src/compiler/generic/early-objdef.lisp

   1 ;;;; type-based constants
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 (in-package "SB!VM")
  13
  14 ;;; Tags for the main low-level types are stored in the low n (usually three)
  15 ;;; bits to identify the type of a machine word.  Certain constraints
  16 ;;; apply:
  17 ;;;   * EVEN-FIXNUM-LOWTAG and ODD-FIXNUM-LOWTAG must be 0 and 4: code
  18 ;;;     which shifts left two places to convert raw integers to tagged
  19 ;;;     fixnums is ubiquitous.
  20 ;;;   * LIST-POINTER-LOWTAG + N-WORD-BYTES = OTHER-POINTER-LOWTAG: NIL
  21 ;;;     is both a cons and a symbol (at the same address) and depends on this.
  22 ;;;     See the definition of SYMBOL in objdef.lisp
  23 ;;;   * OTHER-POINTER-LOWTAG > 4: Some code in the SPARC backend,
  24 ;;;     which uses bit 2 of the ALLOC register to indicate that
  25 ;;;     PSEUDO-ATOMIC is on, doesn't strip the low bits of reg_ALLOC
  26 ;;;     before ORing in OTHER-POINTER-LOWTAG within a PSEUDO-ATOMIC
  27 ;;;     section.
  28 ;;;   * OTHER-IMMEDIATE-0-LOWTAG are spaced 4 apart: various code wants to
  29 ;;;     iterate through these
  30 ;;;   * Allocation code on Alpha wants lowtags for heap-allocated
  31 ;;;     objects to be odd.
  32 ;;; (These are just the ones we know about as of sbcl-0.7.1.22. There
  33 ;;; might easily be more, since these values have stayed highly
  34 ;;; constrained for more than a decade, an inviting target for
  35 ;;; inventive abstraction-phobic maintainers.:-)
  36 ;;;
  37 ;;; Another way to look at lowtags is that there is no one lowtag
  38 ;;; length.  On 32-bit platforms, fixnums and other-immediates have a
  39 ;;; lowtag length of two bits, and pointers have a lowtag length of
  40 ;;; three bits.  On 64-bit platforms, fixnums and pointers gain an
  41 ;;; extra bit, and six "pad" lowtags waste the extra encoding space so
  42 ;;; obtained.
  43 ;;;
  44 ;;;  x00 -- fixnum
  45 ;;;  x10 -- other-immediate
  46 ;;;  001 -- instance-pointer
  47 ;;;  011 -- list-pointer
  48 ;;;  101 -- fun-pointer
  49 ;;;  111 -- other-pointer
  50 ;;;
  51 ;;; If you change the tag layout, check the various functions in
  52 ;;; src/runtime/runtime.h to see if they need to be updated, along
  53 ;;; with print_obj() in src/runtime/print.c, possibly gc_init_tables()
  54 ;;; in src/runtime/gc-common-c and possibly the code in src/code/room.
  55 (eval-when (:compile-toplevel :load-toplevel :execute)
  56   ;; The EVAL-WHEN is necessary (at least for Lispworks), because the
  57   ;; second DEFENUM uses the value of OTHER-IMMEDIATE-0-LOWTAG, which is
  58   ;; defined in the first DEFENUM. -- AL 20000216
  59   #!+#.(cl:if (cl:= 64 sb!vm:n-word-bits) '(and) '(or))
  60   (defenum ()
  61     even-fixnum-lowtag
  62     other-immediate-0-lowtag
  63     pad0-lowtag
  64     instance-pointer-lowtag
  65     pad1-lowtag
  66     other-immediate-1-lowtag
  67     pad2-lowtag
  68     list-pointer-lowtag
  69     odd-fixnum-lowtag
  70     other-immediate-2-lowtag
  71     pad3-lowtag
  72     fun-pointer-lowtag
  73     pad4-lowtag
  74     other-immediate-3-lowtag
  75     pad5-lowtag
  76     other-pointer-lowtag)
  77   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
  78   (defenum ()
  79     even-fixnum-lowtag
  80     instance-pointer-lowtag
  81     other-immediate-0-lowtag
  82     list-pointer-lowtag
  83     odd-fixnum-lowtag
  84     fun-pointer-lowtag
  85     other-immediate-1-lowtag
  86     other-pointer-lowtag))
  87
  88 (def!constant nil-value
  89     (+ static-space-start n-word-bytes other-pointer-lowtag))
  90
  91 (defconstant-eqx fixnum-lowtags
  92     #.(let ((fixtags nil))
  93         (do-external-symbols (sym "SB!VM")
  94           (let* ((name (symbol-name sym))
  95                  (len (length name)))
  96             (when (and (boundp sym)
  97                        (integerp (symbol-value sym))
  98                        (> len 7)
  99                        (string= name "-LOWTAG" :start1 (- len 7))
 100                        (zerop (logand (symbol-value sym) fixnum-tag-mask)))
 101               (push sym fixtags))))
 102         `',(sort fixtags #'string< :key #'symbol-name))
 103   #'equal)
 104
 105 ;;; the heap types, stored in 8 bits of the header of an object on the
 106 ;;; heap, to identify the type of the heap object (which'll be at
 107 ;;; least two machine words, often more)
 108 ;;;
 109 ;;; Note: the order specified here is not critical for correctness,
 110 ;;; but (FIXME) with %TEST-HEADERS as currently defined, BIGNUM must
 111 ;;; be first, and COMPLEX-ARRAY must be last.
