| blob | 0a932453d5b856b77dc77b46ebf7bdfca40b893f |
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.
163 ;;;
164 ;;; When doing a non-negated check, we call MAYBE-WEAKEN-CHECK to
165 ;;; weaken the test to a convenient supertype (conditional on policy.)
166 ;;; If SPEED is 3, or DEBUG-INFO is not particularly important (DEBUG
167 ;;; <= 1), then we allow weakened checks to be simple, resulting in
168 ;;; less informative error messages, but saving space and possibly
169 ;;; time.
170 ;;;
171 ;;; FIXME: I don't quite understand this, but it looks as though
172 ;;; that means type checks are weakened when SPEED=3 regardless of
173 ;;; the SAFETY level, which is not the right thing to do.
179 and c in types
180 and a in original-types
181 and i from 0
184 c)
192 into hairy-res
193 collect cc into simple-res
202 ;;; Determines whether CAST's assertion is:
203 ;;; -- checkable by the back end (:SIMPLE), or
204 ;;; -- not checkable by the back end, but checkable via an explicit
205 ;;; test in type check conversion (:HAIRY), or
206 ;;; -- not reasonably checkable at all (:TOO-HAIRY).
207 ;;;
208 ;;; We may check only fixed number of values; in any case the number
209 ;;; of generated values is trusted. If we know the number of produced
210 ;;; values, all of them are checked; otherwise if we know the number
211 ;;; of consumed -- only they are checked; otherwise the check is not
212 ;;; performed.
213 ;;;
214 ;;; A type is simply checkable if all the type assertions have a
215 ;;; TYPE-CHECK-TEMPLATE. In this :SIMPLE case, the second value is a
216 ;;; list of the type restrictions specified for the leading positional
217 ;;; values.
218 ;;;
219 ;;; Old comment:
220 ;;;
221 ;;; We force a check to be hairy even when there are fixed values
222 ;;; if we are in a context where we may be forced to use the
223 ;;; unknown values convention anyway. This is because IR2tran can't
224 ;;; generate type checks for unknown values lvars but people could
225 ;;; still be depending on the check being done. We only care about
226 ;;; EXIT and RETURN (not MV-COMBINATION) since these are the only
227 ;;; contexts where the ultimate values receiver
228 ;;;
229 ;;; In the :HAIRY case, the second value is a list of triples of
230 ;;; the form:
231 ;;; (NOT-P TYPE ORIGINAL-TYPE)
232 ;;;
233 ;;; If true, the NOT-P flag indicates a test that the corresponding
234 ;;; value is *not* of the specified TYPE. ORIGINAL-TYPE is the type
235 ;;; asserted on this value in the lvar, for use in error
236 ;;; messages. When NOT-P is true, this will be different from TYPE.
237 ;;;
238 ;;; This allows us to take what has been proven about CAST's argument
239 ;;; type into consideration. If it is cheaper to test for the
240 ;;; difference between the derived type and the asserted type, then we
241 ;;; check for the negation of this type instead.
251 nil)
262 ;; we [almost] know how many values are produced
266 ;; backend checks only consumed values
268 n-required))
270 ;; exactly one value is consumed
282 force-hairy
283 n-required))))
286 ;; we know the number of consumed values
289 n-consumed
292 n-consumed
294 force-hairy
295 n-required))
299 ;;; Do we want to do a type check?
305 ;; The theory is that the type assertion is from a
306 ;; declaration in (or on) the callee, so the callee should be
307 ;; able to do the check. We want to let the callee do the
308 ;; check, because it is possible that by the time of call
309 ;; that declaration will be changed and we do not want to
310 ;; make people recompile all calls to a function when they
311 ;; were originally compiled with a bad declaration. (See also
312 ;; bug 35.)
322 ;;; Return true if CAST's value is an lvar whose type the back end is
323 ;;; likely to want to check. Since we don't know what template the
324 ;;; back end is going to choose to implement the continuation's DEST,
325 ;;; we use a heuristic. We always return T unless:
326 ;;; -- nobody uses the value, or
327 ;;; -- safety is totally unimportant, or
328 ;;; -- the lvar is an argument to an unknown function, or
329 ;;; -- the lvar is an argument to a known function that has
330 ;;; no IR2-CONVERT method or :FAST-SAFE templates that are
331 ;;; compatible with the call's type.
338 #+nil
341 nil)
349 (:full
354 ;; :ERROR means that we have an invalid syntax of
355 ;; the call and the callee will detect it before
356 ;; thinking about types.
358 (:known
361 t
370 ;;; Return a lambda form that we can convert to do a hairy type check
371 ;;; of the specified TYPES. TYPES is a list of the format returned by
372 ;;; LVAR-CHECK-TYPES in the :HAIRY case.
373 ;;;
374 ;;; Note that we don't attempt to check for required values being
375 ;;; unsupplied. Such checking is impossible to efficiently do at the
376 ;;; source level because our fixed-values conventions are optimized
377 ;;; for the common MV-BIND case.
381 'dummy
388 (%type-check-error
389 ,temp
391 temps
392 types)
395 ;;; Splice in explicit type check code immediately before CAST. This
396 ;;; code receives the value(s) that were being passed to CAST-VALUE,
397 ;;; checks the type(s) of the value(s), then passes them further.
408 atype)
422 ;;; Check all possible arguments of CAST and emit type warnings for
423 ;;; those with type errors. If the value of USE is being used for a
424 ;;; variable binding, we figure out which one for source context. If
425 ;;; the value is a constant, we print it specially.
446 pos)))))))
449 :format-control
450 "~:[This~;~:*~A~] is not a ~<~%~9T~:;~S:~>~% ~S"
451 :format-arguments
456 :format-control
457 "~:[Result~;~:*~A~] is a ~S, ~<~%~9T~:;not a ~S.~>"
458 :format-arguments
462 ;;; Loop over all blocks in COMPONENT that have TYPE-CHECK set,
463 ;;; looking for CASTs with TYPE-CHECK T. We do two mostly unrelated
464 ;;; things: detect compile-time type errors and determine if and how
465 ;;; to do run-time type checks.
466 ;;;
467 ;;; If there is a compile-time type error, then we mark the CAST and
468 ;;; emit a warning if appropriate. This part loops over all the uses
469 ;;; of the continuation, since after we convert the check, the
470 ;;; :DELETED kind will inhibit warnings about the types of other uses.
471 ;;;
472 ;;; If the cast is too complex to be checked by the back end, or is
473 ;;; better checked with explicit code, then convert to an explicit
474 ;;; test. Assertions that can checked by the back end are passed
475 ;;; through. Assertions that can't be tested are flamed about and
476 ;;; marked as not needing to be checked.
477 ;;;
478 ;;; If we determine that a type check won't be done, then we set
479 ;;; TYPE-CHECK to :NO-CHECK. In the non-hairy cases, this is just to
480 ;;; prevent us from wasting time coming to the same conclusion again
481 ;;; on a later iteration. In the hairy case, we must indicate to LTN
482 ;;; that it must choose a safe implementation, since IR2 conversion
483 ;;; will choke on the check.
484 ;;;
485 ;;; The generation of the type checks is delayed until all the type
486 ;;; check decisions have been made because the generation of the type
487 ;;; checks creates new nodes whose derived types aren't always updated
488 ;;; which may lead to inappropriate template choices due to the
489 ;;; modification of argument types.
494 ;; CAST-EXTERNALLY-CHECKABLE-P wants the backward pass
502 ;; it is possible that NODE was marked :EXTERNAL by
503 ;; the previous pass
513 (:hairy
515 (:too-hairy
519 "type assertion too complex to check:~% ~S."