| blob | 5bcdee08cd4f86aa3a46893a00f1e182f7b84399 |
1 ;;;; This file implements type check generation. This is a phase that
2 ;;;; runs at the very end of IR1. If a type check is too complex for
3 ;;;; the back end to directly emit in-line, then we transform the check
4 ;;;; into an explicit conditional using TYPEP.
6 ;;;; This software is part of the SBCL system. See the README file for
7 ;;;; more information.
8 ;;;;
9 ;;;; This software is derived from the CMU CL system, which was
10 ;;;; written at Carnegie Mellon University and released into the
11 ;;;; public domain. The software is in the public domain and is
12 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
13 ;;;; files for more information.
16 \f
17 ;;;; cost estimation
19 ;;; Return some sort of guess about the cost of a call to a function.
20 ;;; If the function has some templates, we return the cost of the
21 ;;; cheapest one, otherwise we return the cost of CALL-NAMED. Calling
22 ;;; this with functions that have transforms can result in relatively
23 ;;; meaningless results (exaggerated costs.)
24 ;;;
25 ;;; We special-case NULL, since it does have a source tranform and is
26 ;;; interesting to us.
38 call-cost)))
40 ;;; Return some sort of guess for the cost of doing a test against
41 ;;; TYPE. The result need not be precise as long as it isn't way out
42 ;;; in space. The units are based on the costs specified for various
43 ;;; templates in the VM definition.
57 nil))))
97 samep)
98 ;; If the supertype is equal in cost to the type, we
99 ;; prefer the supertype. This produces a closer
100 ;; approximation of the right thing in the presence of
101 ;; poor cost info.
103 min-type stype
104 min-cost stype-cost))))))
105 ;; This used to return the *UNIVERSAL-TYPE* if no supertype was found,
106 ;; but that's too liberal: it's far too easy for the user to create
107 ;; a union type (which are excluded above), and then trick the compiler
108 ;; into trusting the union type... and finally ending up corrupting the
109 ;; heap once a bad object sneaks past the missing type check.
111 min-type
112 type)))
126 \f
127 ;;;; checking strategy determination
129 ;;; Return the type we should test for when we really want to check
130 ;;; for TYPE. If type checking policy is "fast", then we return a
131 ;;; weaker type if it is easier to check. First we try the defined
132 ;;; type weakenings, then look for any predicate that is cheaper.
140 ;;; This is like VALUES-TYPES, only we mash any complex function types
141 ;;; to FUNCTION.
148 type))
149 res)
150 count)))
152 ;;; Switch to disable check complementing, for evaluation.
155 ;;; LVAR is an lvar we are doing a type check on and TYPES is a list
156 ;;; of types that we are checking its values against. If we have
157 ;;; proven that LVAR generates a fixed number of values, then for each
158 ;;; value, we check whether it is cheaper to then difference between
159 ;;; the proven type and the corresponding type in TYPES. If so, we opt
160 ;;; for a :HAIRY check with that test negated. Otherwise, we try to do
161 ;;; a simple test, and if that is impossible, we do a hairy test with
162 ;;; non-negated types. If true, FORCE-HAIRY forces a hairy type check.
168 and c in types
169 and a in original-types
170 and i from 0
173 c)
181 into hairy-res
182 collect cc into simple-res
191 ;;; Determines whether CAST's assertion is:
192 ;;; -- checkable by the back end (:SIMPLE), or
193 ;;; -- not checkable by the back end, but checkable via an explicit
194 ;;; test in type check conversion (:HAIRY), or
195 ;;; -- not reasonably checkable at all (:TOO-HAIRY).
196 ;;;
197 ;;; We may check only fixed number of values; in any case the number
198 ;;; of generated values is trusted. If we know the number of produced
199 ;;; values, all of them are checked; otherwise if we know the number
200 ;;; of consumed -- only they are checked; otherwise the check is not
201 ;;; performed.
202 ;;;
203 ;;; A type is simply checkable if all the type assertions have a
204 ;;; TYPE-CHECK-TEMPLATE. In this :SIMPLE case, the second value is a
205 ;;; list of the type restrictions specified for the leading positional
206 ;;; values.
207 ;;;
208 ;;; Old comment:
209 ;;;
210 ;;; We force a check to be hairy even when there are fixed values
211 ;;; if we are in a context where we may be forced to use the
212 ;;; unknown values convention anyway. This is because IR2tran can't
213 ;;; generate type checks for unknown values lvars but people could
214 ;;; still be depending on the check being done. We only care about
215 ;;; EXIT and RETURN (not MV-COMBINATION) since these are the only
216 ;;; contexts where the ultimate values receiver
217 ;;;
218 ;;; In the :HAIRY case, the second value is a list of triples of
219 ;;; the form:
220 ;;; (NOT-P TYPE ORIGINAL-TYPE)
221 ;;;
222 ;;; If true, the NOT-P flag indicates a test that the corresponding
223 ;;; value is *not* of the specified TYPE. ORIGINAL-TYPE is the type
224 ;;; asserted on this value in the lvar, for use in error
225 ;;; messages. When NOT-P is true, this will be different from TYPE.
226 ;;;
227 ;;; This allows us to take what has been proven about CAST's argument
228 ;;; type into consideration. If it is cheaper to test for the
229 ;;; difference between the derived type and the asserted type, then we
230 ;;; check for the negation of this type instead.
240 nil)
251 ;; we [almost] know how many values are produced
255 ;; backend checks only consumed values
257 n-required))
259 ;; exactly one value is consumed
271 force-hairy
272 n-required))))
275 ;; we know the number of consumed values
278 n-consumed
281 n-consumed
283 force-hairy
284 n-required))
288 ;;; Do we want to do a type check?
