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cf10678f AW |
1 | ;;; TREE-IL -> GLIL compiler |
2 | ||
3 | ;; Copyright (C) 2001,2008,2009 Free Software Foundation, Inc. | |
4 | ||
53befeb7 NJ |
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. | |
9 | ;;;; | |
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. | |
14 | ;;;; | |
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 | |
cf10678f AW |
18 | |
19 | ;;; Code: | |
20 | ||
21 | (define-module (language tree-il analyze) | |
66d3e9a3 | 22 | #:use-module (srfi srfi-1) |
4b856371 | 23 | #:use-module (srfi srfi-9) |
cf10678f | 24 | #:use-module (system base syntax) |
4b856371 | 25 | #:use-module (system base message) |
cf10678f | 26 | #:use-module (language tree-il) |
4b856371 LC |
27 | #:export (analyze-lexicals |
28 | report-unused-variables)) | |
cf10678f | 29 | |
66d3e9a3 AW |
30 | ;; Allocation is the process of assigning storage locations for lexical |
31 | ;; variables. A lexical variable has a distinct "address", or storage | |
32 | ;; location, for each procedure in which it is referenced. | |
33 | ;; | |
34 | ;; A variable is "local", i.e., allocated on the stack, if it is | |
35 | ;; referenced from within the procedure that defined it. Otherwise it is | |
36 | ;; a "closure" variable. For example: | |
37 | ;; | |
38 | ;; (lambda (a) a) ; a will be local | |
39 | ;; `a' is local to the procedure. | |
40 | ;; | |
41 | ;; (lambda (a) (lambda () a)) | |
42 | ;; `a' is local to the outer procedure, but a closure variable with | |
43 | ;; respect to the inner procedure. | |
44 | ;; | |
45 | ;; If a variable is ever assigned, it needs to be heap-allocated | |
46 | ;; ("boxed"). This is so that closures and continuations capture the | |
47 | ;; variable's identity, not just one of the values it may have over the | |
48 | ;; course of program execution. If the variable is never assigned, there | |
49 | ;; is no distinction between value and identity, so closing over its | |
50 | ;; identity (whether through closures or continuations) can make a copy | |
51 | ;; of its value instead. | |
52 | ;; | |
53 | ;; Local variables are stored on the stack within a procedure's call | |
54 | ;; frame. Their index into the stack is determined from their linear | |
55 | ;; postion within a procedure's binding path: | |
cf10678f AW |
56 | ;; (let (0 1) |
57 | ;; (let (2 3) ...) | |
58 | ;; (let (2) ...)) | |
59 | ;; (let (2 3 4) ...)) | |
60 | ;; etc. | |
61 | ;; | |
5af166bd AW |
62 | ;; This algorithm has the problem that variables are only allocated |
63 | ;; indices at the end of the binding path. If variables bound early in | |
64 | ;; the path are not used in later portions of the path, their indices | |
65 | ;; will not be recycled. This problem is particularly egregious in the | |
66 | ;; expansion of `or': | |
67 | ;; | |
68 | ;; (or x y z) | |
69 | ;; -> (let ((a x)) (if a a (let ((b y)) (if b b z)))) | |
70 | ;; | |
71 | ;; As you can see, the `a' binding is only used in the ephemeral `then' | |
72 | ;; clause of the first `if', but its index would be reserved for the | |
73 | ;; whole of the `or' expansion. So we have a hack for this specific | |
