1 ;;;; various primitive memory access VOPs for the x86 VM
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 ;;;; data object ref/set stuff
17 (:args (object :scs (descriptor-reg)))
18 (:info name offset lowtag)
20 (:results (result :scs (descriptor-reg any-reg)))
22 (loadw result object offset lowtag)))
24 (define-vop (set-slot)
25 (:args (object :scs (descriptor-reg))
26 (value :scs (descriptor-reg any-reg immediate)))
27 (:temporary (:sc descriptor-reg) temp)
28 (:info name offset lowtag)
32 (if (sc-is value immediate)
33 (let ((val (tn-value value)))
34 (move-immediate (make-ea :qword
36 :disp (- (* offset n-word-bytes)
42 (+ nil-value (static-symbol-offset val)))
44 (logior (ash (char-code val) n-widetag-bits)
47 ;; Else, value not immediate.
48 (storew value object offset lowtag))))
52 ;;;; symbol hacking VOPs
54 ;;; these next two cf the sparc version, by jrd.
55 ;;; FIXME: Deref this ^ reference.
58 ;;; The compiler likes to be able to directly SET symbols.
61 (:args (symbol :scs (descriptor-reg))
62 (value :scs (descriptor-reg any-reg)))
63 (:temporary (:sc descriptor-reg) tls)
64 ;;(:policy :fast-safe)
66 (let ((global-val (gen-label))
68 (loadw tls symbol symbol-tls-index-slot other-pointer-lowtag)
70 (inst jmp :z global-val)
71 (inst cmp (make-ea :qword :base thread-base-tn :scale 1 :index tls)
72 no-tls-value-marker-widetag)
73 (inst jmp :z global-val)
74 (inst mov (make-ea :qword :base thread-base-tn :scale 1 :index tls)
77 (emit-label global-val)
78 (storew value symbol symbol-value-slot other-pointer-lowtag)
81 ;; unithreaded it's a lot simpler ...
83 (define-vop (set cell-set)
84 (:variant symbol-value-slot other-pointer-lowtag))
86 ;;; Do a cell ref with an error check for being unbound.
87 ;;; XXX stil used? I can't see where -dan
88 (define-vop (checked-cell-ref)
89 (:args (object :scs (descriptor-reg) :target obj-temp))
90 (:results (value :scs (descriptor-reg any-reg)))
93 (:save-p :compute-only)
94 (:temporary (:sc descriptor-reg :from (:argument 0)) obj-temp))
96 ;;; With Symbol-Value, we check that the value isn't the trap object. So
97 ;;; Symbol-Value of NIL is NIL.
99 (define-vop (symbol-value)
100 (:translate symbol-value)
102 (:args (object :scs (descriptor-reg) :to (:result 1)))
103 (:results (value :scs (descriptor-reg any-reg)))
105 (:save-p :compute-only)
107 (let* ((check-unbound-label (gen-label))
108 (err-lab (generate-error-code vop unbound-symbol-error object))
109 (ret-lab (gen-label)))
110 (loadw value object symbol-tls-index-slot other-pointer-lowtag)
111 (inst mov value (make-ea :qword :base thread-base-tn
112 :index value :scale 1))
113 (inst cmp value no-tls-value-marker-widetag)
114 (inst jmp :ne check-unbound-label)
115 (loadw value object symbol-value-slot other-pointer-lowtag)
116 (emit-label check-unbound-label)
117 (inst cmp value unbound-marker-widetag)
118 (inst jmp :e err-lab)
119 (emit-label ret-lab))))
122 (define-vop (fast-symbol-value symbol-value)
123 ;; KLUDGE: not really fast, in fact, because we're going to have to
124 ;; do a full lookup of the thread-local area anyway. But half of
125 ;; the meaning of FAST-SYMBOL-VALUE is "do not signal an error if
126 ;; unbound", which is used in the implementation of COPY-SYMBOL. --
129 (:translate symbol-value)
131 (let ((ret-lab (gen-label)))
132 (loadw value object symbol-tls-index-slot other-pointer-lowtag)
134 (make-ea :qword :base thread-base-tn :index value :scale 1))
135 (inst cmp value no-tls-value-marker-widetag)
136 (inst jmp :ne ret-lab)
