l2 := typecheck.Conv(n.Args[1].(*ir.MakeExpr).Len, types.Types[types.TINT])
	l2 = typecheck.Expr(l2)
	n.Args[1] = l2 // walkAppendArgs expects l2 in n.List.Second().

	walkAppendArgs(n, init)

	l1 := n.Args[0]
	l2 = n.Args[1] // re-read l2, as it may have been updated by walkAppendArgs

	var nodes []ir.Node

	// if l2 >= 0 (likely happens), do nothing

			return mapfast64ptr
		}
		// Two-word object, at least one of which is a pointer.
		// Use the slow path.
	case types.ASTRING:
		return mapfaststr
	}
	return mapslow
}

func walkAppendArgs(n *ir.CallExpr, init *ir.Nodes) {
	walkExprListSafe(n.Args, init)

	// walkExprListSafe will leave OINDEX (s[n]) alone if both s
	// and n are name or literal, but those may index the slice we're