74 | ;; case. A proper solution would be some sort of liveness analysis, and | |
75 | ;; not our linear allocation algorithm. | |
76 | ;; | |
66d3e9a3 AW |
77 | ;; Closure variables are captured when a closure is created, and stored |
78 | ;; in a vector. Each closure variable has a unique index into that | |
79 | ;; vector. | |
80 | ;; | |
9059993f AW |
81 | ;; There is one more complication. Procedures bound by <fix> may, in |
82 | ;; some cases, be rendered inline to their parent procedure. That is to | |
83 | ;; say, | |
84 | ;; | |
85 | ;; (letrec ((lp (lambda () (lp)))) (lp)) | |
86 | ;; => (fix ((lp (lambda () (lp)))) (lp)) | |
87 | ;; => goto FIX-BODY; LP: goto LP; FIX-BODY: goto LP; | |
88 | ;; ^ jump over the loop ^ the fixpoint lp ^ starting off the loop | |
89 | ;; | |
90 | ;; The upshot is that we don't have to allocate any space for the `lp' | |
91 | ;; closure at all, as it can be rendered inline as a loop. So there is | |
92 | ;; another kind of allocation, "label allocation", in which the | |
93 | ;; procedure is simply a label, placed at the start of the lambda body. | |
94 | ;; The label is the gensym under which the lambda expression is bound. | |
95 | ;; | |
96 | ;; The analyzer checks to see that the label is called with the correct | |
97 | ;; number of arguments. Calls to labels compile to rename + goto. | |
98 | ;; Lambda, the ultimate goto! | |
99 | ;; | |
66d3e9a3 AW |
100 | ;; |
101 | ;; The return value of `analyze-lexicals' is a hash table, the | |
102 | ;; "allocation". | |
103 | ;; | |
104 | ;; The allocation maps gensyms -- recall that each lexically bound | |
105 | ;; variable has a unique gensym -- to storage locations ("addresses"). | |
106 | ;; Since one gensym may have many storage locations, if it is referenced | |
107 | ;; in many procedures, it is a two-level map. | |
108 | ;; | |
109 | ;; The allocation also stored information on how many local variables | |
9059993f AW |
110 | ;; need to be allocated for each procedure, lexicals that have been |
111 | ;; translated into labels, and information on what free variables to | |
112 | ;; capture from its lexical parent procedure. | |
66d3e9a3 AW |
113 | ;; |
114 | ;; That is: | |
115 | ;; | |
116 | ;; sym -> {lambda -> address} | |
9059993f | 117 | ;; lambda -> (nlocs labels . free-locs) |
66d3e9a3 | 118 | ;; |
9059993f AW |
119 | ;; address ::= (local? boxed? . index) |
120 | ;; labels ::= ((sym . lambda-vars) ...) | |
66d3e9a3 AW |
121 | ;; free-locs ::= ((sym0 . address0) (sym1 . address1) ...) |
122 | ;; free variable addresses are relative to parent proc. | |
123 | ||
124 | (define (make-hashq k v) | |
125 | (let ((res (make-hash-table))) | |
126 | (hashq-set! res k v) | |
127 | res)) | |
cf10678f AW |
128 | |
129 | (define (analyze-lexicals x) | |
66d3e9a3 AW |
130 | ;; bound-vars: lambda -> (sym ...) |
131 | ;; all identifiers bound within a lambda | |
9059993f | 132 | (define bound-vars (make-hash-table)) |
66d3e9a3 AW |
133 | ;; free-vars: lambda -> (sym ...) |
134 | ;; all identifiers referenced in a lambda, but not bound | |
135 | ;; NB, this includes identifiers referenced by contained lambdas | |