137 (loadw value object symbol-value-slot other-pointer-lowtag)
138 (emit-label ret-lab))))
141 (define-vop (symbol-value)
142 (:translate symbol-value)
144 (:args (object :scs (descriptor-reg) :to (:result 1)))
145 (:results (value :scs (descriptor-reg any-reg)))
147 (:save-p :compute-only)
149 (let ((err-lab (generate-error-code vop unbound-symbol-error object)))
150 (loadw value object symbol-value-slot other-pointer-lowtag)
151 (inst cmp value unbound-marker-widetag)
152 (inst jmp :e err-lab))))
155 (define-vop (fast-symbol-value cell-ref)
156 (:variant symbol-value-slot other-pointer-lowtag)
158 (:translate symbol-value))
160 (defknown locked-symbol-global-value-add (symbol fixnum) fixnum ())
162 (define-vop (locked-symbol-global-value-add)
163 (:args (object :scs (descriptor-reg) :to :result)
164 (value :scs (any-reg) :target result))
165 (:arg-types * tagged-num)
166 (:results (result :scs (any-reg) :from (:argument 1)))
168 (:translate locked-symbol-global-value-add)
169 (:result-types tagged-num)
174 (inst add (make-ea :qword :base object
175 :disp (- (* symbol-value-slot n-word-bytes)
176 other-pointer-lowtag))
183 (:args (object :scs (descriptor-reg)))
186 (:temporary (:sc descriptor-reg #+nil(:from (:argument 0))) value)
188 (let ((check-unbound-label (gen-label)))
189 (loadw value object symbol-tls-index-slot other-pointer-lowtag)
191 (make-ea :qword :base thread-base-tn :index value :scale 1))
192 (inst cmp value no-tls-value-marker-widetag)
193 (inst jmp :ne check-unbound-label)
194 (loadw value object symbol-value-slot other-pointer-lowtag)
195 (emit-label check-unbound-label)
196 (inst cmp value unbound-marker-widetag)
197 (inst jmp (if not-p :e :ne) target))))
203 (:args (object :scs (descriptor-reg)))
207 (inst cmp (make-ea-for-object-slot object symbol-value-slot
208 other-pointer-lowtag)
209 unbound-marker-widetag)
210 (inst jmp (if not-p :e :ne) target)))
213 (define-vop (symbol-hash)
215 (:translate symbol-hash)
216 (:args (symbol :scs (descriptor-reg)))
217 (:results (res :scs (any-reg)))
218 (:result-types positive-fixnum)
220 ;; The symbol-hash slot of NIL holds NIL because it is also the
221 ;; cdr slot, so we have to strip off the three low bits to make sure
222 ;; it is a fixnum. The lowtag selection magic that is required to
223 ;; ensure this is explained in the comment in objdef.lisp
224 (loadw res symbol symbol-hash-slot other-pointer-lowtag)
225 (inst and res (lognot #b111))))
227 ;;;; fdefinition (FDEFN) objects
229 (define-vop (fdefn-fun cell-ref) ; /pfw - alpha
230 (:variant fdefn-fun-slot other-pointer-lowtag))
232 (define-vop (safe-fdefn-fun)
233 (:args (object :scs (descriptor-reg) :to (:result 1)))
234 (:results (value :scs (descriptor-reg any-reg)))
236 (:save-p :compute-only)
238 (loadw value object fdefn-fun-slot other-pointer-lowtag)
239 (inst cmp value nil-value)
240 (let ((err-lab (generate-error-code vop undefined-fun-error object)))
241 (inst jmp :e err-lab))))
243 (define-vop (set-fdefn-fun)
245 (:translate (setf fdefn-fun))
246 (:args (function :scs (descriptor-reg) :target result)
247 (fdefn :scs (descriptor-reg)))
248 (:temporary (:sc unsigned-reg) raw)
249 (:temporary (:sc byte-reg) type)
250 (:results (result :scs (descriptor-reg)))
252 (load-type type function (- fun-pointer-lowtag))
254 (make-ea :byte :base function
255 :disp (- (* simple-fun-code-offset n-word-bytes)
256 fun-pointer-lowtag)))
257 (inst cmp type simple-fun-header-widetag)
258 (inst jmp :e NORMAL-FUN)
259 (inst lea raw (make-fixup "closure_tramp" :foreign))
