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guile/module/language/tree-il/canonicalize.scm
Andy Wingo 403d78f915 Tree-il post-order rewriter no longer destructive
* module/language/tree-il.scm (pre-post-order): New helper, like
  pre-order! and post-order! but not destructive.
  (post-order): Implement in terms of pre-post-order, and rename from
  post-order!.

* module/ice-9/compile-psyntax.scm (squeeze-tree-il):
* module/language/tree-il/canonicalize.scm (canonicalize):
* module/language/tree-il/fix-letrec.scm (fix-letrec):
* module/language/tree-il/primitives.scm (resolve-primitives): Use
  post-order, and rename from the destructive
  variants (squeeze-tree-il!, canonicalize!, etc).  Adapt callers.

* test-suite/tests/tree-il.test (strip-source): Adapt to post-order.

* test-suite/tests/cse.test:
* test-suite/tests/peval.test:
* module/language/tree-il/optimize.scm: Adapt callers.
2013-06-10 22:46:08 +02:00

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3.1 KiB
Scheme

;;; Tree-il canonicalizer
;; Copyright (C) 2011, 2012, 2013 Free Software Foundation, Inc.
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;; Code:
(define-module (language tree-il canonicalize)
#:use-module (language tree-il)
#:use-module (ice-9 match)
#:use-module (srfi srfi-1)
#:export (canonicalize))
(define (tree-il-any proc exp)
(tree-il-fold (lambda (exp res)
(or res (proc exp)))
(lambda (exp res)
(or res (proc exp)))
(lambda (exp res) res)
#f exp))
(define (canonicalize x)
(post-order
(lambda (x)
(match x
(($ <let> src () () () body)
body)
(($ <letrec> src _ () () () body)
body)
(($ <fix> src () () () body)
body)
(($ <dynlet> src () () body)
body)
(($ <lambda> src meta #f)
;; Give a body to case-lambda with no clauses.
(make-lambda
src meta
(make-lambda-case
#f '() #f #f #f '() '()
(make-primcall
#f
'throw
(list (make-const #f 'wrong-number-of-args)
(make-const #f #f)
(make-const #f "Wrong number of arguments")
(make-const #f '())
(make-const #f #f)))
#f)))
(($ <prompt> src tag body handler)
(define (escape-only? handler)
(match handler
(($ <lambda-case> _ (_ . _) _ _ _ _ (cont . _) body #f)
(not (tree-il-any (lambda (x)
(and (lexical-ref? x)
(eq? (lexical-ref-gensym x) cont)))
body)))
(else #f)))
(define (thunk-application? x)
(match x
(($ <call> _
($ <lambda> _ _ ($ <lambda-case> _ () #f #f #f))
()) #t)
(_ #f)))
(define (make-thunk-application body)
(define thunk
(make-lambda #f '()
(make-lambda-case #f '() #f #f #f '() '() body #f)))
(make-call #f thunk '()))
;; This code has a nasty job to do: to ensure that either the
;; handler is escape-only, or the body is the application of a
;; thunk. Sad but true.
(if (or (escape-only? handler)
(thunk-application? body))
x
(make-prompt src tag (make-thunk-application body) handler)))
(_ x)))
x))