Xevolver XML Framework -- XevXml
XevXml is a framework for user-defined code transformations based on XML. XevXml provides interconversion between an abstract syntax tree (AST) of a C/Fortran code and an XML document. The XML document is exposed to users. Hence, the users can use any XML tools for user-defined AST transformations, and then generate a transformed version of the C/Fortran code.
Xevolver XML (XevXml) is one of software products developed by the Xevolver project supported by JST "Post-Peta" CREST. The purpose of this project is to help migration of legacy HPC applications to new-generation systems by improving their performance portabilities across system generations. Since the top priority is usually given to performance, an HPC application is often optimized and specialized for a particular HPC system. As a result, the performance is not portable to other systems. To make matters worse, such system-aware, system-specific code optimizations are likely to be scattered over the application code. This is one main reason why HPC application migration is so painful. It is not affordable to reoptimize the whole code whenever a new system becomes available.
XevXml is developed for XML-based AST transformations as an easy way to provide user-defined code transformations. The current implementation of XevXml is built on top of the ROSE compiler framework. XevXml converts a ROSE's AST to an XML document, and exposes it to programmers. So the programmers can use any XML-related technologies and tools to transform the AST. Then, the transformed AST is given back to the ROSE compiler framework so that the AST is unparsed to generate a transformed application code. Instead of directly modifying an application code, programmers can define their own code transformations to optimize the code for each system. System-specific optimizations are represented as XML translation rules, which can be defined separately from an application code. This leads to separation between application requirements and system requirements, expecting a lower migration cost of HPC applications to new systems.
- ROSE compiler infrastructure -- http://rosecompiler.org/
- Apache Xerces C++ 3.1.1 -- http://xerces.apache.org/
- Apache Xalan C++ 1.0 -- http://xml.apache.org/xalan-c/
- PicoJSON -- https://github.com/kazuho/picojson
XevXml provides two basic commands,
former converts a C/Fortran code into an XML document, which is output
to the standard output. The latter reads an XML document from the
standard input and unparses it to generate a C/Fortran code. For
example, equivalent transformation of
is as follows.
% src2xml sample.c | xml2src sample-equiv.c
src2xml generates an XML document that contains necessary
information for rebuilding the AST. Each XML element corresponds one
AST node of Sage III AST classes that are used in the ROSE compiler
framework. An XML element may have some attributes. For example, an
AST node of a function declaration,
SgFunctionDefinition, needs the
function name at rebuilding.
If a translation rule is written in an XSLT file,
test.xsl, the rule
is applied to an AST by
% src2xml sample.c | xsltexec test.xsl| xml2src sample-equiv.c
To append additional information to XML documents, a developer can
customize two internal C++ classes,
XevXmlVisitor. The former class traverses an AST of Sage III classes
used in ROSE, and translates it to an XML AST. The latter traverses an
XML AST to rebuild ROSE's AST.
XevSageVisitor visits an AST node, it writes an XML element
whose name is the same as the class name of an AST node,
SgVarRefExp. When writing XML attributes of each XML element,
attribSgXXXX method is invoked. Similarily, when writing the child
nodes of each XML element,
inodeSgXXXX method is invoked.Therefore,
by overloading those methods, a developer can customize XML documents
generated by the
XevXmlVisitor visits an XML element,
is invoked. Therefore, by overloading such a method, a developer can
customize the rebuliding process of an AST.
This project is released under the BSD 2-clause license
Copyright (C) 2010-2015 Hiroyuki TAKIZAWA. All rights reserved.
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