1 #include "c.h"
2
3
4 #define SWSIZE 512
5
6 #define den(i,j) ((j-buckets[i]+1.0)/(v[j]-v[buckets[i]]+1))
7
8 struct code codehead = { Start };
9 Code codelist = &codehead;
10 float density = 0.5;
11 Table stmtlabs;
12
13 static int foldcond(Tree e1, Tree e2);
14 static void caselabel(Swtch, long, int);
15 static void cmp(int, Symbol, long, int);
16 static Tree conditional(int);
17 static void dostmt(int, Swtch, int);
18 static int equal(Symbol, Symbol);
19 static void forstmt(int, Swtch, int);
20 static void ifstmt(int, int, Swtch, int);
21 static Symbol localaddr(Tree);
22 static void stmtlabel(void);
23 static void swstmt(int, int, int);
24 static void whilestmt(int, Swtch, int);
code(int kind)25 Code code(int kind) {
26 Code cp;
27
28 if (!reachable(kind))
29 warning("unreachable code\n");
30
31 NEW(cp, FUNC);
32 cp->kind = kind;
33 cp->prev = codelist;
34 cp->next = NULL;
35 codelist->next = cp;
36 codelist = cp;
37 return cp;
38 }
reachable(int kind)39 int reachable(int kind) {
40
41 if (kind > Start) {
42 Code cp;
43 for (cp = codelist; cp->kind < Label; )
44 cp = cp->prev;
45 if (cp->kind == Jump || cp->kind == Switch)
46 return 0;
47 }
48 return 1;
49 }
addlocal(Symbol p)50 void addlocal(Symbol p) {
51 if (!p->defined) {
52 code(Local)->u.var = p;
53 p->defined = 1;
54 p->scope = level;
55 }
56 }
definept(Coordinate * p)57 void definept(Coordinate *p) {
58 Code cp = code(Defpoint);
59
60 cp->u.point.src = p ? *p : src;
61 cp->u.point.point = npoints;
62 if (ncalled > 0) {
63 int n = findcount(cp->u.point.src.file,
64 cp->u.point.src.x, cp->u.point.src.y);
65 if (n > 0)
66 refinc = (float)n/ncalled;
67 }
68 if (glevel > 2) locus(identifiers, &cp->u.point.src);
69 if (events.points && reachable(Gen))
70 {
71 Tree e = NULL;
72 apply(events.points, &cp->u.point.src, &e);
73 if (e)
74 listnodes(e, 0, 0);
75 }
76 }
statement(int loop,Swtch swp,int lev)77 void statement(int loop, Swtch swp, int lev) {
78 float ref = refinc;
79
80 if (Aflag >= 2 && lev == 15)
81 warning("more than 15 levels of nested statements\n");
82 switch (t) {
83 case IF: ifstmt(genlabel(2), loop, swp, lev + 1);
84 break;
85 case WHILE: whilestmt(genlabel(3), swp, lev + 1); break;
86 case DO: dostmt(genlabel(3), swp, lev + 1); expect(';');
87 break;
88
89 case FOR: forstmt(genlabel(4), swp, lev + 1);
90 break;
91 case BREAK: walk(NULL, 0, 0);
92 definept(NULL);
93 if (swp && swp->lab > loop)
94 branch(swp->lab + 1);
95 else if (loop)
96 branch(loop + 2);
97 else
98 error("illegal break statement\n");
99 t = gettok(); expect(';');
100 break;
101
102 case CONTINUE: walk(NULL, 0, 0);
103 definept(NULL);
104 if (loop)
105 branch(loop + 1);
106 else
107 error("illegal continue statement\n");
108 t = gettok(); expect(';');
109 break;
110
111 case SWITCH: swstmt(loop, genlabel(2), lev + 1);
112 break;
113 case CASE: {
114 int lab = genlabel(1);
115 if (swp == NULL)
116 error("illegal case label\n");
117 definelab(lab);
118 while (t == CASE) {
119 static char stop[] = { IF, ID, 0 };
120 Tree p;
121 t = gettok();
122 p = constexpr(0);
