Netlist.pm

#** @file Netlist.pm
# @verbatim
#-------------------------------------------------------------------------------
#  University of Applied Sciences Technikum Wien
#
#  Department of Embedded Systems
#  http://embsys.technikum-wien.at
#
#  Josef Ressel Center for Verification of Embedded Computing Systems
#  http://vecs.technikum-wien.at
#
#-------------------------------------------------------------------------------
#  File:              Netlist.pm
#  Created on:        29.04.2015
#  $LastChangedBy$
#  $LastChangedDate$
#
#  Description:
#
#  FIJI Netlist class: Functions to instrument & export a Verilog::Netlist
#-------------------------------------------------------------------------------
# @endverbatim
#*

## @file Netlist.pm
# @brief Contains class \ref FIJI::Netlist

## @class FIJI::Netlist
# @brief Functions to instrument & export a Verilog::Netlist
package FIJI::Netlist;

use strict;
use warnings;

use Scalar::Util 'blessed';
use Log::Log4perl qw(get_logger :easy);
use File::Basename qw(basename);

use Verilog::Netlist 99.415;
use Verilog::Language 99.415;
use Data::Dumper;

use FIJI::VHDL;

use constant HIERSEP               => "|";
use constant FIJI_NAMESPACE_PREFIX      => "fiji_";
use constant FIJI_PORT_IN_POSTFIX  => "_inj_i";
use constant FIJI_PORT_OUT_POSTFIX => "_ori_o";
use constant MAX_UNIQUE_TRIES => 10;

use constant FIJI_LOGO => <<logo_end;
//  FIJIFIJIFIJIFIJIFIJIFIJIFIJIFIJIFIJIFIJI
//  FIJIFIJIFIJIFIJIF   FIJIFIJIFIJIFIJIFIJI
//  FIJIFIJIFIJIFIJ    IFIJIFIJIFIJIFIJIFIJI
//  FIJIF       FI           IJIFIJIFIJIFIJI
//  FIJIFIJIFI            JIFIJIFIJIFIJIFIJI
//  FIJIFIJI            FIJIFIJIFIJIFIJIFIJI
//  FIJIFI    JI   IFI   IJIFIJIFIJIFIJIFIJI
//  FIJIF   FIJ   JIFIJ   JIFIJIFIJIFIJIFIJI
//  FIJIFIJIFI   IJIFIJI   IFIJIFIJIFIJIFIJI
//  FIJIFIJIF    IJIFIJIFIJIFIJIFIJIFIJIFIJI
//  FIJIFIJI    FIJIFIJIFIJIFIJIFIJIFIJIFIJI
//  FIJIFIJ     FIJIF           FIJIFIJIFIJI
//  FIJIFI     IFI      Fault      IFIJIFIJI
//  FIJIF             InJection     FIJIFIJI
//  FIJ              Instrumenter    IJIFIJI
//  F                                    IJI
//  FIJIFIJIFIJIFIJIFIJIFIJIFIJIFIJIFIJIFIJI
logo_end

## @function public new ()
# @brief creates a new FIJI::Netlist object
#
# @returns the newly created FIJI::Netlist object
sub new {

    my ($class) = @_;

    my $self = {};
    bless $self, $class;

    $self->{'nl'} = new Verilog::Netlist(

        # options => $opt,
        # keep_comments => 1, # include comments in netlist
        link_read_nonfatal => 1,    # do not fail if module description not found
        use_vars           => 1,
    );
    return $self;
}

## @method public read_file ($filename)
# @brief Tries to read a Verilog netlist from the given file
#
# @param filename    The Verilog file to read
#
# @returns 1   if an error occurred
# @returns 0   if successful
sub read_file {
    my $logger = get_logger("");
    my ($self, $filename) = @_;

    ## Netlist synthesized from VHDL could contain SV keywords at this point.
    Verilog::Language::language_standard("1364-2001");

    $logger->info("Reading in netlist from file \"$filename\".");
    eval {
        $self->{'nl'}->read_file(filename => $filename);    # read Verilog file
        $self->{'nl'}->link();                              # Read in any sub-modules
    };

    if ($self->{'nl'}->errors() != 0 || $@) {
        $logger->error("Could not parse $filename!", $@ ? "\n" . $@ : "");
        return 1;
    }

    $self->{'filename'} = $filename;

    $logger->info("Successfully read in netlist from file \"$filename\".");
    return 0;
}

