runtime: use morePointers and isPointer in more places

This makes this code better self-documenting and makes it easier to
find these places in the future.

Change-Id: I31dc5598ae67f937fb9ef26df92fd41d01e983c3
Reviewed-on: https://go-review.googlesource.com/22631Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/cgocall.go

@@ -559,12 +559,11 @@ func cgoCheckUnknownPointer(p unsafe.Pointer, msg string) (base, i uintptr) {
 		}
 		n := span.elemsize
 		for i = uintptr(0); i < n; i += sys.PtrSize {
-			bits := hbits.bits()
-			if i >= 2*sys.PtrSize && bits&bitMarked == 0 {
+			if i >= 2*sys.PtrSize && !hbits.morePointers() {
 				// No more possible pointers.
 				break
 			}
-			if bits&bitPointer != 0 {
+			if hbits.isPointer() {
 				if cgoIsGoPointer(*(*unsafe.Pointer)(unsafe.Pointer(base + i))) {
 					panic(errorString(msg))
 				}

src/runtime/mgcmark.go

@@ -1132,11 +1132,10 @@ func scanobject(b uintptr, gcw *gcWork) {
 		// in the type bit for the one word. The only one-word objects
 		// are pointers, or else they'd be merged with other non-pointer
 		// data into larger allocations.
-		bits := hbits.bits()
-		if i >= 2*sys.PtrSize && bits&bitMarked == 0 {
+		if i >= 2*sys.PtrSize && !hbits.morePointers() {
 			break // no more pointers in this object
 		}
-		if bits&bitPointer == 0 {
+		if !hbits.isPointer() {
 			continue // not a pointer
 		}