NAME

Verilog-Perl - Overview of Verilog language packages for Perl

DESCRIPTION

The Verilog-Perl distribution provides Perl parsing and utilities for the Verilog Language. This file provides an overview of the distribution, for specific details on each component, see that component's manpage.

You may also want to try the AUTO features present in <http://www.veripool.org/verilog-mode> Verilog-Mode.

INSTALLATION

Skip this section if Verilog-Perl has already been installed.

   $ cpan
   cpan> install Verilog-Perl

SCRIPTS

The following scripts are installed by Verilog-Perl:

vhier

Vhier reads the Verilog files passed on the command line and outputs a tree of all of the filenames, modules, and cells referenced by that file.

vpassert

Vpassert will read the specified Verilog files and preprocess special PLI assertions.

vppreproc

Vppreproc (Verilog-Perl Pre Processor) reads the Verilog files passed on the command line and outputs preprocessed output.

vrename

Vrename will allow a signal to be changed across all levels of the design hierarchy, or to create a cross reference of signal names.

PACKAGES

Verilog::Getopt

Verilog::Getopt provides standardized handling of options similar to Verilog/VCS and cc/GCC.

Verilog::Language

Verilog::Language provides general utilities for using the Verilog Language, such as parsing numbers or determining what keywords exist.

Verilog::Netlist

Verilog::Netlist reads and holds interconnect information about a whole design database.

Verilog::Netlist::Cell

A Verilog::Netlist::Cell object is created by Verilog::Netlist for every instantiation in the current module.

Verilog::Netlist::ContAssign

A Verilog::Netlist::ContAssign object is created by Verilog::Netlist for every continuous assignment in the current module.

Verilog::Netlist::File

Verilog::Netlist::File allows Verilog::Netlist objects to be read and written in Verilog format.

Verilog::Netlist::Module

A Verilog::Netlist::Module object is created by Verilog::Netlist for every module in the design.

Verilog::Netlist::Net

A Verilog::Netlist::Net object is created by Verilog::Netlist::Module for every signal and input/output declaration in the current module.

Verilog::Netlist::Pin

A Verilog::Netlist::Pin object is created by Verilog::Netlist::Cell for for each pin connection on a cell.

Verilog::Netlist::Port

A Verilog::Netlist::Port object is created by Verilog::Netlist::Module for every port connection in the module.

Verilog::Netlist::Subclass

The Verilog::Netlist::Subclass is used as a base class for all Verilog::Netlist::* structures.

Verilog::Parser

Verilog::Parser will tokenize a Verilog file and invoke various callback methods.

Verilog::Preproc

Verilog::Preproc reads Verilog files, and preprocesses them according to the Verilog specification. Programs can be easily converted from reading a IO::File into reading preprocessed output from Verilog::Preproc.

Verilog::SigParse

Verilog::SigParser builds upon the Verilog::Parser package to provide callbacks for when a signal is declared, a module instantiated, or a module defined.

WHICH PARSER PACKAGE?

If you are starting a new application which needs to parse the Verilog language you have several tools available to you. Which you pick depends on how low level and complete the information you need is.

VParseBison.y

The low level VParse* source files may be of use when you need a starting point for your own a full C++ SystemVerilog grammar parser, using Bison and Flex. It understands most of the SystemVerilog 2017 grammar (1800-2017 Appendix A).

Verilog::Preproc

Verilog::Preproc is useful when you need only post-preprocessed text output, or a list of defines, includes, etc. It can preprocess a file, or be used to provide the Verilog macro language on top of synthesis scripts. It understands and implements all preprocessor features of SystemVerilog 2017.

Verilog::Parser

Verilog::Parser is useful when you need to tokenize or write source filters (where you need everything including whitespace). It can take raw files, or preprocessed input, and generates callbacks. It understands all SystemVerilog 2017 keywords.

Abstract Syntax Tree

Verilog::Parser knows enough to make a complete Abstract Syntax Tree (AST) of Verilog syntax. This represents all major constructs such as a "module" as a data structure, but does not interconnect the AST nodes as would be needed to follow signals. Not all keywords have been implemented; many are parsed but otherwise ignored. A complete Ast tree would allow any arbitrary transformation of Verilog syntax (everything is known excluding whitespace). Long term the authors would be interested in collaborating on a general parser, but for now, applications can leverate the C++ code or use Verilator's XML output (below).

