;;; pointer
(def!constant lowtag-limit (ash 1 n-lowtag-bits))
;;; the number of tag bits used for a fixnum
-(def!constant n-fixnum-tag-bits (1- n-lowtag-bits))
+(def!constant n-fixnum-tag-bits
+ (if (= 64 sb!vm:n-word-bits)
+ ;; On 64-bit targets, this may be as low as 1 (for 63-bit
+ ;; fixnums) and as high as 3 (for 61-bit fixnums). The
+ ;; constraint on the low end is that we need at least one bit
+ ;; to determine if a value is a fixnum or not, and the
+ ;; constraint on the high end is that it must not exceed
+ ;; WORD-SHIFT (defined below) due to the use of unboxed
+ ;; word-aligned byte pointers as boxed values in various
+ ;; places. FIXME: This should possibly be exposed for
+ ;; configuration via customize-target-features.
+ 1
+ ;; On 32-bit targets, this may be as low as 2 (for 30-bit
+ ;; fixnums) and as high as 2 (for 30-bit fixnums). The
+ ;; constraint on the low end is simple overcrowding of the
+ ;; lowtag space, and the constraint on the high end is that it
+ ;; must not exceed WORD-SHIFT.
+ (1- n-lowtag-bits)))
;;; the fixnum tag mask
(def!constant fixnum-tag-mask (1- (ash 1 n-fixnum-tag-bits)))
+;;; the bit width of fixnums
+(def!constant n-fixnum-bits (- n-word-bits n-fixnum-tag-bits))
;;; the bit width of positive fixnums
-(def!constant n-positive-fixnum-bits (- n-word-bits n-fixnum-tag-bits 1))
+(def!constant n-positive-fixnum-bits (1- n-fixnum-bits))
;;; the number of bits to shift between word addresses and byte addresses
(def!constant word-shift (1- (integer-length (/ n-word-bits n-byte-bits))))
(def!constant widetag-mask (1- (ash 1 n-widetag-bits)))
(def!constant sb!xc:most-positive-fixnum
- (1- (ash 1 (- n-word-bits n-lowtag-bits)))
+ (1- (ash 1 n-positive-fixnum-bits))
#!+sb-doc
"the fixnum closest in value to positive infinity")
(def!constant sb!xc:most-negative-fixnum
- (ash -1 (- n-word-bits n-lowtag-bits))
+ (ash -1 n-positive-fixnum-bits)
#!+sb-doc
"the fixnum closest in value to negative infinity")
+(def!constant most-positive-word (1- (expt 2 n-word-bits))
+ "The most positive integer that is of type SB-EXT:WORD.")
+
(def!constant most-positive-exactly-single-float-fixnum
- (min #xffffff most-positive-fixnum))
+ (min #xffffff sb!xc:most-positive-fixnum))
(def!constant most-negative-exactly-single-float-fixnum
- (max #x-ffffff most-negative-fixnum))
+ (max #x-ffffff sb!xc:most-negative-fixnum))
(def!constant most-positive-exactly-double-float-fixnum
- (min #x1fffffffffffff most-positive-fixnum))
+ (min #x1fffffffffffff sb!xc:most-positive-fixnum))
(def!constant most-negative-exactly-double-float-fixnum
- (max #x-1fffffffffffff most-negative-fixnum))
+ (max #x-1fffffffffffff sb!xc:most-negative-fixnum))
;;;; Point where continuous area starting at dynamic-space-start bumps into
;;;; next space.