"The atom model is not the best model for some architectures The atom model makes sense only for Mach-O, but it’s used everywhere. I guess that we originally expected that we would be able to model the linker’s behavior beautifully using the atom model because the atom model seemed like a superset of the section model. Although it can, it turned out that it’s not necessarily natural and efficient model for ELF or PE/COFF on which section-based linking is expected."
https://llvm.cc/t/llvmdev-lld-improvement-plan/274
"The atom model is not the best model for some architectures The atom model makes sense only for Mach-O, but it’s used everywhere. I guess that we originally expected that we would be able to model the linker’s behavior beautifully using the atom model because the atom model seemed like a superset of the section model. Although it can, it turned out that it’s not necessarily natural and efficient model for ELF or PE/COFF on which section-based linking is expected."