cmd/compile: replace classnames with Class.String

Since the slice of names is almost exactly the same as what stringer is
already generating for us.

Passes toolstash -cmp on std cmd.

Change-Id: I3f1e95efc690c0108236689e721627f00f79a461
Reviewed-on: https://go-review.googlesource.com/77190
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>

src/cmd/compile/internal/gc/fmt.go

@@ -232,16 +232,6 @@ func (o Op) oconv(s fmt.State, flag FmtFlag, mode fmtMode) {
 	fmt.Fprint(s, o.String())
 }
 
-var classnames = []string{
-	"Pxxx",
-	"PEXTERN",
-	"PAUTO",
-	"PAUTOHEAP",
-	"PPARAM",
-	"PPARAMOUT",
-	"PFUNC",
-}
-
 type (
 	fmtMode int
 
@@ -439,11 +429,7 @@ func (n *Node) jconv(s fmt.State, flag FmtFlag) {
 	}
 
 	if n.Class() != 0 {
-		if int(n.Class()) < len(classnames) {
-			fmt.Fprintf(s, " class(%s)", classnames[n.Class()])
-		} else {
-			fmt.Fprintf(s, " class(%d?)", n.Class())
-		}
+		fmt.Fprintf(s, " class(%v)", n.Class())
 	}
 
 	if n.Colas() {

src/cmd/compile/internal/gc/ssa.go

@@ -179,7 +179,7 @@ func buildssa(fn *Node, worker int) *ssa.Func {
 		case PFUNC:
 			// local function - already handled by frontend
 		default:
-			s.Fatalf("local variable with class %s unimplemented", classnames[n.Class()])
+			s.Fatalf("local variable with class %v unimplemented", n.Class())
 		}
 	}
 
@@ -3394,7 +3394,7 @@ func (s *state) addr(n *Node, bounded bool) *ssa.Value {
 			// that cse works on their addresses
 			return s.newValue1A(ssa.OpAddr, t, n, s.sp)
 		default:
-			s.Fatalf("variable address class %v not implemented", classnames[n.Class()])
+			s.Fatalf("variable address class %v not implemented", n.Class())
 			return nil
 		}
 	case OINDREGSP: