Use Context::for_function to simplify the code.

lib/filetests/src/test_regalloc.rs

@@ -39,10 +39,7 @@ impl SubTest for TestRegalloc {
 
     fn run(&self, func: Cow<Function>, context: &Context) -> Result<()> {
         let isa = context.isa.expect("register allocator needs an ISA");
-
-        // Create a compilation context, and drop in the function.
-        let mut comp_ctx = cretonne_codegen::Context::new();
-        comp_ctx.func = func.into_owned();
+        let mut comp_ctx = cretonne_codegen::Context::for_function(func.into_owned());
 
         comp_ctx.compute_cfg();
         // TODO: Should we have an option to skip legalization?