_t i = 0; i < children.size(); i++)
            if (children[i]->type == AST_WIRE) {
                children[i]->simplify(false, false, false, stage, -1, false, false);
                current_ast_mod->children.push_back(children[i]);
                current_scope[children[i]->str] = children[i];
            } else
                new_children.push_back(children[i]);

        children.swap(new_children);
        did_something = true;
        str.clear();
    }

    // simplify unconditional generate block
    if (type == AST_GENBLOCK && children.size() != 0)
    {
        if (!str.empty()) {
            std::map<std::string, std::string> name_map;
            expand_genblock(std::string(), str + ".", name_map);
        }

        for (size_t i = 0; i < children.size(); i++) {
            children[i]->simplify(false, false, false, stage, -1, false, false);
            current_ast_mod->children.push_back(children[i]);
        }

        children.clear();
        did_something = true;
    }

    // simplify generate-if blocks
    if (type == AST_GENIF && children.size() != 0)
    {
        AstNode *buf = children[0]->clone();
        while (buf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
        if (buf->type != AST_CONSTANT) {
            // for (auto f : log_files)
            //  dumpAst(f, "verilog-ast> ");
            log_error("Condition for generate if at %s:%d is not constant!\n", filename.c_str(), linenum);
        }
        if (buf->asBool() != 0) {
            delete buf;
            buf = children[1]->clone();
        } else {
            delete buf;
            buf = children.size() > 2 ? children[2]->clone() : NULL;
        }

        if (buf)
        {
            if (buf->type != AST_GENBLOCK)
                buf = new AstNode(AST_GENBLOCK, buf);

            if (!buf->str.empty()) {
                std::map<std::string, std::string> name_map;
                buf->expand_genblock(std::string(), buf->str + ".", name_map);
            }

            for (size_t i = 0; i < buf->children.size(); i++) {
                buf->children[i]->simplify(false, false, false, stage, -1, false, false);
                current_ast_mod->children.push_back(buf->children[i]);
            }

            buf->children.clear();
            delete buf;
        }

        delete_children();
        did_something = true;
    }

    // simplify generate-case blocks
    if (type == AST_GENCASE && children.size() != 0)
    {
        AstNode *buf = children[0]->clone();
        while (buf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
        if (buf->type != AST_CONSTANT) {
            // for (auto f : log_files)
            //  dumpAst(f, "verilog-ast> ");
            log_error("Condition for generate case at %s:%d is not constant!\n", filename.c_str(), linenum);
        }

        bool ref_signed = buf->is_signed;
        RTLIL::Const ref_value = buf->bitsAsConst();
        delete buf;

        AstNode *selected_case = NULL;
        for (size_t i = 1; i < children.size(); i++)
        {
            log_assert(children.at(i)->type == AST_COND);

            AstNode *this_genblock = NULL;
            for (auto child : children.at(i)->children) {
                log_assert(this_genblock == NULL);
                if (child->type == AST_GENBLOCK)
                    this_genblock = child;
            }

            for (auto child : children.at(i)->children)
            {
                if (child->type == AST_DEFAULT) {
                    if (selected_case == NULL)
                        selected_case = this_genblock;
                    continue;
                }
                if (child->type == AST_GENBLOCK)
                    continue;

                buf = child->clone();
                while (buf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                if (buf->type != AST_CONSTANT) {
                    // for (auto f : log_files)
                    //  dumpAst(f, "verilog-ast> ");
                    log_error("Expression in generate case at %s:%d is not constant!\n", filename.c_str(), linenum);
                }

                bool is_selected = RTLIL::const_eq(ref_value, buf->bitsAsConst(), ref_signed && buf->is_signed, ref_signed && buf->is_signed, 1).as_bool();
                delete buf;

                if (is_selected) {
                    selected_case = this_genblock;
                    i = children.size();
                    break;
                }
            }
        }

        if (selected_case != NULL)
        {
            log_assert(selected_case->type == AST_GENBLOCK);
            buf = selected_case->clone();

            if (!buf->str.empty()) {
                std::map<std::string, std::string> name_map;
                buf->expand_genblock(std::string(), buf->str + ".", name_map);
            }

            for (size_t i = 0; i < buf->children.size(); i++) {
                buf->children[i]->simplify(false, false, false, stage, -1, false, false);
                current_ast_mod->children.push_back(buf->children[i]);
            }

            buf->children.clear();
            delete buf;
        }

        delete_children();
        did_something = true;
    }

    // unroll cell arrays
    if (type == AST_CELLARRAY)
    {
        if (!children.at(0)->range_valid)
            log_error("Non-constant array range on cell array at %s:%d.\n", filename.c_str(), linenum);

        newNode = new AstNode(AST_GENBLOCK);
        int num = std::max(children.at(0)->range_left, children.at(0)->range_right) - std::min(children.at(0)->range_left, children.at(0)->range_right) + 1;

        for (int i = 0; i < num; i++) {
            int idx = children.at(0)->range_left > children.at(0)->range_right ? children.at(0)->range_right + i : children.at(0)->range_right - i;
            AstNode *new_cell = children.at(1)->clone();
            newNode->children.push_back(new_cell);
            new_cell->str += stringf("[%d]", idx);
            if (new_cell->type == AST_PRIMITIVE) {
                log_error("Cell arrays of primitives are currently not supported at %s:%d.\n", filename.c_str(), linenum);
            } else {
                log_assert(new_cell->children.at(0)->type == AST_CELLTYPE);
                new_cell->children.at(0)->str = stringf("$array:%d:%d:%s", i, num, new_cell->children.at(0)->str.c_str());
            }
        }

        goto apply_newNode;
    }

    // replace primitives with assignmens
    if (type == AST_PRIMITIVE)
    {
        if (children.size() < 2)
            log_error("Insufficient number of arguments for primitive `%s' at %s:%d!\n",
                    str.c_str(), filename.c_str(), linenum);

        std::vector<AstNode*> children_list;
        for (auto child : children) {
            log_assert(child->type == AST_ARGUMENT);
            log_assert(child->children.size() == 1);
            children_list.push_back(child->children[0]);
            child->children.clear();
            delete child;
        }
        children.clear();

        if (str == "bufif0" || str == "bufif1" || str == "notif0" || str == "notif1")
        {
            if (children_list.size() != 3)
                log_error("Invalid number of arguments for primitive `%s' at %s:%d!\n",
                        str.c_str(), filename.c_str(), linenum);

            std::vector<RTLIL::State> z_const(1, RTLIL::State::Sz);

            AstNode *mux_input = children_list.at(1);
            if (str == "notif0" || str == "notif1") {
                mux_input = new AstNode(AST_BIT_NOT, mux_input);
            }
            AstNode *node = new AstNode(AST_TERNARY, children_list.at(2));
            if (str == "bufif0") {
                node->children.push_back(AstNode::mkconst_bits(z_const, false));
                node->children.push_back(mux_input);
            } else {
                node->children.push_back(mux_input);
                node->children.push_back(AstNode::mkconst_bits(z_const, false));
            }

            str.clear();
            type = AST_ASSIGN;
            children.push_back(children_list.at(0));
            children.push_back(node);
            did_something = true;
        }
        else
        {
            AstNodeType op_type = AST_NONE;
            bool invert_results = false;

            if (str == "and")
                op_type = AST_BIT_AND;
            if (str == "nand")
                op_type = AST_BIT_AND, invert_results = true;
            if (str == "or")
                op_type = AST_BIT_OR;
            if (str == "nor")
                op_type = AST_BIT_OR, invert_results = true;
            if (str == "xor")
                op_type = AST_BIT_XOR;
            if (str == "xnor")
                op_type = AST_BIT_XOR, invert_results = true;
            if (str == "buf")
                op_type = AST_POS;
            if (str == "not")
                op_type = AST_POS, invert_results = true;
            log_assert(op_type != AST_NONE);

            AstNode *node = children_list[1];
            if (op_type != AST_POS)
                for (size_t i = 2; i < children_list.size(); i++)
                    node = new AstNode(op_type, node, children_list[i]);
            if (invert_results)
                node = new AstNode(AST_BIT_NOT, node);

            str.clear();
            type = AST_ASSIGN;
            children.push_back(children_list[0]);
            children.push_back(node);
            did_something = true;
        }
    }

    // replace dynamic ranges in left-hand side expressions (e.g. "foo[bar] <= 1'b1;") with
    // a big case block that selects the correct single-bit assignment.
    if (type == AST_ASSIGN_EQ || type == AST_ASSIGN_LE) {
        if (children[0]->type != AST_IDENTIFIER || children[0]->children.size() == 0)
            goto skip_dynamic_range_lvalue_expansion;
        if (children[0]->children[0]->range_valid || did_something)
            goto skip_dynamic_range_lvalue_expansion;
        if (children[0]->id2ast == NULL || children[0]->id2ast->type != AST_WIRE)
            goto skip_dynamic_range_lvalue_expansion;
        if (!children[0]->id2ast->range_valid)
            goto skip_dynamic_range_lvalue_expansion;
        int source_width = children[0]->id2ast->range_left - children[0]->id2ast->range_right + 1;
        int result_width = 1;
        AstNode *shift_expr = NULL;
        AstNode *range = children[0]->children[0];
        if (range->children.size() == 1) {
            shift_expr = range->children[0]->clone();
        } else {
            shift_expr = range->children[1]->clone();
            AstNode *left_at_zero_ast = range->children[0]->clone();
            AstNode *right_at_zero_ast = range->children[1]->clone();
            while (left_at_zero_ast->simplify(true, true, false, stage, -1, false, false)) { }
            while (right_at_zero_ast->simplify(true, true, false, stage, -1, false, false)) { }
            if (left_at_zero_ast->type != AST_CONSTANT || right_at_zero_ast->type != AST_CONSTANT)
                log_error("Unsupported expression on dynamic range select on signal `%s' at %s:%d!\n",
                        str.c_str(), filename.c_str(), linenum);
            result_width = abs(int(left_at_zero_ast->integer - right_at_zero_ast->integer)) + 1;
        }
        did_something = true;
        newNode = new AstNode(AST_CASE, shift_expr);
        for (int i = 0; i <= source_width-result_width; i++) {
            int start_bit = children[0]->id2ast->range_right + i;
            AstNode *cond = new AstNode(AST_COND, mkconst_int(start_bit, true));
            AstNode *lvalue = children[0]->clone();
            lvalue->delete_children();
            lvalue->children.push_back(new AstNode(AST_RANGE,
                    mkconst_int(start_bit+result_width-1, true), mkconst_int(start_bit, true)));
            cond->children.push_back(new AstNode(AST_BLOCK, new AstNode(type, lvalue, children[1]->clone())));
            newNode->children.push_back(cond);
        }
        goto apply_newNode;
    }
skip_dynamic_range_lvalue_expansion:;

    if (stage > 1 && type == AST_ASSERT && current_block != NULL)
    {
        std::stringstream sstr;
        sstr << "$assert$" << filename << ":" << linenum << "$" << (autoidx++);
        std::string id_check = sstr.str() + "_CHECK", id_en = sstr.str() + "_EN";

