Initial public commit of ISLE prototype DSL compiler.

cranelift/isle/examples/test.isle

@@ -0,0 +1,12 @@
+(type u32 (primitive u32))
+(type A (enum (A1 (x u32)) (A2 (x u32))))
+(type B (enum (B1 (x u32)) (B2 (x u32))))
+
+(decl Input (A) u32)
+(extractor Input get_input) ;; fn get_input<C>(ctx: &mut C, ret: u32) -> Option<(A,)>
+
+(decl Lower (A) B)
+
+(rule
+  (Lower (A.A1 sub @ (Input (A.A2 42))))
+  (B.B2 sub))