1 ;;;; type-based constants
3 ;;;; This software is part of the SBCL system. See the README file for
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.
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
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
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.:-)
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
45 ;;; x10 -- other-immediate
46 ;;; 001 -- instance-pointer
47 ;;; 011 -- list-pointer
48 ;;; 101 -- fun-pointer
49 ;;; 111 -- other-pointer
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 'late-objdef.lisp'
54 ;;; 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
62 other-immediate-0-lowtag
64 instance-pointer-lowtag
66 other-immediate-1-lowtag
70 other-immediate-2-lowtag
74 other-immediate-3-lowtag
80 instance-pointer-lowtag
81 other-immediate-0-lowtag
85 other-immediate-1-lowtag
86 other-pointer-lowtag
))
88 (def!constant nil-value
89 (+ static-space-start n-word-bytes other-pointer-lowtag
))
91 (defconstant-eqx fixnum-lowtags
92 #.
(let ((fixtags nil
))
93 (do-external-symbols (sym "SB!VM")
94 (let* ((name (symbol-name sym
))
96 (when (and (boundp sym
)
97 (integerp (symbol-value sym
))
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
))
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)
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.
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.
117 ;;; * BIGNUM + RATIO (+ FIXNUM) = RATIONAL
119 ;;; * SINGLE-FLOAT + DOUBLE-FLOAT + LONG-FLOAT = FLOAT
120 ;;; But: There's not a snowball's chance that #!+long-float works.
121 ;;; changeset 7646ae obliterated LONG-FLOAT-WIDETAG.
123 ;;; * RATIONAL + FLOAT = REAL
125 ;;; * (FIXME: COMPLEX example, which needs fixing anyway -- see
126 ;;; UPGRADED-COMPLEX-PART-TYPE)
128 ;;; * SIMPLE-ARRAY-* = (SIMPLE-ARRAY * (*))
130 ;;; * SIMPLE-ARRAY-NIL + SIMPLE-BASE-STRING = SIMPLE-STRING
132 ;;; * SIMPLE-ARRAY + COMPLEX-ARRAYOID = (SATISFIES ARRAY-HEADER-P)
134 ;;; In addition, with
135 ;;; sufficient care we can cause extra combinations to appear with
136 ;;; differences in only one bit, permitting a more efficient type
137 ;;; test. As an example, if SIMPLE-BASE-STRING = 0xA6 and
138 ;;; COMPLEX-BASE-STRING = 0xE6, then the type test for BASE-STRING is
140 ;;; AND tag, ~0x40, tag
141 ;;; ANDcc tag, 0xA6, tag
144 ;;; rather than two separate tests and jumps.
145 ;;; However, the cases where this is possible are few, and I'm not sure if
146 ;;; that happened before or after rearrangement of widetags in change 30eccf.
147 ;;; At present on 64-bit target with unicode we have:
148 ;;; (logcount (logxor complex-character-string-widetag simple-character-string-widetag)) = 2
149 ;;; (logcount (logxor complex-base-string-widetag simple-base-string-widetag)) = 2
150 ;;; (logcount (logxor complex-vector-nil-widetag simple-array-nil-widetag)) = 3
151 ;;; (logcount (logxor complex-bit-vector-widetag simple-bit-vector-widetag)) = 1
152 ;;; and we have one winner. The situation is slightly different for 32-bit.
154 ;; FIXME: our nomenclature is baffling in more ways than implied by comments in
155 ;; package-data-list regarding use of the word "complex" in both a numerical
156 ;; sense and "non-simple" sense:
157 ;; - There is no widetag specific to (AND (VECTOR T) (NOT SIMPLE-ARRAY)), i.e.
158 ;; COMPLEX-VECTOR-WIDETAG is not the complex version of SIMPLE-VECTOR-WIDETAG
159 ;; which is, in part, why the comment in x86/type-vops about optimizing a test
160 ;; for (VECTOR T) is wrong.
161 ;; - simple-array-nil should be named simple-rank-1-array-nil, though I think
162 ;; simple-vector-nil is fine despite some reluctance to glue the particles
163 ;; "simple" and "vector" together due to overtones of the standard meaning.
164 ;; We could rename things that mean vector of wild type to VECTOR-*
165 ;; and simple vector of T to SIMPLE-VECTOR-T. Just because CL says that
166 ;; SIMPLE-VECTOR means the latter doesn't make it right for SBCL internals.