        AstNode *wire_check = new AstNode(AST_WIRE);
        wire_check->str = id_check;
        current_ast_mod->children.push_back(wire_check);
        current_scope[wire_check->str] = wire_check;
        while (wire_check->simplify(true, false, false, 1, -1, false, false)) { }

        AstNode *wire_en = new AstNode(AST_WIRE);
        wire_en->str = id_en;
        current_ast_mod->children.push_back(wire_en);
        current_ast_mod->children.push_back(new AstNode(AST_INITIAL, new AstNode(AST_BLOCK, new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), AstNode::mkconst_int(0, false, 1)))));
        current_ast_mod->children.back()->children[0]->children[0]->children[0]->str = id_en;
        current_scope[wire_en->str] = wire_en;
        while (wire_en->simplify(true, false, false, 1, -1, false, false)) { }

        std::vector<RTLIL::State> x_bit;
        x_bit.push_back(RTLIL::State::Sx);

        AstNode *assign_check = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_bits(x_bit, false));
        assign_check->children[0]->str = id_check;

        AstNode *assign_en = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_int(0, false, 1));
        assign_en->children[0]->str = id_en;

        AstNode *default_signals = new AstNode(AST_BLOCK);
        default_signals->children.push_back(assign_check);
        default_signals->children.push_back(assign_en);
        current_top_block->children.insert(current_top_block->children.begin(), default_signals);

        assign_check = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), new AstNode(AST_REDUCE_BOOL, children[0]->clone()));
        assign_check->children[0]->str = id_check;

        assign_en = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_int(1, false, 1));
        assign_en->children[0]->str = id_en;

        newNode = new AstNode(AST_BLOCK);
        newNode->children.push_back(assign_check);
        newNode->children.push_back(assign_en);

        AstNode *assertnode = new AstNode(AST_ASSERT);
        assertnode->children.push_back(new AstNode(AST_IDENTIFIER));
        assertnode->children.push_back(new AstNode(AST_IDENTIFIER));
        assertnode->children[0]->str = id_check;
        assertnode->children[1]->str = id_en;
        assertnode->attributes.swap(attributes);
        current_ast_mod->children.push_back(assertnode);

        goto apply_newNode;
    }

    if (stage > 1 && type == AST_ASSERT && children.size() == 1)
    {
        children[0] = new AstNode(AST_REDUCE_BOOL, children[0]->clone());
        children.push_back(mkconst_int(1, false, 1));
        did_something = true;
    }

    // found right-hand side identifier for memory -> replace with memory read port
    if (stage > 1 && type == AST_IDENTIFIER && id2ast != NULL && id2ast->type == AST_MEMORY && !in_lvalue &&
            children[0]->type == AST_RANGE && children[0]->children.size() == 1) {
        newNode = new AstNode(AST_MEMRD, children[0]->children[0]->clone());
        newNode->str = str;
        newNode->id2ast = id2ast;
        goto apply_newNode;
    }

    // assignment with memory in left-hand side expression -> replace with memory write port
    if (stage > 1 && (type == AST_ASSIGN_EQ || type == AST_ASSIGN_LE) && children[0]->type == AST_IDENTIFIER &&
            children[0]->id2ast && children[0]->id2ast->type == AST_MEMORY && children[0]->id2ast->children.size() >= 2 &&
            children[0]->id2ast->children[0]->range_valid && children[0]->id2ast->children[1]->range_valid &&
            (children[0]->children.size() == 1 || children[0]->children.size() == 2) && children[0]->children[0]->type == AST_RANGE)
    {
        std::stringstream sstr;
        sstr << "$memwr$" << children[0]->str << "$" << filename << ":" << linenum << "$" << (autoidx++);
        std::string id_addr = sstr.str() + "_ADDR", id_data = sstr.str() + "_DATA", id_en = sstr.str() + "_EN";

        if (type == AST_ASSIGN_EQ)
            log_warning("Blocking assignment to memory in line %s:%d is handled like a non-blocking assignment.\n",
                    filename.c_str(), linenum);

        int mem_width, mem_size, addr_bits;
        children[0]->id2ast->meminfo(mem_width, mem_size, addr_bits);

        AstNode *wire_addr = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(addr_bits-1, true), mkconst_int(0, true)));
        wire_addr->str = id_addr;
        current_ast_mod->children.push_back(wire_addr);
        current_scope[wire_addr->str] = wire_addr;
        while (wire_addr->simplify(true, false, false, 1, -1, false, false)) { }

        AstNode *wire_data = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(mem_width-1, true), mkconst_int(0, true)));
        wire_data->str = id_data;
        current_ast_mod->children.push_back(wire_data);
        current_scope[wire_data->str] = wire_data;
        while (wire_data->simplify(true, false, false, 1, -1, false, false)) { }

        AstNode *wire_en = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(mem_width-1, true), mkconst_int(0, true)));
        wire_en->str = id_en;
        current_ast_mod->children.push_back(wire_en);
        current_scope[wire_en->str] = wire_en;
        while (wire_en->simplify(true, false, false, 1, -1, false, false)) { }

        std::vector<RTLIL::State> x_bits_addr, x_bits_data, set_bits_en;
        for (int i = 0; i < addr_bits; i++)
            x_bits_addr.push_back(RTLIL::State::Sx);
        for (int i = 0; i < mem_width; i++)
            x_bits_data.push_back(RTLIL::State::Sx);
        for (int i = 0; i < mem_width; i++)
            set_bits_en.push_back(RTLIL::State::S1);

        AstNode *assign_addr = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_bits(x_bits_addr, false));
        assign_addr->children[0]->str = id_addr;

        AstNode *assign_data = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_bits(x_bits_data, false));
        assign_data->children[0]->str = id_data;

        AstNode *assign_en = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_int(0, false, mem_width));
        assign_en->children[0]->str = id_en;

        AstNode *default_signals = new AstNode(AST_BLOCK);
        default_signals->children.push_back(assign_addr);
        default_signals->children.push_back(assign_data);
        default_signals->children.push_back(assign_en);
        current_top_block->children.insert(current_top_block->children.begin(), default_signals);

        assign_addr = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), children[0]->children[0]->children[0]->clone());
        assign_addr->children[0]->str = id_addr;

        if (children[0]->children.size() == 2)
        {
            if (children[0]->children[1]->range_valid)
            {
                int offset = children[0]->children[1]->range_right;
                int width = children[0]->children[1]->range_left - offset + 1;

                std::vector<RTLIL::State> padding_x(offset, RTLIL::State::Sx);

                for (int i = 0; i < mem_width; i++)
                    set_bits_en[i] = offset <= i && i < offset+width ? RTLIL::State::S1 : RTLIL::State::S0;

                assign_data = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER),
                        new AstNode(AST_CONCAT, mkconst_bits(padding_x, false), children[1]->clone()));
                assign_data->children[0]->str = id_data;

                assign_en = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_bits(set_bits_en, false));
                assign_en->children[0]->str = id_en;
            }
            else
            {
                AstNode *the_range = children[0]->children[1];
                AstNode *left_at_zero_ast = the_range->children[0]->clone();
                AstNode *right_at_zero_ast = the_range->children.size() >= 2 ? the_range->children[1]->clone() : left_at_zero_ast->clone();
                AstNode *offset_ast = right_at_zero_ast->clone();

                while (left_at_zero_ast->simplify(true, true, false, 1, -1, false, false)) { }
                while (right_at_zero_ast->simplify(true, true, false, 1, -1, false, false)) { }
                if (left_at_zero_ast->type != AST_CONSTANT || right_at_zero_ast->type != AST_CONSTANT)
                    log_error("Unsupported expression on dynamic range select on signal `%s' at %s:%d!\n", str.c_str(), filename.c_str(), linenum);
                int width = left_at_zero_ast->integer - right_at_zero_ast->integer + 1;

                for (int i = 0; i < mem_width; i++)
                    set_bits_en[i] = i < width ? RTLIL::State::S1 : RTLIL::State::S0;

                assign_data = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER),
                        new AstNode(AST_SHIFT_LEFT, children[1]->clone(), offset_ast->clone()));
                assign_data->children[0]->str = id_data;

                assign_en = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER),
                        new AstNode(AST_SHIFT_LEFT, mkconst_bits(set_bits_en, false), offset_ast->clone()));
                assign_en->children[0]->str = id_en;

                delete left_at_zero_ast;
                delete right_at_zero_ast;
                delete offset_ast;
            }
        }
        else
        {
            assign_data = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), children[1]->clone());
            assign_data->children[0]->str = id_data;

            assign_en = new AstNode(AST_ASSIGN_LE, new AstNode(AST_IDENTIFIER), mkconst_bits(set_bits_en, false));
            assign_en->children[0]->str = id_en;
        }

        newNode = new AstNode(AST_BLOCK);
        newNode->children.push_back(assign_addr);
        newNode->children.push_back(assign_data);
        newNode->children.push_back(assign_en);

        AstNode *wrnode = new AstNode(AST_MEMWR);
        wrnode->children.push_back(new AstNode(AST_IDENTIFIER));
        wrnode->children.push_back(new AstNode(AST_IDENTIFIER));
        wrnode->children.push_back(new AstNode(AST_IDENTIFIER));
        wrnode->str = children[0]->str;
        wrnode->children[0]->str = id_addr;
        wrnode->children[1]->str = id_data;
        wrnode->children[2]->str = id_en;
        current_ast_mod->children.push_back(wrnode);

        goto apply_newNode;
    }

    // replace function and task calls with the code from the function or task
    if ((type == AST_FCALL || type == AST_TCALL) && !str.empty())
    {
        if (type == AST_FCALL)
        {
            if (str == "\\$clog2")
            {
                if (children.size() != 1)
                    log_error("System function %s got %d arguments, expected 1 at %s:%d.\n",
                            RTLIL::unescape_id(str).c_str(), int(children.size()), filename.c_str(), linenum);

