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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 contains random utilities used for manipulating the IR1
;;; representation.
;;;
;;; Written by Rob MacLachlan
;;;
(in-package 'c)
;;;; Cleanup hackery:
;;; Node-Enclosing-Cleanup -- Interface
;;; Return the innermost cleanup enclosing Node, or NIL if there is none in
;;; its function. If Node has no cleanup, but is in a let, then we must still
;;; check the environment that the call is in.
(defun node-enclosing-cleanup (node)
(declare (type node node))
(let ((env (node-lexenv node)))
(or (lexenv-cleanup env)
(let ((lambda (lexenv-lambda env)))
(and (member (functional-kind lambda) '(:mv-let :let))
(node-enclosing-cleanup (let-combination lambda)))))))
;;; Insert-Cleanup-Code -- Interface
;;;
;;; Convert the Form in a block inserted between Block1 and Block2 as an
;;; implicit MV-Prog1. The inserted block is returned. Node is used for IR1
;;; context when converting the form. Note that the block is not assigned a
;;; number, and is linked into the DFO at the beginning. We indicate that we
;;; have trashed the DFO by setting Component-Reanalyze. If Cleanup is
;;; supplied, then convert with that cleanup.
(defun insert-cleanup-code (block1 block2 node form &optional cleanup)
(declare (type cblock block1 block2) (type node node)
(type (or cleanup null) cleanup))
(with-ir1-environment node
(let* ((start (make-continuation))
(block (continuation-starts-block start))
(cont (make-continuation))
(*lexical-environment*
(if cleanup
(make-lexenv :cleanup cleanup)
*lexical-environment*)))
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(change-block-successor block1 block2 block)
(link-blocks block block2)
(ir1-convert start cont form)
(setf (block-last block) (continuation-use cont))
block)))
;;;; Continuation use hacking:
;;; Find-Uses -- Interface
;;;
;;; Return a list of all the nodes which use Cont.
;;;
(proclaim '(function find-uses (continuation) list))
(defun find-uses (cont)
(ecase (continuation-kind cont)
((:block-start :deleted-block-start)
(block-start-uses (continuation-block cont)))
(:inside-block (list (continuation-use cont)))
(:unused nil)))
;;; Delete-Continuation-Use -- Interface
;;;
;;; Update continuation use information so that Node is no longer a use of
;;; its Cont. If the old continuation doesn't start its block, then we don't
;;; update the Block-Start-Uses, since it will be deleted when we are done.
;;;
;;; Note: if you call this function, you may have to do a
;;; REOPTIMIZE-CONTINUATION to inform IR1 optimization that something has
;;; changed.
;;;
(proclaim '(function delete-continuation-use (node) void))
(defun delete-continuation-use (node)
(let* ((cont (node-cont node))
(block (continuation-block cont)))
(ecase (continuation-kind cont)
(:deleted)
((:block-start :deleted-block-start)
(let ((uses (delete node (block-start-uses block))))
(setf (block-start-uses block) uses)
(setf (continuation-use cont)
(if (cdr uses) nil (car uses)))))
(:inside-block
(setf (continuation-kind cont) :unused)
(setf (continuation-block cont) nil)
(setf (continuation-use cont) nil)
(setf (continuation-next cont) nil)))
(setf (node-cont node) nil)))
;;; Add-Continuation-Use -- Interface
;;;
;;; Update continuation use information so that Node uses Cont. If Cont is
;;; :Unused, then we set its block to Node's Node-Block (which must be set.)
;;;
;;; Note: if you call this function, you may have to do a
;;; REOPTIMIZE-CONTINUATION to inform IR1 optimization that something has
;;; changed.
;;;
(proclaim '(function add-continuation-use (node continuation) void))
(defun add-continuation-use (node cont)
(assert (not (node-cont node)))
(let ((block (continuation-block cont)))
(ecase (continuation-kind cont)
(:deleted)
(:unused
(assert (not block))
(let ((block (node-block node)))
(assert block)
(setf (continuation-block cont) block))
(setf (continuation-kind cont) :inside-block)
(setf (continuation-use cont) node))
((:block-start :deleted-block-start)
(let ((uses (cons node (block-start-uses block))))
(setf (block-start-uses block) uses)
(setf (continuation-use cont)
(if (cdr uses) nil (car uses)))))))
(setf (node-cont node) cont))
;;; Immediately-Used-P -- Interface
;;;
;;; Return true if Cont is the Node-Cont for Node and Cont is transferred to
;;; immediately after the evaluation of Node.
