1 ;;;; This file implements the constraint propagation phase of the
2 ;;;; compiler, which uses global flow analysis to obtain dynamic type
5 ;;;; This software is part of the SBCL system. See the README file for
8 ;;;; This software is derived from the CMU CL system, which was
9 ;;;; written at Carnegie Mellon University and released into the
10 ;;;; public domain. The software is in the public domain and is
11 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
12 ;;;; files for more information.
16 (defstruct (constraint
17 (:include sset-element)
18 (:constructor make-constraint (number kind x y not-p))
20 ;; the kind of constraint we have:
23 ;; X is a LAMBDA-VAR and Y is a CTYPE. The value of X is
24 ;; constrained to be of type Y.
27 ;; X is a lambda-var and Y is a CTYPE. The relation holds
28 ;; between X and some object of type Y.
31 ;; X is a LAMBDA-VAR Y is a LAMBDA-VAR or a CONSTANT. The
32 ;; relation is asserted to hold.
33 (kind nil :type (member typep < > eql))
34 ;; The operands to the relation.
35 (x nil :type lambda-var)
36 (y nil :type (or ctype lambda-var constant))
37 ;; If true, negates the sense of the constraint, so the relation
39 (not-p nil :type boolean))
41 (defvar *constraint-number*)
43 ;;; Return a constraint for the specified arguments. We only create a
44 ;;; new constraint if there isn't already an equivalent old one,
45 ;;; guaranteeing that all equivalent constraints are EQ. This
46 ;;; shouldn't be called on LAMBDA-VARs with no CONSTRAINTS set.
47 (defun find-constraint (kind x y not-p)
48 (declare (type lambda-var x) (type (or constant lambda-var ctype) y)
52 (do-sset-elements (con (lambda-var-constraints x) nil)
53 (when (and (eq (constraint-kind con) kind)
54 (eq (constraint-not-p con) not-p)
55 (type= (constraint-y con) y))
58 (do-sset-elements (con (lambda-var-constraints x) nil)
59 (when (and (eq (constraint-kind con) kind)
60 (eq (constraint-not-p con) not-p)
61 (eq (constraint-y con) y))
64 (do-sset-elements (con (lambda-var-constraints x) nil)
65 (when (and (eq (constraint-kind con) kind)
66 (eq (constraint-not-p con) not-p)
67 (let ((cx (constraint-x con)))
73 (let ((new (make-constraint (incf *constraint-number*) kind x y not-p)))
74 (sset-adjoin new (lambda-var-constraints x))
75 (when (lambda-var-p y)
76 (sset-adjoin new (lambda-var-constraints y)))
79 ;;; If REF is to a LAMBDA-VAR with CONSTRAINTs (i.e. we can do flow
80 ;;; analysis on it), then return the LAMBDA-VAR, otherwise NIL.
81 #!-sb-fluid (declaim (inline ok-ref-lambda-var))
82 (defun ok-ref-lambda-var (ref)
83 (declare (type ref ref))
84 (let ((leaf (ref-leaf ref)))
85 (when (and (lambda-var-p leaf)
86 (lambda-var-constraints leaf))
89 ;;; If CONT's USE is a REF, then return OK-REF-LAMBDA-VAR of the USE,
91 #!-sb-fluid (declaim (inline ok-cont-lambda-var))
92 (defun ok-cont-lambda-var (cont)
93 (declare (type continuation cont))
94 (let ((use (continuation-use cont)))
96 (ok-ref-lambda-var use))))
98 ;;; Add the indicated test constraint to BLOCK, marking the block as
99 ;;; having a new assertion when the constriant was not already
100 ;;; present. We don't add the constraint if the block has multiple
101 ;;; predecessors, since it only holds on this particular path.
102 (defun add-test-constraint (block fun x y not-p)
103 (unless (rest (block-pred block))
104 (let ((con (find-constraint fun x y not-p))
105 (old (or (block-test-constraint block)
106 (setf (block-test-constraint block) (make-sset)))))
107 (when (sset-adjoin con old)
108 (setf (block-type-asserted block) t))))
111 ;;; Add complementary constraints to the consequent and alternative
112 ;;; blocks of IF. We do nothing if X is NIL.
113 #!-sb-fluid (declaim (inline add-complement-constraints))
114 (defun add-complement-constraints (if fun x y not-p)
116 (add-test-constraint (if-consequent if) fun x y not-p)
117 (add-test-constraint (if-alternative if) fun x y (not not-p)))
120 ;;; Add test constraints to the consequent and alternative blocks of
121 ;;; the test represented by USE.
