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Re: [ljc] JVM support for unsigned arithmetic

From: user 8.
Sent on: Tuesday, August 28, 2012 11:59 PM
Hi Ben,

Thanks for your message.

Yeah... I'd like to know more about inner details of implementation, 
like intrinsics.

> In general, I think that JIT-based techniques for unsigned arithmetic
> can be problematic precisely because they don't sit within the overall
> language or platform specification.

This is unfortunate that the "hardware" (i.e: JVM) restricts the 
platform from being considered in certain HPC scenarios. :(


Richard Gomes
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On 28/08/12 23:21, Ben Evans wrote:
> Hi Mike,
> On Tue, Aug 28, 2012 at 9:53 PM, Michael Barker <[address removed]> wrote:
>>> And no... no JIT magic/optimization can be applied.
>> For the overflow case, I thought it would be fairly straight forward
>> for the JVM to implement an intrinsic to provide machine specific
>> assembly.  Is there are reason why this technique can be applied?
> Did you mean "Are there reasons why this technique can't be applied"?
> Richard - are you aware of how HotSpot can utilize highly
> machine-specific code using techniques like intrinsics? If not, this
> could well be an interesting topic for us to discuss at the next
> OpenJDK hack day.
> In general, I think that JIT-based techniques for unsigned arithmetic
> can be problematic precisely because they don't sit within the overall
> language or platform specification.
> However, expecting HPC techniques to be defined by a standard which
> only specifies the interpreted form of the language seems also to be a
> problematic way of approaching the issue. I'm not sure there are any
> easy answers here. :(
> Thanks,
> Ben
> --
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