[clang] [llvm] [ThinLTO] Support dead RTTI data elimination under -fno-split-lto-unit (PR #126336)

[Mingming Liu via cfe-commits]

https://github.com/mingmingl-llvm commented:

I tried this patch on an internal data center application and it reduced the `.data.rel.ro` section size by 3.69% and the number of `_ZTS` or `_ZTI` prefixed entries by ~27% ~ 28%.

Despite the good size savings, the numbers make me curious about what are the remaining ~73% ~ 74% entries. Taking a further look shows these preserved RTTIs come from vtables whose superclass has its type-id accessed.



https://github.com/llvm/llvm-project/pull/126336