Feature

The x64 backend has a helper named emit_cmp in inst.isle that is used when emitting comparisons. Currently it will always use x64_cmp to emit the comparison, but for cases of equality comparisons with 0, x64_test would be a better choice. Additionally, the select lowering does not use emit_cmp right now, and could be refactored to do so with this change in place.

Benefit

This will generate better code for cases where emit_cmp is used to compile a use of icmp in the x64 backend.