## @method public get_toplevel_port_names ()
# @brief retrieves the port names of all toplevel modules
#
# @returns an array of Verilog::Port references
sub get_toplevel_port_names {
    my ($self, $dir) = @_;
    my $ports_ref = [];
    foreach my $mod ($self->{'nl'}->top_modules_sorted) {
        foreach my $port ($mod->ports) {
            if (   !defined($dir)
                || ($dir eq "o" && $port->direction eq "out")
                || ($dir eq "i" && $port->direction eq "in"))
            {
                push @{$ports_ref}, $port->name;
            }
        }
    }
    return $ports_ref;
}

## @method public get_toplevel_module ()
# @brief retrieves the port names of all toplevel modules
#
# @returns a Verilog::Module reference
sub get_toplevel_module {
    my ($self) = @_;
    my @m      = $self->{'nl'}->top_modules_sorted;
    my $n      = @m;
    return $m[0] if ($n == 1);
    return "More than one toplevel module present in netlist." if ($n > 1);
    return "No toplevel module found.";
}

## @method public get_nets ()
# @brief retrieves all nets in the netlist
#
# @returns an array of hashes for all nets containing:
# 'name' the name of the net
# 'path' the hierarchical path of the net
# 'net'  the Verilog::Netlist::Net reference to the net
sub get_nets {
    my ($self) = @_;

    # my $nets_ref = {'metadata' => [], 'names' => [], 'nets' => []};
    my $nets_ref = [];
    my $hier     = "";
    foreach my $mod ($self->{'nl'}->top_modules_sorted) {
        $self->_get_subnets($nets_ref, $mod, $hier);
    }
    return $nets_ref;
}

sub _extract_low_high {
    my ($in_low, $in_high) = @_;
    my ($out_low, $out_high);

    # msb might be lower than lsb if index range is "upto" -> swap
    if ($in_high < $in_low) {
        $out_low = $in_high;
        $out_high = $in_low;
    } else {
        $out_low = $in_low;
        $out_high = $in_high;
    }
    return ($out_low, $out_high);
}

#** @method private _get_subnets ($nets_ref,$mod,$hier)
# @brief retrieves all nets in the given module
#
# @param nets_ref    the central reference to push found nets (name,path,netref) to
# @param mod         the module to search
# @param hier        a string representing the current hierarchy level, separated
#                    be HIERSEP
sub _get_subnets {

    my $logger = get_logger("");
    my ($self, $nets_ref, $mod, $hier) = @_;

    my $thishier = $hier;
    $thishier .= HIERSEP if $thishier ne "";
    $thishier .= $mod->name;

    foreach my $n ($mod->nets) {
        if (defined($n->msb) && defined($n->lsb)) {
            my ($low, $high) = _extract_low_high($n->lsb, $n->msb);
            for (my $sub = $low ; $sub <= $high ; $sub++) {
                my $thisnet_ref = {name => $n->name . "[$sub]", path => $thishier, net => $n, index => $sub};
                push(@{$nets_ref}, $thisnet_ref);
            }
        } else {
            my $thisnet_ref = {name => $n->name, path => $thishier, net => $n};
            push(@{$nets_ref}, $thisnet_ref);
        }

    }

    foreach my $cell ($mod->cells) {
        if (defined($cell->submod)) {
            $self->_get_subnets($nets_ref, $cell->submod, $thishier);
        }
    }
}

## @function private _check_name_in_hierarchy ($startmod,$name)
# @brief checks if a given name exists
# checks if the $name exists as port, net, or cell name in the instantiation tree.
#
# @param startmod    the module to start with
# @param name        the name to check against
sub _check_name_in_hierarchy {

    my $logger = get_logger("");
    my ($startmod, $name) = @_;
    my $nl = $startmod->netlist;

    $logger->debug("Checking \"" . $startmod->name . "\" for name \"$name\"");

    # check if a net is named the same
    for my $net ($startmod->nets) {
        if ($net->name eq $name) {
            my $msg = "Name \"$name\" does already exist as net in " . $startmod->name;
            return $msg;
        }
    }

    # check if a port is named the same
    for my $port ($startmod->ports) {
        if ($port->name eq $name) {
            my $msg = "Name \"$name\" does already exist as port in " . $startmod->name;
            return $msg;
        }
    }

    for my $cell ($startmod->cells) {
        if ($cell->name eq $name) {
            my $msg = "Name \"$name\" does already exist as cell in " . $startmod->name;
            return $msg;
        }
    }

