[lworld+vector] RFR: 8311675: [lworld+vector] Max Species support. [v4]

[Xiaohong Gong]

On Tue, 17 Oct 2023 01:58:54 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> src/hotspot/cpu/x86/vm_version_x86.cpp line 3232:
>> 
>>> 3230:     size = (VM_Version::supports_avx512bw()) ? 64 : 32;
>>> 3231:   // Use flag to limit vector size.
>>> 3232:   size = MIN2(size,(int)MaxVectorSize);
>> 
>> Since `MaxVectorSize` is a C2 specific version, what the behavior if c2 is disabled? Do you think we need consider `#if COMPILER2` here?
>
> We do have a dependency on C2 one way or other,  I think we should preserve the existing behaviour which will return a -1 value.

This makes jdk build failure with `--configure-args --with-jvm-features=-compiler2 --configure-args --with-jvm-variants=client`. So maybe we have to separate with `#ifdef COMPILER2` and return `-1` for another path.

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PR Review Comment: https://git.openjdk.org/valhalla/pull/931#discussion_r1361439332