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;;;; This file implements type check generation. This is a phase that
;;;; runs at the very end of IR1. If a type check is too complex for
;;;; the back end to directly emit in-line, then we transform the check
;;;; into an explicit conditional using TYPEP.
;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.
(in-package "SB!C")
;;;; cost estimation
;;; Return some sort of guess about the cost of a call to a function.
;;; If the function has some templates, we return the cost of the
;;; cheapest one, otherwise we return the cost of CALL-NAMED. Calling
;;; this with functions that have transforms can result in relatively
;;; meaningless results (exaggerated costs.)
;;; We special-case NULL, since it does have a source tranform and is
;;; interesting to us.
(defun fun-guessed-cost (name)
(declare (symbol name))
(let ((info (info :function :info name))
(call-cost (template-cost (template-or-lose 'call-named))))
(if info
(let ((templates (fun-info-templates info)))
(if templates
(template-cost (first templates))
(case name
(null (template-cost (template-or-lose 'if-eq)))
(t call-cost))))
;;; Return some sort of guess for the cost of doing a test against
;;; TYPE. The result need not be precise as long as it isn't way out
;;; in space. The units are based on the costs specified for various
;;; templates in the VM definition.
(defun type-test-cost (type)
(declare (type ctype type))
(or (when (eq type *universal-type*)
(when (eq type *empty-type*)
(let ((check (type-check-template type)))
(if check
(template-cost check)
(let ((found (cdr (assoc type *backend-type-predicates*
:test #'type=))))
(if found
(+ (fun-guessed-cost found) (fun-guessed-cost 'eq))
(typecase type
(reduce #'+ (compound-type-types type) :key 'type-test-cost))
(* (member-type-size type)
(fun-guessed-cost 'eq)))
(* (if (numeric-type-complexp type) 2 1)
(if (csubtypep type (specifier-type 'fixnum)) 'fixnump 'numberp))
(+ 1
(if (numeric-type-low type) 1 0)
(if (numeric-type-high type) 1 0))))
(+ (type-test-cost (specifier-type 'cons))
(fun-guessed-cost 'car)
(type-test-cost (cons-type-car-type type))
(fun-guessed-cost 'cdr)
(type-test-cost (cons-type-cdr-type type))))
(fun-guessed-cost 'typep)))))
(defun weaken-integer-type (type &key range-only)
;; FIXME: Our canonicalization isn't quite ideal for this. We get
;; types such as:
;; here, and weakening that into
;; is too much work to do here ... but if we canonicalized things
;; differently, we could get it for free with trivial changes here.
(labels ((weaken-integer-type-part (type base)
(cond ((intersection-type-p type)
(let ((new (specifier-type base)))
(dolist (part (intersection-type-types type))
(when (if range-only
(numeric-type-p part)
(not (unknown-type-p part)))
(setf new (type-intersection
new (weaken-integer-type-part part t)))))
((union-type-p type)
(let ((low t) (high t) (rest *empty-type*))
(flet ((maximize (bound)
(if (and bound high)
(setf high (if (eq t high)
(max high bound)))
(setf high nil)))
(minimize (bound)
(if (and bound low)
(setf low (if (eq t low)
(min low bound)))
(setf low nil))))
(dolist (part (union-type-types type))
(let ((weak (weaken-integer-type-part part t)))
(cond ((numeric-type-p weak)
(minimize (numeric-type-low weak))
(maximize (numeric-type-high weak)))
((not range-only)
(setf rest (type-union rest weak)))))))
(if (eq t low)
(type-union rest
`(integer ,(or low '*) ,(or high '*)))))))
(weaken-integer-type-part type 'integer)))
(weaken-type :hash-bits 8
:hash-function (lambda (x)
(logand (type-hash-value x) #xFF)))
((type eq))
(declare (type ctype type))
(cond ((named-type-p type)
((csubtypep type (specifier-type 'integer))
;; Simple range checks are not that expensive, and we *don't*
;; want to accidentally lose eg. array bounds checks due to
;; weakening, so for integer types we simply collapse all
;; ranges into one.
