RFR: JDK-8323497: On x64, use 32-bit immediate moves for narrow klass base if possible [v3]

[Quan Anh Mai]

On Wed, 21 Feb 2024 13:57:23 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Why do you need to whole space to lie between 0 and 4G then, it seems you only want to have the base being < 4G, then the top of the klass space can be upto size + 4G
>
> Ah, right, good catch.

And yes, you are correct that this only applies when `optimize_for_zero_base` is `false`. Since in the other case we have already tried a much larger space up to $2^{32 + LogKlassAlignmentInBytes}$.

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PR Review Comment: https://git.openjdk.org/jdk/pull/17340#discussion_r1497614800