123 if (generic(p->op) == CNST && isint(p->type)) {
124 if (swp) {
125 needconst++;
126 p = cast(p, swp->sym->type);
127 if (p->type->op == UNSIGNED)
128 p->u.v.i = extend(p->u.v.u, p->type);
129 needconst--;
130 caselabel(swp, p->u.v.i, lab);
131 }
132 } else {
133 error("case label must be a constant integer expression\n");
134 }
135 test(':', stop);
136 }
137 statement(loop, swp, lev);
138 } break;
139 case DEFAULT: if (swp == NULL)
140 error("illegal default label\n");
141 else if (swp->deflab)
142 error("extra default label\n");
143 else {
144 swp->deflab = findlabel(swp->lab);
145 definelab(swp->deflab->u.l.label);
146 }
147 t = gettok();
148 expect(':');
149 statement(loop, swp, lev); break;
150 case RETURN: {
151 Type rty = freturn(cfunc->type);
152 t = gettok();
153 definept(NULL);
154 if (t != ';')
155 if (rty == voidtype) {
156 error("extraneous return value\n");
157 expr(0);
158 retcode(NULL);
159 } else
160 retcode(expr(0));
161 else {
162 if (rty != voidtype)
163 warning("missing return value\n");
164 retcode(NULL);
165 }
166 branch(cfunc->u.f.label);
167 } expect(';');
168 break;
169
170 case '{': compound(loop, swp, lev + 1); break;
171 case ';': definept(NULL); t = gettok(); break;
172 case GOTO: walk(NULL, 0, 0);
173 definept(NULL);
174 t = gettok();
175 if (t == ID) {
176 Symbol p = lookup(token, stmtlabs);
177 if (p == NULL) {
178 p = install(token, &stmtlabs, 0, FUNC);
179 p->scope = LABELS;
180 p->u.l.label = genlabel(1);
181 p->src = src;
182 }
183 use(p, src);
184 branch(p->u.l.label);
185 t = gettok();
186 } else {
187 error("missing label in goto\n");
188 } expect(';');
189 break;
190
191 case ID: if (getchr() == ':') {
192 stmtlabel();
193 statement(loop, swp, lev);
194 break;
195 }
196 default: definept(NULL);
197 if (kind[t] != ID) {
198 error("unrecognized statement\n");
199 t = gettok();
200 } else {
201 Tree e = expr0(0);
202 listnodes(e, 0, 0);
203 if (nodecount == 0 || nodecount > 200)
204 walk(NULL, 0, 0);
205 else if (glevel)
206 walk(NULL, 0, 0);
207 deallocate(STMT);
208 } expect(';');
209 break;
210
211 }
212 if (kind[t] != IF && kind[t] != ID
213 && t != '}' && t != EOI) {
214 static char stop[] = { IF, ID, '}', 0 };
215 error("illegal statement termination\n");
216 skipto(0, stop);
217 }
218 refinc = ref;
219 }
220
ifstmt(int lab,int loop,Swtch swp,int lev)221 static void ifstmt(int lab, int loop, Swtch swp, int lev) {
222 t = gettok();
223 expect('(');
224 definept(NULL);
225 walk(conditional(')'), 0, lab);
226 refinc /= 2.0;
227 statement(loop, swp, lev);
228 if (t == ELSE) {
229 branch(lab + 1);
230 t = gettok();
231 definelab(lab);
232 statement(loop, swp, lev);
233 if (findlabel(lab + 1)->ref)
234 definelab(lab + 1);
235 } else
236 definelab(lab);
237 }
conditional(int tok)238 static Tree conditional(int tok) {
239 Tree p = expr(tok);
240
241 if (Aflag > 1 && isfunc(p->type))
242 warning("%s used in a conditional expression\n",
243 funcname(p));
244 return cond(p);
245 }
stmtlabel(void)246 static void stmtlabel(void) {
247 Symbol p = lookup(token, stmtlabs);
248
249 if (p == NULL) {
