1 ;;; Continuation-passing style (CPS) intermediate language (IL)
3 ;; Copyright (C) 2013 Free Software Foundation, Inc.
5 ;;;; This library is free software; you can redistribute it and/or
6 ;;;; modify it under the terms of the GNU Lesser General Public
7 ;;;; License as published by the Free Software Foundation; either
8 ;;;; version 3 of the License, or (at your option) any later version.
10 ;;;; This library is distributed in the hope that it will be useful,
11 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
12 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ;;;; Lesser General Public License for more details.
15 ;;;; You should have received a copy of the GNU Lesser General Public
16 ;;;; License along with this library; if not, write to the Free Software
17 ;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 ;;; A pass to adapt expressions to the arities of their continuations,
22 ;;; and to rewrite some tail expressions as primcalls to "return".
26 (define-module (language cps arities)
27 #:use-module (ice-9 match)
28 #:use-module ((srfi srfi-1) #:select (fold))
29 #:use-module (srfi srfi-26)
30 #:use-module (language cps)
31 #:use-module (language cps dfg)
32 #:use-module (language cps primitives)
33 #:export (fix-arities))
35 (define (fix-clause-arities clause)
36 (let ((conts (build-local-cont-table clause))
38 (($ $cont _ _ ($ $kentry _ ($ $cont ktail) _)) ktail))))
39 (define (visit-term term)
40 (rewrite-cps-term term
42 ($letk ,(map visit-cont conts) ,(visit-term body)))
43 (($ $letrec names syms funs body)
44 ($letrec names syms (map fix-arities funs) ,(visit-term body)))
48 (define (adapt-exp nvals k exp)
51 (rewrite-cps-term (lookup-cont k conts)
53 ,(let-gensyms (kvoid kunspec unspec)
55 ($letk* ((kunspec #f ($kargs (unspec) (unspec)
57 ($primcall 'return (unspec)))))
58 (kvoid #f ($kargs () ()
59 ($continue kunspec ($void)))))
60 ($continue kvoid ,exp)))))
61 (($ $ktrunc arity kargs)
62 ,(rewrite-cps-term arity
63 (($ $arity () () #f () #f)
64 ($continue kargs ,exp))
66 ,(let-gensyms (kvoid kvalues void)
68 ($letk* ((kvalues #f ($kargs ('void) (void)
70 ($primcall 'values (void)))))
71 (kvoid #f ($kargs () ()
74 ($continue kvoid ,exp)))))))
80 ($letk ((k* #f ($kargs () () ($continue k ($void)))))
81 ($continue k* ,exp)))))))
83 (rewrite-cps-term (lookup-cont k conts)
85 ,(rewrite-cps-term exp
87 ($continue ktail ($primcall 'return (sym))))
91 ($letk ((k* #f ($kargs (v) (v)
93 ($primcall 'return (v))))))
94 ($continue k* ,exp)))))))
95 (($ $ktrunc arity kargs)
96 ,(rewrite-cps-term arity
97 (($ $arity (_) () #f () #f)
98 ($continue kargs ,exp))
100 ,(let-gensyms (kvalues value)
102 ($letk ((kvalues #f ($kargs ('value) (value)
104 ($primcall 'values (value))))))
105 ($continue kvalues ,exp)))))))
107 ,(let-gensyms (k* drop)
109 ($letk ((k* #f ($kargs ('drop) (drop)
110 ($continue k ($values ())))))
111 ($continue k* ,exp)))))
113 ($continue k ,exp))))))
115 (define (visit-exp k exp)
116 (rewrite-cps-term exp
121 ,(adapt-exp 1 k exp))
123 ,(adapt-exp 1 k (fix-arities exp)))
125 ;; In general, calls have unknown return arity. For that
126 ;; reason every non-tail call has an implicit adaptor
127 ;; continuation to adapt the return to the target
128 ;; continuation, and we don't need to do any adapting here.
130 (($ $primcall 'return (arg))
131 ;; Primcalls to return are in tail position.
132 ($continue ktail ,exp))
133 (($ $primcall (? (lambda (name)
134 (and (not (prim-rtl-instruction name))
135 (not (branching-primitive? name))))))
137 (($ $primcall name args)
138 ,(match (prim-arity name)
140 (if (= in (length args))
141 (adapt-exp out k exp)
144 ($letk ((k* #f ($kargs ('prim) (p*)
145 ($continue k ($call p* args)))))
146 ($continue k* ($prim name)))))))))
148 ;; Values nodes are inserted by CPS optimization passes, so
149 ;; we assume they are correct.
152 ($continue k ,exp))))
154 (define (visit-cont cont)
155 (rewrite-cps-cont cont
156 (($ $cont sym src ($ $kargs names syms body))
157 (sym src ($kargs names syms ,(visit-term body))))
158 (($ $cont sym src ($ $kclause arity body))
159 (sym src ($kclause ,arity ,(visit-cont body))))
163 (rewrite-cps-cont clause
164 (($ $cont sym src ($ $kentry self tail clauses))
165 (sym src ($kentry self ,tail ,(map visit-cont clauses)))))))
167 (define (fix-arities fun)
169 (($ $fun meta free body)
170 ($fun meta free ,(fix-clause-arities body)))))