RFR (L): 8003868: fix shark for latest HotSpot and LLVM [Was: Re: RFR: Fix shark for latest Hotspot and LLVM]

Roman Kennke rkennke at redhat.com
Mon Nov 26 04:58:29 PST 2012

Am Montag, den 26.11.2012, 09:50 +0000 schrieb Andrew Haley:
> On 11/23/2012 05:14 PM, Roman Kennke wrote:
> > 
> > Alright, I found another fairly grave bug that I would like to include a
> > fix for: apparently, a 'fence' is not enough of a memory barrier for
> > volatile putfield/getfield (duh). Which basically broke all of j.u.c.
> > LLVM offers atomic loads and stores, which seem to be exactly what is
> > needed for volatile field access. However, it does not provide helper
> > functions for those in llvm::IRBuilder so I wrote my own. This should be
> > the final patch for now (unless you find something else).
> > 
> > http://cr.openjdk.java.net/~rkennke/shark/webrev.03/
> I note that you've used llvm::SequentiallyConsistent for all the atomic
> accesses.  This looks right to me, but if there's any doubt you could
> ask Doug Lea.

Yeah. Except for monitorenter and monitorexit, where I used Acquire and
Release (which I believe is right too, at least it seems *very*
sensible :-) ). The other access flags (unordered and monotonic) don't
seem to have a mapping in Java, except maybe in some of the many Unsafe
intrinsics, but they are not implemented in Shark (yet).


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