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From Egor Pasko <egor.pa...@gmail.com>
Subject Re: [DRLVM][JIT] write barrier broken by new jit opts?
Date Thu, 11 Jan 2007 17:03:36 GMT
On the 0x25B day of Apache Harmony Mikhail Fursov wrote:
> On 1/11/07, Alexey Varlamov <alexey.v.varlamov@gmail.com> wrote:
> >
> > Hmm, AFAIU "optimized" arraycopy has no GC specifics. Moreover it is,
> > like API magics, codegen-specific and I do not quite see how it can be
> > expressed in vmmagics...
> 
> 
> One of the GC specific issues is WB :) But we can have several options how
> optimize array copy in JIT: make a loop and remove call, use special CPU
> instructions...
> After some thoughts I agree that VM magic is not the best candidate here and
> additional WB method to report several entries at once can be a better
> solution.

Yes, that pretty looks like JIT internals (a special inst for rep
mov). 

The problem with current impl is that it is not easy to read. Writing
the most of JIT-arraycopy in Java would help. So, to be elegant at the
maximum we could make a "JIT-magic-in-Java" -- a simple method that
does all the exceptions & slowpath tricks in Java leaving the fastpath
to JIT. This JIT-magic can be resolved and inlined in translator.

-- 
Egor Pasko


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