[dev.cc] reflect: interfaces contain only pointers

[This CL is part of the removal of C code from package runtime.
See golang.org/s/dev.cc for an overview.]

Adjustments for changes made in CL 169360043.
This change is already present in the dev.garbage branch.

LGTM=r
R=r
CC=austin, golang-codereviews, iant, khr
https://golang.org/cl/167520044

src/reflect/type.go

@@ -1533,12 +1533,8 @@ func (gc *gcProg) appendProg(t *rtype) {
 			gc.appendProg(e)
 		}
 	case Interface:
-		gc.appendWord(bitsMultiWord)
-		if t.NumMethod() == 0 {
-			gc.appendWord(bitsEface)
-		} else {
-			gc.appendWord(bitsIface)
-		}
+		gc.appendWord(bitsPointer)
+		gc.appendWord(bitsPointer)
 	case Struct:
 		c := t.NumField()
 		for i := 0; i < c; i++ {
@@ -1594,7 +1590,6 @@ func (gc *gcProg) align(a uintptr) {
 const (
 	bitsScalar  = 1
 	bitsPointer = 2
-	bitsMultiWord = 3
 
 	bitsIface = 2
 	bitsEface = 3

src/runtime/gcinfo_test.go

@@ -62,12 +62,10 @@ func verifyGCInfo(t *testing.T, name string, p interface{}, mask0 []byte) {
 func nonStackInfo(mask []byte) []byte {
 	// BitsDead is replaced with BitsScalar everywhere except stacks.
 	mask1 := make([]byte, len(mask))
-	mw := false
 	for i, v := range mask {
-		if !mw && v == BitsDead {
+		if v == BitsDead {
 			v = BitsScalar
 		}
-		mw = !mw && v == BitsMultiWord
 		mask1[i] = v
 	}
 	return mask1
@@ -84,7 +82,6 @@ const (
 	BitsDead = iota
 	BitsScalar
 	BitsPointer
-	BitsMultiWord
 )
 
 const (
@@ -188,6 +185,6 @@ var (
 
 	infoString = []byte{BitsPointer, BitsDead}
 	infoSlice  = []byte{BitsPointer, BitsDead, BitsDead}
-	infoEface  = []byte{BitsMultiWord, BitsEface}
-	infoIface  = []byte{BitsMultiWord, BitsIface}
+	infoEface  = []byte{BitsPointer, BitsPointer}
+	infoIface  = []byte{BitsPointer, BitsPointer}
 )