250 p = install(token, &stmtlabs, 0, FUNC);
251 p->scope = LABELS;
252 p->u.l.label = genlabel(1);
253 p->src = src;
254 }
255 if (p->defined)
256 error("redefinition of label `%s' previously defined at %w\n", p->name, &p->src);
257
258 p->defined = 1;
259 definelab(p->u.l.label);
260 t = gettok();
261 expect(':');
262 }
forstmt(int lab,Swtch swp,int lev)263 static void forstmt(int lab, Swtch swp, int lev) {
264 int once = 0;
265 Tree e1 = NULL, e2 = NULL, e3 = NULL;
266 Coordinate pt2, pt3;
267
268 t = gettok();
269 expect('(');
270 definept(NULL);
271 if (kind[t] == ID)
272 e1 = texpr(expr0, ';', FUNC);
273 else
274 expect(';');
275 walk(e1, 0, 0);
276 pt2 = src;
277 refinc *= 10.0;
278 if (kind[t] == ID)
279 e2 = texpr(conditional, ';', FUNC);
280 else
281 expect(';');
282 pt3 = src;
283 if (kind[t] == ID)
284 e3 = texpr(expr0, ')', FUNC);
285 else {
286 static char stop[] = { IF, ID, '}', 0 };
287 test(')', stop);
288 }
289 if (e2) {
290 once = foldcond(e1, e2);
291 if (!once)
292 branch(lab + 3);
293 }
294 definelab(lab);
295 statement(lab, swp, lev);
296 definelab(lab + 1);
297 definept(&pt3);
298 if (e3)
299 walk(e3, 0, 0);
300 if (e2) {
301 if (!once)
302 definelab(lab + 3);
303 definept(&pt2);
304 walk(e2, lab, 0);
305 } else {
306 definept(&pt2);
307 branch(lab);
308 }
309 if (findlabel(lab + 2)->ref)
310 definelab(lab + 2);
311 }
swstmt(int loop,int lab,int lev)312 static void swstmt(int loop, int lab, int lev) {
313 Tree e;
314 struct swtch sw;
315 Code head, tail;
316
317 t = gettok();
318 expect('(');
319 definept(NULL);
320 e = expr(')');
321 if (!isint(e->type)) {
322 error("illegal type `%t' in switch expression\n",
323 e->type);
324 e = retype(e, inttype);
325 }
326 e = cast(e, promote(e->type));
327 if (generic(e->op) == INDIR && isaddrop(e->kids[0]->op)
328 && e->kids[0]->u.sym->type == e->type
329 && !isvolatile(e->kids[0]->u.sym->type)) {
330 sw.sym = e->kids[0]->u.sym;
331 walk(NULL, 0, 0);
332 } else {
333 sw.sym = genident(REGISTER, e->type, level);
334 addlocal(sw.sym);
335 walk(asgn(sw.sym, e), 0, 0);
336 }
337 head = code(Switch);
338 sw.lab = lab;
339 sw.deflab = NULL;
340 sw.ncases = 0;
341 sw.size = SWSIZE;
342 sw.values = newarray(SWSIZE, sizeof *sw.values, FUNC);
343 sw.labels = newarray(SWSIZE, sizeof *sw.labels, FUNC);
344 refinc /= 10.0;
345 statement(loop, &sw, lev);
346 if (sw.deflab == NULL) {
347 sw.deflab = findlabel(lab);
348 definelab(lab);
349 if (sw.ncases == 0)
350 warning("switch statement with no cases\n");
351 }
352 if (findlabel(lab + 1)->ref)
353 definelab(lab + 1);
354 tail = codelist;
355 codelist = head->prev;
356 codelist->next = head->prev = NULL;
357 if (sw.ncases > 0)
358 swgen(&sw);
359 branch(lab);
360 head->next->prev = codelist;
361 codelist->next = head->next;
362 codelist = tail;
363 }
caselabel(Swtch swp,long val,int lab)364 static void caselabel(Swtch swp, long val, int lab) {
365 int k;
366
367 if (swp->ncases >= swp->size)
368 {
369 long *vals = swp->values;
370 Symbol *labs = swp->labels;
371 swp->size *= 2;
372 swp->values = newarray(swp->size, sizeof *swp->values, FUNC);
