RFR (M): 8000805: JMM issue: short loads are non-atomic

Vitaly Davidovich vitalyd at gmail.com
Fri Oct 19 16:22:46 PDT 2012

Hi Vladimir,

Just curious - in the ad files you didn't put ins_cost() for most of the
new matches, is that intentional?


Sent from my phone
On Oct 19, 2012 2:40 PM, "Vladimir Ivanov" <vladimir.x.ivanov at oracle.com>

> http://cr.openjdk.java.net/~**vlivanov/8000805/webrev.00/<http://cr.openjdk.java.net/~vlivanov/8000805/webrev.00/>
> 282 lines changed: 255 ins; 27 del; 0 mod
> Ideal transformations during parsing & IGVN may rematerialize loads in
> order to reify useful information (like signed/unsigned load). Such
> behavior breaks JMM - instead of a single atomic load, multiple loads are
> performed violating consistency of loaded data.
> The fix is to disable such transformations at all, but perform relevant
> optimizations during matching.
> It fixes only C2 part of problem. С1 has similar deficiency, but it'll be
> addressed separately.
> Testing: failing test, test for new matching rules, JPRT, CTW (x86, x64 &
> sparc).
> Best regards,
> Vladimir Ivanov
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