                AstNode *buf = children[0]->clone();
                while (buf->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                if (buf->type != AST_CONSTANT)
                    log_error("Failed to evaluate system function `%s' with non-constant value at %s:%d.\n", str.c_str(), filename.c_str(), linenum);

                RTLIL::Const arg_value = buf->bitsAsConst();
                if (arg_value.as_bool())
                    arg_value = const_sub(arg_value, 1, false, false, GetSize(arg_value));
                delete buf;

                uint32_t result = 0;
                for (size_t i = 0; i < arg_value.bits.size(); i++)
                    if (arg_value.bits.at(i) == RTLIL::State::S1)
                        result = i + 1;

                newNode = mkconst_int(result, false);
                goto apply_newNode;
            }

            if (str == "\\$ln" || str == "\\$log10" || str == "\\$exp" || str == "\\$sqrt" || str == "\\$pow" ||
                    str == "\\$floor" || str == "\\$ceil" || str == "\\$sin" || str == "\\$cos" || str == "\\$tan" ||
                    str == "\\$asin" || str == "\\$acos" || str == "\\$atan" || str == "\\$atan2" || str == "\\$hypot" ||
                    str == "\\$sinh" || str == "\\$cosh" || str == "\\$tanh" || str == "\\$asinh" || str == "\\$acosh" || str == "\\$atanh")
            {
                bool func_with_two_arguments = str == "\\$pow" || str == "\\$atan2" || str == "\\$hypot";
                double x = 0, y = 0;

                if (func_with_two_arguments) {
                    if (children.size() != 2)
                        log_error("System function %s got %d arguments, expected 2 at %s:%d.\n",
                                RTLIL::unescape_id(str).c_str(), int(children.size()), filename.c_str(), linenum);
                } else {
                    if (children.size() != 1)
                        log_error("System function %s got %d arguments, expected 1 at %s:%d.\n",
                                RTLIL::unescape_id(str).c_str(), int(children.size()), filename.c_str(), linenum);
                }

                if (children.size() >= 1) {
                    while (children[0]->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                    if (!children[0]->isConst())
                        log_error("Failed to evaluate system function `%s' with non-constant argument at %s:%d.\n",
                                RTLIL::unescape_id(str).c_str(), filename.c_str(), linenum);
                    int child_width_hint = width_hint;
                    bool child_sign_hint = sign_hint;
                    children[0]->detectSignWidth(child_width_hint, child_sign_hint);
                    x = children[0]->asReal(child_sign_hint);
                }

                if (children.size() >= 2) {
                    while (children[1]->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                    if (!children[1]->isConst())
                        log_error("Failed to evaluate system function `%s' with non-constant argument at %s:%d.\n",
                                RTLIL::unescape_id(str).c_str(), filename.c_str(), linenum);
                    int child_width_hint = width_hint;
                    bool child_sign_hint = sign_hint;
                    children[1]->detectSignWidth(child_width_hint, child_sign_hint);
                    y = children[1]->asReal(child_sign_hint);
                }

                newNode = new AstNode(AST_REALVALUE);
                if (str == "\\$ln")         newNode->realvalue = ::log(x);
                else if (str == "\\$log10") newNode->realvalue = ::log10(x);
                else if (str == "\\$exp")   newNode->realvalue = ::exp(x);
                else if (str == "\\$sqrt")  newNode->realvalue = ::sqrt(x);
                else if (str == "\\$pow")   newNode->realvalue = ::pow(x, y);
                else if (str == "\\$floor") newNode->realvalue = ::floor(x);
                else if (str == "\\$ceil")  newNode->realvalue = ::ceil(x);
                else if (str == "\\$sin")   newNode->realvalue = ::sin(x);
                else if (str == "\\$cos")   newNode->realvalue = ::cos(x);
                else if (str == "\\$tan")   newNode->realvalue = ::tan(x);
                else if (str == "\\$asin")  newNode->realvalue = ::asin(x);
                else if (str == "\\$acos")  newNode->realvalue = ::acos(x);
                else if (str == "\\$atan")  newNode->realvalue = ::atan(x);
                else if (str == "\\$atan2") newNode->realvalue = ::atan2(x, y);
                else if (str == "\\$hypot") newNode->realvalue = ::hypot(x, y);
                else if (str == "\\$sinh")  newNode->realvalue = ::sinh(x);
                else if (str == "\\$cosh")  newNode->realvalue = ::cosh(x);
                else if (str == "\\$tanh")  newNode->realvalue = ::tanh(x);
                else if (str == "\\$asinh") newNode->realvalue = ::asinh(x);
                else if (str == "\\$acosh") newNode->realvalue = ::acosh(x);
                else if (str == "\\$atanh") newNode->realvalue = ::atanh(x);
                else log_abort();
                goto apply_newNode;
            }

            if (current_scope.count(str) != 0 && current_scope[str]->type == AST_DPI_FUNCTION)
            {
                AstNode *dpi_decl = current_scope[str];

                std::string rtype, fname;
                std::vector<std::string> argtypes;
                std::vector<AstNode*> args;

                rtype = RTLIL::unescape_id(dpi_decl->children.at(0)->str);
                fname = RTLIL::unescape_id(dpi_decl->children.at(1)->str);

                for (int i = 2; i < GetSize(dpi_decl->children); i++)
                {
                    if (i-2 >= GetSize(children))
                        log_error("Insufficient number of arguments in DPI function call at %s:%d.\n", filename.c_str(), linenum);

                    argtypes.push_back(RTLIL::unescape_id(dpi_decl->children.at(i)->str));
                    args.push_back(children.at(i-2)->clone());
                    while (args.back()->simplify(true, false, false, stage, -1, false, true)) { }

                    if (args.back()->type != AST_CONSTANT && args.back()->type != AST_REALVALUE)
                        log_error("Failed to evaluate DPI function with non-constant argument at %s:%d.\n", filename.c_str(), linenum);
                }

                newNode = dpi_call(rtype, fname, argtypes, args);

                for (auto arg : args)
                    delete arg;

                goto apply_newNode;
            }

            if (current_scope.count(str) == 0 || current_scope[str]->type != AST_FUNCTION)
                log_error("Can't resolve function name `%s' at %s:%d.\n", str.c_str(), filename.c_str(), linenum);
        }
        if (type == AST_TCALL) {
            if (str == "\\$readmemh" || str == "\\$readmemb")
            {
                if (GetSize(children) < 2 || GetSize(children) > 4)
                    log_error("System function %s got %d arguments, expected 2-4 at %s:%d.\n",
                            RTLIL::unescape_id(str).c_str(), int(children.size()), filename.c_str(), linenum);

                AstNode *node_filename = children[0]->clone();
                while (node_filename->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                if (node_filename->type != AST_CONSTANT)
                    log_error("Failed to evaluate system function `%s' with non-constant 1st argument at %s:%d.\n", str.c_str(), filename.c_str(), linenum);

                AstNode *node_memory = children[1]->clone();
                while (node_memory->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                if (node_memory->type != AST_IDENTIFIER || node_memory->id2ast == nullptr || node_memory->id2ast->type != AST_MEMORY)
                    log_error("Failed to evaluate system function `%s' with non-memory 2nd argument at %s:%d.\n", str.c_str(), filename.c_str(), linenum);

                int start_addr = -1, finish_addr = -1;

                if (GetSize(children) > 2) {
                    AstNode *node_addr = children[2]->clone();
                    while (node_addr->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                    if (node_addr->type != AST_CONSTANT)
                        log_error("Failed to evaluate system function `%s' with non-constant 3rd argument at %s:%d.\n", str.c_str(), filename.c_str(), linenum);
                    start_addr = node_addr->asInt(false);
                }

                if (GetSize(children) > 3) {
                    AstNode *node_addr = children[3]->clone();
                    while (node_addr->simplify(true, false, false, stage, width_hint, sign_hint, false)) { }
                    if (node_addr->type != AST_CONSTANT)
                        log_error("Failed to evaluate system function `%s' with non-constant 4th argument at %s:%d.\n", str.c_str(), filename.c_str(), linenum);
                    finish_addr = node_addr->asInt(false);
                }

                newNode = readmem(str == "\\$readmemh", node_filename->bitsAsConst().decode_string(), node_memory->id2ast, start_addr, finish_addr);
                goto apply_newNode;
            }

            if (current_scope.count(str) == 0 || current_scope[str]->type != AST_TASK)
                log_error("Can't resolve task name `%s' at %s:%d.\n", str.c_str(), filename.c_str(), linenum);
        }

        AstNode *decl = current_scope[str];

        std::stringstream sstr;
        sstr << "$func$" << str << "$" << filename << ":" << linenum << "$" << (autoidx++) << "$";
        std::string prefix = sstr.str();

        bool recommend_const_eval = false;
        bool require_const_eval = in_param ? false : has_const_only_constructs(recommend_const_eval);
        if ((in_param || recommend_const_eval || require_const_eval) && !decl->attributes.count("\\via_celltype"))
        {
            bool all_args_const = true;
            for (auto child : children) {
                while (child->simplify(true, false, false, 1, -1, false, true)) { }
                if (child->type != AST_CONSTANT)
                    all_args_const = false;
            }

            if (all_args_const) {
                AstNode *func_workspace = current_scope[str]->clone();
                newNode = func_workspace->eval_const_function(this);
                delete func_workspace;
                goto apply_newNode;
            }

            if (in_param)
                log_error("Non-constant function call in constant expression at %s:%d.\n", filename.c_str(), linenum);
            if (require_const_eval)
                log_error("Function %s can only be called with constant arguments at %s:%d.\n", str.c_str(), filename.c_str(), linenum);
        }

        size_t arg_count = 0;
        std::map<std::string, std::string> replace_rules;

        if (current_block == NULL)
        {
            log_assert(type == AST_FCALL);

