RFR: 8320448: Accelerate IndexOf using AVX2 [v19]

[Scott Gibbons]

On Thu, 16 May 2024 18:09:04 GMT, Scott Gibbons <sgibbons at openjdk.org> wrote:

>> src/hotspot/cpu/x86/stubGenerator_x86_64_string.cpp line 418:
>> 
>>> 416:       __ cmpq(haystack_len, 0x10);
>>> 417:       __ ja_b(L_moreThan16);
>>> 418: 
>> 
>> An assert here to check for header size >= 16 would be good. 
>> Also a comment here would he good, something like: 
>> // Copy 16 or 32 bytes prior to haystack end onto stack 
>> // This will possibly including some object header bytes when haystack length is less than 16 or 32 bytes // Set the new haystack address to beginning of copied haystack on stack adjusting for extra bytes copied
>
> I don't know how to assert header size >= 16 bytes, so I'll add a comment stating such.  If you can tell me how to assert, I'll add that code in place of the comment.

Fixed in library_call.cpp

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PR Review Comment: https://git.openjdk.org/jdk/pull/16753#discussion_r1617955173