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88 lines
3.4 KiB
Scheme
88 lines
3.4 KiB
Scheme
;;; Continuation-passing style (CPS) intermediate language (IL)
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;; Copyright (C) 2013, 2014, 2015 Free Software Foundation, Inc.
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;;;; This library is free software; you can redistribute it and/or
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;;;; modify it under the terms of the GNU Lesser General Public
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;;;; License as published by the Free Software Foundation; either
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;;;; version 3 of the License, or (at your option) any later version.
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;;;;
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;;;; This library is distributed in the hope that it will be useful,
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;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;;;; Lesser General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU Lesser General Public
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;;;; License along with this library; if not, write to the Free Software
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;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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;;; Commentary:
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;;;
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;;; Primcalls that don't correspond to VM instructions are treated as if
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;;; they are calls, and indeed the later reify-primitives pass turns
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;;; them into calls. Because no return arity checking is done for these
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;;; primitives, if a later optimization pass simplifies the primcall to
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;;; a VM operation, the tail of the simplification has to be a
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;;; primcall to 'values. Most of these primcalls can be elided, and
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;;; that is the job of this pass.
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;;;
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;;; Code:
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(define-module (language cps elide-values)
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#:use-module (ice-9 match)
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#:use-module (language cps)
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#:use-module (language cps utils)
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#:use-module (language cps with-cps)
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#:use-module (language cps intmap)
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#:export (elide-values))
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(define (inline-values cps k src args)
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(match (intmap-ref cps k)
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(($ $ktail)
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(with-cps cps
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(build-term
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($continue k src ($values args)))))
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(($ $kreceive ($ $arity req () rest () #f) kargs)
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(cond
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((and (not rest) (= (length args) (length req)))
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(with-cps cps
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(build-term
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($continue kargs src ($values args)))))
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((and rest (>= (length args) (length req)))
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(let ()
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(define (build-rest cps k tail)
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(match tail
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(()
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(with-cps cps
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(build-term ($continue k src ($const '())))))
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((v . tail)
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(with-cps cps
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(letv rest)
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(letk krest ($kargs ('rest) (rest)
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($continue k src ($primcall 'cons (v rest)))))
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($ (build-rest krest tail))))))
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(with-cps cps
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(letv rest)
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(letk krest ($kargs ('rest) (rest)
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($continue kargs src
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($values ,(append (list-head args (length req))
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(list rest))))))
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($ (build-rest krest (list-tail args (length req)))))))
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(else (with-cps cps #f))))))
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(define (elide-values conts)
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(with-fresh-name-state conts
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(persistent-intmap
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(intmap-fold
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(lambda (label cont out)
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(match cont
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(($ $kargs names vars ($ $continue k src ($ $primcall 'values args)))
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(call-with-values (lambda () (inline-values out k src args))
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(lambda (out term)
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(if term
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(let ((cont (build-cont ($kargs names vars ,term))))
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(intmap-replace! out label cont))
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out))))
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(_ out)))
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conts
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conts))))
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