122 (defun add-test-constraints (use if)
123 (declare (type node use) (type cif if))
126 (add-complement-constraints if 'typep (ok-ref-lambda-var use)
127 (specifier-type 'null) t))
129 (let ((name (continuation-function-name
130 (basic-combination-fun use)))
131 (args (basic-combination-args use)))
133 ((%typep %instance-typep)
134 (let ((type (second args)))
135 (when (constant-continuation-p type)
136 (let ((val (continuation-value type)))
137 (add-complement-constraints if 'typep
138 (ok-cont-lambda-var (first args))
141 (specifier-type val))
144 (let* ((var1 (ok-cont-lambda-var (first args)))
146 (var2 (ok-cont-lambda-var arg2)))
149 (add-complement-constraints if 'eql var1 var2 nil))
150 ((constant-continuation-p arg2)
151 (add-complement-constraints if 'eql var1
153 (continuation-use arg2))
156 (let* ((arg1 (first args))
157 (var1 (ok-cont-lambda-var arg1))
159 (var2 (ok-cont-lambda-var arg2)))
161 (add-complement-constraints if name var1 (continuation-type arg2)
164 (add-complement-constraints if (if (eq name '<) '> '<)
165 var2 (continuation-type arg1)
168 (let ((ptype (gethash name *backend-predicate-types*)))
170 (add-complement-constraints if 'typep
171 (ok-cont-lambda-var (first args))
175 ;;; Set the TEST-CONSTRAINT in the successors of BLOCK according to
176 ;;; the condition it tests.
177 (defun find-test-constraints (block)
178 (declare (type cblock block))
179 (let ((last (block-last block)))
181 (let ((use (continuation-use (if-test last))))
183 (add-test-constraints use last)))))
185 (setf (block-test-modified block) nil)
188 ;;; Compute the initial flow analysis sets for BLOCK:
189 ;;; -- For any lambda-var ref with a type check, add that constraint.
190 ;;; -- For any lambda-var set, delete all constraints on that var, and add
191 ;;; those constraints to the set nuked by this block.
192 (defun find-block-type-constraints (block)
193 (declare (type cblock block))
194 (let ((gen (make-sset)))
195 (collect ((kill nil adjoin))
197 (let ((test (block-test-constraint block)))
199 (sset-union gen test)))
201 (do-nodes (node cont block)
204 (when (continuation-type-check cont)
205 (let ((var (ok-ref-lambda-var node)))
207 (let* ((atype (continuation-derived-type cont))
208 (con (find-constraint 'typep var atype nil)))
209 (sset-adjoin con gen))))))
211 (let ((var (set-var node)))
212 (when (lambda-var-p var)
214 (let ((cons (lambda-var-constraints var)))
216 (sset-difference gen cons))))))))
218 (setf (block-in block) nil)
219 (setf (block-gen block) gen)
220 (setf (block-kill block) (kill))
221 (setf (block-out block) (copy-sset gen))
222 (setf (block-type-asserted block) nil)
225 ;;; Return true if X is an integer NUMERIC-TYPE.
226 (defun integer-type-p (x)
227 (declare (type ctype x))
228 (and (numeric-type-p x)
229 (eq (numeric-type-class x) 'integer)
230 (eq (numeric-type-complexp x) :real)))
232 ;;; Given that an inequality holds on values of type X and Y, return a
233 ;;; new type for X. If GREATER is true, then X was greater than Y,
234 ;;; otherwise less. If OR-EQUAL is true, then the inequality was
235 ;;; inclusive, i.e. >=.
237 ;;; If GREATER (or not), then we max (or min) in Y's lower (or upper)
238 ;;; bound into X and return that result. If not OR-EQUAL, we can go
239 ;;; one greater (less) than Y's bound.
240 (defun constrain-integer-type (x y greater or-equal)
241 (declare (type numeric-type x y))
248 (if greater (numeric-type-low x) (numeric-type-high x)))
250 (if (and (numeric-type-low x) (numeric-type-high x)
251 (> (numeric-type-low x) (numeric-type-high x)))
254 (let* ((x-bound (bound x))
255 (y-bound (exclude (bound y)))
256 (new-bound (cond ((not x-bound) y-bound)
257 ((not y-bound) x-bound)
258 (greater (max x-bound y-bound))
259 (t (min x-bound y-bound))))
260 (res (copy-numeric-type x)))
262 (setf (numeric-type-low res) new-bound)
263 (setf (numeric-type-high res) new-bound))
266 ;;; Return true if X is a float NUMERIC-TYPE.
