internal/gclayout: make gclayout values constants

The previous versions calculated at init() prevented `interp` from running
in many cases, increasing compile times due to the increased need to revert
the partially interpreted results and also increasing binary runtime because
fewer optimizations had happened during interp.

src/runtime/string.go

@@ -60,7 +60,7 @@ func stringConcat(x, y _string) _string {
 		return x
 	} else {
 		length := x.length + y.length
-		buf := alloc(length, gclayout.NoPtrs)
+		buf := alloc(length, gclayout.NoPtrs.AsPtr())
 		memcpy(buf, unsafe.Pointer(x.ptr), x.length)
 		memcpy(unsafe.Add(buf, x.length), unsafe.Pointer(y.ptr), y.length)
 		return _string{ptr: (*byte)(buf), length: length}
@@ -73,7 +73,7 @@ func stringFromBytes(x struct {
 	len uintptr
 	cap uintptr
 }) _string {
-	buf := alloc(x.len, gclayout.NoPtrs)
+	buf := alloc(x.len, gclayout.NoPtrs.AsPtr())
 	memcpy(buf, unsafe.Pointer(x.ptr), x.len)
 	return _string{ptr: (*byte)(buf), length: x.len}
 }
@@ -84,7 +84,7 @@ func stringToBytes(x _string) (slice struct {
 	len uintptr
 	cap uintptr
 }) {
-	buf := alloc(x.length, gclayout.NoPtrs)
+	buf := alloc(x.length, gclayout.NoPtrs.AsPtr())
 	memcpy(buf, unsafe.Pointer(x.ptr), x.length)
 	slice.ptr = (*byte)(buf)
 	slice.len = x.length
@@ -101,7 +101,7 @@ func stringFromRunes(runeSlice []rune) (s _string) {
 	}
 
 	// Allocate memory for the string.
-	s.ptr = (*byte)(alloc(s.length, gclayout.NoPtrs))
+	s.ptr = (*byte)(alloc(s.length, gclayout.NoPtrs.AsPtr()))
 
 	// Encode runes to UTF-8 and store the resulting bytes in the string.
 	index := uintptr(0)