    # find any module instantiating the current start module
    foreach my $mod ($nl->modules) {
        foreach my $cell ($mod->cells) {
            if (defined $cell->submod && $cell->submod == $startmod) {
                my $msg = _check_name_in_hierarchy($mod, $name);
                return $msg if defined $msg;
            }
        }
    }

    return undef;
}

## @function private _add_port_to_hierarchy ($startmod,$name,$function,$index,$indent)
# @brief adds a port to all modules starting from a leaf node
#
# @param startmod    the module to start with
# @param name        the port name to be generated
# @param function    the function of this port in FIJI (FIJI::VHDL->FIJI_PORTTYPE_xxx)
# @param index       for ORIGINAL,MODIFIED and FAULT_DETECT: the index of this net
# @param indent      optional, needed just for formatting logging output
#
# @returns undef if the given port $name is already found
# @returns Verilog::Port reference to the new port if successful
sub _add_port_to_hierarchy {

    my $logger = get_logger("");
    my ($startmod, $name, $function, $index, $indent) = @_;
    my $nl        = $startmod->netlist;
    my $direction = "undef";
    if (!defined $indent) {
        $indent = "";
    } else {
        $indent .= "  ";
    }

    return undef if ($startmod->find_port($name));

    $logger->debug($indent . "Adding port \"$name\" to module \"" . $startmod->name . "\"");

    # decide direction
    if (   $function == FIJI::VHDL->FIJI_PORTTYPE_MODIFIED
        || $function == FIJI::VHDL->FIJI_PORTTYPE_RESET_TO_DUT)
    {
        $direction = "in";
    } else {
        $direction = "out";
    }

    # generate port
    my $np = $startmod->new_port(name => $name, direction => $direction);

    # set port type for wrapper generation
    $np->userdata(FIJI::VHDL->FIJI_USERDATA_PORTTYPE, $function);

    # set indices
    if (   $function == FIJI::VHDL->FIJI_PORTTYPE_MODIFIED
        || $function == FIJI::VHDL->FIJI_PORTTYPE_ORIGINAL)
    {
        $np->userdata(FIJI::VHDL->FIJI_USERDATA_FIU_INDEX, $index);
    } elsif ($function == FIJI::VHDL->FIJI_PORTTYPE_FAULT_DETECTION) {
        $np->userdata(FIJI::VHDL->FIJI_USERDATA_FD_INDEX, $index);
    }

    # let Verilog-Perl create a new net for the new port.
    $startmod->link;

    # find all modules instantiating the current module
    foreach my $mod ($nl->modules_sorted) {
        foreach my $cell ($mod->cells) {
            if (defined $cell->submod && $cell->submod == $startmod) {
                $logger->debug($indent . "Adding pin \"$name\" to cell \"" . $cell->name . "\"");
                $logger->debug($indent . "Connecting pin \"" . $cell->name . HIERSEP . $name . "\" to port \"" . $np->module->name . HIERSEP . $np->name . "\"");
                $cell->new_pin(
                    name     => $name,
                    portname => $np->name,
                    netnames => [{'netname' => $np->net->name}],
                );

                # let verilog-perl find the net and port.
                # @FIXME sufficient to link "mod" here?
                $mod->link;
                _add_port_to_hierarchy($mod, $name, $function, $index, $indent);
            }
        }
    }

    return $np;
}

## @method public net_add_function($net, $function, $port_name, $index)
# @brief Generate external access to a single net
#
# Performs the following steps:
#    1.  check if the default port name does not yet exist
#    1a. if it exists, generate a new net name
#    2.  add a port through the entire hierarchy
#    3.  assign the net to the port using a contassign statement
#
# @param net         the Verilog::Net object to be used
# @param function    the function out of FIJI::VHDL->FIJI_PORTTYPE_xxx
# @param port_name   how the port shall be named (will be prefixed with "fiji_")
# @param index       for some FIJI_PORTTYPEs, an index is needed (FIU and Fault Detect)
#
# @returns undef
sub net_add_function {
    my $logger = get_logger("");
    my ($self, $net, $function, $port_name, $index) = @_;

    $logger->debug("Adding function to \"" . $net->module->name . "\", net \"" . $net->name . "\"");

    my $prefix = "fiji_";

    my $unique_name = _unique_name($net->module,$prefix.$port_name);

    if (!defined $unique_name) {
        $logger->error("Could not find a unique name for prefix ".$prefix.$port_name)
    }

    $logger->debug("\"" . $unique_name . "\" can be used as fiji connector");
    my $op = _add_port_to_hierarchy($net->module, $unique_name, $function, $index);

    $logger->debug("Connecting Port \"" . $op->name . "\" to net \"" . $net->name . "\"");

