RFR: JDK-8318119: Invalid narrow Klass base on aarch64 post 8312018

[Andrew Haley]

On Tue, 17 Oct 2023 14:58:18 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> The way movk mode is currently implemented is to apply the right-shifted base to the narrow Klass ID, then to left-shift the thing to get Klass*

There's no need to left shift the Klass if we're using `movk` mode. Shift should be zero. We should always use a zero shift, 4G aligned, class space. That's how it was intended to work when I wrote it.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16215#discussion_r1363546179