On Thu, 13 Feb 2025 01:52:05 GMT, Chris Plummer <cjplum...@openjdk.org> wrote:
> > So it's about a 5% footprint increase to go from LOW to HIGH, and about a 10% > footprint savings to go from LOW to SIZE. What specific gcc -O flag do each > of these map to? I figure SIZE == -Os, HIGH == -O3. Not sure about LOW, but > if it is -O1, then -Os will probably give a performance increase since it is > -O2 minus some code bloat optimizations and plus some code size optimizations. Please see https://github.com/openjdk/jdk/blob/master/make/autoconf/flags-cflags.m4#L310 On gcc/clang , SIZE is indeed -OS ; HIGH is -O3; LOW (=NORM) is -O2 . 'minus some code bloat optimizations' yes some alignment (-falign*) options are omitted with -Os (see https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html Btw what is also interesting is LTO optimization ; with gcc this has high optimization and for some libs quite large size reduction because at link time it can remove/rearrange quite a lot of code leading to smaller libs . But currently we have LTO support only for hotspot. ------------- PR Comment: https://git.openjdk.org/jdk/pull/23563#issuecomment-2655959995