    # connect the net to the newly created port
    $net->module->new_contassign(
        keyword => "assign",
        lhs     => $op->name,
        rhs     => $net->name,
        module  => $op->module,
        netlist => $op->module->netlist
    );

    return undef;
}

# tries to generate a unique but recognizable net name by appending a
# random hex number if necessary
sub _unique_name {
    my $logger = get_logger("");
    my ($mod,$requested_name) = @_;

    # check if requested name is OK
    my $msg = _check_name_in_hierarchy($mod, $requested_name);
    
    if (!defined $msg) {
        return $requested_name;
    }

    # else try up to 10 times to generate a unique name by appending
    # a 4-digit random hex number
    for (my $tries = 0; $tries < MAX_UNIQUE_TRIES; $tries++) {
        my $name = sprintf("%s_%04x", $requested_name, rand(0xffff));
        $msg = _check_name_in_hierarchy($mod, $name);
        return $name if (!defined $msg);
    }
    
    return undef
}

# take a possible escaped identifier and make it a legal _and_ sane verilog identifier
sub _sanitize_identifier {
    my $insane = shift;

    # Verilog allows "non-alphanumeric" characters in identifiers if they start with a backslash and end with whitespace (escaped identifiers) but we don't want to.
    my $sane = ($insane =~ s/[^a-zA-Z0-9_]+/_/gr);
    # VHDL signals must not contain multiple subsequent underscores
    $sane =~ s/__+/_/g;
    return $sane
}

sub generate_contassign {
    my $logger = get_logger("");
    my ($module, $lhs, $rhs) = @_;
    $logger->trace("Setting \"$lhs = $rhs\"");
    $module->new_contassign(
        keyword => "assign",
        lhs     => $lhs,
        rhs     => $rhs,
        module  => $module,
        netlist => $module->netlist
    );
}

## @method public instrument_net($net,$fiu_idx, $driver, $driver_type)
# @brief instruments a single net for fault injection
#
# This method performs the following steps
#   1. tries to determine the driver, or otherwise prompts the user to select it
#   2. generate external access output and input ports
#   3. interconnects these ports to the matching driver and driven cells
#
# @param net_path        the Verilog::Net to instrument
# @param fiu_idx         the FIU number this external access shall be connected to
# @param driver_path     the path to the driver of this net (optional but depends on driver_type)
# @param driver_type     the type of the driver (can be PIN, PORT, ASSIGN) (optional but depends on driver_path)
#
# @returns STRING          if an error occurred
# @returns undef           if successful
sub instrument_net {

    my $logger = get_logger("");
    my ($self, $net_path, $fiu_idx, $driver_path, $driver_type) = @_;
    my $msg;

    # split hierarchical net path
    my $net_descriptor = $self->get_netdescriptor_from_path($net_path);

    if (ref($net_descriptor) ne "HASH") {
        return $net_descriptor;
    }

    my $net = $net_descriptor->{'net'};
    my $msb = $net_descriptor->{'msb'};
    my $lsb = $net_descriptor->{'lsb'};
    my $mod = $net_descriptor->{'mod'};
    my $idx = '';
    my $idx_postfix = '';

    # We need to produce names for the i/o ports that route the signals
    # to the FIC. To allow to instrument multiple indices of a single
    # signal we need to make these names unique thus we even include the
    # indices if used.
    if (defined $msb && defined $lsb) {
        if ($msb ne $lsb) {
            # We dont support the instrumentation of vectors (only sinlge indices of busses).
            return "The given net to instrument is a vector with multiple bits.\nThis is not supported.\nMay you want to instrument a single bit of said vector instead?";
            # $idx         = "[".$msb.":".$lsb."]";
            # $idx_postfix = "_".$msb."_".$lsb."_";
        } else {
            $idx         = "[".$msb."]";
            $idx_postfix = "_".$msb."_";
        }
    }

    $logger->info("Instrumenting \"" . $net->module->name . "\", net \"" . $net->name.$idx . "\"");

    my $output_name = (FIJI_NAMESPACE_PREFIX . $net->name . $idx_postfix . FIJI_PORT_OUT_POSTFIX);
    $output_name = _sanitize_identifier($output_name);
    my $input_name  = (FIJI_NAMESPACE_PREFIX . $net->name . $idx_postfix . FIJI_PORT_IN_POSTFIX);
    $input_name = _sanitize_identifier($input_name);

    # generate unique name for output port, return with error message if that fails
    my $unique_output_name = _unique_name($mod, $output_name);
    return "Could not generate unique name for prefix $output_name" if (!defined $unique_output_name);

