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

[Matthias Baesken]

On Wed, 29 Oct 2025 14:32:04 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> 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.

I can find a few other libs besides libfontmanager where we see some size reduction (performance improvement will be hard to prove without good benchmarks on lib level).
The for those libs set LTO = true; and add a global  on/off  configure arg to enable this.  This way, we do not cause issues for distributors because still the configure flag must be set; but provide an easy way to enable it and use lto on JDK lib level (and it will be easy to add it for more libs if it is seen as beneficial).

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PR Comment: https://git.openjdk.org/jdk/pull/27976#issuecomment-3468662909