On Wed, 23 Mar 2022 12:25:08 GMT, Magnus Ihse Bursie <i...@openjdk.org> wrote:
> [JDK-8247872](https://bugs.openjdk.java.net/browse/JDK-8247872) (upgrade > HarfBuzz to 2.7.2) caused build time to go up with 24 seconds on my reference > linux machine. This was one of the four culprits that caused a 25-30% build > time regression over the last two years. > > The problem here was that the new HarfBuzz code caught really bad behaviour > from gcc when compiling with optimizations. The official HarfBuzz build does > not use any -O flags at all for gcc, so presumably the HarfBuzz team is: > > a) not thinking compiler optimization is important for the performance of > this library, and > b) unaware that their code causes such a headache for gcc. > > (Other compilers fare much better: visual studio makes no difference at all, > and for clang just a small regression was observed.) > > The current optimization level was introduced by > [JDK-8255790](https://bugs.openjdk.java.net/browse/JDK-8255790), which were > really about moving libharfbuzz compilation back into libfontmanager. I could > find no comments/discussion relating to the change of optimization level, so > I assume it was incidental, and just seemed good at the time. > > This patch changes the optimization level to `SIZE` (which is the closest > thing we have to no optimization level) on gcc. This pull request has now been integrated. Changeset: 2c43ecb4 Author: Magnus Ihse Bursie <i...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/2c43ecb43fa3c94b69478039f1cd70ed4a577768 Stats: 9 lines in 1 file changed: 8 ins; 1 del; 0 mod 8283323: libharfbuzz optimization level results in extreme build times Reviewed-by: erikj, prr ------------- PR: https://git.openjdk.java.net/jdk/pull/7919