    $logger->debug("\"" . $unique_output_name . "\" will be used as fiji connector (output)");
    my $op = _add_port_to_hierarchy($mod, $unique_output_name, FIJI::VHDL->FIJI_PORTTYPE_ORIGINAL, $fiu_idx);

    # generate unique name for input port, return with error message if that fails
    my $unique_input_name = _unique_name($mod, $input_name);
    return "Could not generate unique name for prefix $input_name" if (!defined $unique_input_name);

    $logger->debug("\"" . $unique_input_name . "\" will be used as fiji connector (input)");
    my $ip = _add_port_to_hierarchy($mod, $unique_input_name, FIJI::VHDL->FIJI_PORTTYPE_MODIFIED, $fiu_idx);

    my %connections;
    my $rv = $self->_get_net_connections($net, \%connections, $msb, $driver_path, $driver_type);
    return $rv if (defined $rv);

    # connecting newly created output to driver
    foreach my $connection (@{$connections{'drivers'}}) {
        if (ref($connection) eq "Verilog::Netlist::Pin") {
            # FIXME: handle concatenations
            # For buses we introduce a dedicated temporary wire to re-route/inject single bits of it.
            # Therefore we can simply leave them alone here.
            if (defined($lsb) && defined($msb)) {
                $logger->warn("Ignoring Pin \"" . $connection->cell->name . HIERSEP . $connection->name . "\" because instrumented net \"" . $net->name . "\" is a bus.");
                next;
            }

            # If the driver is a pin of a cell, connect this pin to the newly created net
            $logger->debug("Original: Connecting (output) pin \"" . $connection->cell->name . HIERSEP . $connection->name . "\" to generated output \"" . $op->name . "\"");
            for my $netname (@{$connection->netnames}) {

                # @FIXME work to be done for Buses
                if (($netname->{'netname'} eq $net->name) && 
                     (!defined $netname->{lsb} || $netname->{lsb} eq $lsb) &&
                     (!defined $netname->{msb} || $netname->{msb} eq $msb)) {
                    $netname->{'netname'} = $op->net->name;
                    # there will never be an indexed newly created port (only single-bit FIUs)
                    $netname->{lsb} = undef;
                    $netname->{msb} = undef;
                }
            }

            #$connection->net(undef);     # resolved by link
            $connection->port(undef);    # resolved by link

        } elsif (ref($connection) eq "Verilog::Netlist::Port") {

                # @FIXME work to be done for Buses
            # if it is a port of a module, connect this port to the newly created net
            $logger->debug("Original: Connecting (input) port \"" . $connection->name . "\" to generated output \"" . $op->name . "\"");
            $connection->net($op->net);
            $mod->new_contassign(
                keyword => "assign",
                lhs     => $op->name,
                rhs     => $connection->name.$idx,
                module  => $mod,
                netlist => $mod->netlist
            );
        } elsif (ref($connection) eq "Verilog::Netlist::ContAssign") {
            # Retrieve net object of LHS of the assignment to determine if it is a bus and if the assignment is to the complete net or a single bit.
            my $lhs_elems = $self->_extract_netstring_elements($connection->lhs);
            my $lhs_net_name = $lhs_elems->{'net_name'};
            my $lhs_net = $mod->find_net($lhs_net_name);
            if (!defined($lhs_net)) {
                my $lhs_port = $mod->find_port($lhs_net_name);
                if (!defined($lhs_port)) {
                    return "Could not find net or port in module \"" . $mod->name . "\" matching LHS of assignment \"" . $connection->lhs . "\" = \"" . $connection->rhs . "\"";
                }
                # FIXME: so this is actually a port...
                $logger->fatal("Found port name in continuous assignment. This is not supported yet.");
                return "BORKED";
            }
            if (!defined($lhs_net->msb)) {
                # If the signal in LHS is not a vector at all we simply drive the new port instead, easy.
                $connection->lhs($op->name);
                $logger->debug("Original: Connecting to generated output \"" . $op->name . "\" continuous assignment of \"" . $connection->rhs . "\"");
            } else {
                # If LHS is a bus however we need more effort.
                # We need to extract the bit we want and drive the new port, but
                # also continue to drive the remaining bits of the vector just like before
                # e.g. when we want to tap [1] of \dumb.non.hierarchical_bus then we need to transform this:
                #   wire   [3:0] wirebus;
                #   wire   [3:0] \dumb.non.hierarchical_bus ;
                #   assign \dumb.non.hierarchical_bus = ~wirebus;
                # into this:
                #   wire   [3:0] wirebus;
                #   wire   [3:0] \dumb.non.hierarchical_bus ;
                #   wire   [3:0] tmp_hierarchical_bus;
                #   assign tmp_hierarchical_bus = ~wirebus;
                #   assign tmp_signal_o = tmp_hierarchical_bus[1];
                #   assign \dumb.non.hierarchical_bus[0] = tmp_hierarchical_bus[0];
                #   assign \dumb.non.hierarchical_bus[1] = tmp_signal_i;
                #   assign \dumb.non.hierarchical_bus[2] = tmp_hierarchical_bus[2];
                #   assign \dumb.non.hierarchical_bus[3] = tmp_hierarchical_bus[3];
                # However, we just need to create the temporary bus once even if more than one bit of it get instrumented...

