RFR: jsr166 jdk9 integration wave 9

Aleksey Shipilev aleksey.shipilev at gmail.com
Thu Aug 11 20:08:23 UTC 2016

On 08/11/2016 09:59 PM, Martin Buchholz wrote:
> On Thu, Aug 11, 2016 at 10:40 AM, Aleksey Shipilev
>> Why doesn't AtomicBoolean.getAndSet use VarHandle.getAndSet, which is
>> hopefully intrinsified completely?
> Good question.  This optimization originated in a suggestion for jdk8,
> where there are no VarHandles.
> VarHandle.getAndSet does not know there are only two values for the int,
> so it is not obvious which one wins.  I can imagine getAndSet being
> compiled to a weak cas loop. 

getAndSet/getAndAdd have a nice rationale for x86: they compile to
xchg/xadd, respectively. This is what I meant about "intrinsified

>> Any benchmarks backing up this optimization?
> I measured a reduction in bytecode!  Does that count? 

I measured x86 instructions count, and you would not believe what it
told me!


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