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guile/module/language/cps/optimize.scm
Andy Wingo ee85e2969f Rotate comparisons down to loop back-edges
* module/language/cps/rotate-loops.scm: New pass.
* module/Makefile.am:
* module/language/cps/optimize.scm: Wire up the new pass.
2015-07-24 16:51:04 +02:00

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;;; Continuation-passing style (CPS) intermediate language (IL)
;; Copyright (C) 2013, 2014, 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:
;;;
;;; Optimizations on CPS.
;;;
;;; Code:
(define-module (language cps optimize)
#:use-module (ice-9 match)
#:use-module (language cps constructors)
#:use-module (language cps contification)
#:use-module (language cps cse)
#:use-module (language cps dce)
#:use-module (language cps elide-values)
#:use-module (language cps licm)
#:use-module (language cps prune-top-level-scopes)
#:use-module (language cps prune-bailouts)
#:use-module (language cps rotate-loops)
#:use-module (language cps self-references)
#:use-module (language cps simplify)
#:use-module (language cps specialize-primcalls)
#:use-module (language cps split-rec)
#:use-module (language cps type-fold)
#:use-module (language cps verify)
#:export (optimize-higher-order-cps
optimize-first-order-cps))
(define (kw-arg-ref args kw default)
(match (memq kw args)
((_ val . _) val)
(_ default)))
(define *debug?* #f)
(define (maybe-verify program)
(if *debug?*
(verify program)
program))
(define-syntax-rule (define-optimizer optimize (pass kw default) ...)
(define* (optimize program #:optional (opts '()))
;; This series of assignments to `program' used to be a series of
;; let* bindings of `program', as you would imagine. In compiled
;; code this is fine because the compiler is able to allocate all
;; let*-bound variable to the same slot, which also means that the
;; garbage collector doesn't have to retain so many copies of the
;; term being optimized. However during bootstrap, the interpreter
;; doesn't do this optimization, leading to excessive data retention
;; as the terms are rewritten. To marginally improve bootstrap
;; memory usage, here we use set! instead. The compiler should
;; produce the same code in any case, though currently it does not
;; because it doesn't do escape analysis on the box created for the
;; set!.
(maybe-verify program)
(set! program
(if (kw-arg-ref opts kw default)
(maybe-verify (pass program))
program))
...
(verify program)
program))
;; Passes that are needed:
;;
;; * Abort contification: turning abort primcalls into continuation
;; calls, and eliding prompts if possible.
;;
;; * Loop peeling. Unrolls the first round through a loop if the
;; loop has effects that CSE can work on. Requires effects
;; analysis. When run before CSE, loop peeling is the equivalent
;; of loop-invariant code motion (LICM).
;;
(define-optimizer optimize-higher-order-cps
(split-rec #:split-rec? #t)
(eliminate-dead-code #:eliminate-dead-code? #t)
(prune-top-level-scopes #:prune-top-level-scopes? #t)
(simplify #:simplify? #t)
(contify #:contify? #t)
(inline-constructors #:inline-constructors? #t)
(specialize-primcalls #:specialize-primcalls? #t)
(elide-values #:elide-values? #t)
(prune-bailouts #:prune-bailouts? #t)
(hoist-loop-invariant-code #:licm? #t)
(eliminate-common-subexpressions #:cse? #t)
(type-fold #:type-fold? #t)
(resolve-self-references #:resolve-self-references? #t)
(eliminate-dead-code #:eliminate-dead-code? #t)
(simplify #:simplify? #t))
(define-optimizer optimize-first-order-cps
(eliminate-dead-code #:eliminate-dead-code? #t)
(rotate-loops #:rotate-loops? #t)
(simplify #:simplify? #t))