                my ($op_rhs, $ip_lhs);
                # If the LHS is a bit range of a vector we have either
                # - generated the net earlier (in the else branch below) or,
                # - it was a bit-wise assignment in the original netlist as well.
                # In any case we only need to generate a temporary net if the assignment is not to a bit of a vector.
                if (defined($lhs_elems->{'lsb'})) {
                    $op_rhs = $connection->rhs;
                    $ip_lhs = $connection->lhs;
                } else {
                    my $tmp_name = FIJI_NAMESPACE_PREFIX . $lhs_net->name . "_tmp";
                    my $unique_tmp_name = _unique_name($mod, $tmp_name);
                    return "Could not generate unique name for prefix ".$tmp_name if (!defined $unique_tmp_name);

                    # Generate intermediate (tmp) bus and assign old RHS to it
                    $logger->debug("Generating intermediate bus to connect split up result of \"" . $connection->rhs . "\"");
                    my $tmp_bus = $mod->new_net(
                        name => _sanitize_identifier($unique_tmp_name),
                        msb => $lhs_net->msb,
                        lsb => $lhs_net->lsb,
                    );
                    generate_contassign($mod, $tmp_bus->name, $connection->rhs);

                    # Connect the individual bits of the tmp bus with the (previous) LHS that we don't want to instrument
                    my ($low, $high) = _extract_low_high($lhs_net->lsb, $lhs_net->msb);
                    for (my $i = $low ; $i <= $high ; $i++) {
                        if ($i != $msb) {
                            generate_contassign($mod, $connection->lhs."[".$i."]", $tmp_bus->name."[".$i."]");
                        }
                    }
                    $op_rhs = $tmp_bus->name . "[".$msb."]";
                    $ip_lhs = $connection->lhs."[".$msb."]";
                }
                # Connect requested bit of the tmp bus with the output port
                $logger->debug("Original: Adding assignment \"" . $op->name . " = " . $op_rhs . "\"");
                generate_contassign($mod, $op->name, $op_rhs);

                $logger->debug("Modified: Adding assignment \"" . $ip_lhs . " =  " . $ip->name . "\"");
                $connection->rhs($ip->name);
                $connection->lhs($ip_lhs);
            }
        } else {
            $logger->debug("Driver instance is neither pin, port nor contassign?");
        }

        # create interconnections for newly created port/pin
        # @TODO needed here or OK linking once after loop?
        # $mod->link;
    }

    # create interconnections for newly created port/pin
    # @TODO needed here or OK linking once after all loops?
    # $mod->link;
    
    # exactly the same for the input
    # connecting newly created input to driven cells
    foreach my $connection (@{$connections{'driven'}}) {
        if (ref($connection) eq "Verilog::Netlist::Pin") {
            for my $netname (@{$connection->netnames}) {
                if ($netname->{'netname'} eq $net->name) {
                    # FIXME: we'll ignore all indexed nets for now but that certainly is not right... or is it?
                    if (!defined($lsb) && !defined($msb)) {
                        $logger->warn("Modified: Connecting (input) pin \"" . $connection->cell->name . HIERSEP . $connection->name . "\" to generated input \"" . $ip->name . "\"");
                        $netname->{'netname'} = $ip->net->name;

                        #$connection->net(undef);     # resolved by link
                        $connection->port(undef);    # resolved by link

