RFR: Store cpu features in AOTCodeCache header [v7]

[Vladimir Kozlov]

On Fri, 25 Jul 2025 14:32:28 GMT, Ashutosh Mehra <asmehra at openjdk.org> wrote:

>> This is the initial version of storing cpu features in the AOTCodeCache to verify runtime env has the same cpu capabilities as the assembly env. It covers both x86 and aarch64.
>> AOTCodeCache header is updated to store the cpu features in arch-dependent form (although its same for currently supported architectures - x86 and aarch64).
>> 
>> It also fixes a bug - the `polling_page_vectors_safepoint_handler_blob` can be null if AVX is not present on a system. This causes crash as this blob's entry point is stored in the address table.
>> I came across this when I did the assembly run with -XX:UseAVX=0 option.
>
> Ashutosh Mehra has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix whitespace issue
>   
>   Signed-off-by: Ashutosh Mehra <asmehra at redhat.com>

This looks good. My testing "passed" - I don't anything which could be caused by these changes.

Please, before pushing it run performance testing with CPU features check and without it (you have flag now) to see if we hit bailouts (no AOT code usage) due to some bug.

Thanks.

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Marked as reviewed by kvn (Committer).

PR Review: https://git.openjdk.org/leyden/pull/84#pullrequestreview-3056159111