            AstNode *wire = NULL;
            for (auto child : decl->children)
                if (child->type == AST_WIRE && child->str == str)
                    wire = child->clone();
            log_assert(wire != NULL);

            wire->str = prefix + str;
            wire->port_id = 0;
            wire->is_input = false;
            wire->is_output = false;

            current_ast_mod->children.push_back(wire);
            while (wire->simplify(true, false, false, 1, -1, false, false)) { }

            AstNode *lvalue = new AstNode(AST_IDENTIFIER);
            lvalue->str = wire->str;

            AstNode *always = new AstNode(AST_ALWAYS, new AstNode(AST_BLOCK,
                    new AstNode(AST_ASSIGN_EQ, lvalue, clone())));
            current_ast_mod->children.push_back(always);

            goto replace_fcall_with_id;
        }

        if (decl->attributes.count("\\via_celltype"))
        {
            std::string celltype = decl->attributes.at("\\via_celltype")->asAttrConst().decode_string();
            std::string outport = str;

            if (celltype.find(' ') != std::string::npos) {
                int pos = celltype.find(' ');
                outport = RTLIL::escape_id(celltype.substr(pos+1));
                celltype = RTLIL::escape_id(celltype.substr(0, pos));
            } else
                celltype = RTLIL::escape_id(celltype);

            AstNode *cell = new AstNode(AST_CELL, new AstNode(AST_CELLTYPE));
            cell->str = prefix.substr(0, GetSize(prefix)-1);
            cell->children[0]->str = celltype;

            for (auto attr : decl->attributes)
                if (attr.first.str().rfind("\\via_celltype_defparam_", 0) == 0)
                {
                    AstNode *cell_arg = new AstNode(AST_PARASET, attr.second->clone());
                    cell_arg->str = RTLIL::escape_id(attr.first.str().substr(strlen("\\via_celltype_defparam_")));
                    cell->children.push_back(cell_arg);
                }

            for (auto child : decl->children)
                if (child->type == AST_WIRE && (child->is_input || child->is_output || (type == AST_FCALL && child->str == str)))
                {
                    AstNode *wire = child->clone();
                    wire->str = prefix + wire->str;
                    wire->port_id = 0;
                    wire->is_input = false;
                    wire->is_output = false;
                    current_ast_mod->children.push_back(wire);
                    while (wire->simplify(true, false, false, 1, -1, false, false)) { }

                    AstNode *wire_id = new AstNode(AST_IDENTIFIER);
                    wire_id->str = wire->str;

                    if ((child->is_input || child->is_output) && arg_count < children.size())
                    {
                        AstNode *arg = children[arg_count++]->clone();
                        AstNode *assign = child->is_input ?
                                new AstNode(AST_ASSIGN_EQ, wire_id->clone(), arg) :
                                new AstNode(AST_ASSIGN_EQ, arg, wire_id->clone());

                        for (auto it = current_block->children.begin(); it != current_block->children.end(); it++) {
                            if (*it != current_block_child)
                                continue;
                            current_block->children.insert(it, assign);
                            break;
                        }
                    }

                    AstNode *cell_arg = new AstNode(AST_ARGUMENT, wire_id);
                    cell_arg->str = child->str == str ? outport : child->str;
                    cell->children.push_back(cell_arg);
                }

            current_ast_mod->children.push_back(cell);
            goto replace_fcall_with_id;
        }

        for (auto child : decl->children)
            if (child->type == AST_WIRE)
            {
                AstNode *wire = child->clone();
                wire->str = prefix + wire->str;
                wire->port_id = 0;
                wire->is_input = false;
                wire->is_output = false;
                current_ast_mod->children.push_back(wire);
                while (wire->simplify(true, false, false, 1, -1, false, false)) { }

                replace_rules[child->str] = wire->str;

                if ((child->is_input || child->is_output) && arg_count < children.size())
                {
                    AstNode *arg = children[arg_count++]->clone();
                    AstNode *wire_id = new AstNode(AST_IDENTIFIER);
                    wire_id->str = wire->str;
                    AstNode *assign = child->is_input ?
                            new AstNode(AST_ASSIGN_EQ, wire_id, arg) :
                            new AstNode(AST_ASSIGN_EQ, arg, wire_id);

                    for (auto it = current_block->children.begin(); it != current_block->children.end(); it++) {
                        if (*it != current_block_child)
                            continue;
                        current_block->children.insert(it, assign);
                        break;
                    }
                }
            }

        for (auto child : decl->children)
            if (child->type != AST_WIRE)
            {
                AstNode *stmt = child->clone();
                stmt->replace_ids(prefix, replace_rules);

                for (auto it = current_block->children.begin(); it != current_block->children.end(); it++) {
                    if (*it != current_block_child)
                        continue;
                    current_block->children.insert(it, stmt);
                    break;
                }
            }

    replace_fcall_with_id:
        if (type == AST_FCALL) {
            delete_children();
            type = AST_IDENTIFIER;
            str = prefix + str;
        }
        if (type == AST_TCALL)
            str = "";
        did_something = true;
    }

    // perform const folding when activated
    if (const_fold)
    {
        bool string_op;
        std::vector<RTLIL::State> tmp_bits;
        RTLIL::Const (*const_func)(const RTLIL::Const&, const RTLIL::Const&, bool, bool, int);
        RTLIL::Const dummy_arg;

