Update to the rustfmt in rust 1.28, which is now stable.

Also, rustfmt's --write-mode=check is now named --check.

lib/codegen/src/binemit/shrink.rs

@@ -38,14 +38,15 @@ pub fn shrink_instructions(func: &mut Function, isa: &TargetIsa) {
                     | InstructionData::RegSpill { .. } => {
                         divert.apply(&func.dfg[inst]);
                         continue;
-                   }
-                   _ => ()
+                    }
+                    _ => (),
                 }
 
                 let ctrl_type = func.dfg.ctrl_typevar(inst);
 
                 // Pick the last encoding with constraints that are satisfied.
-                let best_enc = isa.legal_encodings(func, &func.dfg[inst], ctrl_type)
+                let best_enc = isa
+                    .legal_encodings(func, &func.dfg[inst], ctrl_type)
                     .filter(|e| encinfo.constraints[e.recipe()].satisfied(inst, &divert, &func))
                     .min_by_key(|e| encinfo.bytes(*e))
                     .unwrap();