(weaken-integer-type type))
(let ((min-cost (type-test-cost type))
(min-type type)
(found-super nil))
(dolist (x *backend-type-predicates*)
(let* ((stype (car x))
(samep (type= stype type)))
(when (or samep
(and (csubtypep type stype)
(not (union-type-p stype))))
(let ((stype-cost (type-test-cost stype)))
(when (or (< stype-cost min-cost)
;; If the supertype is equal in cost to the type, we
;; prefer the supertype. This produces a closer
;; approximation of the right thing in the presence of
;; poor cost info.
(setq found-super t
min-type stype
min-cost stype-cost))))))
;; This used to return the *UNIVERSAL-TYPE* if no supertype was found,
;; but that's too liberal: it's far too easy for the user to create
;; a union type (which are excluded above), and then trick the compiler
;; into trusting the union type... and finally ending up corrupting the
;; heap once a bad object sneaks past the missing type check.
(if found-super
(defun weaken-values-type (type)
(declare (type ctype type))
(cond ((eq type *wild-type*) type)
((not (values-type-p type))
(weaken-type type))
(make-values-type :required (mapcar #'weaken-type
(values-type-required type))
:optional (mapcar #'weaken-type
(values-type-optional type))
:rest (acond ((values-type-rest type)
(weaken-type it)))))))
;;;; checking strategy determination
;;; Return the type we should test for when we really want to check
;;; for TYPE. If type checking policy is "fast", then we return a
;;; weaker type if it is easier to check. First we try the defined
;;; type weakenings, then look for any predicate that is cheaper.
(defun maybe-weaken-check (type policy)
(declare (type ctype type))
(ecase (policy policy type-check)
(0 *wild-type*)
(2 (weaken-values-type type))
(3 type)))
;;; This is like VALUES-TYPES, only we mash any complex function types
;;; to FUNCTION.
(defun no-fun-values-types (type)
(declare (type ctype type))
(multiple-value-bind (res count) (values-types type)
(values (mapcar (lambda (type)
(if (fun-type-p type)
(specifier-type 'function)
;;; Switch to disable check complementing, for evaluation.
(defvar *complement-type-checks* t)
;;; LVAR is an lvar we are doing a type check on and TYPES is a list
;;; of types that we are checking its values against. If we have
;;; proven that LVAR generates a fixed number of values, then for each
;;; value, we check whether it is cheaper to then difference between
;;; the proven type and the corresponding type in TYPES. If so, we opt
;;; for a :HAIRY check with that test negated. Otherwise, we try to do
;;; a simple test, and if that is impossible, we do a hairy test with
;;; non-negated types. If true, FORCE-HAIRY forces a hairy type check.
(defun maybe-negate-check (lvar types original-types force-hairy n-required)
(declare (type lvar lvar) (list types original-types))
(let ((ptypes (values-type-out (lvar-derived-type lvar) (length types))))
(multiple-value-bind (hairy-res simple-res)
(loop for p in ptypes
and c in types
and a in original-types
and i from 0
for cc = (if (>= i n-required)
(type-union c (specifier-type 'null))
for diff = (type-difference p cc)
collect (if (and diff
(< (type-test-cost diff)
(type-test-cost cc))
(list t diff a)
(list nil cc a))
into hairy-res
collect cc into simple-res
finally (return (values hairy-res simple-res)))
(cond ((or force-hairy (find-if #'first hairy-res))
(values :hairy hairy-res))
((every #'type-check-template simple-res)
(values :simple simple-res))
(values :hairy hairy-res))))))
;;; Determines whether CAST's assertion is:
;;; -- checkable by the back end (:SIMPLE), or
;;; -- not checkable by the back end, but checkable via an explicit
;;; test in type check conversion (:HAIRY), or
;;; -- not reasonably checkable at all (:TOO-HAIRY).
;;; We may check only fixed number of values; in any case the number
;;; of generated values is trusted. If we know the number of produced
;;; values, all of them are checked; otherwise if we know the number
;;; of consumed -- only they are checked; otherwise the check is not
;;; performed.
