[aarch64-port-dev ] [16] RFR(S): 8251525: AARCH64: Faster Math.signum(fp)

[Vladimir Kozlov]

Please, run changes through jdk/submit before push. Current fix caused tier1 failure:

https://bugs.openjdk.java.net/browse/JDK-8252779

Thanks,
Vladimir K

PS: currently jdk/submit under planned maintenance until Sep 7

On 9/3/20 5:03 AM, Dmitry Chuyko wrote:
> I pushed the change for signum, and opened an RFE [1] for fp re-materialization on aarch64. We've made some experiments 
> already. On N1 simply enabling it makes workloads like Lucene geo search ~0.7% faster, will get back with more data.
> 
> I haven't made RFE for "Constants as TEMPs" but will be glad to participate.
> 
> -Dmitry
> 
> [1] https://bugs.openjdk.java.net/browse/JDK-8252760
> 
> On 9/3/20 11:34 AM, Andrew Haley wrote:
>> On 02/09/2020 18:40, Vladimir Ivanov wrote:
>>> C2 doesn't rematerialize FP constants on AArch64
>> I think that's probably right, even though a few FP constants are
>> cheap. Loads from L1 usually have a 4 (or 5) cycle latency, which can
>> make spilling constants expensive around calls. We could be smarter
>> about this.
>>