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From Egor Pasko <egor.pa...@gmail.com>
Subject Re: [drlvm][opt][translator] What dose JavaLabelPrepass do?
Date Thu, 17 Jan 2008 12:41:08 GMT
On the 0x3CE day of Apache Harmony Simon Chow wrote:
> On 17 Jan 2008 13:31:05 +0300, Egor Pasko <egor.pasko@gmail.com> wrote:
> >
> > On the 0x3CE day of Apache Harmony Simon Chow wrote:
> > > On 17 Jan 2008 11:08:54 +0300, Egor Pasko <egor.pasko@gmail.com> wrote:
> > > >
> > > > On the 0x3CD day of Apache Harmony Simon Chow wrote:
> > > > > I am studying OPT in jitrino. For understanding the process of
> > building
> > > > CFG,
> > > > > I have read some code of JavaByteCodeTranslator.
> > > > > In the constructor of JavaByteCodeTranslator, there is an additional
> > > > pass
> > > > > named JavaLabelPrepass,
> > > > > I would like to ask what is the exact purpose of this pass?
> > > >
> > > > the purpose is to mark basic blocks and inference stack variables and
> > > > local variables with their types.
> > > >
> > > > This information goes to the input of JavaByteCodeTranslator, which in
> > > > single pass goes through each bytecode instruction and converts it to
> > > > operand-based representation from the stack-based in bytecode.
> > > >
> > > > The problem is a little tricky (with variable merging logic) and
> > > > current design is poor.
> > > >
> > > > > Besides this, It is seems that the translator part will be refined,
> > > > which I
> > > > > saw in the wiki. Has it already been done in the current version?
> > > > > Thanks!
> > > >
> > > > no, translator is not refined, low priority task.
> > > >
> > > > Why do you study the process of building CFG? If you want to do
> > > > something with it, I would suggest to try some other place since all
> > > > JIT people here will agree that debugging JavalabelPrepass is
> > > > brain-damaging.
> > >
> > >
> > > Thank!
> > > I am doing a project for combining static compiler with dynamic
> > compilation
> > > environment (jitrino.OPT)
> > > As first step, now I am planning to translate the Harmony IR to WHIRL.
> >
> > hm, do you have a kind of draft design document on how you want to do
> > this? ..probably Harmony gurus can give some valuable input having
> > read this doc.
> 
> 
> There is no document for this yet, but I will write one in the next few days
> after having a discussion with others in my group.
> Our static compilation platform is Open64, some of my teammates are working
> on it.

just to make sure.. is the primary goal to replace/enhance Jitrino.OPT
on IPF machines? Oh, those itanics..

> I only have a little understanding of jitrino.OPT.
> For achieving higher performance, which part or phases of jitrino.OPT could
> be refined or replaced by Open64 optimization?
> Could you give me some suggestion?

I am afraid I am not familiar with Open64 at all, and there are
concerns using a mix of Jitrino.OPT and Open64 since the latter is
licensed under GPL. So, do not show me their code :)

Jitrino.OPT/IPF is rather immature/experimental/untested/etc. So, if
using Jitrino.OPT on IPF consider throwing away the code generator
(but take care about generating the right calling convention and
VM-related stuff like threading)

As for the High-level optimizations, I do not know, where Open64 is
better, maybe Xiaofeng knows? :)

I may try to forsee something: Fortran & C compilers have more freedom
for code motion and prefetch optimizations than a Java JIT compiler
(which has a more dynamic nature), so, when ported to Java realities a
C compiler is likely to behave not very cool.

I would suggest you to enhance Jitrino IPF codegenerator in
if-conversion and register allocation, that looks like more
interesting and performance-beneficial. However, I am not sure if it
suits you good as a subject of research.

Did you try running DRLVM on IPF? Does it work? Does it even compile?

> By the way, This idea is original from Xiaofeng :)
> 
> Thank you every much!
> 
> > But I can not find more information for the CFG structure in jitrino.OPT,
> > > which leads me to read the code in translation part. :(
> > > Any advice for this?
> >
> > there is no complete reference guide for HIR instructions yet. Once I
> > gave advice on this:
> >
> > http://article.gmane.org/gmane.comp.java.harmony.devel/24474/
> >
> > feel free to ask specific questions on CFG and instructions :)
> >
> > --
> > Egor Pasko
> >
> >
> 
> 
> -- 
> From : Simon.Chow@Software School of Fudan University

-- 
Egor Pasko


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