This change adds support for a OneofDef (upb_oneofdef), which represents
a 'oneof' as introduced by Protocol Buffers. This is semantically a
union type that contains fields and in turn may be added to a
MessageDef. This change does not alter parsing or the handler
abstraction in any way, because a oneof has impact only at a higher
semantic level (i.e., any sort of storage of the fields in a message
object), which is user-specific with respect to upb.
Many improvements, too many to mention. One significant
perf regression warrants investigation:
omitfp.parsetoproto2_googlemessage1.upb_jit: 343 -> 252 (-26.53)
plain.parsetoproto2_googlemessage1.upb_jit: 334 -> 251 (-24.85)
25% regression for this benchmark is bad, but since I don't think
there's any fundamental design issue that caused it I'm going to
go ahead with the commit anyway. Can investigate and fix later.
Other benchmarks were neutral or showed slight improvement.
Josh Haberman
Chris Fallin
Joshua Haberman