After the unwind rework (commit 2d5db92a) the space used to save
clobbered registers now lies between the nominal SP and the FP.
Therefore, the size of that space should now be included in the
frame size as reported by frame_size(), since this value is used
to compute the nominal_sp_to_fp offset.
This crate contains the core Cranelift code generator. It translates code from an intermediate representation into executable machine code.