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From Egor Pasko <egor.pa...@gmail.com>
Subject Re: [drlvm][jit][abcd] HARMONY-1788 Inequality graph generation from HIR
Date Thu, 07 Dec 2006 17:52:13 GMT
On the 0x237 day of Apache Harmony Naveen Neelakantam wrote:
> On Dec 5, 2006, at 1:12 PM, Egor Pasko wrote:
> >On the 0x233 day of Apache Harmony Naveen Neelakantam wrote:
> >> Hello Egor,
> >> 
> >> I'm almost too embarrassed to ask, but if I started looking at your
> >> ABCD code now, would it still be useful?
> >
> >It actually *is* useful!
> >
> >I have been busy with stability issues during this period, thus made
> >no progress in ABCD since my last update to HARMONY-1788. I want to
> >finish this work not later than January. If you have time to do it
> >faster, you can take it. I will be fixing Jitrino.OPT here and there
> >for a while yet...
> 
> OK, great!  I will try to move the code forward then.
> 
> If I understand your code correctly, the pass currently builds the
> ABCD inequality graph, but does not invoke the demand solver.  As a
> first step, I am considering invoking the demand solver on every
> bounds check (for both the upper bound and lower bound problems).  A
> better choice might be to invoke the solver on "hot" checks, but
> that can be investigated once things are working.  Does this sound
> reasonable?

I think, invoking the solver on each bound check is reasonable. It
should not be slow. TODOs are:
* run the solver on each instruction
  BTW, IMHO:
  we have to invoke demandProve twice for each bound check to be safe
  with integer overflows. For example, for LB check:
  * demandProve(-1 < x)
  * demandProve(x < +infinity),
  for UB check:
  * demandProve(x < A.length)
  * demandProve(-infinity < x)
* make the per-VM-session counter of eliminated checks, use
  Jitrino::DeInit(), use -XcleanupOnExit
* compare the numbers between old and new implementations
* test (there are some great JIRAs on bounds checks: HARMONY-2144,
  HARMONY-2147, HARMONY-2191)

any comments are welcome, thanks for doing this!

-- 
Egor Pasko


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