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"); expect(';');
188 break;
189
190 case ID: if (getchr() == ':') {
191 stmtlabel();
192 statement(loop, swp, lev);
193 break;
194 }
195 default: definept(NULL);
196 if (kind[t] != ID) {
197 error("unrecognized statement\n");
198 t = gettok();
199 } else {
200 Tree e = expr0(0);
201 listnodes(e, 0, 0);
202 if (nodecount == 0 || nodecount > 200)
203 walk(NULL, 0, 0);
204 else if (glevel) walk(NULL, 0, 0);
205 deallocate(STMT);
206 } expect(';');
207 break;
208
209 }
210 if (kind[t] != IF && kind[t] != ID
211 && t != '}' && t != EOI) {
212 static char stop[] = { IF, ID, '}', 0 };
213 error("illegal statement termination\n");
214 skipto(0, stop);
215 }
216 refinc = ref;
217 }
218
ifstmt(int lab,int loop,Swtch swp,int lev)219 static void ifstmt(int lab, int loop, Swtch swp, int lev) {
220 t = gettok();
221 expect('(');
222 definept(NULL);
223 walk(conditional(')'), 0, lab);
224 refinc /= 2.0;
225 statement(loop, swp, lev);
226 if (t == ELSE) {
227 branch(lab + 1);
228 t = gettok();
229 definelab(lab);
230 statement(loop, swp, lev);
231 if (findlabel(lab + 1)->ref)
232 definelab(lab + 1);
233 } else
234 definelab(lab);
235 }
conditional(int tok)236 static Tree conditional(int tok) {
237 Tree p = expr(tok);
238
239 if (Aflag > 1 && isfunc(p->type))
240 warning("%s used in a conditional expression\n",
241 funcname(p));
242 return cond(p);
243 }
stmtlabel(void)244 static void stmtlabel(void) {
245 Symbol p = lookup(token, stmtlabs);
246
247 if (p == NULL) {
248 p = install(token, &stmtlabs, 0, FUNC);
249 p->scope = LABELS;
250 p->u.l.label = genlabel(1);
251 p->src = src;
252 }
253 if (p->defined)
254 error("redefinition of label `%s' previously defined at %w\n", p->name, &p->src);
255
256 p->defined = 1;
257 definelab(p->u.l.label);
258 t = gettok();
259 expect(':');
260 }
forstmt(int lab,Swtch swp,int lev)261 static void forstmt(int lab, Swtch swp, int lev) {
262 int once = 0;
263 Tree e1 = NULL, e2 = NULL, e3 = NULL;
264 Coordinate pt2, pt3;
265
266 t = gettok();
267 expect('(');
268 definept(NULL);
269 if (kind[t] == ID)
270 e1 = texpr(expr0, ';', FUNC);
271 else
272 expect(';');
273 walk(e1, 0, 0);
274 pt2 = src;
275 refinc *= 10.0;
276 if (kind[t] == ID)
277 e2 = texpr(conditional, ';', FUNC);
278 else
279 expect(';');
280 pt3 = src;
281 if (kind[t] == ID)
282 e3 = texpr(expr0, ')', FUNC);
283 else {
284 static char stop[] = { IF, ID, '}', 0 };
285 test(')', stop);
286 }
287 if (e2) {
288 once = foldcond(e1, e2);
289 if (!once)
290 branch(lab + 3);
291 }
292 definelab(lab);
293 statement(lab, swp, lev);
294 definelab(lab + 1);
295 definept(&pt3);
296 if (e3)
297 walk(e3, 0, 0);
298 if (e2) {
299 if (!once)
300 definelab(lab + 3);
301 definept(&pt2);
302 walk(e2, lab, 0);
303 } else {
304 definept(&pt2);
305 branch(lab);
306 }
307 if (findlabel(lab + 2)->ref)
308 definelab(lab + 2);
309 }
swstmt(int loop,int lab,int lev)310 static void swstmt(int loop, int lab, int lev) {
311 Tree e;
312 struct swtch sw;
313 Code head, tail;
314
315 t = gettok();
316 expect('(');
317 definept(NULL);
318 e = expr(')');
319 if (!isint(e->type)) {
320 error("illegal type `%t' in switch expression\n",
321 e->type);
