On Mon, 26 Oct 2026 22:23:12 GMT, Benjamin Peterson <[email protected]> wrote:
> Add `-fpch-instantiate-templates` to the clang precompiled header generation > command. > > Testing with `make hotspot`, I observe a 40% reduction in build CPU time for > a release build. On a 56 core machine, this reduces the wall time of the same > command by 25% (45.94s -> 34.5s). > > > > > --------- > - [x] I confirm that I make this contribution in accordance with the [OpenJDK > Interim AI Policy](https://openjdk.org/legal/ai). I believe it's already true that a build with precompiled headers can fail while a build without precompiled headers can succeed and vice versa? I saw a GCC patch for `-fpch-instantiate-templates` was submitted last week. Assuming it's even accepted, though, it'll take years to be generally available. My understanding is that MSVC's precompiled header implementation has a behavior equivalent to `-fpch-instantiate-templates`. So, the JDK is already exposed to this flavor of PCH. As you say, I also observed that the `access*` files weigh heavily on compilation time. This flag is certainly the low hanging fruit. ------------- PR Comment: https://git.openjdk.org/jdk/pull/33576#issuecomment-6442519490