261 (storew function fdefn fdefn-fun-slot other-pointer-lowtag)
262 (storew raw fdefn fdefn-raw-addr-slot other-pointer-lowtag)
263 (move result function)))
265 (define-vop (fdefn-makunbound)
267 (:translate fdefn-makunbound)
268 (:args (fdefn :scs (descriptor-reg) :target result))
269 (:results (result :scs (descriptor-reg)))
271 (storew nil-value fdefn fdefn-fun-slot other-pointer-lowtag)
272 (storew (make-fixup "undefined_tramp" :foreign)
273 fdefn fdefn-raw-addr-slot other-pointer-lowtag)
274 (move result fdefn)))
276 ;;;; binding and unbinding
278 ;;; BIND -- Establish VAL as a binding for SYMBOL. Save the old value and
279 ;;; the symbol on the binding stack and stuff the new value into the
284 (:args (val :scs (any-reg descriptor-reg))
285 (symbol :scs (descriptor-reg)))
286 (:temporary (:sc descriptor-reg :offset rax-offset) rax)
287 (:temporary (:sc unsigned-reg) tls-index temp bsp)
289 (let ((tls-index-valid (gen-label))
290 (get-tls-index-lock (gen-label))
291 (release-tls-index-lock (gen-label)))
292 (load-binding-stack-pointer bsp)
293 (loadw tls-index symbol symbol-tls-index-slot other-pointer-lowtag)
294 (inst add bsp (* binding-size n-word-bytes))
295 (store-binding-stack-pointer bsp)
296 (inst or tls-index tls-index)
297 (inst jmp :ne tls-index-valid)
300 (emit-label get-tls-index-lock)
304 (inst cmpxchg (make-ea-for-symbol-value *tls-index-lock*) temp)
305 (inst jmp :ne get-tls-index-lock)
306 ;; now with the lock held, see if the symbol's tls index has
307 ;; been set in the meantime
308 (loadw tls-index symbol symbol-tls-index-slot other-pointer-lowtag)
309 (inst or tls-index tls-index)
310 (inst jmp :ne release-tls-index-lock)
311 ;; allocate a new tls-index
312 (load-symbol-value tls-index *free-tls-index*)
313 (inst add tls-index 8) ;XXX surely we can do this more
314 (store-symbol-value tls-index *free-tls-index*) ;succintly
315 (inst sub tls-index 8)
316 (storew tls-index symbol symbol-tls-index-slot other-pointer-lowtag)
317 (emit-label release-tls-index-lock)
318 (store-symbol-value 0 *tls-index-lock*))
320 (emit-label tls-index-valid)
322 (make-ea :qword :base thread-base-tn :scale 1 :index tls-index))
323 (storew temp bsp (- binding-value-slot binding-size))
324 (storew symbol bsp (- binding-symbol-slot binding-size))
325 (inst mov (make-ea :qword :base thread-base-tn :scale 1 :index tls-index)
330 (:args (val :scs (any-reg descriptor-reg))
331 (symbol :scs (descriptor-reg)))
332 (:temporary (:sc unsigned-reg) temp bsp)
334 (load-symbol-value bsp *binding-stack-pointer*)
335 (loadw temp symbol symbol-value-slot other-pointer-lowtag)
336 (inst add bsp (* binding-size n-word-bytes))
337 (store-symbol-value bsp *binding-stack-pointer*)
338 (storew temp bsp (- binding-value-slot binding-size))
339 (storew symbol bsp (- binding-symbol-slot binding-size))
340 (storew val symbol symbol-value-slot other-pointer-lowtag)))
346 (:temporary (:sc unsigned-reg) symbol value bsp tls-index)
348 (load-binding-stack-pointer bsp)
349 (loadw symbol bsp (- binding-symbol-slot binding-size))
350 (loadw value bsp (- binding-value-slot binding-size))
352 (loadw tls-index symbol symbol-tls-index-slot other-pointer-lowtag)
353 (inst mov (make-ea :qword :base thread-base-tn :scale 1 :index tls-index)
356 (storew 0 bsp (- binding-symbol-slot binding-size))
357 (storew 0 bsp (- binding-value-slot binding-size))
358 (inst sub bsp (* binding-size n-word-bytes))
359 (store-binding-stack-pointer bsp)))
363 (:temporary (:sc unsigned-reg) symbol value bsp)