;;;
(defun immediately-used-p (cont node)
(declare (type continuation cont) (type node node))
(and (eq (node-cont node) cont)
(not (eq (continuation-kind cont) :deleted))
(let ((cblock (continuation-block cont))
(nblock (node-block node)))
(or (eq cblock nblock)
(let ((succ (block-succ nblock)))
(and (= (length succ) 1)
(eq (first succ) cblock)))))))
;;;; Continuation substitution:
;;; Substitute-Continuation -- Interface
;;;
;;; In Old's Dest, replace Old with New. New's Dest must initially be NIL.
;;; When we are done, we call Flush-Dest on Old to clear its Dest and to note
;;; potential optimization opportunities.
;;;
(defun substitute-continuation (new old)
(declare (type continuation old new))
(assert (not (continuation-dest new)))
(let ((dest (continuation-dest old)))
(etypecase dest
((or ref bind))
(cif (setf (if-test dest) new))
(cset (setf (set-value dest) new))
(creturn (setf (return-result dest) new))
(exit (setf (exit-value dest) new))
(basic-combination
(if (eq old (basic-combination-fun dest))
(setf (basic-combination-fun dest) new)
(setf (basic-combination-args dest)
(nsubst new old (basic-combination-args dest))))))
(flush-dest old)
(setf (continuation-dest new) dest))
(undefined-value))
;;; Ensure-Block-Start -- Interface
;;;
;;; Ensure that Cont is the start of a block (or deleted) so that the use
;;; set can be freely manipulated.
;;; -- If the continuation is :Unused or is :Inside-Block and the Cont of Last
;;; in its block, then we make it the start of a new deleted block.
;;; -- If the continuation is :Inside-Block inside a block, then we split the
;;; block using Node-Ends-Block, which makes the continuation be a
;;; :Block-Start.
;;;
(defun ensure-block-start (cont)
(declare (type continuation cont))
(let ((kind (continuation-kind cont)))
(ecase kind
((:deleted :block-start :deleted-block-start))
((:unused :inside-block)
(let ((block (continuation-block cont)))
(cond ((or (eq kind :unused)
(eq (node-cont (block-last block)) cont))
(setf (continuation-block cont)
(make-block-key :start cont :component nil))
(setf (continuation-kind cont) :deleted-block-start))
(t
(node-ends-block (continuation-use cont))))))))
(undefined-value))
;;; Substitute-Continuation-Uses -- Interface
;;;
;;; Replace all uses of Old with uses of New, where New has an arbitary
;;; number of uses. If New will end up with more than one use, then we must
;;; arrange for it to start a block if it doesn't already.
;;;
(defun substitute-continuation-uses (new old)
(declare (type continuation old new))
(unless (and (eq (continuation-kind new) :unused)
(eq (continuation-kind old) :inside-block))
(ensure-block-start new))
(do-uses (node old)
(delete-continuation-use node)
(add-continuation-use node new))
(reoptimize-continuation new)
(undefined-value))
;;;; Misc shortand functions:
;;; NODE-xxx -- Interface
(proclaim '(inline node-block node-home-lambda node-environment
node-tlf-number))
(defun node-block (node)
(declare (type node node))
(the cblock (continuation-block (node-prev node))))
;;;
(defun node-home-lambda (node)
(lambda-home (lexenv-lambda (node-lexenv node))))
(defun node-environment (node)
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(the environment (lambda-environment (lexenv-lambda (node-lexenv node)))))
;;; BLOCK-xxx-CLEANUP -- Interface
;;;
;;; Return the enclosing cleanup for environment of the first or last node
;;; in Block.
