RFR: 8370438: Offer link time optimization support on library level [v5]

[Matthias Baesken]

On Tue, 4 Nov 2025 16:49:06 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.
>
> Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use lto configure flags in hs build

Here are the lib sizes of  libsplashscreen  without / with lto for our toolchains at SAP (gcc 13.2.0, VS2022, Xcode 15.4) 


jdk opt / opt+LTO
1.5M / 1.5M  aix_ppc64/images/jdk/lib/libsplashscreen.so
304K / 220K  linux_aarch64/images/jdk/lib/libsplashscreen.so
292K / 180K  linux_alpine_x86_64/images/jdk/lib/libsplashscreen.so
376K / 228K  linux_ppc64le/images/jdk/lib/libsplashscreen.so
288K / 176K  linux_x86_64/images/jdk/lib/libsplashscreen.so
388K / 240K  darwinaarch64/images/jdk/lib/libsplashscreen.dylib
304K / 196K  darwinintel64/images/jdk/lib/libsplashscreen.dylib
204K / 204K  windows x86_64/images/jdk/bin/splashscreen.dll

pdb / debuginfo size :
jdk opt / opt+LTO
1.4M / 984K  linux_aarch64/images/jdk/lib/libsplashscreen.debuginfo
1.4M / 924K  linux_alpine_x86_64/images/jdk/lib/libsplashscreen.debuginfo
1.4M / 976K  linux_ppc64le/images/jdk/lib/libsplashscreen.debuginfo
1.4M / 924K  linux_x86_64/images/jdk/lib/libsplashscreen.debuginfo
352K / 344K  windows x86_64/images/jdk/bin/splashscreen.dll.pdb

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PR Comment: https://git.openjdk.org/jdk/pull/27976#issuecomment-3492076027