;;; -*- Package: C; Log: C.Log -*- ;;; ;;; ********************************************************************** ;;; This code was written as part of the Spice Lisp project at ;;; Carnegie-Mellon University, and has been placed in the public domain. ;;; If you want to use this code or any part of Spice Lisp, please contact ;;; Scott Fahlman (FAHLMAN@CMUC). ;;; ********************************************************************** ;;; ;;; 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. ;;; ;;; Written by Rob MacLachlan ;;; (in-package 'c) ;;;; Cost estimation: ;;; Function-Cost -- Internal ;;; ;;; 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 randomly special-case NULL, since it does have a source tranform and is ;;; interesting to us. ;;; (defun function-cost (name) (declare (symbol name)) (let ((info (info function info name)) (call-cost (template-cost (template-or-lose 'call-named)))) (if info (let ((templates (function-info-templates info))) (if templates (template-cost (first templates)) (case name (null (template-cost (template-or-lose 'if-eq))) (t call-cost)))) call-cost))) ;;; Type-Test-Cost -- Internal ;;; ;;; 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 (let ((check (type-check-template type))) (if check (template-cost check) (let ((found (cdr (assoc type *type-predicates* :test #'type=)))) (if found (function-cost found) nil)))) (typecase type (union-type (collect ((res 0 +)) (dolist (mem (union-type-types type)) (res (type-test-cost mem))) (res))) (member-type (* (length (member-type-members type)) (function-cost 'eq))) (numeric-type (* (if (numeric-type-complexp type) 2 1) (function-cost (if (csubtypep type (specifier-type 'fixnum)) 'fixnump 'numberp)) (+ 1 (if (numeric-type-low type) 1 0) (if (numeric-type-high type) 1 0)))) (t (function-cost 'typep))))) ;;;; Checking strategy determination: ;;; MAYBE-NEGATE-CHECK -- Internal ;;; ;;; Cont is a continuation 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 Cont generates a fixed number of values, then for each value, we check ;;; whether it is cheaper to then difference between the 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. ;;; (defun maybe-negate-check (cont types) (declare (type continuation cont) (list types)) (multiple-value-bind (ptypes count) (values-types (continuation-proven-type cont)) (if (eq count :unknown) (if (every #'type-check-template types) (values :simple types) (values :hairy (mapcar #'(lambda (x) (list nil x x)) types))) (let ((res (mapcar #'(lambda (p c) (let ((diff (type-difference p c))) (if (and diff (< (type-test-cost diff) (type-test-cost c))) (list t diff c) (list nil c c)))) ptypes types))) (if (and (not (find-if #'first res)) (every #'type-check-template types)) (values :simple types) (values :hairy res)))))) ;;; CONTINUATION-CHECK-TYPES -- Interface ;;; ;;; Determines whether Cont'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). ;;; ;;; A type is checkable if it either represents a fixed number of values (as ;;; determined by VALUES-TYPES), or it is the assertion for an MV-Bind. 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. ;;; ;;; In the :HAIRY case, the second value is a list of triples of the form: ;;; (Not-P Type Original-Type) ;;; ;;; 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 continuation, 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 Cont's 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 continuation-check-types (cont) (declare (type continuation cont)) (let ((type (continuation-asserted-type cont)) (dest (continuation-dest cont))) (assert (not (eq type *wild-type*))) (multiple-value-bind (types count) (values-types type) (cond ((not (eq count :unknown)) (maybe-negate-check cont types)) ((and (mv-combination-p dest) (eq (basic-combination-kind dest) :local)) (assert (values-type-p type)) (maybe-negate-check cont (args-type-optional type))) (t (values :too-hairy nil)))))) ;;; Probable-Type-Check-P -- Internal ;;; ;;; Return true if Cont is a continuation whose type the back end is likely ;;; to want to check. 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, or ;;; -- Speed or space is more important that safety, or ;;; -- the continuation is an argument to an unknown function, or ;;; -- the continuation 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. ;;; ;;; We must only return nil when it is *certain* that a check will not be done, ;;; since if we pass up this chance to do the check, it will be too late. The ;;; penalty for being too conservative is duplicated type checks. ;;; ;;; We always return true if there is a compile-time type error on the ;;; continuation, so that this error will be signalled at runtime as well. ;;; (defun probable-type-check-p (cont) (declare (type continuation cont)) (let ((dest (continuation-dest cont))) (cond ((eq (continuation-type-check cont) :error)) ((or (not dest) (policy dest (or (> speed safety) (> space safety)))) nil) ((basic-combination-p dest) (let ((kind (basic-combination-kind dest))) (cond ((eq cont (basic-combination-fun dest)) t) ((eq kind :local) t) ((eq kind :full) nil) ((function-info-ir2-convert kind) t) (t (dolist (template (function-info-templates kind) nil) (when (and (eq (template-policy template) :fast-safe) (valid-function-use dest (template-type template))) (return t))))))) (t t)))) ;;; Make-Type-Check-Form -- Internal ;;; ;;; Return