JDK-8307137: aarch64 MacroAssembler::lookup_interface_method could use conditional compare instead of branch

[Andrew Haley]

On 5/2/23 01:36, Peter Kessler OS wrote:
> I agree that for the first few elements on the key-value array, the result is not promising, because of the need to check after the loop for which condition caused the loop to exit. 

Right, so it depends on the distribution of deep interface hierarchies, and
how often searches happen.

> But for searches that go further down the array, ccmp is a win on the machine I've tried it on (an Ampere Altra).
> 
> Here's a table of times in nanoseconds for making 1B interface calls to various depths in an interface hierarchy, in a clone of JDK-21+19, and in JDK-21+19 with the loops done with ccmp:
> 
> Test       clone JDK-21+19   ccmp JDK-21+19
> Interface 1  9,753,623,061   9,751,264,492
> Interface 2 10,512,917,318   10,654,232,119
> Interface 3 11,554,908,217   11,635,931,298
> Interface 4 15,501,591,613   12,926,417,745
> Interface 5 18,472,136,372   14,559,380,750
> Interface 6 19,369,030,295   16,389,137,458
> Interface 7 20,543,012,798   18,119,622,732
> Interface 8 21,947,230,096   18,918,257,70
Thanks. Where is this benchmark?

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
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