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;;; Continuation-passing style (CPS) intermediate language (IL)
;; Copyright (C) 2015 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
;;; Commentary:
;;;
;;; Some arithmetic operations have multiple implementations: one
;;; polymorphic implementation that works on all kinds of numbers, like
;;; `add', and one or more specialized variants for unboxed numbers of
;;; some kind, like `fadd'. If we can replace a polymorphic
;;; implementation with a monomorphic implementation, we should do so --
;;; it will speed up the runtime and avoid boxing numbers.
;;;
;;; A polymorphic operation can be specialized if its result is
;;; specialized. To specialize an operation, we manually unbox its
;;; arguments and box its return value, relying on CSE to remove boxes
;;; where possible.
;;;
;;; Code:
(define-module (language cps specialize-numbers)
#:use-module (ice-9 match)
#:use-module (language cps)
#:use-module (language cps intmap)
#:use-module (language cps renumber)
#:use-module (language cps types)
#:use-module (language cps utils)
#:use-module (language cps with-cps)
#:export (specialize-numbers))
(define (specialize-f64-binop cps k src op a b)
(let ((fop (match op
('add 'fadd)
('sub 'fsub)
('mul 'fmul)
('div 'fdiv))))
(with-cps cps
(letv f64-a f64-b result)
(letk kbox ($kargs ('result) (result)
($continue k src
($primcall 'f64->scm (result)))))
(letk kop ($kargs ('f64-b) (f64-b)
($continue kbox src
($primcall fop (f64-a f64-b)))))
(letk kunbox-b ($kargs ('f64-a) (f64-a)
($continue kop src
($primcall 'scm->f64 (b)))))
(build-term
($continue kunbox-b src
($primcall 'scm->f64 (a)))))))
(define (specialize-numbers cps)
(define (visit-cont label cont cps types)
(match cont
(($ $kfun)
(values cps (infer-types cps label)))
(($ $kargs names vars
($ $continue k src
($ $primcall (and op (or 'add 'sub 'mul 'div)) (a b))))
(match (intmap-ref cps k)
(($ $kargs (_) (result))
(call-with-values (lambda ()
(lookup-post-type types label result 0))
(lambda (type min max)
(values
(if (eqv? type &flonum)
(with-cps cps
(let$ body (specialize-f64-binop k src op a b))
(setk label ($kargs names vars ,body)))
cps)
types))))))
(_ (values cps types))))
;; Type inference wants a renumbered graph; OK.
(let ((cps (renumber cps)))
(with-fresh-name-state cps
(values (intmap-fold visit-cont cps cps #f)))))
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