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828ed94469
* .dir-locals.el: Add with-fresh-name-state. * module/language/cps.scm (fresh-label, fresh-var): Signal an error if the counters are not initialized. (with-fresh-name-state): New macro. (make-cont-folder): New macro, generates an n-ary folder. (compute-max-label-and-var): New function, uses make-cont-folder. (fold-conts): Use make-cont-folder. (let-gensyms): Remove. * module/language/cps/arities.scm: * module/language/cps/closure-conversion.scm: * module/language/cps/constructors.scm: * module/language/cps/dce.scm: * module/language/cps/elide-values.scm: * module/language/cps/reify-primitives.scm: * module/language/cps/specialize-primcalls.scm: Use let-fresh instead of let-gensyms, and wrap in a with-fresh-name-state as needed. * module/language/tree-il/compile-cps.scm: Remove hack to avoid importing let-gensyms from (language tree-il).
108 lines
4.6 KiB
Scheme
108 lines
4.6 KiB
Scheme
;;; Continuation-passing style (CPS) intermediate language (IL)
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;; Copyright (C) 2013, 2014 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 (srfi srfi-26)
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#:use-module (language cps)
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#:use-module (language cps dfg)
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#:export (elide-values))
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(define (elide-values* fun)
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(let ((conts (build-local-cont-table
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(match fun (($ $fun src meta free body) body)))))
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(define (visit-cont cont)
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(rewrite-cps-cont cont
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(($ $cont sym ($ $kargs names syms body))
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(sym ($kargs names syms ,(visit-term body))))
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(($ $cont sym ($ $kentry self tail clauses))
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(sym ($kentry self ,tail ,(map visit-cont clauses))))
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(($ $cont sym ($ $kclause arity body))
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(sym ($kclause ,arity ,(visit-cont body))))
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(($ $cont)
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,cont)))
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(define (visit-term term)
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(rewrite-cps-term term
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(($ $letk conts body)
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($letk ,(map visit-cont conts)
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,(visit-term body)))
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(($ $letrec names syms funs body)
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($letrec names syms (map elide-values* funs)
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,(visit-term body)))
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(($ $continue k src ($ $primcall 'values vals))
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,(rewrite-cps-term (lookup-cont k conts)
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(($ $ktail)
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($continue k src ($values vals)))
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(($ $kreceive ($ $arity req () rest () #f) kargs)
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,(cond
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((and (not rest) (= (length vals) (length req)))
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(build-cps-term
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($continue kargs src ($values vals))))
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((and rest (>= (length vals) (length req)))
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(let-fresh (krest) (rest)
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(let ((vals* (append (list-head vals (length req))
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(list rest))))
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(build-cps-term
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($letk ((krest ($kargs ('rest) (rest)
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($continue kargs src
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($values vals*)))))
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,(let lp ((tail (list-tail vals (length req)))
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(k krest))
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(match tail
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(()
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(build-cps-term ($continue k src
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($const '()))))
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((v . tail)
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(let-fresh (krest) (rest)
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(build-cps-term
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($letk ((krest ($kargs ('rest) (rest)
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($continue k src
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($primcall 'cons
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(v rest))))))
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,(lp tail krest))))))))))))
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(else term)))
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(($ $kargs args)
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,(if (< (length vals) (length args))
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term
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(let ((vals (list-head vals (length args))))
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(build-cps-term
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($continue k src ($values vals))))))))
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(($ $continue k src (and fun ($ $fun)))
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($continue k src ,(elide-values* fun)))
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(($ $continue)
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,term)))
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(rewrite-cps-exp fun
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(($ $fun src meta free body)
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($fun src meta free ,(visit-cont body))))))
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(define (elide-values fun)
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(with-fresh-name-state fun
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(elide-values* fun)))
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