267 (defun float-type-p (x)
268 (declare (type ctype x))
269 (and (numeric-type-p x)
270 (eq (numeric-type-class x) 'float)
271 (eq (numeric-type-complexp x) :real)))
273 ;;; Exactly the same as CONSTRAIN-INTEGER-TYPE, but for float numbers.
274 (defun constrain-float-type (x y greater or-equal)
275 (declare (type numeric-type x y))
276 ;; Unless :PROPAGATE-FLOAT-TYPE is in target features, then
277 ;; SB!C::BOUND-VALUE (used in the code below) is not defined, so we
278 ;; just return X without trying to calculate additional constraints.
279 #!-propagate-float-type (declare (ignore y greater or-equal))
280 #!-propagate-float-type x
281 #!+propagate-float-type
282 (labels ((exclude (x)
294 (if greater (numeric-type-low x) (numeric-type-high x)))
295 (max-lower-bound (x y)
296 ;; Both x and y are not null. Find the max.
297 (let ((res (max (bound-value x) (bound-value y))))
298 ;; An open lower bound is greater than a close
299 ;; lower bound because the open bound doesn't
300 ;; contain the bound, so choose an open lower
302 (set-bound res (or (consp x) (consp y)))))
303 (min-upper-bound (x y)
304 ;; Same as above, but for the min of upper bounds
305 ;; Both x and y are not null. Find the min.
306 (let ((res (min (bound-value x) (bound-value y))))
307 ;; An open upper bound is less than a closed
308 ;; upper bound because the open bound doesn't
309 ;; contain the bound, so choose an open lower
311 (set-bound res (or (consp x) (consp y)))))
313 (let ((x-lo (numeric-type-low x))
314 (x-hi (numeric-type-high x)))
315 (if (and x-lo x-hi (> (bound-value x-lo) (bound-value x-hi)))
318 (let* ((x-bound (bound x))
319 (y-bound (exclude (bound y)))
320 (new-bound (cond ((not x-bound)
325 (max-lower-bound x-bound y-bound))
327 (min-upper-bound x-bound y-bound))))
328 (res (copy-numeric-type x)))
330 (setf (numeric-type-low res) new-bound)
331 (setf (numeric-type-high res) new-bound))
334 ;;; Given the set of CONSTRAINTS for a variable and the current set of
335 ;;; restrictions from flow analysis IN, set the type for REF
337 (defun constrain-ref-type (ref constraints in)
338 (declare (type ref ref) (type sset constraints in))
339 (let ((var-cons (copy-sset constraints)))
340 (sset-intersection var-cons in)
341 (let ((res (single-value-type (node-derived-type ref)))
342 (not-res *empty-type*)
343 (leaf (ref-leaf ref)))
344 (do-sset-elements (con var-cons)
345 (let* ((x (constraint-x con))
346 (y (constraint-y con))
347 (not-p (constraint-not-p con))
348 (other (if (eq x leaf) y x))
349 (kind (constraint-kind con)))
353 (setq not-res (type-union not-res other))
354 (setq res (type-intersection res other))))
356 (let ((other-type (leaf-type other)))
358 (when (and (constant-p other)
359 (member-type-p other-type))
360 (setq not-res (type-union not-res other-type)))
361 (let ((leaf-type (leaf-type leaf)))
362 (when (or (constant-p other)
363 (and (csubtypep other-type leaf-type)
364 (not (type= other-type leaf-type))))
365 (change-ref-leaf ref other)
366 (when (constant-p other) (return)))))))
368 (cond ((and (integer-type-p res) (integer-type-p y))
369 (let ((greater (eq kind '>)))
370 (let ((greater (if not-p (not greater) greater)))
372 (constrain-integer-type res y greater not-p)))))
373 #!+constrain-float-type
374 ((and (float-type-p res) (float-type-p y))
375 (let ((greater (eq kind '>)))
376 (let ((greater (if not-p (not greater) greater)))
378 (constrain-float-type res y greater not-p)))))
381 (let* ((cont (node-cont ref))
382 (dest (continuation-dest cont)))
383 (cond ((and (if-p dest)
384 (csubtypep (specifier-type 'null) not-res)
385 (eq (continuation-asserted-type cont) *wild-type*))
386 (setf (node-derived-type ref) *wild-type*)
387 (change-ref-leaf ref (find-constant 't)))
389 (derive-node-type ref (or (type-difference res not-res)
394 ;;; Deliver the results of constraint propagation to REFs in BLOCK.
