Run the verifier in the Context methods when it is enabled.

The test drivers can stop calling comp_ctx.verify because legalize() and
regalloc() do it themselves now.

This also makes it possible for those two passes to return other
CtonError codes in the future, not just verifier errors.

src/utils.rs

@@ -2,6 +2,7 @@
 
 use cretonne::ir::entities::AnyEntity;
 use cretonne::{ir, verifier, write_function};
+use cretonne::result::CtonError;
 use std::fmt::Write;
 use std::fs::File;
 use std::io::{Result, Read};
@@ -45,6 +46,15 @@ pub fn pretty_verifier_error(func: &ir::Function, err: verifier::Error) -> Strin
     msg
 }
 
+/// Pretty-print a Cretonne error.
+pub fn pretty_error(func: &ir::Function, err: CtonError) -> String {
+    if let CtonError::Verifier(e) = err {
+        pretty_verifier_error(func, e)
+    } else {
+        err.to_string()
+    }
+}
+
 #[test]
 fn test_match_directive() {
     assert_eq!(match_directive("; foo: bar  ", "foo:"), Some("bar"));