mirror/guile
mirror/guile
1
Fork 0
mirror of https://git.savannah.gnu.org/git/guile.git synced 2025-05-27 23:40:24 +02:00
Code Activity

Simplification renumbers instead of local prune-continuation pass

Browse source 
* module/language/cps/simplify.scm (simplify): Use renumbering instead
  of rolling our own prune-continuations pass.
This commit is contained in:
Andy Wingo 2014-04-01 15:56:45 +02:00
parent 7c4977e699
commit c79c02d694
1 changed files with 4 additions and 51 deletions
Download patch file Download diff file Expand all files Collapse all files

55
module/language/cps/simplify.scm
View file

@ -30,58 +30,9 @@
#:use-module (srfi srfi-26)
#:use-module (language cps)
#:use-module (language cps dfg)
#:use-module (language cps renumber)
#:export (simplify))
;; Currently we just try to bypass all $values nodes that we can. This
;; is eta-reduction on continuations. Then we prune unused
;; continuations. Note that this pruning is just a quick clean-up; for
;; a real fixed-point pass that can eliminate unused loops, the
;; dead-code elimination pass is there for you. But DCE introduces new
;; nullary $values nodes (as replacements for expressions whose values
;; aren't used), making it useful for this pass to include its own
;; little pruner.
(define* (prune-continuations fun #:optional (dfg (compute-dfg fun)))
(let ((cfa (analyze-control-flow fun dfg)))
(define (must-visit-cont cont)
(or (visit-cont cont)
(error "cont must be reachable" cont)))
(define (visit-cont cont)
(match cont
(($ $cont sym cont)
(and (cfa-k-idx cfa sym #:default (lambda (k) #f))
(rewrite-cps-cont cont
(($ $kargs names syms body)
(sym ($kargs names syms ,(visit-term body))))
(($ $kentry self tail clause)
(sym ($kentry self ,tail ,(and clause (visit-cont clause)))))
(($ $kclause arity body alternate)
(sym ($kclause ,arity ,(must-visit-cont body)
,(and alternate (visit-cont alternate)))))
((or ($ $kreceive) ($ $kif))
(sym ,cont)))))))
(define (visit-conts conts)
(filter-map visit-cont conts))
(define (visit-term term)
(match term
(($ $letk conts body)
(let ((body (visit-term body)))
(match (visit-conts conts)
(() body)
(conts (build-cps-term ($letk ,conts ,body))))))
(($ $letrec names syms funs body)
(build-cps-term
($letrec names syms (map (cut prune-continuations <> dfg) funs)
,(visit-term body))))
(($ $continue k src (and fun ($ $fun)))
(build-cps-term
($continue k src ,(prune-continuations fun dfg))))
(($ $continue k src exp)
term)))
(rewrite-cps-exp fun
(($ $fun src meta free body)
($fun src meta free ,(must-visit-cont body))))))
(define (compute-eta-reductions fun)
(let ((table (make-hash-table)))
(define (visit-cont cont)
@ -283,4 +234,6 @@
(visit-fun fun)))
(define (simplify fun)
(prune-continuations (eta-reduce (beta-reduce fun))))
;; Renumbering prunes continuations that are made unreachable by
;; eta/beta reductions.
(renumber (eta-reduce (beta-reduce fun))))