Integrated: 8269559: AArch64: Implement string_compare intrinsic in SVE

[David Holmes]

We are seeing a large number of Aarch64 test failures in our CI after 
this push. Somewhat bizarre failure modes:
- truncated classfiles
- unexpected EOF encountered
- illegal state reading a stream

I think we will need to back this change out while this is investigated 
further.

David
-----

On 14/10/2021 3:30 pm, TatWai Chong wrote:
> On Mon, 16 Aug 2021 20:59:55 GMT, TatWai Chong <duke at openjdk.java.net> wrote:
> 
>> This patch implements string_compare intrinsic in SVE.
>> It supports all LL, LU, UL and UU comparisons.
>>
>> As we haven't found an existing benchmark to measure performance impact,
>> we created a benchmark derived from the test [1] for this evaluation.
>> This benchmark is attached to this patch.
>>
>> Besides, remove the unused temporary register `vtmp3` from the existing
>> match rules for StrCmp.
>>
>> The result below shows all varients can be benefited largely.
>> Command: make exploded-test TEST="micro:StringCompareToDifferentLength"
>>
>> Benchmark    (size)  Mode  Cnt   Score Speedup Units
>> compareToLL      24  avgt   10      1.0x       ms/op
>> compareToLL      36  avgt   10      1.0x       ms/op
>> compareToLL      72  avgt   10      1.0x       ms/op
>> compareToLL     128  avgt   10      1.4x       ms/op
>> compareToLL     256  avgt   10      1.8x       ms/op
>> compareToLL     512  avgt   10      2.7x       ms/op
>> compareToLU      24  avgt   10      1.6x       ms/op
>> compareToLU      36  avgt   10      1.8x       ms/op
>> compareToLU      72  avgt   10      2.3x       ms/op
>> compareToLU     128  avgt   10      3.8x       ms/op
>> compareToLU     256  avgt   10      4.7x       ms/op
>> compareToLU     512  avgt   10      6.3x       ms/op
>> compareToUL      24  avgt   10      1.6x       ms/op
>> compareToUL      36  avgt   10      1.7x       ms/op
>> compareToUL      72  avgt   10      2.2x       ms/op
>> compareToUL     128  avgt   10      3.3x       ms/op
>> compareToUL     256  avgt   10      4.4x       ms/op
>> compareToUL     512  avgt   10      6.1x       ms/op
>> compareToUU      24  avgt   10      1.0x       ms/op
>> compareToUU      36  avgt   10      1.0x       ms/op
>> compareToUU      72  avgt   10      1.4x       ms/op
>> compareToUU     128  avgt   10      2.2x       ms/op
>> compareToUU     256  avgt   10      2.6x       ms/op
>> compareToUU     512  avgt   10      3.7x       ms/op
>>
>> [1] https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/compiler/intrinsics/string/TestStringCompareToDifferentLength.java
> 
> This pull request has now been integrated.
> 
> Changeset: 8b1b6f9f
> Author:    TatWai Chong <tatwai.chong at arm.com>
> Committer: Nick Gasson <ngasson at openjdk.org>
> URL:       https://git.openjdk.java.net/jdk/commit/8b1b6f9fb375bbc2de339ad8f526ca4d5f83dc70
> Stats:     517 lines in 11 files changed: 421 ins; 1 del; 95 mod
> 
> 8269559: AArch64: Implement string_compare intrinsic in SVE
> 
> Reviewed-by: ngasson, aph
> 
> -------------
> 
> PR: https://git.openjdk.java.net/jdk/pull/5129
>