Verilog::SigParser

Verilog::SigParser is useful when you need a list of modules, signals, ports, functions, etc. It requires a preprocessed file (from Verilog::Preproc), and can parse all SystemVerilog 2017 files, but only provides callbacks on certain interesting things. The SigParser operates only on a file at a time; it does not interconnect signals nor perform any elaboration (resolution of parameters).

Verilog::Netlist

Verilog::Netlist is useful for when you need the hierarchy, and a list of signals per module, pins per cell, etc. It builds upon the output of Verilog::SigParser, so requires preprocessed files (from Verilog::Preproc). It parses all SystemVerilog 2017 files, but not all SystemVerilog constructs are loaded into objects. Verilog::Netlist interconnects modules with instantiations but does not perform any elaboration (resolution of parameters).

VPI

Using the VPI is the best way to access the behavior of the design. It is not part of this package as it requires a compliant simulator and C++ code to call the VPI, and understands as much of the language as the simulator supports. This allows writing lint checks and full knowledge of all parts of the code. The VPI can operate ONLY on an elaborated design (where all parameters are resolved). Walking a VPI tree general requires a good deal of work compared to simple scripting (though little work compared to writing a parser from scratch).

Verilator

The Verilator program also contains a very similar front end as Verilog-Perl and can create XML output showing the abstract syntax tree. Verilator also understands how to elaborate and connect complex pins and types, but supports mostly only the synthesis subset of SystemVerilog.

If you're looking to parse only synthesizable code this is the recommended route.

Verilog-Mode for Emacs

Although not a parser, a common requested use of Verilog-Perl is to automatically make shell modules and interconnect modules. Verilog-Mode is a better solution to this problem, as it results in completely portable code; the program (Verilog-Mode) isn't needed for others to update the design. It's also in very common usage, including by many IP providers.

FAQ

Why do I get "unexpected `do'" or "unexpected `bit'" errors?

Do, bit, ref, return, and other words are now SystemVerilog keywords. You should change your code to not use them to insure it works with newer tools. Alternatively, surround them by the Verilog 2005/SystemVerilog begin_keywords pragma to indicate Verilog 2001 code.

   `begin_keywords "1364-2001"
      integer bit; initial bit = 1;
   `end_keywords
    

Alternatively use the --language (for vhier) or Verilog::Language::language_standard call to specify "1364-2001", or for really old code, "1364-1995".

But, again, you really should fix the Verilog code.

With Verilog::Netlist how do I resolve signal widths that include parameters down to constants?

Unfortunately parameter resolution is part of elaboration. Verilog-Perl doesn't do elaboration as it requires a good fraction of a complete simulator implementation. Many applications can work around this limitation, if yours still requires elaboration you're stuck with using Verilator or the VPI, see the sections above.

DISTRIBUTION

Verilog-Perl is part of the <http://www.veripool.org/> free Verilog EDA software tool suite. The latest version is available from CPAN and from <http://www.veripool.org/verilog-perl>.

Copyright 2000-2019 by Wilson Snyder. This package is free software; you can redistribute it and/or modify it under the terms of either the GNU Lesser General Public License Version 3 or the Perl Artistic License Version 2.0.

This code is provided with no warranty of any kind, and is used entirely at your own risk.

AUTHORS

Wilson Snyder <wsnyder@wsnyder.org>

SEE ALSO

vhier, vpassert, vppreproc, vrename

Verilog::EditFiles, Verilog::Getopt, Verilog::Language Verilog::Netlist, Verilog::Parser, Verilog::Preproc, Verilog::SigParser

Verilog::Netlist::Cell, Verilog::Netlist::ContAssign, Verilog::Netlist::File, Verilog::Netlist::Interface, Verilog::Netlist::ModPort, Verilog::Netlist::Module, Verilog::Netlist::Net, Verilog::Netlist::Pin, Verilog::Netlist::Port, Verilog::Netlist::Subclass,

And the <http://www.veripool.org/verilog-mode>Verilog-Mode package for Emacs.