        switch (type)
        {
        case AST_IDENTIFIER:
            if (current_scope.count(str) > 0 && (current_scope[str]->type == AST_PARAMETER || current_scope[str]->type == AST_LOCALPARAM)) {
                if (current_scope[str]->children[0]->type == AST_CONSTANT) {
                    if (children.size() != 0 && children[0]->type == AST_RANGE && children[0]->range_valid) {
                        std::vector<RTLIL::State> data;
                        bool param_upto = current_scope[str]->range_valid && current_scope[str]->range_swapped;
                        int param_offset = current_scope[str]->range_valid ? current_scope[str]->range_right : 0;
                        int param_width = current_scope[str]->range_valid ? current_scope[str]->range_left - current_scope[str]->range_right + 1 :
                                GetSize(current_scope[str]->children[0]->bits);
                        int tmp_range_left = children[0]->range_left, tmp_range_right = children[0]->range_right;
                        if (param_upto) {
                            tmp_range_left = (param_width + 2*param_offset) - children[0]->range_right - 1;
                            tmp_range_right = (param_width + 2*param_offset) - children[0]->range_left - 1;
                        }
                        for (int i = tmp_range_right; i <= tmp_range_left; i++) {
                            int index = i - param_offset;
                            if (0 <= index && index < param_width)
                                data.push_back(current_scope[str]->children[0]->bits[index]);
                            else
                                data.push_back(RTLIL::State::Sx);
                        }
                        newNode = mkconst_bits(data, false);
                    } else
                    if (children.size() == 0)
                        newNode = current_scope[str]->children[0]->clone();
                } else
                if (current_scope[str]->children[0]->isConst())
                    newNode = current_scope[str]->children[0]->clone();
            }
            else if (at_zero && current_scope.count(str) > 0 && (current_scope[str]->type == AST_WIRE || current_scope[str]->type == AST_AUTOWIRE)) {
                newNode = mkconst_int(0, sign_hint, width_hint);
            }
            break;
        case AST_BIT_NOT:
            if (children[0]->type == AST_CONSTANT) {
                RTLIL::Const y = RTLIL::const_not(children[0]->bitsAsConst(width_hint, sign_hint), dummy_arg, sign_hint, false, width_hint);
                newNode = mkconst_bits(y.bits, sign_hint);
            }
            break;
        case AST_TO_SIGNED:
        case AST_TO_UNSIGNED:
            if (children[0]->type == AST_CONSTANT) {
                RTLIL::Const y = children[0]->bitsAsConst(width_hint, sign_hint);
                newNode = mkconst_bits(y.bits, type == AST_TO_SIGNED);
            }
            break;
        if (0) { case AST_BIT_AND:  const_func = RTLIL::const_and;  }
        if (0) { case AST_BIT_OR:   const_func = RTLIL::const_or;   }
        if (0) { case AST_BIT_XOR:  const_func = RTLIL::const_xor;  }
        if (0) { case AST_BIT_XNOR: const_func = RTLIL::const_xnor; }
            if (children[0]->type == AST_CONSTANT && children[1]->type == AST_CONSTANT) {
                RTLIL::Const y = const_func(children[0]->bitsAsConst(width_hint, sign_hint),
                        children[1]->bitsAsConst(width_hint, sign_hint), sign_hint, sign_hint, width_hint);
                newNode = mkconst_bits(y.bits, sign_hint);
            }
            break;
        if (0) { case AST_REDUCE_AND:  const_func = RTLIL::const_reduce_and;  }
        if (0) { case AST_REDUCE_OR:   const_func = RTLIL::const_reduce_or;   }
        if (0) { case AST_REDUCE_XOR:  const_func = RTLIL::const_reduce_xor;  }
        if (0) { case AST_REDUCE_XNOR: const_func = RTLIL::const_reduce_xnor; }
        if (0) { case AST_REDUCE_BOOL: const_func = RTLIL::const_reduce_bool; }
            if (children[0]->type == AST_CONSTANT) {
                RTLIL::Const y = const_func(RTLIL::Const(children[0]->bits), dummy_arg, false, false, -1);
                newNode = mkconst_bits(y.bits, false);
            }
            break;
        case AST_LOGIC_NOT:
            if (children[0]->type == AST_CONSTANT) {
                RTLIL::Const y = RTLIL::const_logic_not(RTLIL::Const(children[0]->bits), dummy_arg, children[0]->is_signed, false, -1);
                newNode = mkconst_bits(y.bits, false);
            } else
            if (children[0]->isConst()) {
                newNode = mkconst_int(children[0]->asReal(sign_hint) == 0, false, 1);
            }
            break;
        if (0) { case AST_LOGIC_AND: const_func = RTLIL::const_logic_and; }
        if (0) { case AST_LOGIC_OR:  const_func = RTLIL::const_logic_or;  }
            if (children[0]->type == AST_CONSTANT && children[1]->type == AST_CONSTANT) {
                RTLIL::Const y = const_func(RTLIL::Const(children[0]->bits), RTLIL::Const(children[1]->bits),
                        children[0]->is_signed, children[1]->is_signed, -1);
                newNode = mkconst_bits(y.bits, false);
            } else
            if (children[0]->isConst() && children[1]->isConst()) {
                if (type == AST_LOGIC_AND)
                    newNode = mkconst_int((children[0]->asReal(sign_hint) != 0) && (children[1]->asReal(sign_hint) != 0), false, 1);
                else
                    newNode = mkconst_int((children[0]->asReal(sign_hint) != 0) || (children[1]->asReal(sign_hint) != 0), false, 1);
            }
            break;
        if (0) { case AST_SHIFT_LEFT:   const_func = RTLIL::const_shl;  }
        if (0) { case AST_SHIFT_RIGHT:  const_func = RTLIL::const_shr;  }
        if (0) { case AST_SHIFT_SLEFT:  const_func = RTLIL::const_sshl; }
        if (0) { case AST_SHIFT_SRIGHT: const_func = RTLIL::const_sshr; }
        if (0) { case AST_POW:          const_func = RTLIL::const_pow; }
            if (children[0]->type == AST_CONSTANT && children[1]->type == AST_CONSTANT) {
                RTLIL::Const y = const_func(children[0]->bitsAsConst(width_hint, sign_hint),
                        RTLIL::Const(children[1]->bits), sign_hint, type == AST_POW ? children[1]->is_signed : false, width_hint);
                newNode = mkconst_bits(y.bits, sign_hint);
            } else
            if (type == AST_POW && children[0]->isConst() && children[1]->isConst()) {
                newNode = new AstNode(AST_REALVALUE);
                newNode->realvalue = pow(children[0]->asReal(sign_hint), children[1]->asReal(sign_hint));
            }
            break;
        if (0) { case AST_LT:  const_func = RTLIL::const_lt; }
        if (0) { case AST_LE:  const_func = RTLIL::const_le; }
        if (0) { case AST_EQ:  const_func = RTLIL::const_eq; }
        if (0) { case AST_NE:  const_func = RTLIL::const_ne; }
        if (0) { case AST_EQX: const_func = RTLIL::const_eqx; }
        if (0) { case AST_NEX: const_func = RTLIL::const_nex; }
        if (0) { case AST_GE:  const_func = RTLIL::const_ge; }
        if (0) { case AST_GT:  const_func = RTLIL::const_gt; }
            if (children[0]->type == AST_CONSTANT && children[1]->type == AST_CONSTANT) {
                int cmp_width = std::max(children[0]->bits.size(), children[1]->bits.size());
                bool cmp_signed = children[0]->is_signed && children[1]->is_signed;
                RTLIL::Const y = const_func(children[0]->bitsAsConst(cmp_width, cmp_signed),
                        children[1]->bitsAsConst(cmp_width, cmp_signed), cmp_signed, cmp_signed, 1);
                newNode = mkconst_bits(y.bits, false);
            } else
            if (children[0]->isConst() && children[1]->isConst()) {
                bool cmp_signed = (children[0]->type == AST_REALVALUE || children[0]->is_signed) && (children[1]->type == AST_REALVALUE || children[1]->is_signed);
                switch (type) {
                case AST_LT:  newNode = mkconst_int(children[0]->asReal(cmp_signed) <  children[1]->asReal(cmp_signed), false, 1); break;
                case AST_LE:  newNode = mkconst_int(children[0]->asReal(cmp_signed) <= children[1]->asReal(cmp_signed), false, 1); break;
                case AST_EQ:  newNode = mkconst_int(children[0]->asReal(cmp_signed) == children[1]->asReal(cmp_signed), false, 1); break;
                case AST_NE:  newNode = mkconst_int(children[0]->asReal(cmp_signed) != children[1]->asReal(cmp_signed), false, 1); break;
                case AST_EQX: newNode = mkconst_int(children[0]->asReal(cmp_signed) == children[1]->asReal(cmp_signed), false, 1); break;
                case AST_NEX: newNode = mkconst_int(children[0]->asReal(cmp_signed) != children[1]->asReal(cmp_signed), false, 1); break;
                case AST_GE:  newNode = mkconst_int(children[0]->asReal(cmp_signed) >= children[1]->asReal(cmp_signed), false, 1); break;
                case AST_GT:  newNode = mkconst_int(children[0]->asReal(cmp_signed) >  children[1]->asReal(cmp_signed), false, 1); break;
                default: log_abort();
                }
            }
            break;
        if (0) { case AST_ADD: const_func = RTLIL::const_add; }
        if (0) { case AST_SUB: const_func = RTLIL::const_sub; }
        if (0) { case AST_MUL: const_func = RTLIL::const_mul; }
        if (0) { case AST_DIV: const_func = RTLIL::const_div; }
        if (0) { case AST_MOD: const_func = RTLIL::const_mod; }
            if (children[0]->type == AST_CONSTANT && children[1]->type == AST_CONSTANT) {
                RTLIL::Const y = const_func(children[0]->bitsAsConst(width_hint, sign_hint),
                        children[1]->bitsAsConst(width_hint, sign_hint), sign_hint, sign_hint, width_hint);
                newNode = mkconst_bits(y.bits, sign_hint);
            } else
            if (children[0]->isConst() && children[1]->isConst()) {
                newNode = new AstNode(AST_REALVALUE);
                switch (type) {
                case AST_ADD: newNode->realvalue = children[0]->asReal(sign_hint) + children[1]->asReal(sign_hint); break;
                case AST_SUB: newNode->realvalue = children[0]->asReal(sign_hint) - children[1]->asReal(sign_hint); break;
                case AST_MUL: newNode->realvalue = children[0]->asReal(sign_hint) * children[1]->asReal(sign_hint); break;
                case AST_DIV: newNode->realvalue = children[0]->asReal(sign_hint) / children[1]->asReal(sign_hint); break;
                case AST_MOD: newNode->realvalue = fmod(children[0]->asReal(sign_hint), children[1]->asReal(sign_hint)); break;
                default: log_abort();
                }
            }
            break;
        if (0) { case AST_POS: const_func = RTLIL::const_pos; }
        if (0) { case AST_NEG: const_func = RTLIL::const_neg; }
            if (children[0]->type == AST_CONSTANT) {
                RTLIL::Const y = const_func(children[0]->bitsAsConst(width_hint, sign_hint), dummy_arg, sign_hint, false, width_hint);
                newNode = mkconst_bits(y.bits, sign_hint);
            } else
            if (children[0]->isConst()) {
                newNode = new AstNode(AST_REALVALUE);
                if (type == AST_POS)
                    newNode->realvalue = +children[0]->asReal(sign_hint);
                else
                    newNode->realvalue = -children[0]->asReal(sign_hint);
            }
            break;
        case AST_TERNARY:
            if (children[0]->isConst())
            {
                bool found_sure_true = false;
                bool found_maybe_true = false;

                if (children[0]->type == AST_CONSTANT)
                    for (auto &bit : children[0]->bits) {
                        if (bit == RTLIL::State::S1)
                            found_sure_true = true;
                        if (bit > RTLIL::State::S1)
                            found_maybe_true = true;
                    }
                else
                    found_sure_true = children[0]->asReal(sign_hint) != 0;

                AstNode *choice = NULL, *not_choice = NULL;
                if (found_sure_true)
                    choice = children[1], not_choice = children[2];
                else if (!found_maybe_true)
                    choice = children[2], not_choice = children[1];

                if (choice != NULL) {
                    if (choice->type == AST_CONSTANT) {
                        int other_width_hint = width_hint;
                        bool other_sign_hint = sign_hint, other_real = false;
                        not_choice->detectSignWidth(other_width_hint, other_sign_hint, &other_real);
                        if (other_real) {
                            newNode = new AstNode(AST_REALVALUE);
                            choice->detectSignWidth(width_hint, sign_hint);
                            newNode->realvalue = choice->asReal(sign_hint);
                        } else {
                            RTLIL::Const y = choice->bitsAsConst(width_hint, sign_hint);
                            if (choice->is_string && y.bits.size() % 8 == 0 && sign_hint == false)
                                newNode = mkconst_str(y.bits);
                            else
                                newNode = mkconst_bits(y.bits, sign_hint);
                        }
                    } else
                    if (choice->isConst()) {
                        newNode = choice->clone();
                    }
                } else if (children[1]->type == AST_CONSTANT && children[2]->type == AST_CONSTANT) {
                    RTLIL::Const a = children[1]->bitsAsConst(width_hint, sign_hint);
                    RTLIL::Const b = children[2]->bitsAsConst(width_hint, sign_hint);
                    log_assert(a.bits.size() == b.bits.size());
                    for (size_t i = 0; i < a.bits.size(); i++)
                        if (a.bits[i] != b.bits[i])
                            a.bits[i] = RTLIL::State::Sx;
                    newNode = mkconst_bits(a.bits, sign_hint);
                } else if (children[1]->isConst() && children[2]->isConst()) {
                    newNode = new AstNode(AST_REALVALUE);
                    if (children[1]->asReal(sign_hint) == children[2]->asReal(sign_hint))
                        newNode->realvalue = children[1]->asReal(sign_hint);
                    else
                        // IEEE Std 1800-2012 Sec. 11.4.11 states that the entry in Table 7-1 for
                        // the data type in question should be returned if the ?: is ambiguous. The
                        // value in Table 7-1 for the 'real' type is 0.0.
                        newNode->realvalue = 0.0;
                }
            }
            break;
        case AST_CONCAT:
            string_op = !children.empty();
            for (auto it = children.begin(); it != children.end(); it++) {
                if ((*it)->type != AST_CONSTANT)
                    goto not_const;
                if (!(*it)->is_string)
                    string_op = false;
                tmp_bits.insert(tmp_bits.end(), (*it)->bits.begin(), (*it)->bits.end());
            }
            newNode = string_op ? mkconst_str(tmp_bits) : mkconst_bits(tmp_bits, false);
            break;
        case AST_REPLICATE:
            if (children.at(0)->type != AST_CONSTANT || children.at(1)->type != AST_CONSTANT)
                goto not_const;
            for (int i = 0; i < children[0]->bitsAsConst().as_int(); i++)
                tmp_bits.insert(tmp_bits.end(), children.at(1)->bits.begin(), children.at(1)->bits.end());
            newNode = children.at(1)->is_string ? mkconst_str(tmp_bits) : mkconst_bits(tmp_bits, false);
            break;
        default:
        not_const:
            break;
        }
    }