322 e = retype(e, inttype);
323 }
324 e = cast(e, promote(e->type));
325 if (generic(e->op) == INDIR && isaddrop(e->kids[0]->op)
326 && e->kids[0]->u.sym->type == e->type
327 && !isvolatile(e->kids[0]->u.sym->type)) {
328 sw.sym = e->kids[0]->u.sym;
329 walk(NULL, 0, 0);
330 } else {
331 sw.sym = genident(REGISTER, e->type, level);
332 addlocal(sw.sym);
333 walk(asgn(sw.sym, e), 0, 0);
334 }
335 head = code(Switch);
336 sw.lab = lab;
337 sw.deflab = NULL;
338 sw.ncases = 0;
339 sw.size = SWSIZE;
340 sw.values = newarray(SWSIZE, sizeof *sw.values, FUNC);
341 sw.labels = newarray(SWSIZE, sizeof *sw.labels, FUNC);
342 refinc /= 10.0;
343 statement(loop, &sw, lev);
344 if (sw.deflab == NULL) {
345 sw.deflab = findlabel(lab);
346 definelab(lab);
347 if (sw.ncases == 0)
348 warning("switch statement with no cases\n");
349 }
350 if (findlabel(lab + 1)->ref)
351 definelab(lab + 1);
352 tail = codelist;
353 codelist = head->prev;
354 codelist->next = head->prev = NULL;
355 if (sw.ncases > 0)
356 swgen(&sw);
357 branch(lab);
358 head->next->prev = codelist;
359 codelist->next = head->next;
360 codelist = tail;
361 }
caselabel(Swtch swp,long val,int lab)362 static void caselabel(Swtch swp, long val, int lab) {
363 int k;
364
365 if (swp->ncases >= swp->size)
366 {
367 long *vals = swp->values;
368 Symbol *labs = swp->labels;
369 swp->size *= 2;
370 swp->values = newarray(swp->size, sizeof *swp->values, FUNC);
371 swp->labels = newarray(swp->size, sizeof *swp->labels, FUNC);
372 for (k = 0; k < swp->ncases; k++) {
373 swp->values[k] = vals[k];
374 swp->labels[k] = labs[k];
375 }
376 }
377 k = swp->ncases;
378 for ( ; k > 0 && swp->values[k-1] >= val; k--) {
379 swp->values[k] = swp->values[k-1];
380 swp->labels[k] = swp->labels[k-1];
381 }
382 if (k < swp->ncases && swp->values[k] == val)
383 error("duplicate case label `%d'\n", val);
384 swp->values[k] = val;
385 swp->labels[k] = findlabel(lab);
386 ++swp->ncases;
387 if (Aflag >= 2 && swp->ncases == 258)
388 warning("more than 257 cases in a switch\n");
389 }
swgen(Swtch swp)390 void swgen(Swtch swp) {
391 int *buckets, k, n;
392 long *v = swp->values;
393
394 buckets = newarray(swp->ncases + 1,
395 sizeof *buckets, FUNC);
396 for (n = k = 0; k < swp->ncases; k++, n++) {
397 buckets[n] = k;
398 while (n > 0 && den(n-1, k) >= density)
399 n--;
400 }
401 buckets[n] = swp->ncases;
402 swcode(swp, buckets, 0, n - 1);
403 }
swcode(Swtch swp,int b[],int lb,int ub)404 void swcode(Swtch swp, int b[], int lb, int ub) {
405 int hilab, lolab, l, u, k = (lb + ub)/2;
406 long *v = swp->values;
407
408 if (k > lb && k < ub) {
409 lolab = genlabel(1);
410 hilab = genlabel(1);
411 } else if (k > lb) {
412 lolab = genlabel(1);
413 hilab = swp->deflab->u.l.label;
414 } else if (k < ub) {
415 lolab = swp->deflab->u.l.label;
416 hilab = genlabel(1);
417 } else
418 lolab = hilab = swp->deflab->u.l.label;
419 l = b[k];
420 u = b[k+1] - 1;
421 if (u - l + 1 <= 3)
422 {
423 int i;
424 for (i = l; i <= u; i++)
425 cmp(EQ, swp->sym, v[i], swp->labels[i]->u.l.label);
426 if (k > lb && k < ub)
427 cmp(GT, swp->sym, v[u], hilab);
428 else if (k > lb)
429 cmp(GT, swp->sym, v[u], hilab);
430 else if (k < ub)
431 cmp(LT, swp->sym, v[l], lolab);