;;;
(defun block-start-cleanup (block)
(declare (type cblock block))
(node-enclosing-cleanup (continuation-next (block-start block))))
;;;
(defun block-end-cleanup (block)
(declare (type cblock block))
(node-enclosing-cleanup (block-last block)))
;;; BLOCK-HOME-LAMBDA -- Interface
;;;
;;; Return the non-let lambda that holds Block's code.
;;;
(defun block-home-lambda (block)
(declare (type cblock block))
(lambda-home (lexenv-lambda (node-lexenv (block-last block)))))
;;; BLOCK-ENVIRONMENT -- Interface
;;;
;;; Return the IR1 environment for Block.
;;;
(defun block-environment (block)
(declare (type cblock block))
(lambda-environment (lexenv-lambda (node-lexenv (block-last block)))))
;;; SOURCE-PATH-TLF-NUMBER -- Interface
;;;
;;; Return the Top Level Form number of path, i.e. the ordinal number of
;;; its orignal source's top-level form in its compilation unit.
;;;
(defun source-path-tlf-number (path)
(declare (list path))
(car (last path)))
;;; SOURCE-PATH-ORIGINAL-SOURCE -- Interface
;;;
;;; Return the (reversed) list for the path in the orignal source (with the
;;; TLF number last.)
;;;
(defun source-path-original-source (path)
(declare (list path))
(cddr (member 'original-source-start path)))
;;; SOURCE-PATH-FORM-NUMBER -- Interface
;;;
;;; Return the Form Number of Path's orignal source inside the Top Level
;;; Form that contains it. This is determined by the order that we walk the
;;; subforms of the top level source form.
;;;
(defun source-path-form-number (path)
(declare (list path))
(cadr (member 'original-source-start path)))
;;; SOURCE-PATH-FORMS -- Interface
;;;
;;; Return a list of all the enclosing forms not in the original source that
;;; converted to get to this form, with the immediate source for node at the
;;; start of the list.
;;;
(defun source-path-forms (path)
(subseq path 0 (position 'original-source-start path)))
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;;; MAKE-LEXENV -- Interface
;;;
;;; Return a new LEXENV just like Default except for the specified slot
;;; values. Values for the alist slots are NCONC'ed to the beginning of the
;;; current value, rather than replacing it entirely.
;;;
(defun make-lexenv (&key (default *lexical-environment*)
functions variables blocks tags type-restrictions
inlines
(lambda (lexenv-lambda default))
(cleanup (lexenv-cleanup default))
(cookie (lexenv-cookie default)))
(macrolet ((frob (var slot)
`(let ((old (,slot default)))
(if ,var
(nconc ,var old)
old))))
(internal-make-lexenv
(frob functions lexenv-functions)
(frob variables lexenv-variables)
(frob blocks lexenv-blocks)
(frob tags lexenv-tags)
(frob type-restrictions lexenv-type-restrictions)
(frob inlines lexenv-inlines)
lambda cleanup cookie)))
#|
functions
variables
blocks
tags
type-restrictions
inlines
|#
;;;; Flow/DFO/Component hackery:
;;; Link-Blocks, Unlink-Blocks -- Interface
;;;
;;; Join or separate Block1 and Block2.
;;;
(defun link-blocks (block1 block2)
(declare (type cblock block1 block2))
(assert (not (member block2 (block-succ block1))))
(push block2 (block-succ block1))
(push block1 (block-pred block2))
(undefined-value))
(declare (type cblock block1 block2))
(assert (member block2 (block-succ block1)))
(setf (block-succ block1)
(delete block2 (block-succ block1)))
(setf (block-pred block2)
(delete block1 (block-pred block2)))
(undefined-value))
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;;; Change-Block-Successor -- Internal
;;;
;;; Swing the succ/pred link between Block and Old to be between Block and
;;; New. If Block ends in an IF, then we have to fix up the
;;; consequent/alternative blocks to point to New.
;;;
(defun change-block-successor (block old new)
(declare (type cblock new old block))
(unlink-blocks block old)
(unless (member new (block-succ block))
(link-blocks block new))
(let ((last (block-last block)))
(when (if-p last)
(macrolet ((frob (slot)
`(when (eq (,slot last) old)
(setf (,slot last) new))))
(frob if-consequent)
(frob if-alternative))))
(undefined-value))
;;; Remove-From-DFO -- Interface
;;;
;;; Unlink a block from the next/prev chain. We also null out the
;;; Component.
