The optimization passes are grouped into several categories. Currently defined categories in dumpfile.h are
IPA optimization passes. Enabled by -ipa
Loop optimization passes. Enabled by -loop.
Inlining passes. Enabled by -inline.
OMP (Offloading and Multi Processing) passes. Enabled by -omp.
Vectorization passes. Enabled by -vec.
All other optimization passes which do not fall into one of the above.
All optimization passes. Enabled by -optall.
By using groups a user could selectively enable optimization information only for a group of passes. By default, the optimization information for all the passes is dumped.