RFR: 8370438: Offer link time optimization support on library level

[Matthias Baesken]

On Fri, 24 Oct 2025 12:58:15 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> We currently have support for LTO (link time optimization) for Hotspot/libjvm, that can be enabled as a JVM feature.
> But for other JDK native libs, we do not have support for this feature.
> LTO and sometimes lead to faster and also in some cases smaller binaries, so support for this might be interesting also for other libs and not only libjvm.

For libfontmanager the lib sizes decrease quite a lot on most platforms if LTO is enabled in the build of the lib.
libfontmanager.so / dylib / dll size  without/with LTO enabled

38M	 / 17M   aix_ppc64
1.8M / 1.1M  linux_aarch64
2.0M / 1.3M  linux_alpine_x86_64
2.3M / 1.4M  linux_ppc64le
1.8M / 1.2M  linux_x86_64

1.4M / 900K   macos aarch64
1.4M / 952K   macos x86_64

932K / 916K   windows x86_64


(however the freetype lib does not show this decrease in lib size when enabling lto)

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PR Comment: https://git.openjdk.org/jdk/pull/27976#issuecomment-3461353345