    // if any of the above set 'newNode' -> use 'newNode' as template to update 'this'
    if (newNode) {
apply_newNode:
        // fprintf(stderr, "----\n");
        // dumpAst(stderr, "- ");
        // newNode->dumpAst(stderr, "+ ");
        log_assert(newNode != NULL);
        newNode->filename = filename;
        newNode->linenum = linenum;
        newNode->cloneInto(this);
        delete newNode;
        did_something = true;
    }

    if (!did_something)
        basic_prep = true;

    return did_something;
}

static void replace_result_wire_name_in_function(AstNode *node, std::string &from, std::string &to)
{
    for (auto &it : node->children)
        replace_result_wire_name_in_function(it, from, to);
    if (node->str == from)
        node->str = to;
}

// replace a readmem[bh] TCALL ast node with a block of memory assignments
AstNode *AstNode::readmem(bool is_readmemh, std::string mem_filename, AstNode *memory, int start_addr, int finish_addr)
{
    AstNode *block = new AstNode(AST_BLOCK);

    std::ifstream f;
    f.open(mem_filename.c_str());

    if (f.fail())
        log_error("Can not open file `%s` for %s at %s:%d.\n", mem_filename.c_str(), str.c_str(), filename.c_str(), linenum);

    log_assert(GetSize(memory->children) == 2 && memory->children[1]->type == AST_RANGE && memory->children[1]->range_valid);
    int range_left =  memory->children[1]->range_left, range_right =  memory->children[1]->range_right;
    int range_min = std::min(range_left, range_right), range_max = std::max(range_left, range_right);

    if (start_addr < 0)
        start_addr = range_min;

    if (finish_addr < 0)
        finish_addr = range_max;

    bool in_comment = false;
    int increment = start_addr <= finish_addr ? +1 : -1;
    int cursor = start_addr;

    while (!f.eof())
    {
        std::string line, token;
        std::getline(f, line);

        for (int i = 0; i < GetSize(line); i++) {
            if (in_comment && line.substr(i, 2) == "*/") {
                line[i] = ' ';
                line[i+1] = ' ';
                in_comment = false;
                continue;
            }
            if (!in_comment && line.substr(i, 2) == "/*")
                in_comment = true;
            if (in_comment)
                line[i] = ' ';
        }

        while (1)
        {
            token = next_token(line, " \t\r\n");
            if (token.empty() || token.substr(0, 2) == "//")
                break;

            if (token[0] == '@') {
                token = token.substr(1);
                const char *nptr = token.c_str();
                char *endptr;
                cursor = strtol(nptr, &endptr, 16);
                if (!*nptr || *endptr)
                    log_error("Can not parse address `%s` for %s at %s:%d.\n", nptr, str.c_str(), filename.c_str(), linenum);
                continue;
            }

            AstNode *value = VERILOG_FRONTEND::const2ast((is_readmemh ? "'h" : "'b") + token);

            block->children.push_back(new AstNode(AST_ASSIGN_EQ, new AstNode(AST_IDENTIFIER, new AstNode(AST_RANGE, AstNode::mkconst_int(cursor, false))), value));
            block->children.back()->children[0]->str = memory->str;
            block->children.back()->children[0]->id2ast = memory;

            if ((cursor == finish_addr) || (increment > 0 && cursor >= range_max) || (increment < 0 && cursor <= range_min))
                break;
            cursor += increment;
        }

        if ((cursor == finish_addr) || (increment > 0 && cursor >= range_max) || (increment < 0 && cursor <= range_min))
            break;
    }

    return block;
}

// annotate the names of all wires and other named objects in a generate block
void AstNode::expand_genblock(std::string index_var, std::string prefix, std::map<std::string, std::string> &name_map)
{
    if (!index_var.empty() && type == AST_IDENTIFIER && str == index_var) {
        current_scope[index_var]->children[0]->cloneInto(this);
        return;
    }

    if ((type == AST_IDENTIFIER || type == AST_FCALL || type == AST_TCALL) && name_map.count(str) > 0)
        str = name_map[str];

    std::map<std::string, std::string> backup_name_map;

    for (size_t i = 0; i < children.size(); i++) {
        AstNode *child = children[i];
        if (child->type == AST_WIRE || child->type == AST_MEMORY || child->type == AST_PARAMETER || child->type == AST_LOCALPARAM ||
                child->type == AST_FUNCTION || child->type == AST_TASK || child->type == AST_CELL) {
            if (backup_name_map.size() == 0)
                backup_name_map = name_map;
            std::string new_name = prefix[0] == '\\' ? prefix.substr(1) : prefix;
            size_t pos = child->str.rfind('.');
            if (pos == std::string::npos)
                pos = child->str[0] == '\\' ? 1 : 0;
            else
                pos = pos + 1;
            new_name = child->str.substr(0, pos) + new_name + child->str.substr(pos);
            if (new_name[0] != '$' && new_name[0] != '\\')
                new_name = prefix[0] + new_name;
            name_map[child->str] = new_name;
            if (child->type == AST_FUNCTION)
                replace_result_wire_name_in_function(child, child->str, new_name);
            else
                child->str = new_name;
            current_scope[new_name] = child;
        }
    }

    for (size_t i = 0; i < children.size(); i++) {
        AstNode *child = children[i];
        if (child->type != AST_FUNCTION && child->type != AST_TASK && child->type != AST_PREFIX)
            child->expand_genblock(index_var, prefix, name_map);
    }

    if (backup_name_map.size() > 0)
        name_map.swap(backup_name_map);
}

// rename stuff (used when tasks of functions are instanciated)
void AstNode::replace_ids(const std::string &prefix, const std::map<std::string, std::string> &rules)
{
    if (type == AST_BLOCK)
    {
        std::map<std::string, std::string> new_rules = rules;
        std::string new_prefix = prefix + str;

        for (auto child : children)
            if (child->type == AST_WIRE) {
                new_rules[child->str] = new_prefix + child->str;
                child->str = new_prefix + child->str;
            }

        for (auto child : children)
            if (child->type != AST_WIRE)
                child->replace_ids(new_prefix, new_rules);
    }
    else
    {
        if (type == AST_IDENTIFIER && rules.count(str) > 0)
            str = rules.at(str);
        for (auto child : children)
            child->replace_ids(prefix, rules);
    }
}

// helper function for mem2reg_as_needed_pass1
static void mark_memories_assign_lhs_complex(std::map<AstNode*, std::set<std::string>> &mem2reg_places,
        std::map<AstNode*, uint32_t> &mem2reg_candidates, AstNode *that)
{
    for (auto &child : that->children)
        mark_memories_assign_lhs_complex(mem2reg_places, mem2reg_candidates, child);

    if (that->type == AST_IDENTIFIER && that->id2ast && that->id2ast->type == AST_MEMORY) {
        AstNode *mem = that->id2ast;
        if (!(mem2reg_candidates[mem] & AstNode::MEM2REG_FL_CMPLX_LHS))
            mem2reg_places[mem].insert(stringf("%s:%d", that->filename.c_str(), that->linenum));
        mem2reg_candidates[mem] |= AstNode::MEM2REG_FL_CMPLX_LHS;
    }
}

// find memories that should be replaced by registers
void AstNode::mem2reg_as_needed_pass1(std::map<AstNode*, std::set<std::string>> &mem2reg_places,
        std::map<AstNode*, uint32_t> &mem2reg_candidates, std::map<AstNode*, uint32_t> &proc_flags, uint32_t &flags)
{
    uint32_t children_flags = 0;
    int ignore_children_counter = 0;

    if (type == AST_ASSIGN || type == AST_ASSIGN_LE || type == AST_ASSIGN_EQ)
    {
        // mark all memories that are used in a complex expression on the left side of an assignment
        for (auto &lhs_child : children[0]->children)
            mark_memories_assign_lhs_complex(mem2reg_places, mem2reg_candidates, lhs_child);

        if (children[0]->type == AST_IDENTIFIER && children[0]->id2ast && children[0]->id2ast->type == AST_MEMORY)
        {
            AstNode *mem = children[0]->id2ast;

            // activate mem2reg if this is assigned in an async proc
            if (flags & AstNode::MEM2REG_FL_ASYNC) {
                if (!(mem2reg_candidates[mem] & AstNode::MEM2REG_FL_SET_ASYNC))
                    mem2reg_places[mem].insert(stringf("%s:%d", filename.c_str(), linenum));
                mem2reg_candidates[mem] |= AstNode::MEM2REG_FL_SET_ASYNC;
            }

            // remember if this is assigned blocking (=)
            if (type == AST_ASSIGN_EQ) {
                if (!(proc_flags[mem] & AstNode::MEM2REG_FL_EQ1))
                    mem2reg_places[mem].insert(stringf("%s:%d", filename.c_str(), linenum));
                proc_flags[mem] |= AstNode::MEM2REG_FL_EQ1;
            }

            // remember where this is
            if (flags & MEM2REG_FL_INIT) {
                if (!(mem2reg_candidates[mem] & AstNode::MEM2REG_FL_SET_INIT))
                    mem2reg_places[mem].insert(stringf("%s:%d", filename.c_str(), linenum));
                mem2reg_candidates[mem] |= AstNode::MEM2REG_FL_SET_INIT;
            } else {
                if (!(mem2reg_candidates[mem] & AstNode::MEM2REG_FL_SET_ELSE))
                    mem2reg_places[mem].insert(stringf("%s:%d", filename.c_str(), linenum));
                mem2reg_candidates[mem] |= AstNode::MEM2REG_FL_SET_ELSE;
            }
        }

        ignore_children_counter = 1;
    }

    if (type == AST_IDENTIFIER && id2ast && id2ast->type == AST_MEMORY)
    {
        AstNode *mem = id2ast;

        // flag if used after blocking assignment (in same proc)
        if ((proc_flags[mem] & AstNode::MEM2REG_FL_EQ1) && !(mem2reg_candidates[mem] & AstNode::MEM2REG_FL_EQ2)) {
            mem2reg_places[mem].insert(stringf("%s:%d", filename.c_str(), linenum));
            mem2reg_candidates[mem] |= AstNode::MEM2REG_FL_EQ2;
        }
    }

