Iterating over the IRGenModules and emitting every
SILCoverageMap in the SILModule meant that we
were emitting N copies of the coverage maps for
parallel IRGen, where N is the number of output
object files.
This has always been wrong, but was previously
saved by the fact that we would drop the coverage
map on the floor if we didn't have the name data
available. This would only be the case for the
IRGenModule that had the emitted entity to
profile, in addition to any IRGenModules that
had inlined the body of a profiled enitity. As
such, this prevented the duplication from being
too egregious. However with the recent change to
emit unused name data in the case where we don't
already have name data available, we're now fully
duplicating every coverage mapping, and emitting a
ton of redundant name data.
Fix things such that we only emit coverage mapping
records for the IRGenModule that corresponds to
the entity being profiled.
rdar://102905496
Previously in WMO builds where IR was multithreaded only the
primary module would emit the coverage mapping leading to only the first
object file to have the __llvm_covmap section. This change emits
coverage for all modules so they are correctly reflected in the final
coverage report.
