To manage expectations, we should document what is expected to work already, what we will possibly fix and what is probably
not going to work till we have finished a better Enzyme integration. All issues should be solved in the next iteration.
This overview should be moved into a real documentation..

Not Working, unlikely to be fixed:

• Differentiating a function having one or more f32 parameters (f64 works and f32 values are allowed inside of the function).
• Not ffi-safe types
• Differentiating a function which accepts or uses a dyn trait object anywhere.
• AD across language barriers
• CUDA and HIP support.
• Using oxide-enzyme in a dependency, rather than in your current main project.

Likely to be fixed

• Only a combined forward+ReverseAD pass is supported at the moment. Enzyme does support ForwardAD and splitting
  the forward and reverse pass of ReverseAD. (Working on it).
• Differentiating a function which uses parallelism (e.g. rayon) other than OpenMP / MPI.
• Differentiating a function using BLAS / Lapack routines. If you compile them with debug symbols it will already work.
  If you use a pre-compiled version it might or might not work, Enzyme doesn't cover all functions yet.

Fixed

• Generating Functions returning one f64 parameter in the return struct.
• Generating Functions returning three or more parameters in the return struct.

Workarounds:

• There is no real workaround for the dyn trait issue, since it requires creating a new vTable. You might be lucky if that object
  is not interacting with your active values, but that's not granted.
• You can cast f32 to f64 values before passing them to the function and cast them back to f32 inside of your function.
• If you want to differentiate functions calling C/C++/Julia/Fortran/... routines, first compile those other languages to .bc bitcode files. Look up the build script on where to place them. You might run into some issues due to missing symbols when using other languages, let me know about your experiences.
• Similar to differentiating across language barriers. Technically it will work if you use rust wrappers around them or if you use the clang version which we build in ~/.cache/enzyme/rustc-<version>-src, but that is probably too messy to set up and also requires looking at https://enzyme.mit.edu/getting_started/CUDAGuide/