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;;; -*- 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))