SIMD auto-vectorization in hotspot

[Vitaly Davidovich]

Great, thanks for that - I think vector unit math will bring some serious
perf gains on quite a bit of code.

Regards,

Vitaly

Sent from my phone
On Jan 17, 2012 1:09 PM, "Vladimir Kozlov" <vladimir.kozlov at oracle.com>
wrote:

> Vitaly Davidovich wrote:
>
>> Awesome, that's great to hear.  Is there a release tentatively scheduled
>> to have this or it's still beyond the current horizon?
>>
>
> It targets jdk 8 and one of future jdk 7 updates. I can't say more precise.
>
>
>> If I may I'd like to petition for a flag being available, ideally in
>> product, to trace diagnostics on this part as well; TraceSuperWord or a new
>> companion, whichever you think makes most sense.
>>
>
> We can do that.
>
> Vladimir
>
>
>> Regards,
>> Vitaly
>>
>> On Jan 17, 2012 3:50 AM, "Vladimir Kozlov" <vladimir.kozlov at oracle.com<mailto:
>> vladimir.kozlov@**oracle.com <vladimir.kozlov at oracle.com>>> wrote:
>>
>>    Vector arithmetic are not generated yet (we have plan to do it).
>>    Only array initialization and array copy is done. I recently added
>>    AVX support to generated 3-operands instructions but only scalar one.
>>
>>    Vladimir
>>
>>    On 1/16/12 11:03 PM, Vitaly Davidovich wrote:
>>
>>        Thanks Kris, I'll take a look.  I should've been clearer in my
>>        question though -- I'm mostly interested in packed math
>>        (integer and floating point).
>>
>>        Cheers
>>
>>        On Tue, Jan 17, 2012 at 1:36 AM, Krystal Mok
>>        <rednaxelafx at gmail.com <mailto:rednaxelafx at gmail.com>
>>        <mailto:rednaxelafx at gmail.com <mailto:rednaxelafx at gmail.com>**>__>
>>        wrote:
>>
>>           Hi,
>>
>>           Apparently, the source code to read is
>>        opto/superword.[hpp|cpp] [1][2]. The flag to trace it is
>>        -XX:+TraceSuperWord.
>>           There's a paper mentioned in [1], which is the origin of the
>>        algorithm used.
>>
>>           An example to see superword in action is a simple array copy
>>        loop:
>>
>>           // byte[] src = ...
>>           // byte[] dest = ...
>>           // assert(src.length == dest.length)
>>           for (int i = 0; i < src.length; i++) {
>>              dest[i] = src[i];
>>           }
>>
>>           This loop will be vectorized by superword and then unrolled a
>>        bit, turning the actual copy into something like: (on
>>           32-bit x86)
>>
>>           movq   0xc(%ecx,%edi,4),%xmm0
>>           movq   %xmm0,0xc(%edx,%edi,4)
>>
>>           HTH,
>>           - Kris
>>
>>           [1]:
>>        http://hg.openjdk.java.net/__**hsx/hotspot-main/hotspot/file/**
>> __tip/src/share/vm/opto/__**superword.hpp<http://hg.openjdk.java.net/__hsx/hotspot-main/hotspot/file/__tip/src/share/vm/opto/__superword.hpp>
>>        <http://hg.openjdk.java.net/**hsx/hotspot-main/hotspot/file/**
>> tip/src/share/vm/opto/**superword.hpp<http://hg.openjdk.java.net/hsx/hotspot-main/hotspot/file/tip/src/share/vm/opto/superword.hpp>
>> >
>>           [2]:
>>        http://hg.openjdk.java.net/__**hsx/hotspot-main/hotspot/file/**
>> __tip/src/share/vm/opto/__**superword.cpp<http://hg.openjdk.java.net/__hsx/hotspot-main/hotspot/file/__tip/src/share/vm/opto/__superword.cpp>
>>        <http://hg.openjdk.java.net/**hsx/hotspot-main/hotspot/file/**
>> tip/src/share/vm/opto/**superword.cpp<http://hg.openjdk.java.net/hsx/hotspot-main/hotspot/file/tip/src/share/vm/opto/superword.cpp>
>> >
>>                  <http://hg.openjdk.java.net/__**
>> hsx/hotspot-main/hotspot/file/**__tip/src/share/vm/opto/__**superword.hpp<http://hg.openjdk.java.net/__hsx/hotspot-main/hotspot/file/__tip/src/share/vm/opto/__superword.hpp>
>>        <http://hg.openjdk.java.net/**hsx/hotspot-main/hotspot/file/**
>> tip/src/share/vm/opto/**superword.hpp<http://hg.openjdk.java.net/hsx/hotspot-main/hotspot/file/tip/src/share/vm/opto/superword.hpp>
>> >>
>>
>>
>>           On Tue, Jan 17, 2012 at 1:45 PM, Vitaly Davidovich
>>        <vitalyd at gmail.com <mailto:vitalyd at gmail.com>
>>        <mailto:vitalyd at gmail.com <mailto:vitalyd at gmail.com>>> wrote:
>>
>>               Hi guys,
>>
>>               Does the -XX:+UseSuperWord (I see it's set to true on
>>        6u23) optimization enable auto-vectorization of certain
>>               loops? If so, are there any switches that can be turned
>>        on (in product VM) to see if vectorization is being
>>               applied or not? In general, would someone be able to
>>        describe the current state of loop vectorization (i.e.
>>               implementation limits, restrictions, etc)? Which ISAs are
>>        supported (i.e. SSE, AVX)? Any other info on this
>>               subject would be greatly appreciated ...
>>
>>               Thanks very much,
>>
>>               Vitaly
>>
>>
>>
>>
>>
>>        --
>>        Vitaly
>>        617-548-7007 <tel:617-548-7007> (mobile)
>>
>>
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