294 ;; The theory is that the type assertion is from a
295 ;; declaration in (or on) the callee, so the callee should be
296 ;; able to do the check. We want to let the callee do the
297 ;; check, because it is possible that by the time of call
298 ;; that declaration will be changed and we do not want to
299 ;; make people recompile all calls to a function when they
300 ;; were originally compiled with a bad declaration. (See also
301 ;; bug 35.)
311 ;;; Return true if CAST's value is an lvar whose type the back end is
312 ;;; likely to be able to check (see GENERATE-TYPE-CHECKS). Since we
313 ;;; don't know what template the back end is going to choose to
314 ;;; implement the continuation's DEST, we use a heuristic.
315 ;;;
316 ;;; We always return T unless nobody uses the value (the backend
317 ;;; cannot check unused LVAR chains).
318 ;;;
319 ;;; The logic used to be more complex, but most of the cases that used
320 ;;; to be checked here are now dealt with differently . FIXME: but
321 ;;; here's one we used to do, don't anymore, but could still benefit
322 ;;; from, if we reimplemented it (elsewhere):
323 ;;;
324 ;;; -- If the lvar is an argument to a known function that has
325 ;;; no IR2-CONVERT method or :FAST-SAFE templates that are
326 ;;; compatible with the call's type: return NIL.
327 ;;;
328 ;;; The code used to look like something like this:
329 ;;; ...
330 ;;; (:known
331 ;;; (let ((info (basic-combination-fun-info dest)))
332 ;;; (if (fun-info-ir2-convert info)
333 ;;; t
334 ;;; (dolist (template (fun-info-templates info) nil)
335 ;;; (when (eq (template-ltn-policy template)
336 ;;; :fast-safe)
337 ;;; (multiple-value-bind (val win)
338 ;;; (valid-fun-use dest (template-type template))
339 ;;; (when (or val (not win)) (return t)))))))))))))
340 ;;;
341 ;;; ADP says: It is still interesting. When we have a :SAFE template
342 ;;; and the type assertion is derived from the destination function
343 ;;; type, the check is unneccessary. We cannot return NIL here (the
344 ;;; whole function has changed its meaning, and here NIL *forces*
345 ;;; hairy check), but the functionality is interesting.
353 ;;; Return a lambda form that we can convert to do a hairy type check
354 ;;; of the specified TYPES. TYPES is a list of the format returned by
355 ;;; LVAR-CHECK-TYPES in the :HAIRY case.
356 ;;;
357 ;;; Note that we don't attempt to check for required values being
358 ;;; unsupplied. Such checking is impossible to efficiently do at the
359 ;;; source level because our fixed-values conventions are optimized
360 ;;; for the common MV-BIND case.
364 'dummy
371 (%type-check-error
372 ,temp
374 temps
375 types)
378 ;;; Splice in explicit type check code immediately before CAST. This
379 ;;; code receives the value(s) that were being passed to CAST-VALUE,
380 ;;; checks the type(s) of the value(s), then passes them further.
391 atype)
405 ;;; Check all possible arguments of CAST and emit type warnings for
406 ;;; those with type errors. If the value of USE is being used for a
407 ;;; variable binding, we figure out which one for source context. If
408 ;;; the value is a constant, we print it specially.
429 pos)))))))
432 :format-control
433 "~:[This~;~:*~A~] is not a ~<~%~9T~:;~S:~>~% ~S"
434 :format-arguments
439 :format-control
440 "~:[Result~;~:*~A~] is a ~S, ~<~%~9T~:;not a ~S.~>"
441 :format-arguments
445 ;;; Loop over all blocks in COMPONENT that have TYPE-CHECK set,
446 ;;; looking for CASTs with TYPE-CHECK T. We do two mostly unrelated
447 ;;; things: detect compile-time type errors and determine if and how
448 ;;; to do run-time type checks.
449 ;;;
450 ;;; If there is a compile-time type error, then we mark the CAST and
451 ;;; emit a warning if appropriate. This part loops over all the uses
452 ;;; of the continuation, since after we convert the check, the
453 ;;; :DELETED kind will inhibit warnings about the types of other uses.
454 ;;;
455 ;;; If the cast is too complex to be checked by the back end, or is
456 ;;; better checked with explicit code, then convert to an explicit
457 ;;; test. Assertions that can checked by the back end are passed
458 ;;; through. Assertions that can't be tested are flamed about and
459 ;;; marked as not needing to be checked.
460 ;;;
461 ;;; If we determine that a type check won't be done, then we set
462 ;;; TYPE-CHECK to :NO-CHECK. In the non-hairy cases, this is just to
463 ;;; prevent us from wasting time coming to the same conclusion again
464 ;;; on a later iteration. In the hairy case, we must indicate to LTN
465 ;;; that it must choose a safe implementation, since IR2 conversion
466 ;;; will choke on the check.
467 ;;;
468 ;;; The generation of the type checks is delayed until all the type
469 ;;; check decisions have been made because the generation of the type
470 ;;; checks creates new nodes whose derived types aren't always updated
471 ;;; which may lead to inappropriate template choices due to the
472 ;;; modification of argument types.
477 ;; CAST-EXTERNALLY-CHECKABLE-P wants the backward pass
485 ;; it is possible that NODE was marked :EXTERNAL by
486 ;; the previous pass
496 (:hairy
498 (:too-hairy
502 "type assertion too complex to check:~% ~S."