1 ;;;; This software is part of the SBCL system. See the README file for
4 ;;;; This software is derived from the CMU CL system, which was
5 ;;;; written at Carnegie Mellon University and released into the
6 ;;;; public domain. The software is in the public domain and is
7 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
8 ;;;; files for more information.
12 (defconstant lowtag-bits 3
14 "Number of bits at the low end of a pointer used for type information.")
16 (defconstant lowtag-mask (1- (ash 1 lowtag-bits))
18 "Mask to extract the low tag bits from a pointer.")
20 (defconstant lowtag-limit (ash 1 lowtag-bits)
22 "Exclusive upper bound on the value of the low tag bits from a pointer.")
24 (defconstant type-bits 8
26 "Number of bits used in the header word of a data block to store the type.")
28 (defconstant type-mask (1- (ash 1 type-bits))
30 "Mask to extract the type from a header word.")
32 ;;; FIXME: Couldn't/shouldn't these be DEFCONSTANT instead of DEFPARAMETER?
33 (defparameter *target-most-positive-fixnum* (1- (ash 1 29))
35 "most-positive-fixnum in the target architecture.")
36 (defparameter *target-most-negative-fixnum* (ash -1 29)
38 "most-negative-fixnum in the target architecture.")