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3652769585
* module/language/cps.scm ($kreceive): Rename from ktrunc. * module/language/cps/arities.scm: * module/language/cps/compile-bytecode.scm: * module/language/cps/dce.scm: * module/language/cps/dfg.scm: * module/language/cps/effects-analysis.scm: * module/language/cps/elide-values.scm: * module/language/cps/simplify.scm: * module/language/cps/slot-allocation.scm: * module/language/cps/verify.scm: * module/language/tree-il/compile-cps.scm: Adapt all users.
467 lines
16 KiB
Scheme
467 lines
16 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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;;; This is the continuation-passing style (CPS) intermediate language
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;;; (IL) for Guile.
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;;;
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;;; There are two kinds of terms in CPS: terms that bind continuations,
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;;; and terms that call continuations.
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;;;
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;;; $letk binds a set of mutually recursive continuations, each one an
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;;; instance of $cont. A $cont declares the name of a continuation, and
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;;; then contains as a subterm the particular continuation instance:
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;;; $kif for test continuations, $kargs for continuations that bind
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;;; values, etc.
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;;;
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;;; $continue nodes call continuations. The expression contained in the
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;;; $continue node determines the value or values that are passed to the
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;;; target continuation: $const to pass a constant value, $values to
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;;; pass multiple named values, etc. $continue nodes also record the source at which
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;;;
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;;; Additionally there is $letrec, a term that binds mutually recursive
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;;; functions. The contification pass will turn $letrec into $letk if
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;;; it can do so. Otherwise, the closure conversion pass will desugar
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;;; $letrec into an equivalent sequence of make-closure primcalls and
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;;; subsequent initializations of the captured variables of the
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;;; closures. You can think of $letrec as pertaining to "high CPS",
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;;; whereas later passes will only see "low CPS", which does not have
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;;; $letrec.
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;;;
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;;; This particular formulation of CPS was inspired by Andrew Kennedy's
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;;; 2007 paper, "Compiling with Continuations, Continued". All Guile
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;;; hackers should read that excellent paper! As in Kennedy's paper,
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;;; continuations are second-class, and may be thought of as basic block
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;;; labels. All values are bound to variables using continuation calls:
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;;; even constants!
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;;;
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;;; There are some Guile-specific quirks as well:
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;;;
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;;; - $kreceive represents a continuation that receives multiple values,
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;;; but which truncates them to some number of required values,
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;;; possibly with a rest list.
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;;;
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;;; - $kentry labels an entry point for a $fun (a function), and
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;;; contains a $ktail representing the formal argument which is the
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;;; function's continuation.
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;;;
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;;; - $kentry also contains $kclause continuations, corresponding to
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;;; the case-lambda clauses of the function. $kclause actually
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;;; contains the clause body. This is because the $kclause
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;;; logically matches or doesn't match a given set of actual
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;;; arguments against a formal arity, then proceeds to a "body"
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;;; continuation (which is a $kargs).
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;;;
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;;; That's to say that a $fun can be matched like this:
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;;;
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;;; (match f
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;;; (($ $fun src meta free
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;;; ($ $cont kentry
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;;; ($ $kentry self ($ $cont ktail _ ($ $ktail))
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;;; (($ $kclause arity
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;;; ($ $cont kbody _ ($ $kargs names syms body)))
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;;; ...))))
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;;; #t))
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;;;
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;;; A $continue to ktail is in tail position. $kentry, $kclause,
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;;; and $ktail will never be seen elsewhere in a CPS term.
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;;;
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;;; - $prompt continues to the body of the prompt, having pushed on a
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;;; prompt whose handler will continue at its "handler"
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;;; continuation. The continuation of the prompt is responsible for
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;;; popping the prompt.
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;;;
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;;; In summary:
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;;;
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;;; - $letk, $letrec, and $continue are terms.
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;;;
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;;; - $cont is a continuation, containing a continuation body ($kargs,
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;;; $kif, etc).
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;;;
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;;; - $continue terms contain an expression ($call, $const, $fun,
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;;; etc).
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;;;
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;;; See (language tree-il compile-cps) for details on how Tree-IL
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;;; converts to CPS.
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;;;
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;;; Code:
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(define-module (language cps)
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#:use-module (ice-9 match)
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#:use-module ((srfi srfi-1) #:select (fold))
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#:use-module (srfi srfi-9)
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#:use-module (srfi srfi-9 gnu)
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#:export (;; Helper.
