RFR: 8305895: Implement JEP 450: Compact Object Headers (Experimental) [v26]

[Sandhya Viswanathan]

On Wed, 9 Oct 2024 17:41:37 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>> Yes, @vpaprotsk could review the changes that we made in src/hotspot/cpu/x86/c2_stubGenerator_x86_64_string.cpp.
>
> Yes, that would be great. In the meantime, I ran a few thousand times the randomized test `java/lang/StringBuffer/ECoreIndexOf.java` with and without compact object headers, on product and debug builds, on different x64 implementations, and found no failures.

Thanks a lot @robcasloz for doing the testing.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1794181528