9059993f | 136 | (define free-vars (make-hash-table)) |
66d3e9a3 AW |
137 | ;; assigned: sym -> #t |
138 | ;; variables that are assigned | |
d97b69d9 | 139 | (define assigned (make-hash-table)) |
5af166bd | 140 | ;; refcounts: sym -> count |
66d3e9a3 | 141 | ;; allows us to detect the or-expansion in O(1) time |
9059993f AW |
142 | (define refcounts (make-hash-table)) |
143 | ;; labels: sym -> lambda-vars | |
144 | ;; for determining if fixed-point procedures can be rendered as | |
145 | ;; labels. lambda-vars may be an improper list. | |
146 | (define labels (make-hash-table)) | |
147 | ||
66d3e9a3 | 148 | ;; returns variables referenced in expr |
d97b69d9 AW |
149 | (define (analyze! x proc labels-in-proc tail? tail-call-args) |
150 | (define (step y) (analyze! y proc labels-in-proc #f #f)) | |
151 | (define (step-tail y) (analyze! y proc labels-in-proc tail? #f)) | |
152 | (define (step-tail-call y args) (analyze! y proc labels-in-proc #f | |
153 | (and tail? args))) | |
154 | (define (recur/labels x new-proc labels) | |
155 | (analyze! x new-proc (append labels labels-in-proc) #t #f)) | |
156 | (define (recur x new-proc) (analyze! x new-proc '() tail? #f)) | |
cf10678f AW |
157 | (record-case x |
158 | ((<application> proc args) | |
d97b69d9 AW |
159 | (apply lset-union eq? (step-tail-call proc args) |
160 | (map step args))) | |
cf10678f AW |
161 | |
162 | ((<conditional> test then else) | |
d97b69d9 | 163 | (lset-union eq? (step test) (step-tail then) (step-tail else))) |
cf10678f AW |
164 | |
165 | ((<lexical-ref> name gensym) | |
5af166bd | 166 | (hashq-set! refcounts gensym (1+ (hashq-ref refcounts gensym 0))) |
d97b69d9 AW |
167 | (if (not (and tail-call-args |
168 | (memq gensym labels-in-proc) | |
169 | (let ((args (hashq-ref labels gensym))) | |
170 | (and (list? args) | |
171 | (= (length args) (length tail-call-args)))))) | |
172 | (hashq-set! labels gensym #f)) | |
66d3e9a3 | 173 | (list gensym)) |
cf10678f AW |
174 | |
175 | ((<lexical-set> name gensym exp) | |
66d3e9a3 | 176 | (hashq-set! assigned gensym #t) |
d97b69d9 | 177 | (hashq-set! labels gensym #f) |
66d3e9a3 | 178 | (lset-adjoin eq? (step exp) gensym)) |
cf10678f AW |
179 | |
180 | ((<module-set> mod name public? exp) | |
181 | (step exp)) | |
182 | ||
183 | ((<toplevel-set> name exp) | |
184 | (step exp)) | |
185 | ||
186 | ((<toplevel-define> name exp) | |
187 | (step exp)) | |
188 | ||
189 | ((<sequence> exps) | |
d97b69d9 AW |
190 | (let lp ((exps exps) (ret '())) |
191 | (cond ((null? exps) '()) | |
192 | ((null? (cdr exps)) | |
193 | (lset-union eq? ret (step-tail (car exps)))) | |
194 | (else | |
195 | (lp (cdr exps) (lset-union eq? ret (step (car exps)))))))) | |
cf10678f AW |
196 | |
197 | ((<lambda> vars meta body) | |
66d3e9a3 AW |
198 | (let ((locally-bound (let rev* ((vars vars) (out '())) |
199 | (cond ((null? vars) out) | |
200 | ((pair? vars) (rev* (cdr vars) | |
201 | (cons (car vars) out))) | |
202 | (else (cons vars out)))))) | |
203 | (hashq-set! bound-vars x locally-bound) | |
204 | (let* ((referenced (recur body x)) | |
205 | (free (lset-difference eq? referenced locally-bound)) | |
