multiplyHigh?

[Schmidt, Lutz]

Hi, 

there is interest from these guys at SAP as well. I would volunteer to cover ppc and s390, once the initial implementation is available. Any ETA guess on that? I’m not pushing, just to get an idea.

Thanks, 
Lutz


On 09.09.2017, 05:22, "hotspot-compiler-dev on behalf of Vladimir Kozlov" <hotspot-compiler-dev-bounces at openjdk.java.net on behalf of vladimir.kozlov at oracle.com> wrote:

    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.
    
    Thanks,
    Vladimir
    
    > 
    > 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.
    >>
    >