373 swp->labels = newarray(swp->size, sizeof *swp->labels, FUNC);
374 for (k = 0; k < swp->ncases; k++) {
375 swp->values[k] = vals[k];
376 swp->labels[k] = labs[k];
377 }
378 }
379 k = swp->ncases;
380 for ( ; k > 0 && swp->values[k-1] >= val; k--) {
381 swp->values[k] = swp->values[k-1];
382 swp->labels[k] = swp->labels[k-1];
383 }
384 if (k < swp->ncases && swp->values[k] == val)
385 error("duplicate case label `%d'\n", val);
386 swp->values[k] = val;
387 swp->labels[k] = findlabel(lab);
388 ++swp->ncases;
389 if (Aflag >= 2 && swp->ncases == 258)
390 warning("more than 257 cases in a switch\n");
391 }
swgen(Swtch swp)392 void swgen(Swtch swp) {
393 int *buckets, k, n;
394 long *v = swp->values;
395
396 buckets = newarray(swp->ncases + 1,
397 sizeof *buckets, FUNC);
398 for (n = k = 0; k < swp->ncases; k++, n++) {
399 buckets[n] = k;
400 while (n > 0 && den(n-1, k) >= density)
401 n--;
402 }
403 buckets[n] = swp->ncases;
404 swcode(swp, buckets, 0, n - 1);
405 }
swcode(Swtch swp,int b[],int lb,int ub)406 void swcode(Swtch swp, int b[], int lb, int ub) {
407 int hilab, lolab, l, u, k = (lb + ub)/2;
408 long *v = swp->values;
409
410 if (k > lb && k < ub) {
411 lolab = genlabel(1);
412 hilab = genlabel(1);
413 } else if (k > lb) {
414 lolab = genlabel(1);
415 hilab = swp->deflab->u.l.label;
416 } else if (k < ub) {
417 lolab = swp->deflab->u.l.label;
418 hilab = genlabel(1);
419 } else
420 lolab = hilab = swp->deflab->u.l.label;
421 l = b[k];
422 u = b[k+1] - 1;
423 if (u - l + 1 <= 3)
424 {
425 int i;
426 for (i = l; i <= u; i++)
427 cmp(EQ, swp->sym, v[i], swp->labels[i]->u.l.label);
428 if (k > lb && k < ub)
429 cmp(GT, swp->sym, v[u], hilab);
430 else if (k > lb)
431 cmp(GT, swp->sym, v[u], hilab);
432 else if (k < ub)
433 cmp(LT, swp->sym, v[l], lolab);
434 else
435 assert(lolab == hilab),
436 branch(lolab);
437 walk(NULL, 0, 0);
438 }
439 else {
440 Tree e;
441 Type ty = signedint(swp->sym->type);
442 Symbol table = genident(STATIC,
443 array(voidptype, u - l + 1, 0), GLOBAL);
444 (*IR->defsymbol)(table);
445 if (!isunsigned(swp->sym->type) || v[l] != 0)
446 cmp(LT, swp->sym, v[l], lolab);
447 cmp(GT, swp->sym, v[u], hilab);
448 e = (*optree['-'])(SUB, cast(idtree(swp->sym), ty), cnsttree(ty, v[l]));
449 if (e->type->size < unsignedptr->size)
450 e = cast(e, unsignedlong);
451 walk(tree(JUMP, voidtype,
452 rvalue((*optree['+'])(ADD, pointer(idtree(table)), e)), NULL),
453 0, 0);
454 code(Switch);
455 codelist->u.swtch.table = table;
456 codelist->u.swtch.sym = swp->sym;
457 codelist->u.swtch.deflab = swp->deflab;
458 codelist->u.swtch.size = u - l + 1;
459 codelist->u.swtch.values = &v[l];
460 codelist->u.swtch.labels = &swp->labels[l];
461 if (v[u] - v[l] + 1 >= 10000)
462 warning("switch generates a huge table\n");
463 }
464 if (k > lb) {
465 assert(lolab != swp->deflab->u.l.label);
466 definelab(lolab);
467 swcode(swp, b, lb, k - 1);
468 }
469 if (k < ub) {
470 assert(hilab != swp->deflab->u.l.label);
471 definelab(hilab);
472 swcode(swp, b, k + 1, ub);
473 }
474 }
cmp(int op,Symbol p,long n,int lab)475 static void cmp(int op, Symbol p, long n, int lab) {