206 | (all-bound (reverse! (hashq-ref bound-vars x)))) | |
207 | (hashq-set! bound-vars x all-bound) | |
208 | (hashq-set! free-vars x free) | |
209 | free))) | |
210 | ||
f4aa8d53 | 211 | ((<let> vars vals body) |
66d3e9a3 AW |
212 | (hashq-set! bound-vars proc |
213 | (append (reverse vars) (hashq-ref bound-vars proc))) | |
214 | (lset-difference eq? | |
d97b69d9 | 215 | (apply lset-union eq? (step-tail body) (map step vals)) |
66d3e9a3 | 216 | vars)) |
cf10678f | 217 | |
f4aa8d53 | 218 | ((<letrec> vars vals body) |
66d3e9a3 AW |
219 | (hashq-set! bound-vars proc |
220 | (append (reverse vars) (hashq-ref bound-vars proc))) | |
221 | (for-each (lambda (sym) (hashq-set! assigned sym #t)) vars) | |
222 | (lset-difference eq? | |
d97b69d9 | 223 | (apply lset-union eq? (step-tail body) (map step vals)) |
66d3e9a3 AW |
224 | vars)) |
225 | ||
c21c89b1 | 226 | ((<fix> vars vals body) |
d97b69d9 AW |
227 | ;; Try to allocate these procedures as labels. |
228 | (for-each (lambda (sym val) (hashq-set! labels sym (lambda-vars val))) | |
229 | vars vals) | |
c21c89b1 AW |
230 | (hashq-set! bound-vars proc |
231 | (append (reverse vars) (hashq-ref bound-vars proc))) | |
d97b69d9 AW |
232 | ;; Step into subexpressions. |
233 | (let* ((var-refs | |
234 | (map | |
235 | ;; Since we're trying to label-allocate the lambda, | |
236 | ;; pretend it's not a closure, and just recurse into its | |
237 | ;; body directly. (Otherwise, recursing on a closure | |
238 | ;; that references one of the fix's bound vars would | |
239 | ;; prevent label allocation.) | |
240 | (lambda (x) | |
241 | (record-case x | |
242 | ((<lambda> (lvars vars) body) | |
243 | (let ((locally-bound | |
244 | (let rev* ((lvars lvars) (out '())) | |
245 | (cond ((null? lvars) out) | |
246 | ((pair? lvars) (rev* (cdr lvars) | |
247 | (cons (car lvars) out))) | |
248 | (else (cons lvars out)))))) | |
249 | (hashq-set! bound-vars x locally-bound) | |
250 | ;; recur/labels, the difference from the closure case | |
251 | (let* ((referenced (recur/labels body x vars)) | |
252 | (free (lset-difference eq? referenced locally-bound)) | |
253 | (all-bound (reverse! (hashq-ref bound-vars x)))) | |
254 | (hashq-set! bound-vars x all-bound) | |
255 | (hashq-set! free-vars x free) | |
256 | free))))) | |
257 | vals)) | |
258 | (vars-with-refs (map cons vars var-refs)) | |
259 | (body-refs (recur/labels body proc vars))) | |
260 | (define (delabel-dependents! sym) | |
261 | (let ((refs (assq-ref vars-with-refs sym))) | |
262 | (if refs | |
263 | (for-each (lambda (sym) | |
264 | (if (hashq-ref labels sym) | |
265 | (begin | |
266 | (hashq-set! labels sym #f) | |
267 | (delabel-dependents! sym)))) | |
268 | refs)))) | |
269 | ;; Stepping into the lambdas and the body might have made some | |
270 | ;; procedures not label-allocatable -- which might have | |
271 | ;; knock-on effects. For example: | |
272 | ;; (fix ((a (lambda () (b))) | |
273 | ;; (b (lambda () a))) | |
274 | ;; (a)) | |
275 | ;; As far as `a' is concerned, both `a' and `b' are | |
276 | ;; label-allocatable. But `b' references `a' not in a proc-tail | |