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$arity
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make-$arity
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;; Terms.
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$letk $continue $letrec
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;; Continuations.
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$cont
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;; Continuation bodies.
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$kif $kreceive $kargs $kentry $ktail $kclause
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;; Expressions.
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$void $const $prim $fun $call $primcall $values $prompt
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;; Building macros.
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let-gensyms
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build-cps-term build-cps-cont build-cps-exp
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rewrite-cps-term rewrite-cps-cont rewrite-cps-exp
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;; Misc.
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parse-cps unparse-cps
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fold-conts fold-local-conts))
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;; FIXME: Use SRFI-99, when Guile adds it.
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(define-syntax define-record-type*
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(lambda (x)
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(define (id-append ctx . syms)
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(datum->syntax ctx (apply symbol-append (map syntax->datum syms))))
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(syntax-case x ()
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((_ name field ...)
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(and (identifier? #'name) (and-map identifier? #'(field ...)))
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(with-syntax ((cons (id-append #'name #'make- #'name))
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(pred (id-append #'name #'name #'?))
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((getter ...) (map (lambda (f)
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(id-append f #'name #'- f))
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#'(field ...))))
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#'(define-record-type name
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(cons field ...)
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pred
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(field getter)
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...))))))
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(define-syntax-rule (define-cps-type name field ...)
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(begin
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(define-record-type* name field ...)
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(set-record-type-printer! name print-cps)))
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(define (print-cps exp port)
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(format port "#<cps ~S>" (unparse-cps exp)))
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;; Helper.
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(define-record-type* $arity req opt rest kw allow-other-keys?)
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;; Terms.
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(define-cps-type $letk conts body)
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(define-cps-type $continue k src exp)
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(define-cps-type $letrec names syms funs body)
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;; Continuations
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(define-cps-type $cont k cont)
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(define-cps-type $kif kt kf)
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(define-cps-type $kreceive arity k)
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(define-cps-type $kargs names syms body)
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(define-cps-type $kentry self tail clauses)
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(define-cps-type $ktail)
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(define-cps-type $kclause arity cont)
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;; Expressions.
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(define-cps-type $void)
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(define-cps-type $const val)
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(define-cps-type $prim name)
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(define-cps-type $fun src meta free body)
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(define-cps-type $call proc args)
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(define-cps-type $primcall name args)
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(define-cps-type $values args)
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(define-cps-type $prompt escape? tag handler)
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(define-syntax let-gensyms
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(syntax-rules ()
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((_ (sym ...) body body* ...)
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(let ((sym (gensym (symbol->string 'sym))) ...)
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body body* ...))))
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(define-syntax build-arity
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(syntax-rules (unquote)
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((_ (unquote exp)) exp)
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((_ (req opt rest kw allow-other-keys?))
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(make-$arity req opt rest kw allow-other-keys?))))
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(define-syntax build-cont-body
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(syntax-rules (unquote $kif $kreceive $kargs $kentry $ktail $kclause)
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((_ (unquote exp))
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exp)
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((_ ($kif kt kf))
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(make-$kif kt kf))
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((_ ($kreceive req rest kargs))
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(make-$kreceive (make-$arity req '() rest '() #f) kargs))
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((_ ($kargs (name ...) (sym ...) body))
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(make-$kargs (list name ...) (list sym ...) (build-cps-term body)))
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((_ ($kargs names syms body))
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(make-$kargs names syms (build-cps-term body)))
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((_ ($kentry self tail (unquote clauses)))
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(make-$kentry self (build-cps-cont tail) clauses))
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((_ ($kentry self tail (clause ...)))
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(make-$kentry self (build-cps-cont tail) (list (build-cps-cont clause) ...)))
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((_ ($ktail))
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(make-$ktail))
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((_ ($kclause arity cont))
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(make-$kclause (build-arity arity) (build-cps-cont cont)))))
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(define-syntax build-cps-cont
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(syntax-rules (unquote)
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((_ (unquote exp)) exp)
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((_ (k cont)) (make-$cont k (build-cont-body cont)))))
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(define-syntax build-cps-exp
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(syntax-rules (unquote
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$void $const $prim $fun $call $primcall $values $prompt)
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((_ (unquote exp)) exp)
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((_ ($void)) (make-$void))
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((_ ($const val)) (make-$const val))
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((_ ($prim name)) (make-$prim name))
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((_ ($fun src meta free body))
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(make-$fun src meta free (build-cps-cont body)))
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((_ ($call proc (arg ...))) (make-$call proc (list arg ...)))