476 Type ty = signedint(p->type);
477
478 listnodes(eqtree(op,
479 cast(idtree(p), ty),
480 cnsttree(ty, n)),
481 lab, 0);
482 }
retcode(Tree p)483 void retcode(Tree p) {
484 Type ty;
485
486 if (p == NULL) {
487 if (events.returns)
488 apply(events.returns, cfunc, NULL);
489 return;
490 }
491 p = pointer(p);
492 ty = assign(freturn(cfunc->type), p);
493 if (ty == NULL) {
494 error("illegal return type; found `%t' expected `%t'\n",
495 p->type, freturn(cfunc->type));
496 return;
497 }
498 p = cast(p, ty);
499 if (retv)
500 {
501 if (iscallb(p))
502 p = tree(RIGHT, p->type,
503 tree(CALL+B, p->type,
504 p->kids[0]->kids[0], idtree(retv)),
505 rvalue(idtree(retv)));
506 else
507 p = asgntree(ASGN, rvalue(idtree(retv)), p);
508 walk(p, 0, 0);
509 if (events.returns)
510 apply(events.returns, cfunc, rvalue(idtree(retv)));
511 return;
512 }
513 if (events.returns)
514 {
515 Symbol t1 = genident(AUTO, p->type, level);
516 addlocal(t1);
517 walk(asgn(t1, p), 0, 0);
518 apply(events.returns, cfunc, idtree(t1));
519 p = idtree(t1);
520 }
521 if (!isfloat(p->type))
522 p = cast(p, promote(p->type));
523 if (isptr(p->type))
524 {
525 Symbol q = localaddr(p);
526 if (q && (q->computed || q->generated))
527 warning("pointer to a %s is an illegal return value\n",
528 q->scope == PARAM ? "parameter" : "local");
529 else if (q)
530 warning("pointer to %s `%s' is an illegal return value\n",
531 q->scope == PARAM ? "parameter" : "local", q->name);
532 }
533 walk(tree(mkop(RET,p->type), p->type, p, NULL), 0, 0);
534 }
definelab(int lab)535 void definelab(int lab) {
536 Code cp;
537 Symbol p = findlabel(lab);
538
539 assert(lab);
540 walk(NULL, 0, 0);
541 code(Label)->u.forest = newnode(LABEL+V, NULL, NULL, p);
542 for (cp = codelist->prev; cp->kind <= Label; )
543 cp = cp->prev;
544 while ( cp->kind == Jump
545 && cp->u.forest->kids[0]
546 && specific(cp->u.forest->kids[0]->op) == ADDRG+P
547 && cp->u.forest->kids[0]->syms[0] == p) {
548 assert(cp->u.forest->kids[0]->syms[0]->u.l.label == lab);
549 p->ref--;
550 assert(cp->next);
551 assert(cp->prev);
552 cp->prev->next = cp->next;
553 cp->next->prev = cp->prev;
554 cp = cp->prev;
555 while (cp->kind <= Label)
556 cp = cp->prev;
557 }
558 }
jump(int lab)559 Node jump(int lab) {
560 Symbol p = findlabel(lab);
561
562 p->ref++;
563 return newnode(JUMP+V, newnode(ADDRG+ttob(voidptype), NULL, NULL, p),
564 NULL, NULL);
565 }
branch(int lab)566 void branch(int lab) {
567 Code cp;
568 Symbol p = findlabel(lab);
569
570 assert(lab);
571 walk(NULL, 0, 0);
572 code(Label)->u.forest = jump(lab);
573 for (cp = codelist->prev; cp->kind < Label; )
574 cp = cp->prev;
575 while ( cp->kind == Label
576 && cp->u.forest->op == LABEL+V
577 && !equal(cp->u.forest->syms[0], p)) {
578 equatelab(cp->u.forest->syms[0], p);
579 assert(cp->next);
580 assert(cp->prev);
581 cp->prev->next = cp->next;
582 cp->next->prev = cp->prev;
583 cp = cp->prev;
584 while (cp->kind < Label)
585 cp = cp->prev;
586 }
587 if (cp->kind == Jump || cp->kind == Switch) {
588 p->ref--;