    // also activate if requested, either by using mem2reg attribute or by declaring array as 'wire' instead of 'reg'
    if (type == AST_MEMORY && (get_bool_attribute("\\mem2reg") || (flags & AstNode::MEM2REG_FL_ALL) || !is_reg))
        mem2reg_candidates[this] |= AstNode::MEM2REG_FL_FORCED;

    if (type == AST_MODULE && get_bool_attribute("\\mem2reg"))
        children_flags |= AstNode::MEM2REG_FL_ALL;

    std::map<AstNode*, uint32_t> *proc_flags_p = NULL;

    if (type == AST_ALWAYS) {
        int count_edge_events = 0;
        for (auto child : children)
            if (child->type == AST_POSEDGE || child->type == AST_NEGEDGE)
                count_edge_events++;
        if (count_edge_events != 1)
            children_flags |= AstNode::MEM2REG_FL_ASYNC;
        proc_flags_p = new std::map<AstNode*, uint32_t>;
    }

    if (type == AST_INITIAL) {
        children_flags |= AstNode::MEM2REG_FL_INIT;
        proc_flags_p = new std::map<AstNode*, uint32_t>;
    }

    uint32_t backup_flags = flags;
    flags |= children_flags;
    log_assert((flags & ~0x000000ff) == 0);

    for (auto child : children)
        if (ignore_children_counter > 0)
            ignore_children_counter--;
        else if (proc_flags_p)
            child->mem2reg_as_needed_pass1(mem2reg_places, mem2reg_candidates, *proc_flags_p, flags);
        else
            child->mem2reg_as_needed_pass1(mem2reg_places, mem2reg_candidates, proc_flags, flags);

    flags &= ~children_flags | backup_flags;

    if (proc_flags_p) {
        for (auto it : *proc_flags_p)
            log_assert((it.second & ~0xff000000) == 0);
        delete proc_flags_p;
    }
}

bool AstNode::mem2reg_check(std::set<AstNode*> &mem2reg_set)
{
    if (type != AST_IDENTIFIER || !id2ast || !mem2reg_set.count(id2ast))
        return false;

    if (children.empty() || children[0]->type != AST_RANGE || GetSize(children[0]->children) != 1)
        log_error("Invalid array access at %s:%d.\n", filename.c_str(), linenum);

    return true;
}

// actually replace memories with registers
void AstNode::mem2reg_as_needed_pass2(std::set<AstNode*> &mem2reg_set, AstNode *mod, AstNode *block)
{
    if (type == AST_BLOCK)
        block = this;

    if ((type == AST_ASSIGN_LE || type == AST_ASSIGN_EQ) && block != NULL &&
            children[0]->mem2reg_check(mem2reg_set) && children[0]->children[0]->children[0]->type != AST_CONSTANT)
    {
        std::stringstream sstr;
        sstr << "$mem2reg_wr$" << children[0]->str << "$" << filename << ":" << linenum << "$" << (autoidx++);
        std::string id_addr = sstr.str() + "_ADDR", id_data = sstr.str() + "_DATA";

        int mem_width, mem_size, addr_bits;
        children[0]->id2ast->meminfo(mem_width, mem_size, addr_bits);

        AstNode *wire_addr = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(addr_bits-1, true), mkconst_int(0, true)));
        wire_addr->str = id_addr;
        wire_addr->is_reg = true;
        wire_addr->attributes["\\nosync"] = AstNode::mkconst_int(1, false);
        mod->children.push_back(wire_addr);
        while (wire_addr->simplify(true, false, false, 1, -1, false, false)) { }

        AstNode *wire_data = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(mem_width-1, true), mkconst_int(0, true)));
        wire_data->str = id_data;
        wire_data->is_reg = true;
        wire_data->attributes["\\nosync"] = AstNode::mkconst_int(1, false);
        mod->children.push_back(wire_data);
        while (wire_data->simplify(true, false, false, 1, -1, false, false)) { }

        log_assert(block != NULL);
        size_t assign_idx = 0;
        while (assign_idx < block->children.size() && block->children[assign_idx] != this)
            assign_idx++;
        log_assert(assign_idx < block->children.size());

        AstNode *assign_addr = new AstNode(AST_ASSIGN_EQ, new AstNode(AST_IDENTIFIER), children[0]->children[0]->children[0]->clone());
        assign_addr->children[0]->str = id_addr;
        block->children.insert(block->children.begin()+assign_idx+1, assign_addr);

        AstNode *case_node = new AstNode(AST_CASE, new AstNode(AST_IDENTIFIER));
        case_node->children[0]->str = id_addr;
        for (int i = 0; i < mem_size; i++) {
            if (children[0]->children[0]->children[0]->type == AST_CONSTANT && int(children[0]->children[0]->children[0]->integer) != i)
                continue;
            AstNode *cond_node = new AstNode(AST_COND, AstNode::mkconst_int(i, false, addr_bits), new AstNode(AST_BLOCK));
            AstNode *assign_reg = new AstNode(type, new AstNode(AST_IDENTIFIER), new AstNode(AST_IDENTIFIER));
            if (children[0]->children.size() == 2)
                assign_reg->children[0]->children.push_back(children[0]->children[1]->clone());
            assign_reg->children[0]->str = stringf("%s[%d]", children[0]->str.c_str(), i);
            assign_reg->children[1]->str = id_data;
            cond_node->children[1]->children.push_back(assign_reg);
            case_node->children.push_back(cond_node);
        }
        block->children.insert(block->children.begin()+assign_idx+2, case_node);

        children[0]->delete_children();
        children[0]->range_valid = false;
        children[0]->id2ast = NULL;
        children[0]->str = id_data;
        type = AST_ASSIGN_EQ;
    }

    if (mem2reg_check(mem2reg_set))
    {
        AstNode *bit_part_sel = NULL;
        if (children.size() == 2)
            bit_part_sel = children[1]->clone();

        if (children[0]->children[0]->type == AST_CONSTANT)
        {
            int id = children[0]->children[0]->integer;
            str = stringf("%s[%d]", str.c_str(), id);

            delete_children();
            range_valid = false;
            id2ast = NULL;
        }
        else
        {
            std::stringstream sstr;
            sstr << "$mem2reg_rd$" << children[0]->str << "$" << filename << ":" << linenum << "$" << (autoidx++);
            std::string id_addr = sstr.str() + "_ADDR", id_data = sstr.str() + "_DATA";

            int mem_width, mem_size, addr_bits;
            id2ast->meminfo(mem_width, mem_size, addr_bits);

            AstNode *wire_addr = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(addr_bits-1, true), mkconst_int(0, true)));
            wire_addr->str = id_addr;
            wire_addr->is_reg = true;
            if (block)
                wire_addr->attributes["\\nosync"] = AstNode::mkconst_int(1, false);
            mod->children.push_back(wire_addr);
            while (wire_addr->simplify(true, false, false, 1, -1, false, false)) { }

            AstNode *wire_data = new AstNode(AST_WIRE, new AstNode(AST_RANGE, mkconst_int(mem_width-1, true), mkconst_int(0, true)));
            wire_data->str = id_data;
            wire_data->is_reg = true;
            if (block)
                wire_data->attributes["\\nosync"] = AstNode::mkconst_int(1, false);
            mod->children.push_back(wire_data);
            while (wire_data->simplify(true, false, false, 1, -1, false, false)) { }

            AstNode *assign_addr = new AstNode(block ? AST_ASSIGN_EQ : AST_ASSIGN, new AstNode(AST_IDENTIFIER), children[0]->children[0]->clone());
            assign_addr->children[0]->str = id_addr;

            AstNode *case_node = new AstNode(AST_CASE, new AstNode(AST_IDENTIFIER));
            case_node->children[0]->str = id_addr;

            for (int i = 0; i < mem_size; i++) {
                if (children[0]->children[0]->type == AST_CONSTANT && int(children[0]->children[0]->integer) != i)
                    continue;
                AstNode *cond_node = new AstNode(AST_COND, AstNode::mkconst_int(i, false, addr_bits), new AstNode(AST_BLOCK));
                AstNode *assign_reg = new AstNode(AST_ASSIGN_EQ, new AstNode(AST_IDENTIFIER), new AstNode(AST_IDENTIFIER));
                assign_reg->children[0]->str = id_data;
                assign_reg->children[1]->str = stringf("%s[%d]", str.c_str(), i);
                cond_node->children[1]->children.push_back(assign_reg);
                case_node->children.push_back(cond_node);
            }

            std::vector<RTLIL::State> x_bits;
            for (int i = 0; i < mem_width; i++)
                x_bits.push_back(RTLIL::State::Sx);

            AstNode *cond_node = new AstNode(AST_COND, new AstNode(AST_DEFAULT), new AstNode(AST_BLOCK));
            AstNode *assign_reg = new AstNode(AST_ASSIGN_EQ, new AstNode(AST_IDENTIFIER), AstNode::mkconst_bits(x_bits, false));
            assign_reg->children[0]->str = id_data;
            cond_node->children[1]->children.push_back(assign_reg);
            case_node->children.push_back(cond_node);

            if (block)
            {
                size_t assign_idx = 0;
                while (assign_idx < block->children.size() && !block->children[assign_idx]->contains(this))
                    assign_idx++;
                log_assert(assign_idx < block->children.size());
                block->children.insert(block->children.begin()+assign_idx, case_node);
                block->children.insert(block->children.begin()+assign_idx, assign_addr);
            }
            else
            {
                AstNode *proc = new AstNode(AST_ALWAYS, new AstNode(AST_BLOCK));
                proc->children[0]->children.push_back(case_node);
                mod->children.push_back(proc);
                mod->children.push_back(assign_addr);
            }

            delete_children();
            range_valid = false;
            id2ast = NULL;
            str = id_data;
        }

        if (bit_part_sel)
            children.push_back(bit_part_sel);
    }

    log_assert(id2ast == NULL || mem2reg_set.count(id2ast) == 0);

    auto children_list = children;
    for (size_t i = 0; i < children_list.size(); i++)
        children_list[i]->mem2reg_as_needed_pass2(mem2reg_set, mod, block);
}