277 | ;; position, which makes `a' not label-allocatable. The | |
278 | ;; knock-on effect is that, when back-propagating this | |
279 | ;; information to `a', `b' will also become not | |
280 | ;; label-allocatable, as it is referenced within `a', which is | |
281 | ;; allocated as a closure. This is a transitive relationship. | |
282 | (for-each (lambda (sym) | |
283 | (if (not (hashq-ref labels sym)) | |
284 | (delabel-dependents! sym))) | |
285 | vars) | |
286 | ;; Now lift bound variables with label-allocated lambdas to the | |
287 | ;; parent procedure. | |
288 | (for-each | |
289 | (lambda (sym val) | |
290 | (if (hashq-ref labels sym) | |
291 | ;; Remove traces of the label-bound lambda. The free | |
292 | ;; vars will propagate up via the return val. | |
293 | (begin | |
294 | (hashq-set! bound-vars proc | |
295 | (append (hashq-ref bound-vars val) | |
296 | (hashq-ref bound-vars proc))) | |
297 | (hashq-remove! bound-vars val) | |
298 | (hashq-remove! free-vars val)))) | |
299 | vars vals) | |
300 | (lset-difference eq? | |
301 | (apply lset-union eq? body-refs var-refs) | |
302 | vars))) | |
c21c89b1 | 303 | |
f4aa8d53 | 304 | ((<let-values> vars exp body) |
bca488f1 AW |
305 | (let ((bound (let lp ((out (hashq-ref bound-vars proc)) (in vars)) |
306 | (if (pair? in) | |
307 | (lp (cons (car in) out) (cdr in)) | |
308 | (if (null? in) out (cons in out)))))) | |
309 | (hashq-set! bound-vars proc bound) | |
310 | (lset-difference eq? | |
d97b69d9 | 311 | (lset-union eq? (step exp) (step-tail body)) |
bca488f1 | 312 | bound))) |
66d3e9a3 AW |
313 | |
314 | (else '()))) | |
315 | ||
9059993f AW |
316 | ;; allocation: sym -> {lambda -> address} |
317 | ;; lambda -> (nlocs labels . free-locs) | |
318 | (define allocation (make-hash-table)) | |
319 | ||
66d3e9a3 AW |
320 | (define (allocate! x proc n) |
321 | (define (recur y) (allocate! y proc n)) | |
322 | (record-case x | |
323 | ((<application> proc args) | |
324 | (apply max (recur proc) (map recur args))) | |
cf10678f | 325 | |
66d3e9a3 AW |
326 | ((<conditional> test then else) |
327 | (max (recur test) (recur then) (recur else))) | |
cf10678f | 328 | |
66d3e9a3 AW |
329 | ((<lexical-set> name gensym exp) |
330 | (recur exp)) | |
331 | ||
332 | ((<module-set> mod name public? exp) | |
333 | (recur exp)) | |
334 | ||
335 | ((<toplevel-set> name exp) | |
336 | (recur exp)) | |
337 | ||
338 | ((<toplevel-define> name exp) | |
339 | (recur exp)) | |
340 | ||
341 | ((<sequence> exps) | |
342 | (apply max (map recur exps))) | |
343 | ||
344 | ((<lambda> vars meta body) | |
345 | ;; allocate closure vars in order | |
346 | (let lp ((c (hashq-ref free-vars x)) (n 0)) | |
347 | (if (pair? c) | |
348 | (begin | |
349 | (hashq-set! (hashq-ref allocation (car c)) | |
350 | x | |
351 | `(#f ,(hashq-ref assigned (car c)) . ,n)) | |
352 | (lp (cdr c) (1+ n))))) | |
353 | ||
354 | (let ((nlocs | |
355 | (let lp ((vars vars) (n 0)) | |
356 | (if (not (null? vars)) | |
357 | ;; allocate args | |
358 | (let ((v (if (pair? vars) (car vars) vars))) | |
359 | (hashq-set! allocation v | |
360 | (make-hashq | |
361 | x `(#t ,(hashq-ref assigned v) . ,n))) | |