a form that we can convert to do a hairy type check of the ;;; specified Types. Types is a list of the format returned by ;;; Continuation-Check-Types in the :HAIRY case. In place of the actual ;;; value(s) we are to check, we use 'Dummy. This constant reference is later ;;; replaced with the actual values continuation. ;;; ;;; 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. ;;; ;;; We can always use Multiple-Value-Bind, since the macro is clever about ;;; binding a single variable. ;;; (defun make-type-check-form (types) (collect ((temps)) (dotimes (i (length types)) (declare (ignore i)) (temps (gensym))) `(multiple-value-bind ,(temps) 'dummy ,@(mapcar #'(lambda (temp type) (let* ((spec (type-specifier (second type))) (test (if (first type) `(not ,spec) spec))) `(unless (typep ,temp ',test) (%type-check-error ,temp ',(type-specifier (third type)))))) (temps) types) (values ,@(temps))))) ;;; Convert-Type-Check -- Internal ;;; ;;; Splice in explicit type check code immediately before the node that its ;;; Cont's Dest. This code receives the value(s) that were being passed to ;;; Cont, checks the type(s) of the value(s), then passes them on to Cont. ;;; We: ;;; -- Ensure that Cont starts a block, so that we can freely manipulate its ;;; uses. ;;; -- Make a new continuation and move Cont's uses to it. Set type set ;;; Type-Check in Cont to :DELETED to indicate that the check has been ;;; done. ;;; -- Make the Dest node start its block so that we can splice in the type ;;; check code. ;;; -- Splice in a new block before the Dest block, giving it all the Dest's ;;; predecessors. ;;; -- Convert the check form, using the new block start as Start and a dummy ;;; continuation as Cont. ;;; -- Set the new block's start and end cleanups to the *start* cleanup of ;;; Prev's block. This overrides the incorrect default from ;;; With-IR1-Environment. ;;; -- Finish off the dummy continuation's block, and change the use to a use ;;; of Cont. (we need to use the dummy continuation to get the control ;;; transfer right, since we want to go to Prev's block, not Cont's.) ;;; Link the new block to Prev's block. ;;; -- Substitute the new continuation for the dummy placeholder argument. ;;; Since no let conversion has been done yet, we can find the placeholder. ;;; The [mv-]combination node from the mv-bind in the check form will be ;;; the Use of the new check continuation. We substitute for the first ;;; argument of this node. ;;; -- Invoke local call analysis to convert the call to a let. ;;; (defun convert-type-check (cont types) (declare (type continuation cont) (list types)) (with-ir1-environment (continuation-dest cont) (ensure-block-start cont) (let* ((new-start (make-continuation)) (dest (continuation-dest cont)) (prev (node-prev dest))) (continuation-starts-block new-start) (substitute-continuation-uses new-start cont) (setf (continuation-%type-check cont) :deleted) (when (continuation-use prev) (node-ends-block (continuation-use prev))) (let* ((prev-block (continuation-block prev)) (prev-cleanup (block-start-cleanup prev-block)) (new-block (continuation-block new-start)) (dummy (make-continuation))) (dolist (block (block-pred prev-block)) (change-block-successor block prev-block new-block)) (ir1-convert new-start dummy (make-type-check-form types)) (assert (eq (continuation-block dummy) new-block)) (setf (block-start-cleanup new-block) prev-cleanup) (setf (block-end-cleanup new-block) prev-cleanup) (let ((node (continuation-use dummy))) (setf (block-last new-block) node) (delete-continuation-use node) (add-continuation-use node cont)) (link-blocks new-block prev-block)) (let* ((node (continuation-use cont)) (args (basic-combination-args node)) (victim (first args))) (assert (and (= (length args) 1) (eq (constant-value (ref-leaf (continuation-use victim))) 'dummy))) (substitute-continuation new-start victim))) (local-call-analyze *current-component*)) (undefined-value)) ;;; Generate-Type-Checks -- Interface ;;; ;;; Loop over all blocks in Component that have TYPE-CHECK set, looking for ;;; continuations 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 a continuation 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. ;;; (defun generate-type-checks (component) (do-blocks (block component) (when (block-type-check block) (do-nodes (node cont block) (when (eq (continuation-type-check cont) t) (let ((dtype (node-derived-type node)) (atype (continuation-asserted-type cont))) (unless (values-types-intersect dtype atype) (setf (continuation-%type-check cont) :error) (when (policy node (>= safety brevity)) (let ((*compiler-error-context* node)) (compiler-warning "Result is a ~S, not a ~S." (type-specifier dtype) (type-specifier atype)))))) (let ((check-p (probable-type-check-p cont))) (multiple-value-bind (check types) (continuation-check-types cont) (ecase check (:simple (unless check-p (setf (continuation-%type-check cont) :no-check))) (:hairy (if check-p (convert-type-check cont types) (setf (continuation-%type-check cont) :no-check))) (:too-hairy (let* ((context (continuation-dest cont)) (*compiler-error-context* context)) (when (policy context (>= safety brevity)) (compiler-note "Type assertion too complex to check:~% ~S." (type-specifier (continuation-asserted-type cont))))) (setf (continuation-%type-check cont) :deleted))))))) (setf (block-type-check block) nil))) (undefined-value))