;;; A type is simply checkable if all the type assertions have a
;;; TYPE-CHECK-TEMPLATE. In this :SIMPLE case, the second value is a
;;; list of the type restrictions specified for the leading positional
;;; values.
;;; Old comment:
;;; We force a check to be hairy even when there are fixed values
;;; if we are in a context where we may be forced to use the
;;; unknown values convention anyway. This is because IR2tran can't
;;; generate type checks for unknown values lvars but people could
;;; still be depending on the check being done. We only care about
;;; EXIT and RETURN (not MV-COMBINATION) since these are the only
;;; contexts where the ultimate values receiver
;;; In the :HAIRY case, the second value is a list of triples of
;;; the form:
;;; If true, the NOT-P flag indicates a test that the corresponding
;;; value is *not* of the specified TYPE. ORIGINAL-TYPE is the type
;;; asserted on this value in the lvar, for use in error
;;; messages. When NOT-P is true, this will be different from TYPE.
;;; This allows us to take what has been proven about CAST's argument
;;; type into consideration. If it is cheaper to test for the
;;; difference between the derived type and the asserted type, then we
;;; check for the negation of this type instead.
(defun cast-check-types (cast force-hairy)
(declare (type cast cast))
(let* ((ctype (coerce-to-values (cast-type-to-check cast)))
(atype (coerce-to-values (cast-asserted-type cast)))
(dtype (node-derived-type cast))
(value (cast-value cast))
(lvar (node-lvar cast))
(dest (and lvar (lvar-dest lvar)))
(n-consumed (cond ((not lvar)
((lvar-single-value-p lvar)
((and (mv-combination-p dest)
(eq (mv-combination-kind dest) :local))
(let ((fun-ref (lvar-use (mv-combination-fun dest))))
(length (lambda-vars (ref-leaf fun-ref)))))))
(n-required (length (values-type-required dtype))))
(aver (not (eq ctype *wild-type*)))
(cond ((and (null (values-type-optional dtype))
(not (values-type-rest dtype)))
;; we [almost] know how many values are produced
(maybe-negate-check value
(values-type-out ctype n-required)
(values-type-out atype n-required)
;; backend checks only consumed values
(not (eql n-required n-consumed))
((lvar-single-value-p lvar)
;; exactly one value is consumed
(principal-lvar-single-valuify lvar)
(flet ((get-type (type)
(acond ((args-type-required type)
(car it))
((args-type-optional type)
(car it))
(t (bug "type ~S is too hairy" type)))))
(multiple-value-bind (ctype atype)
(values (get-type ctype) (get-type atype))
(maybe-negate-check value
(list ctype) (list atype)
((and (mv-combination-p dest)
(eq (mv-combination-kind dest) :local))
;; we know the number of consumed values
(maybe-negate-check value
(adjust-list (values-type-types ctype)
(adjust-list (values-type-types atype)
(values :too-hairy nil)))))
;;; Return T is the cast appears to be from the declaration of the callee,
;;; and should be checked externally -- that is, by the callee and not the caller.
(defun cast-externally-checkable-p (cast)
(declare (type cast cast))
(let* ((lvar (node-lvar cast))
(dest (and lvar (lvar-dest lvar))))
(and (combination-p dest)
;; The theory is that the type assertion is from a declaration on the
;; callee, so the callee should be able to do the check. We want to
;; let the callee do the check, because it is possible that by the
;; time of call that declaration will be changed and we do not want
;; to make people recompile all calls to a function when they were
;; originally compiled with a bad declaration.
;; ALMOST-IMMEDIATELY-USED-P ensures that we don't delegate casts
;; that occur before nodes that can cause observable side effects --
;; most commonly other non-external casts: so the order in which
;; possible type errors are signalled matches with the evaluation
;; order.
