Vladimir Kozlov vladimir.kozlov at
Sat Sep 9 03:22:04 UTC 2017

On 9/8/17 8:17 AM, Dmitrij wrote:
> Hi Andrew,
> I support the idea of intrinsifying Math.multiplyHigh method: it seems like it will be very effective to implement at 
> least on aarch64 and x86_64 using umulh and mulq instructions.
> Vladimir, what do you think?

Nobody asked to intrinsify these methods before because they are new in JDK 9 I think.

> If there are no other volunteer I'd be happy to do this.

Yes, please do that for both: aarch64 and x64. Add jtreg hotspot test too, please.


> Enhancing java.lang.Math intrinsics situation for aarch64 port is on my todo list.
> Thanks,
> Dmitrij
> On 08.09.2017 17:38, Andrew Haley wrote:
>> I notice that Math.multiplyHigh(long, long) doesn't use a C2 intrinsic,
>> even on machines with appropriate C2 patterns.  So it's rather slow.
>> JDK-5100935, No way to access the 64-bit integer multiplication of
>> 64-bit CPUs efficiently, is closed, even though there is still no
>> efficient way to do this.  Is writing an intrinsic for multiplyHigh on
>> someone's to-do list?  I see no bug for it.

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