589 codelist->prev->next = NULL;
590 codelist = codelist->prev;
591 } else {
592 codelist->kind = Jump;
593 if (cp->kind == Label
594 && cp->u.forest->op == LABEL+V
595 && equal(cp->u.forest->syms[0], p))
596 warning("source code specifies an infinite loop");
597 }
598 }
equatelab(Symbol old,Symbol new)599 void equatelab(Symbol old, Symbol new) {
600 assert(old->u.l.equatedto == NULL);
601 old->u.l.equatedto = new;
602 new->ref++;
603 }
equal(Symbol lprime,Symbol dst)604 static int equal(Symbol lprime, Symbol dst) {
605 assert(dst && lprime);
606 for ( ; dst; dst = dst->u.l.equatedto)
607 if (lprime == dst)
608 return 1;
609 return 0;
610 }
611 /* dostmt - do statement while ( expression ) */
dostmt(int lab,Swtch swp,int lev)612 static void dostmt(int lab, Swtch swp, int lev) {
613 refinc *= 10.0;
614 t = gettok();
615 definelab(lab);
616 statement(lab, swp, lev);
617 definelab(lab + 1);
618 expect(WHILE);
619 expect('(');
620 definept(NULL);
621 walk(conditional(')'), lab, 0);
622 if (findlabel(lab + 2)->ref)
623 definelab(lab + 2);
624 }
625
626 /* foldcond - check if initial test in for(e1;e2;e3) S is necessary */
foldcond(Tree e1,Tree e2)627 static int foldcond(Tree e1, Tree e2) {
628 int op = generic(e2->op);
629 Symbol v;
630
631 if (e1 == 0 || e2 == 0)
632 return 0;
633 if (generic(e1->op) == ASGN && isaddrop(e1->kids[0]->op)
634 && generic(e1->kids[1]->op) == CNST) {
635 v = e1->kids[0]->u.sym;
636 e1 = e1->kids[1];
637 } else
638 return 0;
639 if ((op==LE || op==LT || op==EQ || op==NE || op==GT || op==GE)
640 && generic(e2->kids[0]->op) == INDIR
641 && e2->kids[0]->kids[0]->u.sym == v
642 && e2->kids[1]->op == e1->op) {
643 e1 = simplify(op, e2->type, e1, e2->kids[1]);
644 if (e1->op == CNST+I)
645 return e1->u.v.i;
646 }
647 return 0;
648 }
649
650 /* localaddr - returns q if p yields the address of local/parameter q; otherwise returns 0 */
localaddr(Tree p)651 static Symbol localaddr(Tree p) {
652 if (p == NULL)
653 return NULL;
654 switch (generic(p->op)) {
655 case INDIR: case CALL: case ARG:
656 return NULL;
657 case ADDRL: case ADDRF:
658 return p->u.sym;
659 case RIGHT: case ASGN:
660 if (p->kids[1])
661 return localaddr(p->kids[1]);
662 return localaddr(p->kids[0]);
663 case COND: {
664 Symbol q;
665 assert(p->kids[1] && p->kids[1]->op == RIGHT);
666 if ((q = localaddr(p->kids[1]->kids[0])) != NULL)
667 return q;
668 return localaddr(p->kids[1]->kids[1]);
669 }
670 default: {
671 Symbol q;
672 if (p->kids[0] && (q = localaddr(p->kids[0])) != NULL)
673 return q;
674 return localaddr(p->kids[1]);
675 }
676 }
677 }
678
679 /* whilestmt - while ( expression ) statement */
whilestmt(int lab,Swtch swp,int lev)680 static void whilestmt(int lab, Swtch swp, int lev) {
681 Coordinate pt;
682 Tree e;
683
684 refinc *= 10.0;
685 t = gettok();
686 expect('(');
687 walk(NULL, 0, 0);
688 pt = src;
689 e = texpr(conditional, ')', FUNC);
690 branch(lab + 1);
691 definelab(lab);
692 statement(lab, swp, lev);
693 definelab(lab + 1);
694 definept(&pt);
695 walk(e, lab, 0);
696 if (findlabel(lab + 2)->ref)
697 definelab(lab + 2);
698 }
699