362 | (lp (if (pair? vars) (cdr vars) '()) (1+ n))) | |
363 | ;; allocate body, return number of additional locals | |
364 | (- (allocate! body x n) n)))) | |
365 | (free-addresses | |
366 | (map (lambda (v) | |
367 | (hashq-ref (hashq-ref allocation v) proc)) | |
9059993f AW |
368 | (hashq-ref free-vars x))) |
369 | (labels (filter cdr | |
370 | (map (lambda (sym) | |
371 | (cons sym (hashq-ref labels sym))) | |
372 | (hashq-ref bound-vars x))))) | |
66d3e9a3 | 373 | ;; set procedure allocations |
9059993f | 374 | (hashq-set! allocation x (cons* nlocs labels free-addresses))) |
66d3e9a3 | 375 | n) |
cf10678f | 376 | |
66d3e9a3 AW |
377 | ((<let> vars vals body) |
378 | (let ((nmax (apply max (map recur vals)))) | |
379 | (cond | |
380 | ;; the `or' hack | |
381 | ((and (conditional? body) | |
382 | (= (length vars) 1) | |
383 | (let ((v (car vars))) | |
384 | (and (not (hashq-ref assigned v)) | |
385 | (= (hashq-ref refcounts v 0) 2) | |
386 | (lexical-ref? (conditional-test body)) | |
387 | (eq? (lexical-ref-gensym (conditional-test body)) v) | |
388 | (lexical-ref? (conditional-then body)) | |
389 | (eq? (lexical-ref-gensym (conditional-then body)) v)))) | |
390 | (hashq-set! allocation (car vars) | |
391 | (make-hashq proc `(#t #f . ,n))) | |
392 | ;; the 1+ for this var | |
393 | (max nmax (1+ n) (allocate! (conditional-else body) proc n))) | |
394 | (else | |
395 | (let lp ((vars vars) (n n)) | |
396 | (if (null? vars) | |
397 | (max nmax (allocate! body proc n)) | |
398 | (let ((v (car vars))) | |
cf10678f AW |
399 | (hashq-set! |
400 | allocation v | |
66d3e9a3 AW |
401 | (make-hashq proc |
402 | `(#t ,(hashq-ref assigned v) . ,n))) | |
403 | (lp (cdr vars) (1+ n))))))))) | |
404 | ||
405 | ((<letrec> vars vals body) | |
406 | (let lp ((vars vars) (n n)) | |
407 | (if (null? vars) | |
408 | (let ((nmax (apply max | |
409 | (map (lambda (x) | |
410 | (allocate! x proc n)) | |
411 | vals)))) | |
412 | (max nmax (allocate! body proc n))) | |
413 | (let ((v (car vars))) | |
414 | (hashq-set! | |
415 | allocation v | |
416 | (make-hashq proc | |
417 | `(#t ,(hashq-ref assigned v) . ,n))) | |
418 | (lp (cdr vars) (1+ n)))))) | |
cf10678f | 419 | |
c21c89b1 | 420 | ((<fix> vars vals body) |
d97b69d9 AW |
421 | (let lp ((in vars) (n n)) |
422 | (if (null? in) | |
423 | (let lp ((vars vars) (vals vals) (nmax n)) | |
424 | (cond | |
425 | ((null? vars) | |
426 | (max nmax (allocate! body proc n))) | |
427 | ((hashq-ref labels (car vars)) | |
428 | ;; allocate label bindings & body inline to proc | |
429 | (lp (cdr vars) | |
430 | (cdr vals) | |
431 | (record-case (car vals) | |
432 | ((<lambda> vars body) | |
433 | (let lp ((vars vars) (n n)) | |
434 | (if (not (null? vars)) | |
435 | ;; allocate bindings | |
436 | (let ((v (if (pair? vars) (car vars) vars))) | |
437 | (hashq-set! | |
438 | allocation v | |
439 | (make-hashq | |
440 | proc `(#t ,(hashq-ref assigned v) . ,n))) | |
441 | (lp (if (pair? vars) (cdr vars) '()) (1+ n))) | |
442 | ;; allocate body | |
443 | (max nmax (allocate! body proc n)))))))) | |
444 | (else | |
445 | ;; allocate closure | |
446 | (lp (cdr vars) | |
447 | (cdr vals) | |