// calulate memory dimensions
void AstNode::meminfo(int &mem_width, int &mem_size, int &addr_bits)
{
    log_assert(type == AST_MEMORY);

    mem_width = children[0]->range_left - children[0]->range_right + 1;
    mem_size = children[1]->range_left - children[1]->range_right;

    if (mem_size < 0)
        mem_size *= -1;
    mem_size += std::min(children[1]->range_left, children[1]->range_right) + 1;

    addr_bits = 1;
    while ((1 << addr_bits) < mem_size)
        addr_bits++;
}

bool AstNode::has_const_only_constructs(bool &recommend_const_eval)
{
    if (type == AST_FOR)
        recommend_const_eval = true;
    if (type == AST_WHILE || type == AST_REPEAT)
        return true;
    if (type == AST_FCALL && current_scope.count(str))
        if (current_scope[str]->has_const_only_constructs(recommend_const_eval))
            return true;
    for (auto child : children)
        if (child->AstNode::has_const_only_constructs(recommend_const_eval))
            return true;
    return false;
}

// helper function for AstNode::eval_const_function()
void AstNode::replace_variables(std::map<std::string, AstNode::varinfo_t> &variables, AstNode *fcall)
{
    if (type == AST_IDENTIFIER && variables.count(str)) {
        int offset = variables.at(str).offset, width = variables.at(str).val.bits.size();
        if (!children.empty()) {
            if (children.size() != 1 || children.at(0)->type != AST_RANGE)
                log_error("Memory access in constant function is not supported in %s:%d (called from %s:%d).\n",
                        filename.c_str(), linenum, fcall->filename.c_str(), fcall->linenum);
            children.at(0)->replace_variables(variables, fcall);
            while (simplify(true, false, false, 1, -1, false, true)) { }
            if (!children.at(0)->range_valid)
                log_error("Non-constant range in %s:%d (called from %s:%d).\n",
                        filename.c_str(), linenum, fcall->filename.c_str(), fcall->linenum);
            offset = std::min(children.at(0)->range_left, children.at(0)->range_right);
            width = std::min(std::abs(children.at(0)->range_left - children.at(0)->range_right) + 1, width);
        }
        offset -= variables.at(str).offset;
        std::vector<RTLIL::State> &var_bits = variables.at(str).val.bits;
        std::vector<RTLIL::State> new_bits(var_bits.begin() + offset, var_bits.begin() + offset + width);
        AstNode *newNode = mkconst_bits(new_bits, variables.at(str).is_signed);
        newNode->cloneInto(this);
        delete newNode;
        return;
    }

    for (auto &child : children)
        child->replace_variables(variables, fcall);
}

// evaluate functions with all-const arguments
AstNode *AstNode::eval_const_function(AstNode *fcall)
{
    std::map<std::string, AstNode*> backup_scope;
    std::map<std::string, AstNode::varinfo_t> variables;
    bool delete_temp_block = false;
    AstNode *block = NULL;

    size_t argidx = 0;
    for (auto child : children)
    {
        if (child->type == AST_BLOCK)
        {
            log_assert(block == NULL);
            block = child;
            continue;
        }

        if (child->type == AST_WIRE)
        {
            while (child->simplify(true, false, false, 1, -1, false, true)) { }
            if (!child->range_valid)
                log_error("Can't determine size of variable %s in %s:%d (called from %s:%d).\n",
                        child->str.c_str(), child->filename.c_str(), child->linenum, fcall->filename.c_str(), fcall->linenum);
            variables[child->str].val = RTLIL::Const(RTLIL::State::Sx, abs(child->range_left - child->range_right)+1);
            variables[child->str].offset = std::min(child->range_left, child->range_right);
            variables[child->str].is_signed = child->is_signed;
            if (child->is_input && argidx < fcall->children.size())
                variables[child->str].val = fcall->children.at(argidx++)->bitsAsConst(variables[child->str].val.bits.size());
            backup_scope[child->str] = current_scope[child->str];
            current_scope[child->str] = child;
            continue;
        }

        log_assert(block == NULL);
        delete_temp_block = true;
        block = new AstNode(AST_BLOCK);
        block->children.push_back(child->clone());
    }

    log_assert(block != NULL);
    log_assert(variables.count(str) != 0);

    while (!block->children.empty())
    {
        AstNode *stmt = block->children.front();

#if 0
        log("-----------------------------------\n");
        for (auto &it : variables)
            log("%20s %40s\n", it.first.c_str(), log_signal(it.second.val));
        stmt->dumpAst(NULL, "stmt> ");
#endif

        if (stmt->type == AST_ASSIGN_EQ)
        {
            stmt->children.at(1)->replace_variables(variables, fcall);
            while (stmt->simplify(true, false, false, 1, -1, false, true)) { }

            if (stmt->type != AST_ASSIGN_EQ)
                continue;

            if (stmt->children.at(1)->type != AST_CONSTANT)
                log_error("Non-constant expression in constant function at %s:%d (called from %s:%d). X\n",
                        stmt->filename.c_str(), stmt->linenum, fcall->filename.c_str(), fcall->linenum);

            if (stmt->children.at(0)->type != AST_IDENTIFIER)
                log_error("Unsupported composite left hand side in constant function at %s:%d (called from %s:%d).\n",
                        stmt->filename.c_str(), stmt->linenum, fcall->filename.c_str(), fcall->linenum);

            if (!variables.count(stmt->children.at(0)->str))
                log_error("Assignment to non-local variable in constant function at %s:%d (called from %s:%d).\n",
                        stmt->filename.c_str(), stmt->linenum, fcall->filename.c_str(), fcall->linenum);

            if (stmt->children.at(0)->children.empty()) {
                variables[stmt->children.at(0)->str].val = stmt->children.at(1)->bitsAsConst(variables[stmt->children.at(0)->str].val.bits.size());
            } else {
                AstNode *range = stmt->children.at(0)->children.at(0);
                if (!range->range_valid)
                    log_error("Non-constant range in %s:%d (called from %s:%d).\n",
                            range->filename.c_str(), range->linenum, fcall->filename.c_str(), fcall->linenum);
                int offset = std::min(range->range_left, range->range_right);
                int width = std::abs(range->range_left - range->range_right) + 1;
                varinfo_t &v = variables[stmt->children.at(0)->str];
                RTLIL::Const r = stmt->children.at(1)->bitsAsConst(v.val.bits.size());
                for (int i = 0; i < width; i++)
                    v.val.bits.at(i+offset-v.offset) = r.bits.at(i);
            }

            delete block->children.front();
            block->children.erase(block->children.begin());
            continue;
        }

        if (stmt->type == AST_FOR)
        {
            block->children.insert(block->children.begin(), stmt->children.at(0));
            stmt->children.at(3)->children.push_back(stmt->children.at(2));
            stmt->children.erase(stmt->children.begin() + 2);
            stmt->children.erase(stmt->children.begin());
            stmt->type = AST_WHILE;
            continue;
        }

        if (stmt->type == AST_WHILE)
        {
            AstNode *cond = stmt->children.at(0)->clone();
            cond->replace_variables(variables, fcall);
            while (cond->simplify(true, false, false, 1, -1, false, true)) { }

            if (cond->type != AST_CONSTANT)
                log_error("Non-constant expression in constant function at %s:%d (called from %s:%d).\n",
                        stmt->filename.c_str(), stmt->linenum, fcall->filename.c_str(), fcall->linenum);

            if (cond->asBool()) {
                block->children.insert(block->children.begin(), stmt->children.at(1)->clone());
            } else {
                delete block->children.front();
                block->children.erase(block->children.begin());
            }

            delete cond;
            continue;
        }

        if (stmt->type == AST_REPEAT)
        {
            AstNode *num = stmt->children.at(0)->clone();
            num->replace_variables(variables, fcall);
            while (num->simplify(true, false, false, 1, -1, false, true)) { }

            if (num->type != AST_CONSTANT)
                log_error("Non-constant expression in constant function at %s:%d (called from %s:%d).\n",
                        stmt->filename.c_str(), stmt->linenum, fcall->filename.c_str(), fcall->linenum);

            block->children.erase(block->children.begin());
            for (int i = 0; i < num->bitsAsConst().as_int(); i++)
                block->children.insert(block->children.begin(), stmt->children.at(1)->clone());

            delete stmt;
            delete num;
            continue;
        }

        if (stmt->type == AST_CASE)
        {
            AstNode *expr = stmt->children.at(0)->clone();
            expr->replace_variables(variables, fcall);
            while (expr->simplify(true, false, false, 1, -1, false, true)) { }

            AstNode *sel_case = NULL;
            for (size_t i = 1; i < stmt->children.size(); i++)
            {
                bool found_match = false;
                log_assert(stmt->children.at(i)->type == AST_COND);

                if (stmt->children.at(i)->children.front()->type == AST_DEFAULT) {
                    sel_case = stmt->children.at(i)->children.back();
                    continue;
                }

                for (size_t j = 0; j+1 < stmt->children.at(i)->children.size() && !found_match; j++)
                {
                    AstNode *cond = stmt->children.at(i)->children.at(j)->clone();
                    cond->replace_variables(variables, fcall);

                    cond = new AstNode(AST_EQ, expr->clone(), cond);
                    while (cond->simplify(true, false, false, 1, -1, false, true)) { }

                    if (cond->type != AST_CONSTANT)
                        log_error("Non-constant expression in constant function at %s:%d (called from %s:%d).\n",
                                stmt->filename.c_str(), stmt->linenum, fcall->filename.c_str(), fcall->linenum);

                    found_match = cond->asBool();
                    delete cond;
                }

                if (found_match) {
                    sel_case = stmt->children.at(i)->children.back();
                    break;
                }
            }

            block->children.erase(block->children.begin());
            if (sel_case)
                block->children.insert(block->children.begin(), sel_case->clone());
            delete stmt;
            delete expr;
            continue;
        }

        if (stmt->type == AST_BLOCK)
        {
            block->children.erase(block->children.begin());
            block->children.insert(block->children.begin(), stmt->children.begin(), stmt->children.end());
            stmt->children.clear();
            delete stmt;
            continue;
        }

        log_error("Unsupported language construct in constant function at %s:%d (called from %s:%d).\n",
                stmt->filename.c_str(), stmt->linenum, fcall->filename.c_str(), fcall->linenum);
        log_abort();
    }

    if (delete_temp_block)
        delete block;

    for (auto &it : backup_scope)
        if (it.second == NULL)
            current_scope.erase(it.first);
        else
            current_scope[it.first] = it.second;

    return AstNode::mkconst_bits(variables.at(str).val.bits, variables.at(str).is_signed);
}

YOSYS_NAMESPACE_END