cmd/compile: give gc.Op a String method, use it

Passes toolstash -cmp.

Change-Id: I915e76374fd64aa2597e6fa47e4fa95ca00ca643
Reviewed-on: https://go-review.googlesource.com/22380
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index f989ad0..964818a 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -969,7 +969,7 @@
 		s.nilCheck(p)
 
 	default:
-		s.Unimplementedf("unhandled stmt %s", opnames[n.Op])
+		s.Unimplementedf("unhandled stmt %s", n.Op)
 	}
 }
 
@@ -1247,7 +1247,7 @@
 	etype := s.concreteEtype(t)
 	x, ok := opToSSA[opAndType{op, etype}]
 	if !ok {
-		s.Unimplementedf("unhandled binary op %s %s", opnames[op], Econv(etype))
+		s.Unimplementedf("unhandled binary op %s %s", op, Econv(etype))
 	}
 	return x
 }
@@ -1405,7 +1405,7 @@
 	etype2 := s.concreteEtype(u)
 	x, ok := shiftOpToSSA[opAndTwoTypes{op, etype1, etype2}]
 	if !ok {
-		s.Unimplementedf("unhandled shift op %s etype=%s/%s", opnames[op], Econv(etype1), Econv(etype2))
+		s.Unimplementedf("unhandled shift op %s etype=%s/%s", op, Econv(etype1), Econv(etype2))
 	}
 	return x
 }
@@ -1414,7 +1414,7 @@
 	etype1 := s.concreteEtype(t)
 	x, ok := opToSSA[opAndType{op, etype1}]
 	if !ok {
-		s.Unimplementedf("unhandled rotate op %s etype=%s", opnames[op], Econv(etype1))
+		s.Unimplementedf("unhandled rotate op %s etype=%s", op, Econv(etype1))
 	}
 	return x
 }
@@ -1729,7 +1729,7 @@
 			case ONE:
 				return s.newValue1(ssa.OpNot, Types[TBOOL], c)
 			default:
-				s.Fatalf("ordered complex compare %s", opnames[n.Op])
+				s.Fatalf("ordered complex compare %s", n.Op)
 			}
 		}
 		return s.newValue2(s.ssaOp(n.Op, n.Left.Type), Types[TBOOL], a, b)
@@ -2088,7 +2088,7 @@
 		return s.append(n, false)
 
 	default:
-		s.Unimplementedf("unhandled expr %s", opnames[n.Op])
+		s.Unimplementedf("unhandled expr %s", n.Op)
 		return nil
 	}
 }
@@ -2632,7 +2632,7 @@
 	case sym != nil:
 		call = s.newValue1A(ssa.OpStaticCall, ssa.TypeMem, sym, s.mem())
 	default:
-		Fatalf("bad call type %s %v", opnames[n.Op], n)
+		Fatalf("bad call type %s %v", n.Op, n)
 	}
 	call.AuxInt = stksize // Call operations carry the argsize of the callee along with them