I would like to see that avr-unknown-gnu-atmega328 works with the latest compiler. Some bug in LLVM broke it[1], because it didn't work starting with versions after nightly-2021-01-07[2]. I know that rust team has nothing to do with this, but they should improve the gcc codegen[3] to be able to run rust on more embedded devices than LLVM has support for. Someone wanted to port his libc written in rust to ia64 and the gcc codegen broke and couldn't compile that.
Do you have experience with AVR assembly and calling conventions? There are only a handful of us looking at this issue, none of us have much bandwidth and we could definitely use your help!
The AVR codegen bug is discussed here: https://github.com/rust-lang/rust/issues/82242#issuecomment-... Seems to be due to the LLVM-AVR patchset somehow expecting gcc-compatible compiler intrinsics (for division), whereas Rust provides intrinsics derived from LLVM's compiler-rt, with different calling conventions.