168 (eval-when (:compile-toplevel
:load-toplevel
:execute
)
169 (defenum (;; The first widetag must be greater than SB!VM:LOWTAG-LIMIT
170 ;; otherwise code in generic/early-type-vops will suffer
171 ;; a long, horrible death. --njf, 2004-08-09
172 :start
#.
(+ (ash 1 n-lowtag-bits
) other-immediate-0-lowtag
)
175 ;; Word bits ; 32 | 64 32 | 64
177 ; [ all numbers are hex ]
178 bignum-widetag
; 0A 11 0A 11
179 ratio-widetag
; 0E 15 0E 15
180 single-float-widetag
; 12 19 12 19
181 double-float-widetag
; 16 1D 16 1D
182 complex-widetag
; 1A 21 1A 21
183 complex-single-float-widetag
; 1E 25 1E 25
184 complex-double-float-widetag
; 22 29 22 29
186 code-header-widetag
; 26 2D 26 2D
188 simple-fun-widetag
; 2A 31 2A 31
189 closure-widetag
; 2E 35 2E 35
190 funcallable-instance-widetag
; 32 39 32 39
192 ;; x86[-64] does not have objects with this widetag,
193 #!+(or x86 x86-64
) unused00-widetag
195 return-pc-widetag
; 36 3D 36 3D
197 value-cell-widetag
; 3A 41 3A 41
198 symbol-widetag
; 3E 45 3E 45
199 character-widetag
; 42 49 42 49
200 sap-widetag
; 46 4D 46 4D
201 unbound-marker-widetag
; 4A 51 4A 51
202 weak-pointer-widetag
; 4E 55 4E 55
203 instance-widetag
; 52 59 52 59
204 fdefn-widetag
; 56 5D 56 5D
206 no-tls-value-marker-widetag
; 5A 61 5A 61
208 unused01-widetag
; 5E 5E
210 simd-pack-widetag
; 65 65
211 unused02-widetag
; 62 69 62 69
212 unused03-widetag
; 66 6D 66 6D
213 unused04-widetag
; 6A 71 6A 71
214 unused05-widetag
; 6E 75 6E 75
215 unused06-widetag
; 72 79 72 79
216 unused07-widetag
; 76 7D 76 7D
218 unused08-widetag
; 7A 7A
220 unused09-widetag
; 7E 7E
222 simple-array-widetag
; 82 81 82 81
223 simple-array-unsigned-byte-2-widetag
; 86 85 86 85
224 simple-array-unsigned-byte-4-widetag
; 8A 89 8A 89
225 simple-array-unsigned-byte-7-widetag
; 8E 8D 8E 8D
226 simple-array-unsigned-byte-8-widetag
; 92 91 92 91
227 simple-array-unsigned-byte-15-widetag
; 96 95 96 95
228 simple-array-unsigned-byte-16-widetag
; 9A 99 9A 99
231 simple-array-unsigned-fixnum-widetag
; 9E A5 9E A5
232 simple-array-unsigned-byte-31-widetag
; A2 9D A2 9D
233 simple-array-unsigned-byte-32-widetag
; A6 A1 A6 A1
235 simple-array-unsigned-fixnum-widetag
; 9E A5 9E A5
237 simple-array-unsigned-byte-63-widetag
; A9 A9
239 simple-array-unsigned-byte-64-widetag
; AD AD
240 simple-array-signed-byte-8-widetag
; AA B1 AA B1
241 simple-array-signed-byte-16-widetag
; AE B5 AE B5
243 simple-array-fixnum-widetag
; B2 BD B2 BD
244 simple-array-signed-byte-32-widetag
; B6 B9 B6 B9
246 simple-array-fixnum-widetag
; B2 BD B2 BD
248 simple-array-signed-byte-64-widetag
; C1 C1
249 simple-array-single-float-widetag
; BA C5 BA C5
250 simple-array-double-float-widetag
; BE C9 BE C9
251 simple-array-complex-single-float-widetag
; C2 CD C2 CD
252 simple-array-complex-double-float-widetag
; C6 D1 C6 D1
253 simple-bit-vector-widetag
; CA D5 CA D5
254 simple-vector-widetag
; CE D9 CE D9
257 simple-array-nil-widetag
; D2 DD D2 DD
258 simple-base-string-widetag
; D6 E1 D6 E1
260 simple-character-string-widetag
; DA E5
262 complex-character-string-widetag
; DE E9
263 complex-base-string-widetag
; E2 ED DA E5
264 complex-vector-nil-widetag
; E6 F1 DE E9
266 complex-bit-vector-widetag
; EA F5 E2 ED
267 complex-vector-widetag
; EE F9 E6 F1
268 complex-array-widetag
; F2 FD EA F5
271 (defconstant-eqx +fun-header-widetags
+
272 '#.