;;;
(proclaim '(function remove-from-dfo (cblock) void))
(defun remove-from-dfo (block)
(let ((next (block-next block))
(prev (block-prev block)))
(setf (block-component block) nil)
(setf (block-next prev) next)
(setf (block-prev next) prev)))
;;; Add-To-DFO -- Interface
;;;
;;; Add Block to the next/prev chain following After. We also set the
;;; Component to be the same as for After.
;;;
(defun add-to-dfo (block after)
(declare (type cblock block after))
(let ((next (block-next after)))
(setf (block-component block) (block-component after))
(setf (block-next after) block)
(setf (block-prev block) after)
(setf (block-next block) next)
(setf (block-prev next) block))
(undefined-value))
;;; Clear-Flags -- Interface
;;;
;;; Set the Flag for all the blocks in Component to NIL, except for the head
;;; and tail which are set to T.
;;;
(proclaim '(function clear-flags (component) void))
(defun clear-flags (component)
(let ((head (component-head component))
(tail (component-tail component)))
(setf (block-flag head) t)
(setf (block-flag tail) t)
(do-blocks (block component)
(setf (block-flag block) nil))))
;;; Make-Empty-Component -- Interface
;;;
;;; Make a component with no blocks in it. The Block-Flag is initially true
;;; in the head and tail blocks.
;;;
(proclaim '(function make-empty-component () component))
(defun make-empty-component ()
(let* ((head (make-block-key :start nil :component nil))
(tail (make-block-key :start nil :component nil))
(res (make-component :head head :tail tail)))
(setf (block-flag head) t)
(setf (block-flag tail) t)
(setf (block-component head) res)
(setf (block-component tail) res)
(setf (block-next head) tail)
(setf (block-prev tail) head)
res))
;;; Node-Ends-Block -- Interface
;;;
;;; Makes Node the Last node in its block, splitting the block if necessary.
;;; The new block is added to the DFO immediately following Node's block.
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;;;
(defun node-ends-block (node)
(declare (type node node))
(let* ((block (node-block node))
(start (node-cont node))
(last (block-last block))
(last-cont (node-cont last)))
(unless (eq last node)
(assert (eq (continuation-kind start) :inside-block))
(let* ((succ (block-succ block))
(new-block
(make-block-key :start start
:component (block-component block)
:start-uses (list (continuation-use start))
:succ succ :last last)))
(setf (continuation-kind start) :block-start)
(dolist (b succ)
(setf (block-pred b)
(cons new-block (remove block (block-pred b)))))
(setf (block-succ block) ())
(setf (block-last block) node)
(link-blocks block new-block)
(add-to-dfo new-block block)
(do ((cont start (node-cont (continuation-next cont))))
((eq cont last-cont)
(when (eq (continuation-kind last-cont) :inside-block)
(setf (continuation-block last-cont) new-block)))
(setf (continuation-block cont) new-block))
(setf (block-type-asserted block) t)
(setf (block-test-modified block) t))))
(undefined-value))
;;;; Deleting stuff:
;;; Delete-Lambda-Var -- Internal
;;;
;;; Deal with deleting the last (read) reference to a lambda-var. We
;;; iterate over all local calls flushing the corresponding argument, allowing
;;; the computation of the argument to be deleted.
;;;
;;; The lambda-var may still have some sets, but this doesn't cause too much
;;; difficulty, since we can efficiently implement write-only variables. We
;;; iterate over the sets, marking their blocks for dead code flushing, since
;;; we can delete sets whose value is unused.
;;;
(defun delete-lambda-var (leaf)
(declare (type lambda-var leaf))
(let* ((fun (lambda-var-home leaf))
(n (position leaf (lambda-vars fun))))
(dolist (ref (leaf-refs fun))
(let* ((cont (node-cont ref))
(dest (continuation-dest cont)))
(when (and (combination-p dest)
(eq (basic-combination-fun dest) cont)
(eq (basic-combination-kind dest) :local))
(let ((args (basic-combination-args dest)))
(flush-dest (elt args n))
(setf (elt args n) nil))))))
(dolist (set (lambda-var-sets leaf))
(setf (block-flush-p (node-block set)) t))
(undefined-value))
;;; REOPTIMIZE-LAMBDA-VAR -- Internal
;;;
;;; Note that something interesting has happened to Var. We only deal with
;;; LET variables, marking the corresponding initial value arg as needing to be
;;; reoptimized.
