RFR: 8345265: Minor improvements for LTO across all compilers [v2]

[Matthias Baesken]

On Fri, 17 Oct 2025 18:43:50 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

> > Hi, at the moment this is HotSpot only; We're unfortunately facing a very severe issue in G1 that can't seem to be solved. I'm currently focusing on making it work for HotSpot before introducing this for the native libraries.
> 
> But as far I understand it will be much easy to implement for libs, do you know any blockers?

Yes, the LTO build worked for the other JDK native libs when I enabled it there some months ago as a test.
(lto support for them is just a hack for now; but compiled nicely for me because those libs are much smaller/simpler than libjvm)

With GCC and LTO enabled, some libs get smaller  e.g. for libfontmanager I saw a while ago 1.7M (without)  to  1.1M (with LTO).
Speed improvements are hard to evaluate, the benchmarks used in OpenJDK often stress Hotspot and not so much single native JDK libs.

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PR Comment: https://git.openjdk.org/jdk/pull/22464#issuecomment-3420865857