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

[Matthias Baesken]

On Fri, 17 Jan 2025 08:26:17 GMT, Julian Waters <jwaters at openjdk.org> wrote:

> > Member
> 
> Fixing the JVM under LTO is likely to be a heavy undertaking, much more so than just unbreaking compilation and linking of the JVM (Ignoring that the JVM later crashes when the newly compiled JDK is used to build parts of itself), I'm not sure it would be feasible under the current Pull Request

I was able to build the OpenJDK with LTO enabled on Linux and Windows (so the new JVM does not crash in the build). I just had to not enable gtest because this is currently not compiling with LTO enabled.  I was able to run a few benchmarks with the LTO enabled JVM , but  as far as I remember a couple of HS jtreg tests fail with LTO enabled  because they have some expectations that might not (yet) work with LTO.

Regarding gtest, I created
https://bugs.openjdk.org/browse/JDK-8346987
8346987: [lto] gtest build fails
 Do you think it would be okay to change the build so that the LTO related flags (in case lto is enabled) do not 'go'  into the gtest build ?

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PR Comment: https://git.openjdk.org/jdk/pull/22464#issuecomment-2597709145