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((_ ($call proc args)) (make-$call proc args))
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((_ ($primcall name (arg ...))) (make-$primcall name (list arg ...)))
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((_ ($primcall name args)) (make-$primcall name args))
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((_ ($values (arg ...))) (make-$values (list arg ...)))
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((_ ($values args)) (make-$values args))
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((_ ($prompt escape? tag handler))
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(make-$prompt escape? tag handler))))
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(define-syntax build-cps-term
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(syntax-rules (unquote $letk $letk* $letconst $letrec $continue)
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((_ (unquote exp))
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exp)
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((_ ($letk (unquote conts) body))
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(make-$letk conts (build-cps-term body)))
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((_ ($letk (cont ...) body))
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(make-$letk (list (build-cps-cont cont) ...)
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(build-cps-term body)))
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((_ ($letk* () body))
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(build-cps-term body))
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((_ ($letk* (cont conts ...) body))
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(build-cps-term ($letk (cont) ($letk* (conts ...) body))))
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((_ ($letconst () body))
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(build-cps-term body))
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((_ ($letconst ((name sym val) tail ...) body))
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(let-gensyms (kconst)
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(build-cps-term
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($letk ((kconst ($kargs (name) (sym) ($letconst (tail ...) body))))
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($continue kconst (let ((props (source-properties val)))
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(and (pair? props) props))
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($const val))))))
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((_ ($letrec names gensyms funs body))
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(make-$letrec names gensyms funs (build-cps-term body)))
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((_ ($continue k src exp))
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(make-$continue k src (build-cps-exp exp)))))
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(define-syntax-rule (rewrite-cps-term x (pat body) ...)
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(match x
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(pat (build-cps-term body)) ...))
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(define-syntax-rule (rewrite-cps-cont x (pat body) ...)
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(match x
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(pat (build-cps-cont body)) ...))
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(define-syntax-rule (rewrite-cps-exp x (pat body) ...)
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(match x
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(pat (build-cps-exp body)) ...))
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(define (parse-cps exp)
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(define (src exp)
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(let ((props (source-properties exp)))
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(and (pair? props) props)))
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(match exp
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;; Continuations.
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(('letconst k (name sym c) body)
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(build-cps-term
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($letk ((k ($kargs (name) (sym)
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,(parse-cps body))))
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($continue k (src exp) ($const c)))))
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(('let k (name sym val) body)
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(build-cps-term
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($letk ((k ($kargs (name) (sym)
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,(parse-cps body))))
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,(parse-cps val))))
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(('letk (cont ...) body)
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(build-cps-term
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($letk ,(map parse-cps cont) ,(parse-cps body))))
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(('k sym body)
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(build-cps-cont
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(sym ,(parse-cps body))))
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(('kif kt kf)
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(build-cont-body ($kif kt kf)))
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(('kreceive req rest k)
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(build-cont-body ($kreceive req rest k)))
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(('kargs names syms body)
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(build-cont-body ($kargs names syms ,(parse-cps body))))
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(('kentry self tail clauses)
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(build-cont-body
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($kentry self ,(parse-cps tail) ,(map parse-cps clauses))))
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(('ktail)
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(build-cont-body
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($ktail)))
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(('kclause (req opt rest kw allow-other-keys?) body)
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(build-cont-body
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($kclause (req opt rest kw allow-other-keys?)
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,(parse-cps body))))
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(('kseq body)
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(build-cont-body ($kargs () () ,(parse-cps body))))
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;; Calls.
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(('continue k exp)
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(build-cps-term ($continue k (src exp) ,(parse-cps exp))))
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(('void)
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(build-cps-exp ($void)))
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(('const exp)
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(build-cps-exp ($const exp)))
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(('prim name)
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(build-cps-exp ($prim name)))
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(('fun meta free body)
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(build-cps-exp ($fun (src exp) meta free ,(parse-cps body))))
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(('letrec ((name sym fun) ...) body)
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(build-cps-term
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($letrec name sym (map parse-cps fun) ,(parse-cps body))))
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(('call proc arg ...)
