RFR: 8365053: Refresh hotspot precompiled.hpp with headers based on current frequency [v14]

[Francesco Andreuzzi]

On Tue, 26 Aug 2025 14:05:33 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> I have just one last request: How did you generate the last version? The script that you used to read the `.d` files has disappeared somewhere along the way, with no replacement. If you could do this with just some simple command line with pipes etc, that command line should be added as a comment to the PCH file. If you used a script, I think that script should be checked in (in `make/scripts`; even if it is a Java file).

Hi, the workflow now is something like this:
- Create a new build configuration with `--with-extra-cxxflags` and `with-extra-cflags` set to `-ftime-trace -ftime-trace-granularity=500`
- Make an hotspot build
- Parse all the `.json` files (in `build/conf-name/hotspot/variant-server/libjvm/objs` with `ClangBuildAnalyzer --all`
- Extract build information with `ClangBuildAnalyzer --analyze`
- Get the top N headers with some bash scripting

The last two steps are in this script: https://github.com/fandreuz/jdk-stuff/blob/master/update_precompiled

I could possibly automate the whole thing, let me know if you think that would be useful. Alternatively, I can write some lines in `building.md`, or add all the steps to the ticket.

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PR Comment: https://git.openjdk.org/jdk/pull/26681#issuecomment-3224770938