                    # } else {
                     # $netname->{lsb} eq $lsb) &&
                     # $netname->{msb} eq $msb)) {
                    # there will never be an indexed newly created port (only single-bit FIUs)
                    # $netname->{lsb} = undef;
                    # $netname->{msb} = undef;
                    }
                }
            }
        } elsif (ref($connection) eq "Verilog::Netlist::Port") {
                # @FIXME work to be done for Buses
            $logger->debug("Modified: Connecting (output) port \"" . $connection->module->name . HIERSEP . $connection->name . "\" to generated input \"" . $ip->name . "\"");
            $mod->new_contassign(
                keyword => "assign",
                lhs     => $connection->name.$idx,
                rhs     => $ip->name,
                module  => $mod,
                netlist => $mod->netlist
            );
        } elsif (ref($connection) eq "Verilog::Netlist::ContAssign") {
            # Retrieve net object of LHS of the assignment to determine if it is a bus and if the assignment is to the complete net or a single bit.
            my $lhs_elems = $self->_extract_netstring_elements($connection->lhs);
            my $lhs_net_name = $lhs_elems->{'net_name'};
            my $lhs_net = $mod->find_net($lhs_net_name);
            if (!defined($lhs_net)) {
                my $lhs_port = $mod->find_port($lhs_net_name);
                if (!defined($lhs_port)) {
                    return "Could not find net or port in module \"" . $mod->name . "\" matching LHS of assignment \"" . $connection->lhs . "\" = \"" . $connection->rhs . "\"";
                }
                # FIXME: so this is actually a port...
                $logger->fatal("Found port name in continuous assignment. This is not supported yet.");
                return "BORKED";
            }
            if (!defined($lhs_net->msb)) {
                # If the signal in LHS is not a vector at all we simply assign the injected net from the new port, easy.
                # However, we need to check for inversions on the RHS and conserve them
                $connection->rhs =~ /^[ \t]*(~)/;
                my $new_rhs = $1 . $ip->name;
                $connection->rhs($new_rhs);
                $logger->debug("Modified: Connecting to generated input \"$new_rhs\" in continuous assignment to \"" . $connection->lhs . "\"");
            } else {
                # FIXME: if LHS is a bus possibly containing one or more wires we need to instrument, we may need to use a temp wire to preserve the old values like for drivers above - I think.
                # $logger->warn("*Would* set RHS of \"" . $connection->lhs . " = " . $connection->rhs . "\" to \"$input_name\"");
                # $connection->rhs($input_name);
            }
        } else {
            $logger->debug("Driven instance is neither pin, port nor contassign?");
        }
    }

    # create interconnections for newly created ports/pins
    # @TODO OK linking once after loop?
    $mod->link;

    # Clean up "loose" wires:
    # If we instrument nets that are only wired through this module from and into others the need for the intermediate wire is removed by the introduction of our instrumentation pins
    my %instrumented_connections;
    $rv = $self->_get_net_connections($net, \%instrumented_connections, $msb, $driver_path, $driver_type);
    return $rv if (defined $rv);

    if (scalar(@{$instrumented_connections{'driven'}}) == 0 && scalar(@{$instrumented_connections{'drivers'}}) == 0 && scalar(@{$instrumented_connections{'connected'}}) == 0) {
        $logger->warn("Instrumenting \"" . $mod->name . "\", net \"" . $net->name.$idx . "\" has lead to a loose wire - removing.");
        $net->delete();
        $mod->link;
    }
    return undef;
}

## @method public validate_driver($net_path, $driver_path, $driver_type)
# @brief Check if the given driver is valid for the given net
#
# Check if the driver specified by $driver_type and $driver_path
# is actually connected to the net specified by $net_path
#
# @param net_path        The hierarchical path of the net, separeted by HIERSEP
# @param driver_path     The hierarchical path of the driver object, separated by HIERSEP
# @param driver_type     The type of the driver object, one of {PIN, PORT, ASSIGN}
#
# @returns STRING          if an error occurred
# @returns undef           if successfull
sub _validate_driver {
    my $logger = get_logger("");
    my ($self, $net_path, $driver_path, $driver_type) = @_;

    my $connection_object = $self->get_connection_object($driver_path, $driver_type);
    my $connections       = {};
    $self->_get_net_connections_from_path($net_path, $connections);

    goto FAIL if (!defined $connection_object);

    my @in_drivers     = grep { $_ == $connection_object } @{$connections->{'drivers'}};
    my @in_connections = grep { $_ == $connection_object } @{$connections->{'connected'}};

    goto FAIL if (@in_drivers == 0 && @in_connections == 0);

    return undef;

FAIL:
    my $msg = "No possible driver found";
    $logger->error($msg);
    return $msg;
}

