RFR: 8276066: Reset LoopPercentProfileLimit for x86 due to suboptimal performance

[Pengfei Li]

On Thu, 28 Oct 2021 12:18:45 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Just for the record, `LoopPercentProfileLimit` was always set to `30` on x86:
>> http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/5fefcbeda616#l6.7
>> 
>> Or am I missing something?
>> 
>> EDIT: Okay, I've seen your comment explaining the details only now.
>
>> Just for the record, `LoopPercentProfileLimit` was always set to `30` on x86: http://hg.openjdk.java.net/jdk9/jdk9/hotspot/rev/5fefcbeda616#l6.7
>> 
> I am already working on optimizing post loop vectorization using vectorAPI masked operations and plan to enhance [SLP post loop ](https://bugs.openjdk.java.net/browse/JDK-8183390) after it.

@jatin-bhateja @TobiHartmann  I have already done a patch to fix and re-enable post loop vectorization using masked operations. My patch fixes several issues and is fully tested. Now the post loop feature works on both x86 AVX-512 and AArch64 SVE. I haven't pushed my patch for review because the dependent patch (https://github.com/openjdk/jdk/pull/5873) has not been merged yet.

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PR: https://git.openjdk.java.net/jdk/pull/6142