Change Details

C identifier name input sections such as __llvm_prf_* are GC roots so they cannot be discarded. Putting these into a section group disables the C identifier name semantics. The ELF section group semantics ensures that group members are retained or discarded as a unit. When a function symbol is discarded, this allows allows linker to discard counters, data and values associated with that function symbol as well. Note that `noduplicates` COMDAT is lowered to zero-flag section group in ELF. We only set this for functions that aren't already in a COMDAT and for those that don't have available_externally linkage since we already use regular COMDAT groups for those.

__start_/__stop_ references retain C identifier name sections such as __llvm_prf_*. Putting these into a section group disables this logic. The ELF section group semantics ensures that group members are retained or discarded as a unit. When a function symbol is discarded, this allows allows linker to discard counters, data and values associated with that function symbol as well. Note that `noduplicates` COMDAT is lowered to zero-flag section group in ELF. We only set this for functions that aren't already in a COMDAT and for those that don't have available_externally linkage since we already use regular COMDAT groups for those.

C identifier name input sections such as __llvm_prf_* are GC roots so__start_/__stop_ references retain C identifier name sections such as they cannot be discarded__llvm_prf_*. Putting these into a section group disables the C identifier name semantics this logic. The ELF section group semantics ensures that group members are retained or discarded as a unit. When a function symbol is discarded, this allows allows linker to discard counters, data and values associated with that function symbol as well. Note that `noduplicates` COMDAT is lowered to zero-flag section group in ELF. We only set this for functions that aren't already in a COMDAT and for those that don't have available_externally linkage since we already use regular COMDAT groups for those.