448 | (max nmax (allocate! (car vals) proc n)))))) | |
449 | ||
450 | (let ((v (car in))) | |
451 | (cond | |
452 | ((hashq-ref assigned v) | |
453 | (error "fixpoint procedures may not be assigned" x)) | |
454 | ((hashq-ref labels v) | |
455 | ;; no binding, it's a label | |
456 | (lp (cdr in) n)) | |
457 | (else | |
458 | ;; allocate closure binding | |
459 | (hashq-set! allocation v (make-hashq proc `(#t #f . ,n))) | |
460 | (lp (cdr in) (1+ n)))))))) | |
c21c89b1 | 461 | |
66d3e9a3 AW |
462 | ((<let-values> vars exp body) |
463 | (let ((nmax (recur exp))) | |
cf10678f | 464 | (let lp ((vars vars) (n n)) |
bca488f1 AW |
465 | (cond |
466 | ((null? vars) | |
467 | (max nmax (allocate! body proc n))) | |
468 | ((not (pair? vars)) | |
469 | (hashq-set! allocation vars | |
470 | (make-hashq proc | |
471 | `(#t ,(hashq-ref assigned vars) . ,n))) | |
472 | ;; the 1+ for this var | |
473 | (max nmax (allocate! body proc (1+ n)))) | |
474 | (else | |
80af1168 AW |
475 | (let ((v (car vars))) |
476 | (hashq-set! | |
477 | allocation v | |
478 | (make-hashq proc | |
479 | `(#t ,(hashq-ref assigned v) . ,n))) | |
480 | (lp (cdr vars) (1+ n)))))))) | |
66d3e9a3 AW |
481 | |
482 | (else n))) | |
cf10678f | 483 | |
d97b69d9 | 484 | (analyze! x #f '() #t #f) |
66d3e9a3 | 485 | (allocate! x #f 0) |
cf10678f AW |
486 | |
487 | allocation) | |
4b856371 LC |
488 | |
489 | \f | |
490 | ;;; | |
491 | ;;; Unused variable analysis. | |
492 | ;;; | |
493 | ||
494 | ;; <binding-info> records are used during tree traversals in | |
495 | ;; `report-unused-variables'. They contain a list of the local vars | |
496 | ;; currently in scope, a list of locals vars that have been referenced, and a | |
497 | ;; "location stack" (the stack of `tree-il-src' values for each parent tree). | |
498 | (define-record-type <binding-info> | |
499 | (make-binding-info vars refs locs) | |
500 | binding-info? | |
501 | (vars binding-info-vars) ;; ((GENSYM NAME LOCATION) ...) | |
502 | (refs binding-info-refs) ;; (GENSYM ...) | |
503 | (locs binding-info-locs)) ;; (LOCATION ...) | |
504 | ||
505 | (define (report-unused-variables tree) | |
506 | "Report about unused variables in TREE. Return TREE." | |
507 | ||
508 | (define (dotless-list lst) | |
509 | ;; If LST is a dotted list, return a proper list equal to LST except that | |
510 | ;; the very last element is a pair; otherwise return LST. | |
511 | (let loop ((lst lst) | |
512 | (result '())) | |
513 | (cond ((null? lst) | |
514 | (reverse result)) | |
515 | ((pair? lst) | |
516 | (loop (cdr lst) (cons (car lst) result))) | |
517 | (else | |
518 | (loop '() (cons lst result)))))) | |
519 | ||
520 | (tree-il-fold (lambda (x info) | |
521 | ;; X is a leaf: extend INFO's refs accordingly. | |
522 | (let ((refs (binding-info-refs info)) | |
523 | (vars (binding-info-vars info)) | |
524 | (locs (binding-info-locs info))) | |
525 | (record-case x | |
526 | ((<lexical-ref> gensym) | |
527 | (make-binding-info vars (cons gensym refs) locs)) | |
528 | (else info)))) | |
529 | ||
530 | (lambda (x info) | |
531 | ;; Going down into X: extend INFO's variable list | |
532 | ;; accordingly. | |
