40ae34194c
detects redundant imports that can be eliminated. for #117772 : In order to facilitate review and modification, split the checking code and removing redundant imports code into two PR.
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.