365 (load-symbol-value bsp *binding-stack-pointer*)
366 (loadw symbol bsp (- binding-symbol-slot binding-size))
367 (loadw value bsp (- binding-value-slot binding-size))
368 (storew value symbol symbol-value-slot other-pointer-lowtag)
369 (storew 0 bsp (- binding-symbol-slot binding-size))
370 (storew 0 bsp (- binding-value-slot binding-size))
371 (inst sub bsp (* binding-size n-word-bytes))
372 (store-symbol-value bsp *binding-stack-pointer*)))
375 (define-vop (unbind-to-here)
376 (:args (where :scs (descriptor-reg any-reg)))
377 (:temporary (:sc unsigned-reg) symbol value bsp #!+sb-thread tls-index)
379 (load-binding-stack-pointer bsp)
384 (loadw symbol bsp (- binding-symbol-slot binding-size))
385 (inst or symbol symbol)
387 (loadw value bsp (- binding-value-slot binding-size))
389 (storew value symbol symbol-value-slot other-pointer-lowtag)
391 (loadw tls-index symbol symbol-tls-index-slot other-pointer-lowtag)
393 (inst mov (make-ea :qword :base thread-base-tn :scale 1 :index tls-index)
395 (storew 0 bsp (- binding-symbol-slot binding-size))
398 (storew 0 bsp (- binding-value-slot binding-size))
399 (inst sub bsp (* binding-size n-word-bytes))
402 (store-binding-stack-pointer bsp)
408 ;;;; closure indexing
410 (define-full-reffer closure-index-ref *
411 closure-info-offset fun-pointer-lowtag
412 (any-reg descriptor-reg) * %closure-index-ref)
414 (define-full-setter set-funcallable-instance-info *
415 funcallable-instance-info-offset fun-pointer-lowtag
416 (any-reg descriptor-reg) * %set-funcallable-instance-info)
418 (define-full-reffer funcallable-instance-info *
419 funcallable-instance-info-offset fun-pointer-lowtag
420 (descriptor-reg any-reg) * %funcallable-instance-info)
422 (define-vop (closure-ref slot-ref)
423 (:variant closure-info-offset fun-pointer-lowtag))
425 (define-vop (closure-init slot-set)
426 (:variant closure-info-offset fun-pointer-lowtag))
428 ;;;; value cell hackery
430 (define-vop (value-cell-ref cell-ref)
431 (:variant value-cell-value-slot other-pointer-lowtag))
433 (define-vop (value-cell-set cell-set)
434 (:variant value-cell-value-slot other-pointer-lowtag))
436 ;;;; structure hackery
438 (define-vop (instance-length)
440 (:translate %instance-length)
441 (:args (struct :scs (descriptor-reg)))
442 (:results (res :scs (unsigned-reg)))
443 (:result-types positive-fixnum)
445 (loadw res struct 0 instance-pointer-lowtag)
446 (inst shr res n-widetag-bits)))
448 (define-full-reffer instance-index-ref * instance-slots-offset
449 instance-pointer-lowtag (any-reg descriptor-reg) * %instance-ref)
451 (define-full-setter instance-index-set * instance-slots-offset
452 instance-pointer-lowtag (any-reg descriptor-reg) * %instance-set)
455 (defknown %instance-set-conditional (instance index t t) t
458 (define-vop (instance-set-conditional)
459 (:translate %instance-set-conditional)
460 (:args (object :scs (descriptor-reg) :to :eval)
461 (slot :scs (any-reg) :to :result)
462 (old-value :scs (descriptor-reg any-reg) :target rax)
463 (new-value :scs (descriptor-reg any-reg)))
464 (:arg-types instance positive-fixnum * *)
465 (:temporary (:sc descriptor-reg :offset rax-offset
466 :from (:argument 2) :to :result :target result) rax)
467 (:results (result :scs (descriptor-reg any-reg)))
468 ;(:guard (backend-featurep :i486))
473 (inst cmpxchg (make-ea :qword :base object :index slot :scale 1
474 :disp (- (* instance-slots-offset n-word-bytes)
475 instance-pointer-lowtag))
481 ;;;; code object frobbing
483 (define-full-reffer code-header-ref * 0 other-pointer-lowtag
