SIMD auto-vectorization in hotspot

[Vitaly Davidovich]

Awesome, that's great to hear.  Is there a release tentatively scheduled to
have this or it's still beyond the current horizon?

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.

Regards,
Vitaly
On Jan 17, 2012 3:50 AM, "Vladimir Kozlov" <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>**> 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>
>>    [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.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>> 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 (mobile)
>>
>
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