Fix linker-plugin-lto only doing thin lto by Flakebi · Pull Request #136840 · rust-lang/rust (original) (raw)

Good question, it seems to change somewhat, but still work in general. I added a test for this.
What changes: Without this change, the test passes when
lib is compiled with O0 and main with O3 and

1. lib uses lto=thin and main uses lto=thin
2. lib uses lto=thin and main uses lto=fat
3. lib uses lto=fat and main uses lto=thin
4. lib uses lto=fat and main uses lto=fat

With this change, all of these keep passing except for case 3 (lib uses lto=fat and main uses lto=thin).
When lib is compiled with O1, O2 or O3, case 3 passes as well.
I assume this is the important case, as the standard library is compiled with optimizations.
(And lto with O0 is kinda questionable, except maybe for nvptx and amdgpu, but they require lto=fat anyway.)