;;;; type-based constants ;;;; This software is part of the SBCL system. See the README file for ;;;; more information. ;;;; ;;;; This software is derived from the CMU CL system, which was ;;;; written at Carnegie Mellon University and released into the ;;;; public domain. The software is in the public domain and is ;;;; provided with absolutely no warranty. See the COPYING and CREDITS ;;;; files for more information. (in-package "SB!VM") ;;; FIXME: It's clever using :SUFFIX -TYPE for these things, but it's ;;; a pain for people just learning to find their way around the code ;;; who want to use lexical search to figure out where things like ;;; EVEN-FIXNUM-LOWTAG are defined. Remove the :SUFFIXes and just expand ;;; out the full names. Or even define them in DEF EVEN-FIXNUM-LOWTAG ;;; style so searches like 'def.*even-fixnum-lowtag' can find them. ;;; Tags for the main low-level types are stored in the low three ;;; bits to identify the type of a machine word. Certain constraints ;;; apply: ;;; * EVEN-FIXNUM-LOWTAG and ODD-FIXNUM-LOWTAG must be 0 and 4: code ;;; which shifts left two places to convert raw integers to tagged ;;; fixnums is ubiquitous. ;;; * LIST-POINTER-LOWTAG + 4 = OTHER-POINTER-LOWTAG: NIL is both a ;;; cons and a symbol (at the same address) and depends on this. ;;; See the definition of SYMBOL in objdef.lisp ;;; * OTHER-POINTER-LOWTAG > 4: Some code in the SPARC backend, ;;; which uses bit 2 of the ALLOC register to indicate that ;;; PSEUDO-ATOMIC is on, doesn't strip the low bits of reg_ALLOC ;;; before ORing in OTHER-POINTER-LOWTAG within a PSEUDO-ATOMIC ;;; section. ;;; (These are just the ones we know about as of sbcl-0.7.1.22. There ;;; might easily be more, since these values have stayed highly ;;; constrained for more than a decade, an inviting target for ;;; inventive abstraction-phobic maintainers.:-) (eval-when (:compile-toplevel :load-toplevel :execute) ;; The EVAL-WHEN is necessary (at least for Lispworks), because the ;; second DEFENUM uses the value of OTHER-IMMEDIATE-0-LOWTAG, which is ;; defined in the first DEFENUM. -- AL 20000216 (defenum (:suffix -lowtag) even-fixnum ;; Note: CMU CL, and SBCL < 0.pre7.39, had FUN-POINTER-LOWTAG ;; here. We swapped FUN-POINTER-LOWTAG and ;; INSTANCE-POINTER-LOWTAG in sbcl-0.pre7.39 in order to help with a ;; low-level pun in the function call sequence on the PPC port. ;; For more information, see the PPC port code. -- WHN 2001-10-03 instance-pointer other-immediate-0 list-pointer odd-fixnum fun-pointer other-immediate-1 other-pointer)) ;;; the heap types, stored in 8 bits of the header of an object on the ;;; heap, to identify the type of the heap object (which'll be at ;;; least two machine words, often more) (defenum (:suffix -widetag :start (+ (ash 1 n-lowtag-bits) other-immediate-0-lowtag) :step (ash 1 (1- n-lowtag-bits))) bignum ratio single-float double-float #!+long-float long-float complex complex-single-float complex-double-float #!+long-float complex-long-float simple-array simple-string simple-bit-vector simple-vector simple-array-nil simple-array-unsigned-byte-2 simple-array-unsigned-byte-4 simple-array-unsigned-byte-8 simple-array-unsigned-byte-16 simple-array-unsigned-byte-32 simple-array-signed-byte-8 simple-array-signed-byte-16 simple-array-signed-byte-30 simple-array-signed-byte-32 simple-array-single-float simple-array-double-float #!+long-float simple-array-long-float simple-array-complex-single-float simple-array-complex-double-float #!+long-float simple-array-complex-long-float complex-string complex-bit-vector complex-vector complex-array code-header simple-fun-header closure-header funcallable-instance-header closure-fun-header return-pc-header value-cell-header symbol-header base-char sap unbound-marker weak-pointer instance-header fdefn) ;;; the different vector subtypes (defenum (:prefix vector- :suffix -subtype) normal unused valid-hashing must-rehash)