JIT code generation for Long/Integer.compare

[Vladimir Kozlov]

I agree with Vitaly. It is better to use pattern matching (and generate 
CmpI3 and CmpL3 nodes) in subnode.cpp because java code is very simple 
and we may match other cases too.

Also suggested changes are not complete since CmpI3 implementation was 
not added to other platforms.

Thanks,
Vladimir

On 9/25/15 7:54 AM, Vitaly Davidovich wrote:
> I must admit it's a bit strange seeing this implemented via intrinsic -
> is this not possible via normal JIT optimizations? There's nothing
> really "intrinsic" about the code.  I get that it's easier
> implementation-wise to latch on to a well known method, but what about
> similar code used without calling compare?
>
> sent from my phone
>
> On Sep 24, 2015 7:11 PM, "Ian Rogers" <irogers at google.com
> <mailto:irogers at google.com>> wrote:
>
>     Agreed. The attached patch eliminates the cmpl3_flag enc_class and
>     implements both cmpl3 and cmpi3 as you suggest.
>
>     Thanks,
>     Ian
>
>     On Thu, Sep 24, 2015 at 12:51 PM, Christian Thalinger
>     <christian.thalinger at oracle.com
>     <mailto:christian.thalinger at oracle.com>> wrote:
>
>         One comment about the .ad change:  please don’t introduce new
>         enc_class methods; use ins_encode %{ %} and MacroAssembler
>         instructions instead, like this one:
>
>            ins_encode %{
>              Register Rp = $p$$Register;
>              Register Rq = $q$$Register;
>              Register Ry = $y$$Register;
>              Label done;
>              __ cmpl(Rp, Rq);
>              __ jccb(Assembler::less, done);
>              __ xorl(Ry, Ry);
>              __ bind(done);
>            %}
>
>         Should be less painful too :-)
>
>>         On Sep 24, 2015, at 8:45 AM, Ian Rogers <irogers at google.com
>>         <mailto:irogers at google.com>> wrote:
>>
>>         Below is a patch to add JIT code generation for
>>         Long/Integer.compare. It has been reviewed internally by
>>         rasbold at google.com <mailto:rasbold at google.com>. I'd like to
>>         open a bug for this, get it reviewed, etc. but I lack a JBS
>>         account. I'd appreciate help in getting this reviewed and merged.
>>
>>         Thanks,
>>         Ian Rogers
>>
>>         Support JIT code generation for Long/Integer.compare as
>>         intrinsics that fold with branches on their result.
>>
>>         Introduce a CmpI3 ideal node mirroring the CmpL3 node, that
>>         implements
>>         Integer.compare. Allow this to fold with a CmpI node.  Spot
>>         Long/Integer.compare
>>         as CmpL3 and CmpI3 nodes.  Add a CmpI3 implementation for
>>         x86-64.  On a
>>         micro-benchmark loop of:
>>             for (int i = 0; i < x.length; i++) {
>>               if (compare(x[i], y[i]) < 0) {
>>                 count++;
>>               }
>>             }
>>         Int speed up averages 1.18x, long speed up averages 2.76x,
>>         over 30 runs of
>>         arrays sized at 5,000,000 elements. This can be improved with
>>         work on
>>         instruction selection.
>>         Raw data:
>>         Int before:  23129us, 99.5% range: 19935us - 26046us
>>         Int after:   19557us, 99.5% range: 16972us - 26072us
>>         Long before: 26935us, 99.5% range: 25776us - 29323us
>>         Long after:   9749us, 99.5% range: 8850us  - 11968us
>>
>>         <cmpi3-jdk9-tdiff.patch>
>
>