SIMD auto-vectorization in hotspot

[Vladimir Kozlov]

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 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>
>            [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>
>         <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)
>