Lower extractlane, scalar_to_vector and splat in ISLE. This PR also makes some changes to the SinkableLoad api * change the return type of sink_load to RegMem as there are more functions available for dealing with RegMem * add reg_mem_to_reg_mem_imm and register it as an automatic conversion
This crate contains the core Cranelift code generator. It translates code from an intermediate representation into executable machine code.