;;;
(defun reoptimize-lambda-var (var)
(declare (type lambda-var var))
(let ((fun (lambda-var-home var)))
(when (and (eq (functional-kind fun) :let)
(leaf-refs var))
(reoptimize-continuation
(elt (basic-combination-args
(continuation-dest
(node-cont
(first (leaf-refs fun)))))
(position var (lambda-vars fun))))))
(undefined-value))
;;; DELETE-FUNCTIONAL -- Interface
;;;
;;; This function deletes functions that have no references. This need only
;;; be called on functions that never had any references, since otherwise
;;; DELETE-REF will handle the deletion.
;;;
(defun delete-functional (fun)
(assert (null (leaf-refs fun)))
(etypecase fun
(optional-dispatch (delete-optional-dispatch fun))
(clambda (delete-lambda fun)))
(undefined-value))
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;;; Delete-Lambda -- Internal
;;;
;;; Deal with deleting the last reference to a lambda. Since there is only
;;; one way into a lambda, deleting the last reference to a lambda ensures that
;;; there is no way to reach any of the code in it. So we just set the
;;; Functional-Kind for Fun and its Lets to :Deleted, causing IR1 optimization
;;; to delete blocks in that lambda.
;;;
;;; If the function isn't a Let, we unlink the function head and tail from
;;; the component head and tail to indicate that the code is unreachable. We
;;; also delete the function Component-Lambdas (it won't be there before local
;;; call analysis, but no matter.)
;;;
;;; If the lambda is an XEP, then we null out the Entry-Function in its
;;; Entry-Function so that people will know that it is not an entry point
;;; anymore.
;;;
(defun delete-lambda (leaf)
(declare (type clambda leaf))
(let ((kind (functional-kind leaf)))
(assert (not (member kind '(:deleted :optional :top-level))))
(setf (functional-kind leaf) :deleted)
(dolist (let (lambda-lets leaf))
(setf (functional-kind let) :deleted))
(if (or (eq kind :let) (eq kind :mv-let))
(let ((home (lambda-home leaf)))
(setf (lambda-lets home) (delete leaf (lambda-lets home))))
(let* ((bind-block (node-block (lambda-bind leaf)))
(component (block-component bind-block))
(return (lambda-return leaf)))
(unlink-blocks (component-head component) bind-block)
(when return
(unlink-blocks (node-block return) (component-tail component)))
(setf (component-lambdas component)
(delete leaf (component-lambdas component)))))
(when (eq kind :external)
(let ((fun (functional-entry-function leaf)))
(setf (functional-entry-function fun) nil)
(when (optional-dispatch-p fun)
(delete-optional-dispatch fun)))))
(undefined-value))
;;; Delete-Optional-Dispatch -- Internal
;;;
;;; Deal with deleting the last reference to an Optional-Dispatch. We have
;;; to be a bit more careful than with lambdas, since Delete-Ref is used both
;;; before and after local call analysis. Afterward, all references to
;;; still-existing optional-dispatches have been moved to the XEP, leaving it
;;; with no references at all. So we look at the XEP to see if an
;;; optional-dispatch is still really being used. But before local call
;;; analysis, there are no XEPs, and all references are direct.
;;;
;;; When we do delete the optional-dispatch, we grovel all of its
;;; entry-points, making them be normal lambdas, and then deleting the ones
;;; with no references. This deletes any e-p lambdas that were either never
;;; referenced, or couldn't be deleted when the last deference was deleted (due
;;; to their :Optional kind.)
;;;
;;; Note that the last optional ep may alias the main entry, so when we process
;;; the main entry, its kind may have been changed to NIL or even converted to
;;; a let.
