My motivation of working on this project is not performance but to make the process of compilation more user-friendly. For example, when I tried this in v12.0
FunctionCompile@Function[{},Range[0.0,5.0,1.5]]
I found the error message very confusing, where I assumed that it should be compilable without problem. I don't know about the progress of development on these issues, but I guess it may have been improved in v12.1.
I typically do not care too much about the performance of Mathematica, otherwise it would be easier for me write LibraryLink functions in C/C++, which almost always happens in my research actually. But it's good to see performance improvements. I feel like it is important to those who are not very familiar with lower-level languages.