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(build-cps-exp ($call proc arg)))
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(('primcall name arg ...)
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(build-cps-exp ($primcall name arg)))
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(('values arg ...)
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(build-cps-exp ($values arg)))
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(('prompt escape? tag handler)
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(build-cps-exp ($prompt escape? tag handler)))
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(_
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(error "unexpected cps" exp))))
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(define (unparse-cps exp)
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(match exp
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;; Continuations.
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(($ $letk (($ $cont k ($ $kargs (name) (sym) body)))
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($ $continue k src ($ $const c)))
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`(letconst ,k (,name ,sym ,c)
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,(unparse-cps body)))
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(($ $letk (($ $cont k ($ $kargs (name) (sym) body))) val)
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`(let ,k (,name ,sym ,(unparse-cps val))
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,(unparse-cps body)))
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(($ $letk conts body)
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`(letk ,(map unparse-cps conts) ,(unparse-cps body)))
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(($ $cont sym body)
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`(k ,sym ,(unparse-cps body)))
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(($ $kif kt kf)
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`(kif ,kt ,kf))
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(($ $kreceive ($ $arity req () rest '() #f) k)
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`(kreceive ,req ,rest ,k))
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(($ $kargs () () body)
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`(kseq ,(unparse-cps body)))
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(($ $kargs names syms body)
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`(kargs ,names ,syms ,(unparse-cps body)))
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(($ $kentry self tail clauses)
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`(kentry ,self ,(unparse-cps tail) ,(map unparse-cps clauses)))
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(($ $ktail)
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`(ktail))
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(($ $kclause ($ $arity req opt rest kw allow-other-keys?) body)
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`(kclause (,req ,opt ,rest ,kw ,allow-other-keys?) ,(unparse-cps body)))
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;; Calls.
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(($ $continue k src exp)
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`(continue ,k ,(unparse-cps exp)))
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(($ $void)
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`(void))
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(($ $const val)
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`(const ,val))
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(($ $prim name)
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`(prim ,name))
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(($ $fun src meta free body)
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`(fun ,meta ,free ,(unparse-cps body)))
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(($ $letrec names syms funs body)
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`(letrec ,(map (lambda (name sym fun)
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(list name sym (unparse-cps fun)))
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names syms funs)
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,(unparse-cps body)))
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(($ $call proc args)
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`(call ,proc ,@args))
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(($ $primcall name args)
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`(primcall ,name ,@args))
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(($ $values args)
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`(values ,@args))
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(($ $prompt escape? tag handler)
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`(prompt ,escape? ,tag ,handler))
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(_
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(error "unexpected cps" exp))))
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(define (fold-conts proc seed fun)
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(define (cont-folder cont seed)
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(match cont
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(($ $cont k cont)
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(let ((seed (proc k cont seed)))
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(match cont
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(($ $kargs names syms body)
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(term-folder body seed))
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(($ $kentry self tail clauses)
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(fold cont-folder (cont-folder tail seed) clauses))
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(($ $kclause arity body)
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(cont-folder body seed))
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(_ seed))))))
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(define (fun-folder fun seed)
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(match fun
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(($ $fun src meta free body)
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(cont-folder body seed))))
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(define (term-folder term seed)
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(match term
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(($ $letk conts body)
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(fold cont-folder (term-folder body seed) conts))
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(($ $continue k src exp)
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(match exp
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(($ $fun) (fun-folder exp seed))
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(_ seed)))
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(($ $letrec names syms funs body)
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(fold fun-folder (term-folder body seed) funs))))
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(fun-folder fun seed))
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(define (fold-local-conts proc seed cont)
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(define (cont-folder cont seed)
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(match cont
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(($ $cont k cont)
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(let ((seed (proc k cont seed)))
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(match cont
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(($ $kargs names syms body)
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(term-folder body seed))
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(($ $kentry self tail clauses)
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(fold cont-folder (cont-folder tail seed) clauses))
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(($ $kclause arity body)
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(cont-folder body seed))
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|
|
|
(_ seed))))))
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|
|
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(define (term-folder term seed)
|
|
(match term
|
|
(($ $letk conts body)
|
|
(fold cont-folder (term-folder body seed) conts))
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|
|
|
(($ $continue) seed)
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|
|
|
(($ $letrec names syms funs body) (term-folder body seed))))
|
|
|
|
(cont-folder cont seed))
|