## @function private _select_driver($connected,$net)
# @brief Prompt the user to select a driver for a net from a set of given cells/outputs
#
# @param connected       list reference containing connected Verilog::Perl instances
# @param net             the Verilog::Perl::Net instance to select the driver for
#
# @returns STRING          if an error occurred
# @returns Driver object   if successful
sub _select_driver {
    my ($connected, $net) = @_;

    print "Select driver for net " . $net->name . ": \n";
    my $di;
    for ($di = 0 ; $di < @{$connected} ; $di++) {
        printf("[%d] %s\n", $di, FIJI::Netlist->_connection_tostr(@{$connected}[$di]));
    }
    printf("[x] none of the above.\n", $di);
    my $sel;
    while (1) {
        $sel = <STDIN>;
        if ($sel =~ m/[0-9]+/ && defined @{$connected}[$sel]) {
            last;
        } elsif ($sel =~ m/[xX]/) {
            my $msg = "No driver selected for net " . $net->name;
            return $msg;
        } else {
            print "Invalid driver.\n";
        }
    }
    return @{$connected}[$sel];
}

## @method private _connection_tostr ($connection,$conn_str_list_ref)
# @brief Stringifies a connection information
#
# The string is in the format \<TYPE\>: \<PATH|TO|Netname\>
# Where '|' can be any HIERSEP and TYPE is one of {PIN, PORT, ASSIGN}
# and optionally pushes a hash {path=>...,type=>...,} onto the list @$conn_str_list_ref
#
# @param connection          the connection to print
# @param conn_str_list_ref   optional list where a hash describing the connection is pushed
#
# @returns STRING  in the format \<TYPE\>: \<PATH|TO|Netname\>
sub _connection_tostr {
    my ($self, $connection, $conn_str_list_ref) = @_;
    my $path;
    my $type;
    my $str;

    if (ref($connection) eq "Verilog::Netlist::Pin") {
        $path = $connection->cell->module->name . HIERSEP . $connection->cell->name . HIERSEP . $connection->name;
        $type = "PIN";
        $str = $type . ": " . $path
    } elsif (ref($connection) eq "Verilog::Netlist::Port") {
        $path = $connection->module->name . HIERSEP . $connection->name;
        $type = "PORT";
        $str = $type . ": " . $path
    } elsif (ref($connection) eq "Verilog::Netlist::ContAssign") {
        $path = $connection->module->name . HIERSEP . $connection->rhs;
        $type = "ASSIGN";
        $str = $type . ": " . $connection->rhs;
    }
    push @{$conn_str_list_ref}, {path => $path, type => $type} if defined $conn_str_list_ref;
    return $str
}

## @method public get_connection_object ($connection_path,$connection_type)
# @brief Retrieves the connection object specified by path and type
#
# Retrieves a reference to the Verilog::Pin, Verilog::Port or Verilog::ContAssign
# Object specified by the parameters
#
# @param connection_path     the hierarchichal PATH|To|the|object
# @param connection_type     the type of the object {PIN,PORT,ASSIGN}
#
# @returns the Verilog::Pin, Verilog::Port or Verilog::ContAssign Object specified by the parameters
sub get_connection_object {
    my $logger = get_logger("");
    my ($self, $connection_path, $connection_type) = @_;

    my $rv;
    my $SEP = HIERSEP;

    if ($connection_type eq "PIN") {
        if ($connection_path =~ /^(.+)\Q$SEP\E(.+)\Q$SEP\E(.+)$/) {

            $logger->debug("Looking for pin named \"$3\" in cell \"$2\" of module \"$1\"...");

            my $mod  = $self->{'nl'}->find_module($1);
            my $cell = $mod->find_cell($2) if (defined $mod);
            my $pin  = $cell->find_pin($3) if (defined $cell);
            $rv = $pin;
        }
    } elsif ($connection_type eq "PORT") {
        if ($connection_path =~ /^(.+)\Q$SEP\E(.+)$/) {

            $logger->debug("Looking for port named \"$2\" in module \"$1\"...");

            my $mod = $self->{'nl'}->find_module($1);
            my $port = $mod->find_port($2) if (defined $mod);
            $rv = $port;
        }
    } elsif ($connection_type eq "ASSIGN") {
        if ($connection_path =~ /^(.+)\Q$SEP\E(.+)$/) {
            my $lhs = $2;

            $logger->debug("Looking for assignment to/from \"$2\" in module \"$1\"...");
            my $mod = $self->{'nl'}->find_module($1);

            if (defined $mod) {
                my $assign;
                for my $a (grep { $_->isa("Verilog::Netlist::ContAssign") } $mod->statements) {
                    if ($a->lhs eq $lhs || $a->rhs =~ /\Q$lhs\E/) {
                        $assign = $a;
                        $logger->debug(sprintf("Constant assignment: \"%s\" = \"%s\"", $a->lhs, $a->rhs));
                        last;
                    }
                }
                $rv = $assign;