;; FIXME: We should let more cases be handled by the callee then we
;; currently do, see:
;; This is not fixable quite here, though, because flow-analysis has
;; deleted the LVAR of the cast by the time we get here, so there is
;; no destination. Perhaps we should mark cases inserted by
;; ASSERT-CALL-TYPE explicitly, and delete those whose destination is
;; deemed unreachable?
(almost-immediately-used-p lvar cast)
(values (values-subtypep (lvar-externally-checkable-type lvar)
(cast-type-to-check cast))))))
;;; Return true if CAST's value is an lvar whose type the back end is
;;; likely to be able to check (see GENERATE-TYPE-CHECKS). Since we
;;; don't know what template the back end is going to choose to
;;; implement the continuation's DEST, we use a heuristic.
;;; We always return T unless nobody uses the value (the backend
;;; cannot check unused LVAR chains).
;;; The logic used to be more complex, but most of the cases that used
;;; to be checked here are now dealt with differently . FIXME: but
;;; here's one we used to do, don't anymore, but could still benefit
;;; from, if we reimplemented it (elsewhere):
;;; -- If the lvar is an argument to a known function that has
;;; no IR2-CONVERT method or :FAST-SAFE templates that are
;;; compatible with the call's type: return NIL.
;;; The code used to look like something like this:
;;; ...
;;; (:known
;;; (let ((info (basic-combination-fun-info dest)))
;;; (if (fun-info-ir2-convert info)
;;; t
;;; (dolist (template (fun-info-templates info) nil)
;;; (when (eq (template-ltn-policy template)
;;; :fast-safe)
;;; (multiple-value-bind (val win)
;;; (valid-fun-use dest (template-type template))
;;; (when (or val (not win)) (return t)))))))))))))
;;; ADP says: It is still interesting. When we have a :SAFE template
;;; and the type assertion is derived from the destination function
;;; type, the check is unneccessary. We cannot return NIL here (the
;;; whole function has changed its meaning, and here NIL *forces*
;;; hairy check), but the functionality is interesting.
(defun probable-type-check-p (cast)
(declare (type cast cast))
(let* ((lvar (node-lvar cast))
(dest (and lvar (lvar-dest lvar))))
(cond ((not dest) nil)
(t t))))
;;; Return a lambda form that we can convert to do a hairy type check
;;; of the specified TYPES. TYPES is a list of the format returned by
;;; LVAR-CHECK-TYPES in the :HAIRY case.
;;; Note that we don't attempt to check for required values being
;;; unsupplied. Such checking is impossible to efficiently do at the
;;; source level because our fixed-values conventions are optimized
;;; for the common MV-BIND case.
(defun make-type-check-form (types)
(let ((temps (make-gensym-list (length types))))
`(multiple-value-bind ,temps
,@(mapcar (lambda (temp type)
(let* ((spec
(let ((*unparse-fun-type-simplify* t))
(type-specifier (second type))))
(test (if (first type) `(not ,spec) spec)))
`(unless (typep ,temp ',test)
',(type-specifier (third type))))))
(values ,@temps))))
;;; Splice in explicit type check code immediately before CAST. This
;;; code receives the value(s) that were being passed to CAST-VALUE,
;;; checks the type(s) of the value(s), then passes them further.
(defun convert-type-check (cast types)
(declare (type cast cast) (type list types))
(let ((value (cast-value cast))
(length (length types)))
(filter-lvar value (make-type-check-form types))
(reoptimize-lvar (cast-value cast))
(setf (cast-type-to-check cast) *wild-type*)
(setf (cast-%type-check cast) nil)
(let* ((atype (cast-asserted-type cast))
(atype (cond ((not (values-type-p atype))
((= length 1)
(single-value-type atype))
:required (values-type-out atype length)))))
(dtype (node-derived-type cast))
(dtype (make-values-type
:required (values-type-out dtype length))))
(setf (cast-asserted-type cast) atype)
(setf (node-derived-type cast) dtype)))
;;; Check all possible arguments of CAST and emit type warnings for
;;; those with type errors. If the value of USE is being used for a
;;; variable binding, we figure out which one for source context. If
;;; the value is a constant, we print it specially.