(list funcallable-instance-widetag simple-fun-widetag closure-widetag
)
275 ;;; Don't use these. They're for Slime, ltk, Conium, hu.dwim.debug
276 ;;; and who-knows-what-else.
277 (defconstant simple-fun-header-widetag simple-fun-widetag
)
278 (defconstant closure-header-widetag closure-widetag
)
280 ;;; the different vector subtypes
282 vector-normal-subtype
283 vector-unused-subtype
284 vector-valid-hashing-subtype
)
286 ;;; These next two constants must not occupy the same byte of a
287 ;;; vector header word as the values in the preceding defenum.
289 ;; A vector tagged as +VECTOR-SHAREABLE+ is logically readonly,
290 ;; and permitted to be shared with another vector per the CLHS standard
291 ;; under the concept of similarity as constant. A vector so tagged is
292 ;; often the print-name of a symbol, or was a literal in source code
293 ;; and loaded from a fasl, or used in a few others situations
294 ;; which warrant sharing.
295 (def!constant
+vector-shareable
+ #x100
)
297 ;; A vector tagged as +VECTOR-SHAREABLE-NONSTD+ is logically readonly,
298 ;; and *not* technically permitted by the standard to be shared.
299 ;; If, despite the apparent prohibition, the user opts to make these
300 ;; shareable, we'll do it. This typically occurs with compilation
301 ;; into memory, where the requirement is that the machine code
302 ;; reference "the same" object as appeared in source, but where,
303 ;; nonetheless, opportunities for sharing abound.
304 (defconstant +vector-shareable-nonstd
+ #x200
)
306 ;;; This is so that COMPILE-FILE knows that things like :ALLOW-OTHER-KEYS
307 ;;; can be immediate constants.
308 #!+(and immobile-space
(not immobile-symbols
))
309 (defconstant +initial-core-symbol-bit
+ 8) ; bit index, not bit value
313 ;; See 'doc/internal-notes/compact-instance' for rationale
314 (defconstant layout-align
#!+64-bit
128 #!-
64-bit
256) ; in bytes
316 ;; FUNCTION-LAYOUT is a fixnum whose bits are ORed in "as-is" with the
317 ;; low half of a closure header to form the full header word.
318 #-sb-xc-host
(defglobal function-layout
0) ; set by genesis
320 ;; The cross-compiler stores FUNCTION-LAYOUT in a more obvious way.
322 (defconstant function-layout
; kludge - verified by genesis
323 (logior (+ fixedobj-space-start layout-align
) instance-pointer-lowtag
)))
326 ;; Run this in the SB-VM or SB!VM package once for each target feature combo.
327 (defun rewrite-widetag-comments ()
328 (rename-file "src/compiler/generic/early-objdef.lisp" "early-objdef.old")
329 (with-open-file (in "src/compiler/generic/early-objdef.old")
330 (with-open-file (out "src/compiler/generic/early-objdef.lisp"
331 :direction
:output
:if-exists
:supersede
)
332 (let* ((target-features
333 (if (find-package "SB-COLD")
334 (symbol-value (find-symbol "*SHEBANG-FEATURES*" "SB-COLD"))
337 (+ (if (= n-word-bits
64) 1 0)
338 (if (member :sb-unicode target-features
) 0 2)))
340 (comment-offset (aref #(3 8 12 17) feature-bits
))
343 (let* ((line (read-line in nil
))
344 (trimmed (and line
(string-left-trim " " line
)))
348 (when (and (zerop state
) (eql 0 (search "bignum-widetag" trimmed
)))
349 (setq state
1 comment-col
(position #\
; line)))
350 (if (and (= state
1) (plusp (length trimmed
))
351 (alpha-char-p (char trimmed
0))
352 (boundp (setq symbol
(read-from-string trimmed
))))
353 (let ((new (make-string (+ comment-col
19)
354 :initial-element
#\Space
)))
356 (replace new
(format nil
"~2,'0X" (symbol-value symbol
))
357 :start1
(+ comment-col comment-offset
))
358 (write-line new out
))
360 (write-line line out
)
361 (if (and (= state
1) (string= line
")"))
362 (setq state
2))))))))))