;;;
(defun delete-optional-dispatch (leaf)
(declare (type optional-dispatch leaf))
(let ((entry (functional-entry-function leaf)))
(unless (and entry (leaf-refs entry))
(assert (or (not entry) (eq (functional-kind entry) :deleted)))
(setf (functional-kind leaf) :deleted)
(flet ((frob (fun)
(unless (eq (functional-kind fun) :deleted)
(assert (eq (functional-kind fun) :optional))
(setf (functional-kind fun) nil)
(let ((refs (leaf-refs fun)))
(cond ((null refs)
(delete-lambda fun))
((null (rest refs))
(maybe-let-convert fun)))))))
(dolist (ep (optional-dispatch-entry-points leaf))
(frob ep))
(when (optional-dispatch-more-entry leaf)
(frob (optional-dispatch-more-entry leaf)))
(let ((main (optional-dispatch-main-entry leaf)))
(when (eq (functional-kind main) :optional)
(frob main))))))
(undefined-value))
;;; Delete-Ref -- Interface
;;;
;;; Do stuff to delete the semantic attachments of a Ref node. When this
;;; leaves zero or one reference, we do a type dispatch off of the leaf to
;;; determine if a special action is appropriate.
;;;
(defun delete-ref (ref)
(declare (type ref ref))
(let* ((leaf (ref-leaf ref))
(refs (delete ref (leaf-refs leaf))))
(setf (leaf-refs leaf) refs)
(cond ((null refs)
(typecase leaf
(lambda-var (delete-lambda-var leaf))
(clambda
(ecase (functional-kind leaf)
((nil :external :let :mv-let :escape :cleanup)
(delete-lambda leaf))
((:deleted :optional))))
(optional-dispatch
(unless (eq (functional-kind leaf) :deleted)
(delete-optional-dispatch leaf)))))
((null (rest refs))
(typecase leaf
(clambda (maybe-let-convert leaf))
(lambda-var (reoptimize-lambda-var leaf))))))
(undefined-value))
;;; Delete-Return -- Interface
;;;
;;; Do stuff to indicate that the return node Node is being deleted. We set
;;; the RETURN to NIL and remove the function from its tail set.
;;;
;;; As a rather random special case, we leave the function in the tail set
;;; when there are uses of the result continuation marked TAIL-P. This is done
;;; to prevent the tail set from being blown away when the back end deletes the
;;; return because it discovers that all calls are tail-recursive.
;;;
(defun delete-return (node)
(declare (type creturn node))
(let* ((fun (return-lambda node))
(tail-set (lambda-tail-set fun)))
(assert (lambda-return fun))
(unless (do-uses (use (return-result node) nil)
(when (node-tail-p use) (return t)))
(setf (tail-set-functions tail-set)
(delete fun (tail-set-functions tail-set)))
(setf (lambda-tail-set fun) nil))
(setf (lambda-return fun) nil))
(undefined-value))
;;; Flush-Dest -- Interface
;;;
;;; This function is called by people who delete nodes; it provides a way to
;;; indicate that the value of a continuation is no longer used. We null out
;;; the Continuation-Dest, set Flush-P in the blocks containing uses of Cont
;;; and set Component-Reoptimize.
;;;
;;; If the continuation is :Deleted, then we don't do anything, since all
;;; semantics have already been flushed. If the continuation is a
;;; :Deleted-Block-Start, then we delete the continuation, since its control
;;; semantics have already been deleted. Deleting the continuation causes its
;;; uses to be reoptimized. If the Prev of the use is deleted, then we blow
;;; off reoptimization.
;;;
(defun flush-dest (cont)
(declare (type continuation cont))
(ecase (continuation-kind cont)
(:deleted)
(:deleted-block-start
(assert (continuation-dest cont))
(setf (continuation-dest cont) nil)
(delete-continuation cont))
((:inside-block :block-start)
(assert (continuation-dest cont))
(setf (continuation-dest cont) nil)
(setf (component-reoptimize (block-component (continuation-block cont)))
t)
(do-uses (use cont)
(let ((prev (node-prev use)))
(unless (eq (continuation-kind prev) :deleted)
(setf (block-attributep (block-flags (continuation-block prev))
flush-p type-asserted)
t))))))
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(setf (continuation-%type-check cont) nil)
(undefined-value))
;;; MARK-FOR-DELETION -- Internal
;;;
;;; Do a graph walk backward from Block, marking all predecessor blocks with
;;; the DELETE-P flag.