432 else
433 assert(lolab == hilab),
434 branch(lolab);
435 walk(NULL, 0, 0);
436 }
437 else {
438 Tree e;
439 Type ty = signedint(swp->sym->type);
440 Symbol table = genident(STATIC,
441 array(voidptype, u - l + 1, 0), GLOBAL);
442 (*IR->defsymbol)(table);
443 if (!isunsigned(swp->sym->type) || v[l] != 0)
444 cmp(LT, swp->sym, v[l], lolab);
445 cmp(GT, swp->sym, v[u], hilab);
446 e = (*optree['-'])(SUB, cast(idtree(swp->sym), ty), cnsttree(ty, v[l]));
447 if (e->type->size < unsignedptr->size)
448 e = cast(e, unsignedlong);
449 walk(tree(JUMP, voidtype,
450 rvalue((*optree['+'])(ADD, pointer(idtree(table)), e)), NULL),
451 0, 0);
452 code(Switch);
453 codelist->u.swtch.table = table;
454 codelist->u.swtch.sym = swp->sym;
455 codelist->u.swtch.deflab = swp->deflab;
456 codelist->u.swtch.size = u - l + 1;
457 codelist->u.swtch.values = &v[l];
458 codelist->u.swtch.labels = &swp->labels[l];
459 if (v[u] - v[l] + 1 >= 10000)
460 warning("switch generates a huge table\n");
461 }
462 if (k > lb) {
463 assert(lolab != swp->deflab->u.l.label);
464 definelab(lolab);
465 swcode(swp, b, lb, k - 1);
466 }
467 if (k < ub) {
468 assert(hilab != swp->deflab->u.l.label);
469 definelab(hilab);
470 swcode(swp, b, k + 1, ub);
471 }
472 }
cmp(int op,Symbol p,long n,int lab)473 static void cmp(int op, Symbol p, long n, int lab) {
474 Type ty = signedint(p->type);
475
476 listnodes(eqtree(op,
477 cast(idtree(p), ty),
478 cnsttree(ty, n)),
479 lab, 0);
480 }
retcode(Tree p)481 void retcode(Tree p) {
482 Type ty;
483
484 if (p == NULL) {
485 if (events.returns)
486 apply(events.returns, cfunc, NULL);
487 return;
488 }
489 p = pointer(p);
490 ty = assign(freturn(cfunc->type), p);
491 if (ty == NULL) {
492 error("illegal return type; found `%t' expected `%t'\n",
493 p->type, freturn(cfunc->type));
494 return;
495 }
496 p = cast(p, ty);
497 if (retv)
498 {
499 if (iscallb(p))
500 p = tree(RIGHT, p->type,
501 tree(CALL+B, p->type,
502 p->kids[0]->kids[0], idtree(retv)),
503 rvalue(idtree(retv)));
504 else
505 p = asgntree(ASGN, rvalue(idtree(retv)), p);
506 walk(p, 0, 0);
507 if (events.returns)
508 apply(events.returns, cfunc, rvalue(idtree(retv)));
509 return;
510 }
511 if (events.returns)
512 {
513 Symbol t1 = genident(AUTO, p->type, level);
514 addlocal(t1);
515 walk(asgn(t1, p), 0, 0);
516 apply(events.returns, cfunc, idtree(t1));
517 p = idtree(t1);
518 }
519 if (!isfloat(p->type))
520 p = cast(p, promote(p->type));
521 if (isptr(p->type))
522 {
523 Symbol q = localaddr(p);
524 if (q && (q->computed || q->generated))
525 warning("pointer to a %s is an illegal return value\n",
526 q->scope == PARAM ? "parameter" : "local");
527 else if (q)
528 warning("pointer to %s `%s' is an illegal return value\n",
529 q->scope == PARAM ? "parameter" : "local", q->name);
530 }
531 walk(tree(mkop(RET,p->type), p->type, p, NULL), 0, 0);
532 }
definelab(int lab)533 void definelab(int lab) {
534 Code cp;
535 Symbol p = findlabel(lab);
536
537 assert(lab);
538 walk(NULL, 0, 0);
539 code(Label)->u.forest = newnode(LABEL+V, NULL, NULL, p);
540 for (cp = codelist->prev; cp->kind <= Label; )
541 cp = cp->prev;
542 while ( cp->kind == Jump
543 && cp->u.forest->kids[0]