484 (any-reg descriptor-reg) * code-header-ref)
486 (define-full-setter code-header-set * 0 other-pointer-lowtag
487 (any-reg descriptor-reg) * code-header-set)
491 ;;;; raw instance slot accessors
493 (define-vop (raw-instance-ref/word)
494 (:translate %raw-instance-ref/word)
496 (:args (object :scs (descriptor-reg)) (index :scs (any-reg)))
497 (:arg-types * tagged-num)
498 (:temporary (:sc unsigned-reg) tmp)
499 (:results (value :scs (unsigned-reg)))
500 (:result-types unsigned-num)
502 (loadw tmp object 0 instance-pointer-lowtag)
503 (inst shr tmp n-widetag-bits)
511 :disp (- (* (1- instance-slots-offset) n-word-bytes)
512 instance-pointer-lowtag)))))
514 (define-vop (raw-instance-set/word)
515 (:translate %raw-instance-set/word)
517 (:args (object :scs (descriptor-reg))
518 (index :scs (any-reg))
519 (value :scs (unsigned-reg) :target result))
520 (:arg-types * tagged-num unsigned-num)
521 (:temporary (:sc unsigned-reg) tmp)
522 (:results (result :scs (unsigned-reg)))
523 (:result-types unsigned-num)
525 (loadw tmp object 0 instance-pointer-lowtag)
526 (inst shr tmp n-widetag-bits)
533 :disp (- (* (1- instance-slots-offset) n-word-bytes)
534 instance-pointer-lowtag))
536 (move result value)))
538 (define-vop (raw-instance-ref/single)
539 (:translate %raw-instance-ref/single)
541 (:args (object :scs (descriptor-reg))
542 (index :scs (any-reg)))
543 (:arg-types * positive-fixnum)
544 (:temporary (:sc unsigned-reg) tmp)
545 (:results (value :scs (single-reg)))
546 (:result-types single-float)
548 (loadw tmp object 0 instance-pointer-lowtag)
549 (inst shr tmp n-widetag-bits)
557 :disp (- (* (1- instance-slots-offset) n-word-bytes)
558 instance-pointer-lowtag)))))
560 (define-vop (raw-instance-set/single)
561 (:translate %raw-instance-set/single)
563 (:args (object :scs (descriptor-reg))
564 (index :scs (any-reg))
565 (value :scs (single-reg) :target result))
566 (:arg-types * positive-fixnum single-float)
567 (:temporary (:sc unsigned-reg) tmp)
568 (:results (result :scs (single-reg)))
569 (:result-types single-float)
571 (loadw tmp object 0 instance-pointer-lowtag)
572 (inst shr tmp n-widetag-bits)
579 :disp (- (* (1- instance-slots-offset) n-word-bytes)
580 instance-pointer-lowtag))
582 (unless (location= result value)
583 (inst movss result value))))
585 (define-vop (raw-instance-ref/double)
586 (:translate %raw-instance-ref/double)
588 (:args (object :scs (descriptor-reg))
589 (index :scs (any-reg)))
590 (:arg-types * positive-fixnum)
591 (:temporary (:sc unsigned-reg) tmp)
592 (:results (value :scs (double-reg)))
593 (:result-types double-float)
595 (loadw tmp object 0 instance-pointer-lowtag)
596 (inst shr tmp n-widetag-bits)
604 :disp (- (* (1- instance-slots-offset) n-word-bytes)
605 instance-pointer-lowtag)))))
607 (define-vop (raw-instance-set/double)
608 (:translate %raw-instance-set/double)
610 (:args (object :scs (descriptor-reg))
611 (index :scs (any-reg))
612 (value :scs (double-reg) :target result))
613 (:arg-types * positive-fixnum double-float)
614 (:temporary (:sc unsigned-reg) tmp)
615 (:results (result :scs (double-reg)))
616 (:result-types double-float)
618 (loadw tmp object 0 instance-pointer-lowtag)
619 (inst shr tmp n-widetag-bits)
626 :disp (- (* (1- instance-slots-offset) n-word-bytes)
627 instance-pointer-lowtag))
629 (unless (location= result value)
630 (inst movsd result value))))
632 (define-vop (raw-instance-ref/complex-single)
633 (:translate %raw-instance-ref/complex-single)
635 (:args (object :scs (descriptor-reg))
636 (index :scs (any-reg)))
