RFR: 8370438: Offer link time optimization support on library level [v2]

[Matthias Baesken]

On Wed, 29 Oct 2025 14:30:43 GMT, Julian Waters <jwaters at openjdk.org> wrote:

> This change on its own doesn't do anything. Do you plan on following up immediately with a set of suggested libs to enable this on? Have you noticed any impact on build performance when enabling this on any JDK libs? I very much doubt any component owner is going to test and apply this on their own. Without that, this is a dead feature and I wouldn't want it to go in.
> 
> I wonder if it would be a good idea to add a global on/off switch (configure arg) for this whole thing, I'm really not sure. It kind of depends on what the impact is. If the impact is unknown, then a global on/off switch, default off, would let every distributor evaluate this on their own. That would of course also require that at least some libs have this enabled.


There was some interest on the lib-level solution here  https://github.com/openjdk/jdk/pull/22464#issuecomment-3423727477  . 'Provide an option for library owners to opt-in, which can be enabled per-library, per-platform and per-compiler after appropriate testing for performance, functionality, and footprint.'

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PR Comment: https://git.openjdk.org/jdk/pull/27976#issuecomment-3461892551