JIT code generation for Long/Integer.compare

[Vitaly Davidovich]

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> 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> 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> wrote:
>>
>> Below is a patch to add JIT code generation for Long/Integer.compare. It
>> has been reviewed internally by 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>
>>
>>
>>
>
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