 112 ;;;
 113 ;;; However, for efficiency, we prefer contiguous sets of widetags for
 114 ;;; "similar" objects, so that type checking can be done with a range
 115 ;;; check, rather than several individual checks.
 116 ;;;
 117 ;;; * BIGNUM + RATIO (+ FIXNUM) = RATIONAL
 118 ;;;
 119 ;;; * SINGLE-FLOAT + DOUBLE-FLOAT + LONG-FLOAT = FLOAT
 120 ;;;
 121 ;;; * RATIONAL + FLOAT = REAL
 122 ;;;
 123 ;;; * (FIXME: COMPLEX example, which needs fixing anyway -- see
 124 ;;;   UPGRADED-COMPLEX-PART-TYPE)
 125 ;;;
 126 ;;; * SIMPLE-ARRAY-* = (SIMPLE-ARRAY * (*))
 127 ;;;
 128 ;;; * SIMPLE-ARRAY-NIL + SIMPLE-BASE-STRING = SIMPLE-STRING
 129 ;;;
 130 ;;; * SIMPLE-ARRAY + COMPLEX-ARRAYOID = (SATISFIES ARRAY-HEADER-P)
 131 ;;;
 132 ;;; In addition, with
 133 ;;; sufficient care we can cause extra combinations to appear with
 134 ;;; differences in only one bit, permitting a more efficient type
 135 ;;; test.  As an example, if SIMPLE-BASE-STRING = 0xA6 and
 136 ;;; COMPLEX-BASE-STRING = 0xE6, then the type test for BASE-STRING is
 137 ;;;
 138 ;;;   AND   tag, ~0x40, tag
 139 ;;;   ANDcc tag,  0xA6, tag
 140 ;;;   JNE   tag, label
 141 ;;;
 142 ;;; rather than two separate tests and jumps
 143 (defenum (;; The first widetag must be greater than SB!VM:LOWTAG-LIMIT
 144           ;; otherwise code in generic/early-type-vops will suffer
 145           ;; a long, horrible death.  --njf, 2004-08-09
 146           :start (+ (ash 1 n-lowtag-bits) other-immediate-0-lowtag)
 147           :step 4)
 148   ;; NOTE: the binary numbers off to the side are only valid for 32-bit
 149   ;; ports; add #b1000 if you want to know the values for 64-bit ports.
 150   ;; And note that the numbers get a little scrambled further down.
