ISLE is a domain specific language (DSL) for instruction selection and lowering clif instructions to vcode's MachInsts in Cranelift.
ISLE is a statically-typed term-rewriting language. You define rewriting rules that map input terms (clif instructions) into output terms (MachInsts). These rules get compiled down into Rust source test that uses a tree of match expressions that is as good or better than what you would have written by hand.