395 ;;; During this pass, we also do local constraint propagation by
396 ;;; adding in constraints as we seem them during the pass through the
398 (defun use-result-constraints (block)
399 (declare (type cblock block))
400 (let ((in (block-in block)))
402 (let ((test (block-test-constraint block)))
404 (sset-union in test)))
406 (do-nodes (node cont block)
409 (let ((var (ref-leaf node)))
410 (when (lambda-var-p var)
411 (let ((con (lambda-var-constraints var)))
413 (constrain-ref-type node con in)
414 (when (continuation-type-check cont)
416 (find-constraint 'typep var
417 (continuation-asserted-type cont)
421 (let ((var (set-var node)))
422 (when (lambda-var-p var)
423 (let ((cons (lambda-var-constraints var)))
425 (sset-difference in cons))))))))))
427 ;;; Return true if VAR would have to be closed over if environment
428 ;;; analysis ran now (i.e. if there are any uses that have a different
429 ;;; home lambda than VAR's home.)
430 (defun closure-var-p (var)
431 (declare (type lambda-var var))
432 (let ((home (lambda-home (lambda-var-home var))))
435 (unless (eq (node-home-lambda node) home)
437 (or (frob (leaf-refs var))
438 (frob (basic-var-sets var))))))
440 ;;; Give an empty constraints set to any var that doesn't have one and
441 ;;; isn't a set closure var. Since a var that we previously rejected
442 ;;; looks identical to one that is new, so we optimistically keep
443 ;;; hoping that vars stop being closed over or lose their sets.
444 (defun init-var-constraints (component)
445 (declare (type component component))
446 (dolist (fun (component-lambdas component))
448 (dolist (var (lambda-vars x))
449 (unless (lambda-var-constraints var)
450 (when (or (null (lambda-var-sets var))
451 (not (closure-var-p var)))
452 (setf (lambda-var-constraints var) (make-sset)))))))
454 (dolist (let (lambda-lets fun))
457 ;;; BLOCK-IN becomes the intersection of the OUT of the prececessors.
459 ;;; out U (in - kill)
461 ;;; BLOCK-KILL is just a list of the lambda-vars killed, so we must
462 ;;; compute the kill set when there are any vars killed. We bum this a
463 ;;; bit by special-casing when only one var is killed, and just using
464 ;;; that var's constraints as the kill set. This set could possibly be
465 ;;; precomputed, but it would have to be invalidated whenever any
466 ;;; constraint is added, which would be a pain.
467 (defun flow-propagate-constraints (block)
468 (let* ((pred (block-pred block))
470 (let ((res (copy-sset (block-out (first pred)))))
471 (dolist (b (rest pred))
472 (sset-intersection res (block-out b)))
475 (when *check-consistency*
476 (let ((*compiler-error-context* (block-last block)))
478 "*** Unreachable code in constraint ~
479 propagation... Bug?")))
481 (kill (block-kill block))
482 (out (block-out block)))
484 (setf (block-in block) in)
486 (sset-union (block-out block) in))
488 (let ((con (lambda-var-constraints (first kill))))
490 (sset-union-of-difference out in con)
491 (sset-union out in))))
493 (let ((kill-set (make-sset)))
495 (let ((con (lambda-var-constraints var)))
497 (sset-union kill-set con))))
498 (sset-union-of-difference (block-out block) in kill-set))))))
500 (defun constraint-propagate (component)
501 (declare (type component component))
502 (init-var-constraints component)
504 (do-blocks (block component)
505 (when (block-test-modified block)
506 (find-test-constraints block)))
508 (do-blocks (block component)
509 (cond ((block-type-asserted block)
510 (find-block-type-constraints block))
512 (setf (block-in block) nil)
513 (setf (block-out block) (copy-sset (block-gen block))))))
515 (setf (block-out (component-head component)) (make-sset))
517 (let ((did-something nil))
519 (do-blocks (block component)
520 (when (flow-propagate-constraints block)
521 (setq did-something t)))
523 (unless did-something (return))
524 (setq did-something nil)))
526 (do-blocks (block component)
527 (use-result-constraints block))