cmd/9g, etc: remove // fallthrough comments

They are vestiges of the c2go transition.

Change-Id: I22672e40373ef77d7a0bf69cfff8017e46353055
Reviewed-on: https://go-review.googlesource.com/9265Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/9g/gsubr.go

@@ -936,11 +936,10 @@ func optoas(op int, t *gc.Type) int {
 		gc.OMUL<<16 | gc.TUINT32,
 		gc.OMUL<<16 | gc.TPTR32,
 		// don't use word multiply, the high 32-bit are undefined.
-		// fallthrough
 		gc.OMUL<<16 | gc.TUINT64,
 		gc.OMUL<<16 | gc.TPTR64:
-		a = ppc64.AMULLD
 		// for 64-bit multiplies, signedness doesn't matter.
+		a = ppc64.AMULLD
 
 	case gc.OMUL<<16 | gc.TFLOAT32:
 		a = ppc64.AFMULS

src/cmd/internal/gc/dcl.go

@@ -836,7 +836,6 @@ func structfield(n *Node) *Type {
 		Yyerror("field annotation must be string")
 		fallthrough
 
-		// fallthrough
 	case CTxxx:
 		f.Note = nil
 	}

src/cmd/internal/gc/esc.go

@@ -729,7 +729,6 @@ func esc(e *EscState, n *Node, up *Node) {
 		}
 		fallthrough
 
-		// fallthrough
 	case OMAKECHAN,
 		OMAKEMAP,
 		OMAKESLICE,
@@ -903,7 +902,6 @@ func escassign(e *EscState, dst *Node, src *Node) {
 		fallthrough
 
 		// Conversions, field access, slice all preserve the input value.
-	// fallthrough
 	case OCONV,
 		OCONVNOP,
 		ODOTMETH,

src/cmd/internal/gc/export.go

@@ -119,7 +119,6 @@ func reexportdep(n *Node) {
 			}
 			fallthrough
 
-			// fallthrough
 		case PEXTERN:
 			if n.Sym != nil && !exportedsym(n.Sym) {
 				if Debug['E'] != 0 {
@@ -160,7 +159,6 @@ func reexportdep(n *Node) {
 		}
 		fallthrough
 
-		// fallthrough
 	case OTYPE:
 		if n.Sym != nil && !exportedsym(n.Sym) {
 			if Debug['E'] != 0 {

src/cmd/internal/gc/fmt.go

@@ -514,7 +514,6 @@ func typefmt(t *Type, flag int) string {
 			}
 			fallthrough
 
-			// fallthrough
 		case FExp:
 			if t.Sym.Pkg == localpkg && t.Vargen != 0 {
 				return fmt.Sprintf("%v·%d", t.Sym, t.Vargen)
@@ -847,7 +846,6 @@ func stmtfmt(n *Node) string {
 		}
 		fallthrough
 
-		// fallthrough
 	case OAS2DOTTYPE, OAS2FUNC, OAS2MAPR, OAS2RECV:
 		f += fmt.Sprintf("%v = %v", Hconv(n.List, obj.FmtComma), Hconv(n.Rlist, obj.FmtComma))
 
@@ -1257,8 +1255,6 @@ func exprfmt(n *Node, prec int) string {
 		}
 		fallthrough
 
-		// fallthrough
-
 	case OARRAYLIT, OMAPLIT:
 		if fmtmode == FErr {
 			return fmt.Sprintf("%v literal", n.Type)

src/cmd/internal/gc/gen.go

@@ -68,8 +68,6 @@ func addrescapes(n *Node) {
 			n.Stackparam.Xoffset = n.Xoffset
 			fallthrough
 
-			// fallthrough
-
 		case PAUTO:
 			n.Class |= PHEAP
 

src/cmd/internal/gc/inl.go

@@ -400,7 +400,6 @@ func inlnode(np **Node) {
 		}
 		fallthrough
 
-		// fallthrough
 	default:
 		for l := n.List; l != nil; l = l.Next {
 			if l.N.Op == OINLCALL {
@@ -421,7 +420,6 @@ func inlnode(np **Node) {
 		}
 		fallthrough
 
-		// fallthrough
 	default:
 		for l := n.Rlist; l != nil; l = l.Next {
 			if l.N.Op == OINLCALL {

src/cmd/internal/gc/walk.go

@@ -1271,7 +1271,6 @@ func walkexpr(np **Node, init **NodeList) {
 		}
 		fallthrough
 
-		// fallthrough
 	case OSLICEARR, OSLICESTR:
 		if n.Right == nil { // already processed
 			goto ret

src/cmd/internal/ld/dwarf.go

@@ -1435,7 +1435,6 @@ func defdwsymb(sym *LSym, s string, t int, v int64, size int64, ver int, gotype
 		}
 		fallthrough
 
-		// fallthrough
 	case 'a', 'p':
 		dt = defgotype(gotype)
 	}

src/cmd/internal/ld/elf.go

@@ -781,7 +781,6 @@ func Elfinit() {
 		}
 		fallthrough
 
-		// fallthrough
 	default:
 		ehdr.phoff = ELF32HDRSIZE
 		/* Must be be ELF32HDRSIZE: first PHdr must follow ELF header */