JDK-8374507 forced me to look into debug info sizes again.

And I remembered that GCC actually have debug-level support, which can select what kind of diagnostic data is in the debug info. See: https://gcc.gnu.org/onlinedocs/gcc-4.5.0/gcc/Debugging-Options.html

Allowing users to configure the debug level allows two major deviations from the default level (2):
 level=1: significantly optimize the debug info data, but still allow backtrace reconstruction; thus solving JDK-8374507
 level=3: add even more debugging info, like macro expansion, into the debug data

I had a patch that I have been using in builds.shipilev.net binaries for years that allows access to that GCC option; and fastdebug bundles were building with level=1 for years as well. This RFE upstreams the variant of that patch.