Rewrite the xml parser in vpr to be based on DTD and auto generated.

[mithro]

Currently the xml parser in vpr is hand coded.

It would be good to rip it out and replace it with a auto-generated xml parser based around a DTD which defines the file format.

Create a XML definition using DTD, XSD or Relax-NG -- unsure the best format... See;

• https://www.tutorialspoint.com/xsd/index.htm
• http://www.relaxng.org/tutorial-20011203.html

Existing XML file formats in order of importance;

• "rr_graph.xml" format - http://vtr-verilog-to-routing.readthedocs.io/en/latest/vpr/file_formats.html#routing-resource-graph-file-format-xml
• "Packed netlist" format - http://vtr-verilog-to-routing.readthedocs.io/en/latest/vpr/file_formats.html#packed-netlist-format-net
• "FPGA architecture description" - http://vtr-verilog-to-routing.readthedocs.io/en/latest/arch/index.html

New XML file formats needing to be created;

• placement file format - http://vtr-verilog-to-routing.readthedocs.io/en/latest/vpr/file_formats.html#placement-file-format-place
• route file file format - http://vtr-verilog-to-routing.readthedocs.io/en/latest/vpr/file_formats.html#routing-file-format-route

The idea is eventually to auto-generate parser / code structures from the definitions; IE see --

• http://www.davekuhlman.org/generateDS.html
• https://www.liquid-technologies.com/xml-schema-to-cpp
• https://www.codalogic.com/lmx/?xmlfwd-xml2cppcom
• https://www.codesynthesis.com/products/xsd/
• https://www.genivia.com/doc/databinding/html/index.html

[mithro]

XML formats include;

• FPGA Architecture Definition
• Routing Graph File Format

[Laksen]

I created schemas for the packed netlist and routing resource formats here: https://gist.github.com/Laksen/dc3fdf65a7eb6bb1186c46381215ac55

They don't match the examples 100% as the examples contain some undocumented values, but that should be easy to change

Gist

VPR XML Schemas

VPR XML Schemas

[Laksen]

I updated some types to use xs:double instead of xs:decimal to allow scientific notation.
Also a preliminary version of the architecture description has been added. There might be a few bits missing, but with the files I could find they almost passed validation.

There were some inconsistencies like default_* names in <fc> attributes where I chose the values from the documentation

https://gist.github.com/Laksen/cf67f1103e5c539bb44cd183d617aee8

Gist

fpga_architecture.xsd

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[mithro]

@Laksen this is awesome! Do you want to send them as a pull request in the https://github.com/SymbiFlow/symbiflow-arch-defs repo? The common/xml directory would be the right place.

GitHub

SymbiFlow/symbiflow-arch-defs

symbiflow-arch-defs - FOSS architecture definitions of FPGA hardware useful for doing PnR device generation.

[mithro]

@Laksen has added a schema for the existing XML formats in the pull request here -> f4pga/f4pga-arch-defs#195 - Thank you so much.

The next steps would be;
a) Figuring out the best way to generate Python and C++ code from the schemas.
b) Designing a new XML format (and appropriate schema) for the placement and route formats from VtR.
c) Using the XML schema's for automatic validation of the files.

[mithro]

https://www.codesynthesis.com/products/xsd/ looks pretty good but is under a GPL license and we really want to keep things open. The alternative is probably to follow an example shown at this page https://blind.guru/bmmlcxx.html and use Python + Jinja2 templates to create C++ code.

CodeSynthesis XSD - XML Data Binding for C++

W3C XML Schema to C++ data binding compiler is an open-source, cross-platform XML Data Binding implementation for C++

Generating C++ from a DTD with Jinja2 and lxml

[mithro]

The best example I have found is https://github.com/mlang/xsdcxx-musicxml

GitHub

mlang/xsdcxx-musicxml

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