RFR: 8370438: Offer link time optimization support on library level [v2]

[Julian Waters]

On Wed, 29 Oct 2025 14:05:18 GMT, Erik Joelsson <erikj at openjdk.org> wrote:

> This change on its own doesn't do anything. Do you plan on following up immediately with a set of suggested libs to enable this on? Have you noticed any impact on build performance when enabling this on any JDK libs? I very much doubt any component owner is going to test and apply this on their own. Without that, this is a dead feature and I wouldn't want it to go in.
> 
> I wonder if it would be a good idea to add a global on/off switch (configure arg) for this whole thing, I'm really not sure. It kind of depends on what the impact is. If the impact is unknown, then a global on/off switch, default off, would let every distributor evaluate this on their own. That would of course also require that at least some libs have this enabled.

I was suggesting a configure switch too, in my fork I have a UTIL_ARG_ENABLE for the configure option and then in LibCommon.gmk and LauncherCommon.gmk I implemented the options as such:

https://github.com/TheShermanTanker/jdk/blob/e3d33aee0270d2ce674367f787bdea77a7ad0c58/make/common/modules/LibCommon.gmk#L33

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PR Comment: https://git.openjdk.org/jdk/pull/27976#issuecomment-3461884343