(defun cast-check-uses (cast)
(declare (type cast cast))
(let* ((lvar (node-lvar cast))
(dest (and lvar (lvar-dest lvar)))
(value (cast-value cast))
(atype (cast-asserted-type cast))
(condition 'type-warning)
(not-ok-uses '()))
(do-uses (use value)
(let ((dtype (node-derived-type use)))
(if (values-types-equal-or-intersect dtype atype)
(setf condition 'type-style-warning)
(push use not-ok-uses))))
(dolist (use (nreverse not-ok-uses))
(let* ((*compiler-error-context* use)
(dtype (node-derived-type use))
(atype-spec (type-specifier atype))
(what (when (and (combination-p dest)
(eq (combination-kind dest) :local))
(let ((lambda (combination-lambda dest))
(pos (position-or-lose
lvar (combination-args dest))))
(format nil "~:[A possible~;The~] binding of ~S"
(and (lvar-has-single-use-p lvar)
(eq (functional-kind lambda) :let))
(leaf-source-name (elt (lambda-vars lambda)
(cond ((and (ref-p use) (constant-p (ref-leaf use)))
(warn condition
"~:[This~;~:*~A~] is not a ~<~%~9T~:;~S:~>~% ~S"
(list what atype-spec
(constant-value (ref-leaf use)))))
(warn condition
"~:[Result~;~:*~A~] is a ~S, ~<~%~9T~:;not a ~S.~>"
(list what (type-specifier dtype) atype-spec)))))))
;;; Loop over all blocks in COMPONENT that have TYPE-CHECK set,
;;; looking for CASTs with TYPE-CHECK T. We do two mostly unrelated
;;; things: detect compile-time type errors and determine if and how
;;; to do run-time type checks.
;;; If there is a compile-time type error, then we mark the CAST and
;;; emit a warning if appropriate. This part loops over all the uses
;;; of the continuation, since after we convert the check, the
;;; :DELETED kind will inhibit warnings about the types of other uses.
;;; If the cast is too complex to be checked by the back end, or is
;;; better checked with explicit code, then convert to an explicit
;;; test. Assertions that can checked by the back end are passed
;;; through. Assertions that can't be tested are flamed about and
;;; marked as not needing to be checked.
;;; If we determine that a type check won't be done, then we set
;;; TYPE-CHECK to :NO-CHECK. In the non-hairy cases, this is just to
;;; prevent us from wasting time coming to the same conclusion again
;;; on a later iteration. In the hairy case, we must indicate to LTN
;;; that it must choose a safe implementation, since IR2 conversion
;;; will choke on the check.
;;; The generation of the type checks is delayed until all the type
;;; check decisions have been made because the generation of the type
;;; checks creates new nodes whose derived types aren't always updated
;;; which may lead to inappropriate template choices due to the
;;; modification of argument types.
(defun generate-type-checks (component)
(collect ((casts))
(do-blocks (block component)
(when (block-type-check block)
;; CAST-EXTERNALLY-CHECKABLE-P wants the backward pass
(do-nodes-backwards (node nil block)
(when (and (cast-p node)
(cast-type-check node))
(cast-check-uses node)
(cond ((cast-externally-checkable-p node)
(setf (cast-%type-check node) :external))
;; it is possible that NODE was marked :EXTERNAL by
;; the previous pass
(setf (cast-%type-check node) t)
(casts (cons node (not (probable-type-check-p node))))))))
(setf (block-type-check block) nil)))
(dolist (cast (casts))
(destructuring-bind (cast . force-hairy) cast
(multiple-value-bind (check types)
(cast-check-types cast force-hairy)
(ecase check
(convert-type-check cast types))
(let ((*compiler-error-context* cast))
(when (policy cast (>= safety inhibit-warnings))
"type assertion too complex to check:~% ~S."
(type-specifier (coerce-to-values (cast-asserted-type cast))))))
(setf (cast-type-to-check cast) *wild-type*)
(setf (cast-%type-check cast) nil)))))))
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