[PATCH] 8217561 : X86: Add floating-point Math.min/max intrinsics, approval request

[B. Blaser]

Hi Vladimir,

I'd like to keep branch predictions commented out until method data is
collected per call-site because current statistics aren't accurate
enough to really improve the following numbers.

I tried Math.min(float) with the current patch [1] on both standard
and reduction scenarios [2] for negative zero, zero, constant and
random arrays (NaN being rather uncommon). I had to make an average
between min(a,b) and its mirror min(b,a) for reductions because of the
asymmetrical API implementation.

To summarize:

              |            pattern          |          array          |
              | blend/min/max | one ucomisd | +/-0.0 | const | random |
--------------|---------------|-------------|--------|-------|--------|
predictable   |    8% gain    |   unused    |  yes   |  yes  |  no    |
unpredictable |   57% gain    |   unused    |  no    |  no   |  yes   |
reduction     |    unused     |  25% gain   |  yes   |  yes  |  yes   |

We see that the suggested fix to use 'ucomisd' for reductions and
'blend/min/max' otherwise is always faster than before. I'll prepare
the final webrev based on all JDK-8217561 changesets very soon.

Thanks,
Bernard

[1] http://hg.openjdk.java.net/jdk/submit/log?rev=branch%28%22JDK-8217561%22%29
[2] http://hg.openjdk.java.net/jdk/submit/file/ab2b1418f0db/test/micro/org/openjdk/bench/vm/compiler/FpMinMaxIntrinsics.java


On Wed, 6 Mar 2019 at 19:03, Vladimir Kozlov <vladimir.kozlov at oracle.com> wrote:
>
> Hi Bernard,
>
> Can you prepare final patch for review? Changesets are good to see incremental changes but I already lost what whole
> changes are.
>
> Also in latest changeset branch prediction code in library_call.cpp is commented. Is this what you want in final changes?
>
> Thanks,
> Vladimir
>
> On 3/4/19 1:15 PM, B. Blaser wrote:
> > On Sat, 2 Mar 2019 at 20:51, Bhateja, Jatin <jatin.bhateja at intel.com> wrote:
> >>
> >> Having multiple selection patterns based on node properties is good if we have
> >> optimized selection patterns with and without properties (in this case reduction)
> >
> > Pushed to jdk/submit as third changeset on branch JDK-8217561:
> >
> > http://hg.openjdk.java.net/jdk/submit/rev/9aa98249f99c
> >
> > I think this is our best solution, could we have a Reviewer feedback
> > for this (hotspot:tier1 is OK on x86_64 xeon)?
> >
> > Thanks,
> > Bernard
> >