At opt-level=0, apply only ABI-affecting attributes to functions This should provide a small perf improvement for debug builds, and should more than cancel out the perf regression from adding noundef (https://github.com/rust-lang/rust/pull/93670#issuecomment-1038347581, #94106). r? `@nikic`
The codegen
crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc dev guide.