 151   ;;   --njf, 2004-08-09
 152   bignum-widetag                            ; 00001010
 153   ratio-widetag                             ; 00001110
 154   single-float-widetag                      ; 00010010
 155   double-float-widetag                      ; 00010110
 156   complex-widetag                           ; 00011010
 157   complex-single-float-widetag              ; 00011110
 158   complex-double-float-widetag              ; 00100010
 159
 160   code-header-widetag                       ; 00100110
 161
 162   simple-fun-header-widetag                 ; 00101010
 163   closure-header-widetag                    ; 00101110
 164   funcallable-instance-header-widetag       ; 00110010
 165
 166   return-pc-header-widetag                  ; 00110110
 167   value-cell-header-widetag                 ; 00111010
 168   symbol-header-widetag                     ; 00111110
 169   character-widetag                         ; 01000010
 170   sap-widetag                               ; 01000110
 171   unbound-marker-widetag                    ; 01001010
 172   weak-pointer-widetag                      ; 01001110
 173   instance-header-widetag                   ; 01010010
 174   fdefn-widetag                             ; 01010110
 175
 176   no-tls-value-marker-widetag               ; 01011010
 177   #!-sb-simd-pack
 178   unused01-widetag
 179   #!+sb-simd-pack
 180   simd-pack-widetag                          ; 01011110
 181   unused02-widetag                          ; 01100010
 182   unused03-widetag                          ; 01100110
 183   unused04-widetag                          ; 01101010
 184   unused05-widetag                          ; 01101110
 185   unused06-widetag                          ; 01110010
 186   unused07-widetag                          ; 01110110
 187   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 188   unused08-widetag                          ; 01111010
 189   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 190   unused09-widetag                          ; 01111110
 191
 192   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 193   unused10-widetag                          ; 10000010
 194   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 195   unused11-widetag                          ; 10000110
 196
 197   simple-array-unsigned-byte-2-widetag      ; 10001010
 198   simple-array-unsigned-byte-4-widetag      ; 10001110
 199   simple-array-unsigned-byte-7-widetag      ; 10010010
 200   simple-array-unsigned-byte-8-widetag      ; 10010110
 201   simple-array-unsigned-byte-15-widetag     ; 10011010
 202   simple-array-unsigned-byte-16-widetag     ; 10011110
 203   simple-array-nil-widetag                  ; 10100010
 204   simple-base-string-widetag                ; 10100110
 205   #!+sb-unicode simple-character-string-widetag
 206   simple-bit-vector-widetag                 ; 10101010
 207   simple-vector-widetag                     ; 10101110
 208   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 209   simple-array-unsigned-fixnum-widetag     ; 10110010
 210   simple-array-unsigned-byte-31-widetag     ; 10110110
 211   simple-array-unsigned-byte-32-widetag     ; 10111010
 212   #!+#.(cl:if (cl:= 64 sb!vm:n-word-bits) '(and) '(or))
 213   simple-array-unsigned-fixnum-widetag
 214   #!+#.(cl:if (cl:= 64 sb!vm:n-word-bits) '(and) '(or))
 215   simple-array-unsigned-byte-63-widetag
 216   #!+#.(cl:if (cl:= 64 sb!vm:n-word-bits) '(and) '(or))
 217   simple-array-unsigned-byte-64-widetag
 218   simple-array-signed-byte-8-widetag        ; 10111110
 219   simple-array-signed-byte-16-widetag       ; 11000010
 220   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 221   simple-array-fixnum-widetag       ; 11000110
 222   simple-array-signed-byte-32-widetag       ; 11001010
 223   #!+#.(cl:if (cl:= 64 sb!vm:n-word-bits) '(and) '(or))
 224   simple-array-fixnum-widetag
 225   #!+#.(cl:if (cl:= 64 sb!vm:n-word-bits) '(and) '(or))
 226   simple-array-signed-byte-64-widetag
 227   simple-array-single-float-widetag         ; 11001110
 228   simple-array-double-float-widetag         ; 11010010
 229   simple-array-complex-single-float-widetag ; 11010110
 230   simple-array-complex-double-float-widetag ; 11011010
 231   simple-array-widetag                      ; 11011110
 232   complex-vector-nil-widetag                ; 11100010
 233   complex-base-string-widetag               ; 11100110
 234   #!+sb-unicode complex-character-string-widetag
 235   complex-bit-vector-widetag                ; 11101010
 236   complex-vector-widetag                    ; 11101110
 237   complex-array-widetag                     ; 11110010
 238
 239   #!+#.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 240   unused12-widetag                          ; 11110110
 241   #!+(and #.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 242           (not sb-unicode))
 243   unused13-widetag                          ; 11111010
 244   #!+(and #.(cl:if (cl:= 32 sb!vm:n-word-bits) '(and) '(or))
 245           (not sb-unicode))
 246   unused14-widetag                          ; 11111110
 247 )
 248
 249 ;;; the different vector subtypes
 250 (defenum ()
 251   vector-normal-subtype
 252   vector-unused-subtype
 253   vector-valid-hashing-subtype)