Integrated: 8283323: libharfbuzz optimization level results in extreme build times

[Magnus Ihse Bursie]

On Wed, 23 Mar 2022 12:25:08 GMT, Magnus Ihse Bursie <ihse at 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 <ihse at 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

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PR: https://git.openjdk.java.net/jdk/pull/7919