RFR: 8365163: [ubsan] left-shift issue in globalDefinitions.hpp

[Kim Barrett]

On Sun, 17 Aug 2025 06:49:47 GMT, Afshin Zafari <azafari at openjdk.org> wrote:

> There was a left-shift of negative value UB in `set_high` function where the high value sign bit is on and is left-shifted 32 bits to put it in high word of the destination address.
> To address it, first the left 32 bits of the provided `high` arg is cleared and then left-shifted 32 bits. 
> 
> Tests:
> mach5 tiers 1-5 {macosx-aarch64, linux-x64, windows-x64} x {debug, product}

Changes requested by kbarrett (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk/pull/26809#pullrequestreview-3126326235