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 completely". >> 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! http://cr.openjdk.java.net/~shade/8162805/BooleanGetAndSet.java Thanks, -Aleksey
