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Avoid accidentally-quadratic use of intmap-keys

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* module/language/cps/utils.scm (compute-reachable-functions): Rework to
not call intmap-keys on a data structure that we are building up in a
loop.
This commit is contained in:
Andy Wingo 2025-01-27 09:38:43 +01:00
parent f109baebc0
commit 624d78625b
1 changed files with 19 additions and 14 deletions
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33
module/language/cps/utils.scm
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@ -1,6 +1,6 @@
;;; Continuation-passing style (CPS) intermediate language (IL) ;;; Continuation-passing style (CPS) intermediate language (IL)
;; Copyright (C) 2013, 2014, 2015, 2017, 2018, 2019, 2020, 2021, 2023 Free Software Foundation, Inc. ;; Copyright (C) 2013-2015,2017-2021,2023,2025 Free Software Foundation, Inc.
;;;; This library is free software; you can redistribute it and/or ;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public ;;;; modify it under the terms of the GNU Lesser General Public
@ -171,12 +171,15 @@ predecessor."
"Compute a mapping LABEL->LABEL..., where each key is a reachable "Compute a mapping LABEL->LABEL..., where each key is a reachable
$kfun and each associated value is the body of the function, as an $kfun and each associated value is the body of the function, as an
intset." intset."
(define (intset-cons i set) (intset-add set i)) (define (visit-fun kfun body to-visit visited)
(define (visit-fun kfun body to-visit) (define (add-function i to-visit)
(if (intset-ref visited i)
to-visit
(intset-add to-visit i)))
(intset-fold (intset-fold
(lambda (label to-visit) (lambda (label to-visit)
(define (return kfun*) (fold intset-cons to-visit kfun*)) (define (return kfun*) (fold add-function to-visit kfun*))
(define (return1 kfun) (intset-add to-visit kfun)) (define (return1 kfun) (add-function kfun to-visit))
(define (return0) to-visit) (define (return0) to-visit)
(match (intmap-ref conts label) (match (intmap-ref conts label)
(($ $kargs _ _ ($ $continue _ _ exp)) (($ $kargs _ _ ($ $continue _ _ exp))
@ -190,20 +193,22 @@ intset."
(_ (return0)))) (_ (return0))))
body body
to-visit)) to-visit))
(let lp ((to-visit (intset kfun)) (visited empty-intmap)) (let lp ((to-visit (intset kfun)) (visited empty-intset) (out empty-intmap))
(let ((to-visit (intset-subtract to-visit (intmap-keys visited)))) (if (eq? to-visit empty-intset)
(if (eq? to-visit empty-intset) out
visited (let ((visited (intset-union to-visit visited)))
(call-with-values (call-with-values
(lambda () (lambda ()
(intset-fold (intset-fold
(lambda (kfun to-visit visited) (lambda (kfun to-visit visited out)
(let ((body (compute-function-body conts kfun))) (let* ((body (compute-function-body conts kfun)))
(values (visit-fun kfun body to-visit) (values (visit-fun kfun body to-visit visited)
(intmap-add visited kfun body)))) visited
(intmap-add out kfun body))))
to-visit to-visit
empty-intset empty-intset
visited)) visited
out))
lp))))) lp)))))
(define* (compute-successors conts #:optional (kfun (intmap-next conts))) (define* (compute-successors conts #:optional (kfun (intmap-next conts)))