;;;
(defun mark-for-deletion (block)
(declare (type cblock block))
(unless (block-delete-p block)
(setf (block-delete-p block) t)
(dolist (pred (block-pred block))
(mark-for-deletion pred)))
(undefined-value))
;;; DELETE-CONTINUATION -- Interface
;;;
;;; Delete Cont, eliminating both control and value semantics. We set
;;; FLUSH-P and COMPONENT-REOPTIMIZE similarly to in FLUSH-DEST. Here we must
;;; get the component from the use block, since the continuation may be a
;;; :DELETED-BLOCK-START.
;;;
;;; If Cont has DEST, then it must be the case that the DEST is unreachable,
;;; since we can't compute the value desired. In this case, we call
;;; MARK-FOR-DELETION to cause the DEST block and its predecessors to tell
;;; people to ignore them, and to cause them to be deleted eventually.
;;;
(defun delete-continuation (cont)
(declare (type continuation cont))
(assert (not (eq (continuation-kind cont) :deleted)))
(do-uses (use cont)
(let ((prev (node-prev use)))
(unless (eq (continuation-kind prev) :deleted)
(let ((block (continuation-block prev)))
(setf (block-attributep (block-flags block) flush-p type-asserted) t)
(setf (component-reoptimize (block-component block)) t)))))
(let ((dest (continuation-dest cont)))
(when dest
(let ((block (node-block dest)))
(unless (block-delete-p block)
(mark-for-deletion block)))))
(setf (continuation-kind cont) :deleted)
(setf (continuation-dest cont) nil)
(setf (continuation-next cont) nil)
(setf (continuation-asserted-type cont) *empty-type*)
(setf (continuation-%derived-type cont) *empty-type*)
(setf (continuation-use cont) nil)
(setf (continuation-block cont) nil)
(setf (continuation-reoptimize cont) nil)
(setf (continuation-%type-check cont) nil)
(setf (continuation-info cont) nil)
(undefined-value))
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(defvar *deletion-ignored-objects* '(t nil))
;;; PRESENT-IN-FORM -- Internal
;;;
;;; Return true if we can find Obj in Form, NIL otherwise. We bound our
;;; recursion so that we don't get lost in circular structures. We ignore the
;;; car of forms if they are a symbol (to prevent confusing function
;;; referencess with variables), and we also ignore anything inside ' or #'.
;;;
(defun present-in-form (obj form depth)
(declare (type (integer 0 20) depth))
(cond ((= depth 20) nil)
((eq obj form) t)
((atom form) nil)
(t
(let ((first (car form))
(depth (1+ depth)))
(if (member first '(quote function))
nil
(or (and (not (symbolp first))
(present-in-form obj first depth))
(do ((l (cdr form) (cdr l))
(n 0 (1+ n)))
((or (atom l) (> n 100))
nil)
(declare (fixnum n))
(when (present-in-form obj (car l) depth)
(return t)))))))))
;;; NOTE-BLOCK-DELETION -- Internal
;;;
;;; This function is called on a block immediately before we delete it. We
;;; check to see if any of the code about to die appeared in the original
;;; source, and emit a note if so.
;;;
;;; If the block was in a lambda is now deleted, but used to be a
;;; optional-dispatch entry point or XEP, then we ignore the whole block. We
;;; also ignore the deletion of CRETURN nodes, since it is somewhat reasonable
;;; for a function to not return, and there is a different note for that case
;;; anyway.
;;;
;;; If the actual source is an atom, then we use a bunch of heuristics to
;;; guess whether this reference really appeared in the original source:
;;; -- If a symbol, it must be interned.
;;; -- It must not be an easily introduced constant (T or NIL).
;;; -- The atom must be "present" in the original source form, and present in
;;; all intervening actual source forms.
