cmd/internal/obj: move Nocache helper to arm back end

The obj.Nocache helper was only used by the arm back end, move it there.

Change-Id: I5c9faf995499991ead1f3d8c8ffc3b6af7346876
Reviewed-on: https://go-review.googlesource.com/20868Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/internal/obj/arm/asm5.go

@@ -419,8 +419,8 @@ func asmoutnacl(ctxt *obj.Link, origPC int32, p *obj.Prog, o *Optab, out []uint3
 			} else {
 				a2 = &q.From
 			}
-			obj.Nocache(q)
-			obj.Nocache(p)
+			nocache(q)
+			nocache(p)
 
 			// insert q after p
 			q.Link = p.Link
@@ -496,8 +496,8 @@ func asmoutnacl(ctxt *obj.Link, origPC int32, p *obj.Prog, o *Optab, out []uint3
 				} else {
 					a2 = &q.From
 				}
-				obj.Nocache(q)
-				obj.Nocache(p)
+				nocache(q)
+				nocache(p)
 
 				// insert q after p
 				q.Link = p.Link
@@ -2829,3 +2829,12 @@ func chipfloat5(ctxt *obj.Link, e float64) int {
 	//print("match %.8lux %.8lux %d\n", l, h, n);
 	return n
 }
+
+func nocache(p *obj.Prog) {
+	p.Optab = 0
+	p.From.Class = 0
+	if p.From3 != nil {
+		p.From3.Class = 0
+	}
+	p.To.Class = 0
+}

src/cmd/internal/obj/arm/obj5.go

@@ -478,7 +478,7 @@ func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
 			}
 
 		case obj.ARET:
-			obj.Nocache(p)
+			nocache(p)
 			if cursym.Text.Mark&LEAF != 0 {
 				if autosize == 0 {
 					p.As = AB

src/cmd/internal/obj/go.go

@@ -60,15 +60,6 @@ func Nopout(p *Prog) {
 	p.To = Addr{}
 }
 
-func Nocache(p *Prog) {
-	p.Optab = 0
-	p.From.Class = 0
-	if p.From3 != nil {
-		p.From3.Class = 0
-	}
-	p.To.Class = 0
-}
-
 func Expstring() string {
 	buf := "X"
 	for i := range exper {