TargetIsa implies a Display of shared and isa-specific flags

lib/cretonne/src/isa/riscv/mod.rs

@@ -13,6 +13,7 @@ use isa::Builder as IsaBuilder;
 use isa::{TargetIsa, RegInfo, RegClass, EncInfo};
 use ir;
 use regalloc;
+use std::fmt;
 
 #[allow(dead_code)]
 struct Isa {
@@ -252,3 +253,9 @@ mod tests {
         assert_eq!(encstr(&*isa, isa.encode(&dfg, &mul32, types::I32)), "R#10c");
     }
 }
+
+impl fmt::Display for Isa {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}\n{}", self.shared_flags, self.isa_flags)
+    }
+}