533 | (let ((refs (binding-info-refs info)) | |
534 | (vars (binding-info-vars info)) | |
535 | (locs (binding-info-locs info)) | |
536 | (src (tree-il-src x))) | |
537 | (define (extend inner-vars inner-names) | |
538 | (append (map (lambda (var name) | |
539 | (list var name src)) | |
540 | inner-vars | |
541 | inner-names) | |
542 | vars)) | |
543 | (record-case x | |
544 | ((<lexical-set> gensym) | |
545 | (make-binding-info vars (cons gensym refs) | |
546 | (cons src locs))) | |
547 | ((<lambda> vars names) | |
548 | (let ((vars (dotless-list vars)) | |
549 | (names (dotless-list names))) | |
550 | (make-binding-info (extend vars names) refs | |
551 | (cons src locs)))) | |
552 | ((<let> vars names) | |
553 | (make-binding-info (extend vars names) refs | |
554 | (cons src locs))) | |
555 | ((<letrec> vars names) | |
556 | (make-binding-info (extend vars names) refs | |
557 | (cons src locs))) | |
c21c89b1 AW |
558 | ((<fix> vars names) |
559 | (make-binding-info (extend vars names) refs | |
560 | (cons src locs))) | |
4b856371 LC |
561 | ((<let-values> vars names) |
562 | (make-binding-info (extend vars names) refs | |
563 | (cons src locs))) | |
564 | (else info)))) | |
565 | ||
566 | (lambda (x info) | |
567 | ;; Leaving X's scope: shrink INFO's variable list | |
568 | ;; accordingly and reported unused nested variables. | |
569 | (let ((refs (binding-info-refs info)) | |
570 | (vars (binding-info-vars info)) | |
571 | (locs (binding-info-locs info))) | |
572 | (define (shrink inner-vars refs) | |
573 | (for-each (lambda (var) | |
574 | (let ((gensym (car var))) | |
575 | ;; Don't report lambda parameters as | |
576 | ;; unused. | |
577 | (if (and (not (memq gensym refs)) | |
578 | (not (and (lambda? x) | |
579 | (memq gensym | |
580 | inner-vars)))) | |
581 | (let ((name (cadr var)) | |
582 | ;; We can get approximate | |
583 | ;; source location by going up | |
584 | ;; the LOCS location stack. | |
585 | (loc (or (caddr var) | |
586 | (find pair? locs)))) | |
587 | (warning 'unused-variable loc name))))) | |
588 | (filter (lambda (var) | |
589 | (memq (car var) inner-vars)) | |
590 | vars)) | |
591 | (fold alist-delete vars inner-vars)) | |
592 | ||
593 | ;; For simplicity, we leave REFS untouched, i.e., with | |
594 | ;; names of variables that are now going out of scope. | |
595 | ;; It doesn't hurt as these are unique names, it just | |
596 | ;; makes REFS unnecessarily fat. | |
597 | (record-case x | |
598 | ((<lambda> vars) | |
599 | (let ((vars (dotless-list vars))) | |
600 | (make-binding-info (shrink vars refs) refs | |
601 | (cdr locs)))) | |
602 | ((<let> vars) | |
603 | (make-binding-info (shrink vars refs) refs | |
604 | (cdr locs))) | |
605 | ((<letrec> vars) | |
606 | (make-binding-info (shrink vars refs) refs | |
607 | (cdr locs))) | |
c21c89b1 AW |
608 | ((<fix> vars) |
609 | (make-binding-info (shrink vars refs) refs | |
610 | (cdr locs))) | |
4b856371 LC |
611 | ((<let-values> vars) |
612 | (make-binding-info (shrink vars refs) refs | |
613 | (cdr locs))) | |
614 | (else info)))) | |
615 | (make-binding-info '() '() '()) | |
616 | tree) | |
617 | tree) |