637 (:arg-types * positive-fixnum)
638 (:temporary (:sc unsigned-reg) tmp)
639 (:results (value :scs (complex-single-reg)))
640 (:result-types complex-single-float)
642 (loadw tmp object 0 instance-pointer-lowtag)
643 (inst shr tmp n-widetag-bits)
646 (let ((real-tn (complex-single-reg-real-tn value)))
652 :disp (- (* (1- instance-slots-offset) n-word-bytes)
653 instance-pointer-lowtag))))
654 (let ((imag-tn (complex-single-reg-imag-tn value)))
660 :disp (+ (* (1- instance-slots-offset) n-word-bytes)
662 (- instance-pointer-lowtag)))))))
664 (define-vop (raw-instance-set/complex-single)
665 (:translate %raw-instance-set/complex-single)
667 (:args (object :scs (descriptor-reg))
668 (index :scs (any-reg))
669 (value :scs (complex-single-reg) :target result))
670 (:arg-types * positive-fixnum complex-single-float)
671 (:temporary (:sc unsigned-reg) tmp)
672 (:results (result :scs (complex-single-reg)))
673 (:result-types complex-single-float)
675 (loadw tmp object 0 instance-pointer-lowtag)
676 (inst shr tmp n-widetag-bits)
679 (let ((value-real (complex-single-reg-real-tn value))
680 (result-real (complex-single-reg-real-tn result)))
681 (inst movss (make-ea :dword
684 :disp (- (* (1- instance-slots-offset) n-word-bytes)
685 instance-pointer-lowtag))
687 (unless (location= value-real result-real)
688 (inst movss result-real value-real)))
689 (let ((value-imag (complex-single-reg-imag-tn value))
690 (result-imag (complex-single-reg-imag-tn result)))
691 (inst movss (make-ea :dword
694 :disp (+ (* (1- instance-slots-offset) n-word-bytes)
696 (- instance-pointer-lowtag)))
698 (unless (location= value-imag result-imag)
699 (inst movss result-imag value-imag)))))
701 (define-vop (raw-instance-ref/complex-double)
702 (:translate %raw-instance-ref/complex-double)
704 (:args (object :scs (descriptor-reg))
705 (index :scs (any-reg)))
706 (:arg-types * positive-fixnum)
707 (:temporary (:sc unsigned-reg) tmp)
708 (:results (value :scs (complex-double-reg)))
709 (:result-types complex-double-float)
711 (loadw tmp object 0 instance-pointer-lowtag)
712 (inst shr tmp n-widetag-bits)
715 (let ((real-tn (complex-double-reg-real-tn value)))
721 :disp (- (* (- instance-slots-offset 2) n-word-bytes)
722 instance-pointer-lowtag))))
723 (let ((imag-tn (complex-double-reg-imag-tn value)))
729 :disp (- (* (1- instance-slots-offset) n-word-bytes)
730 instance-pointer-lowtag))))))
732 (define-vop (raw-instance-set/complex-double)
733 (:translate %raw-instance-set/complex-double)
735 (:args (object :scs (descriptor-reg))
736 (index :scs (any-reg))
737 (value :scs (complex-double-reg) :target result))
738 (:arg-types * positive-fixnum complex-double-float)
739 (:temporary (:sc unsigned-reg) tmp)
740 (:results (result :scs (complex-double-reg)))
741 (:result-types complex-double-float)
743 (loadw tmp object 0 instance-pointer-lowtag)
744 (inst shr tmp n-widetag-bits)
747 (let ((value-real (complex-double-reg-real-tn value))
748 (result-real (complex-double-reg-real-tn result)))
749 (inst movsd (make-ea :dword
752 :disp (- (* (- instance-slots-offset 2) n-word-bytes)
753 instance-pointer-lowtag))
755 (unless (location= value-real result-real)
756 (inst movsd result-real value-real)))
757 (let ((value-imag (complex-double-reg-imag-tn value))
758 (result-imag (complex-double-reg-imag-tn result)))
759 (inst movsd (make-ea :dword
762 :disp (- (* (1- instance-slots-offset) n-word-bytes)
763 instance-pointer-lowtag))
765 (unless (location= value-imag result-imag)
766 (inst movsd result-imag value-imag)))))