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From Gregory Shimansky <gshiman...@apache.org>
Subject Re: [drlvm][opt][translator] What dose JavaLabelPrepass do?
Date Thu, 17 Jan 2008 12:50:26 GMT
Egor Pasko said the following on 17.01.2008 15:41:
> 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?

It runs in interpreter mode ATM. On JIT there is something bad 
happening, a classloader helper is called with a class handle NULL and 
fails on assertion that it shouldn't be NULL. How this NULL handle was 
passed to the helper I don't know because I didn't debug compiled code.

DRLVM compiles on old SLES9 gcc 3.3.3 but fails to compile on SLES10 gcc 
4.1.2. The reason is several assembly files which new assembler doesn't 
like (some compiler directives have to be removed) and a couple of C++ 
errors coming from Jitrino code. I didn't fix assembly yet because I 
can't test whether the result would actually work since I can't get to 
the end of DRLVM build.

-- 
Gregory


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