;;;
(defun note-block-deletion (block)
(let ((home (block-home-lambda block)))
(unless (and (eq (functional-kind home) :deleted)
(or (functional-entry-function home)
(let ((od (lambda-optional-dispatch home)))
(and od
(not (eq (optional-dispatch-main-entry od)
home))))))
(do-nodes (node cont block)
(let* ((path (node-source-path node))
(first (first path)))
(when (or (eq first 'original-source-start)
(and (atom first)
(or (not (symbolp first))
(symbol-package first))
(not (member first *deletion-ignored-objects*))
(every #'(lambda (x)
(present-in-form first x 0))
(source-path-forms path))
(present-in-form first (find-original-source path)
0)))
(unless (return-p node)
(let ((*compiler-error-context* node))
(compiler-note "Deleting unreachable code.")))
(return))))))
(undefined-value))
;;; Delete-Block -- Interface
;;;
;;; This function does what is necessary to eliminate the code in it from
;;; the IR1 representation. This involves unlinking it from its predecessors
;;; and successors and deleting various node-specific semantic information.
;;;
;;; We mark the Start as has having no next and remove the last node from
;;; its Cont's uses. We also flush the DEST for all continuations whose values
;;; are received by nodes in the block.
;;;
(defun delete-block (block)
(declare (type cblock block))
(assert (block-component block) () "Block is already deleted.")
(note-block-deletion block)
(setf (block-delete-p block) t)
(let* ((last (block-last block))
(cont (node-cont last)))
(delete-continuation-use last)
(if (eq (continuation-kind cont) :unused)
(delete-continuation cont)
(reoptimize-continuation cont)))
(dolist (b (block-pred block))
(unlink-blocks b block))
(dolist (b (block-succ block))
(unlink-blocks block b))
(do-nodes (node cont block)
(typecase node
(ref (delete-ref node))
(basic-combination
(when (and (eq (basic-combination-kind node) :local)
;; Not already deleted...
(continuation-use (basic-combination-fun node)))
(let ((fun (combination-lambda node)))
(when (member (functional-kind fun) '(:let :mv-let))
(delete-lambda fun))))
(flush-dest (basic-combination-fun node))
(dolist (arg (basic-combination-args node))
(when arg (flush-dest arg))))
(cif
(flush-dest (if-test node)))
(bind
(let ((lambda (bind-lambda node)))
(unless (eq (functional-kind lambda) :deleted)
(assert (member (functional-kind lambda) '(:let :mv-let)))
(delete-lambda lambda))))
(exit
(let ((value (exit-value node))
(entry (exit-entry node)))
(flush-dest value))
(when entry
(setf (entry-exits entry)
(delete node (entry-exits entry))))))
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(creturn
(flush-dest (return-result node))
(delete-return node))
(cset
(flush-dest (set-value node))
(let ((var (set-var node)))
(setf (basic-var-sets var)
(delete node (basic-var-sets var))))))
(delete-continuation (node-prev node)))
(remove-from-dfo block)
(undefined-value))
;;; Unlink-Node -- Interface
;;;
;;; Delete a node from a block, deleting the block if there are no nodes
;;; left. We remove the node from the uses of its CONT, but we don't deal with
;;; cleaning up any type-specific semantic attachments. If the CONT is :UNUSED
;;; after deleting this use, then we delete CONT. (Note :UNUSED is not the
;;; same as no uses. A continuation will only become :UNUSED if it was
;;; :INSIDE-BLOCK before.)
;;;
;;; If the node is the last node, there must be exactly one successor. We
;;; link all of our precedessors to the successor and unlink the block. In
;;; this case, we return T, otherwise NIL. If no nodes are left, and the block
;;; is a successor of itself, then we replace the only node with a degenerate
;;; exit node. This provides a way to represent the bodyless infinite loop,
;;; given the prohibition on empty blocks in IR1.
;;;
(defun unlink-node (node)
(declare (type node node))
(let* ((cont (node-cont node))
(next (continuation-next cont))
(prev (node-prev node))
(block (continuation-block prev))
(prev-kind (continuation-kind prev))
(last (block-last block)))
(unless (eq (continuation-kind cont) :deleted)
(delete-continuation-use node)
(when (eq (continuation-kind cont) :unused)
(assert (not (continuation-dest cont)))
(delete-continuation cont)))
(setf (block-type-asserted block) t)
(setf (block-test-modified block) t)