544 && specific(cp->u.forest->kids[0]->op) == ADDRG+P
545 && cp->u.forest->kids[0]->syms[0] == p) {
546 assert(cp->u.forest->kids[0]->syms[0]->u.l.label == lab);
547 p->ref--;
548 assert(cp->next);
549 assert(cp->prev);
550 cp->prev->next = cp->next;
551 cp->next->prev = cp->prev;
552 cp = cp->prev;
553 while (cp->kind <= Label)
554 cp = cp->prev;
555 }
556 }
jump(int lab)557 Node jump(int lab) {
558 Symbol p = findlabel(lab);
559
560 p->ref++;
561 return newnode(JUMP+V, newnode(ADDRG+ttob(voidptype), NULL, NULL, p),
562 NULL, NULL);
563 }
branch(int lab)564 void branch(int lab) {
565 Code cp;
566 Symbol p = findlabel(lab);
567
568 assert(lab);
569 walk(NULL, 0, 0);
570 code(Label)->u.forest = jump(lab);
571 for (cp = codelist->prev; cp->kind < Label; )
572 cp = cp->prev;
573 while ( cp->kind == Label
574 && cp->u.forest->op == LABEL+V
575 && !equal(cp->u.forest->syms[0], p)) {
576 equatelab(cp->u.forest->syms[0], p);
577 assert(cp->next);
578 assert(cp->prev);
579 cp->prev->next = cp->next;
580 cp->next->prev = cp->prev;
581 cp = cp->prev;
582 while (cp->kind < Label)
583 cp = cp->prev;
584 }
585 if (cp->kind == Jump || cp->kind == Switch) {
586 p->ref--;
587 codelist->prev->next = NULL;
588 codelist = codelist->prev;
589 } else {
590 codelist->kind = Jump;
591 if (cp->kind == Label
592 && cp->u.forest->op == LABEL+V
593 && equal(cp->u.forest->syms[0], p))
594 warning("source code specifies an infinite loop");
595 }
596 }
equatelab(Symbol old,Symbol new)597 void equatelab(Symbol old, Symbol new) {
598 assert(old->u.l.equatedto == NULL);
599 old->u.l.equatedto = new;
600 new->ref++;
601 }
equal(Symbol lprime,Symbol dst)602 static int equal(Symbol lprime, Symbol dst) {
603 assert(dst && lprime);
604 for ( ; dst; dst = dst->u.l.equatedto)
605 if (lprime == dst)
606 return 1;
607 return 0;
608 }
609 /* dostmt - do statement while ( expression ) */
dostmt(int lab,Swtch swp,int lev)610 static void dostmt(int lab, Swtch swp, int lev) {
611 refinc *= 10.0;
612 t = gettok();
613 definelab(lab);
614 statement(lab, swp, lev);
615 definelab(lab + 1);
616 expect(WHILE);
617 expect('(');
618 definept(NULL);
619 walk(conditional(')'), lab, 0);
620 if (findlabel(lab + 2)->ref)
621 definelab(lab + 2);
622 }
623
624 /* foldcond - check if initial test in for(e1;e2;e3) S is necessary */
foldcond(Tree e1,Tree e2)625 static int foldcond(Tree e1, Tree e2) {
626 int op = generic(e2->op);
627 Symbol v;
628
629 if (e1 == 0 || e2 == 0)
630 return 0;
631 if (generic(e1->op) == ASGN && isaddrop(e1->kids[0]->op)
632 && generic(e1->kids[1]->op) == CNST) {
633 v = e1->kids[0]->u.sym;
634 e1 = e1->kids[1];
635 } else
636 return 0;
637 if ((op==LE || op==LT || op==EQ || op==NE || op==GT || op==GE)
638 && generic(e2->kids[0]->op) == INDIR
639 && e2->kids[0]->kids[0]->u.sym == v
640 && e2->kids[1]->op == e1->op) {
641 e1 = simplify(op, e2->type, e1, e2->kids[1]);
642 if (e1->op == CNST+I)
643 return e1->u.v.i;
644 }
645 return 0;
646 }
647
648 /* localaddr - returns q if p yields the address of local/parameter q; otherwise returns 0 */
localaddr(Tree p)649 static Symbol localaddr(Tree p) {
650 if (p == NULL)
651 return NULL;
652 switch (generic(p->op)) {
653 case INDIR: case CALL: case ARG:
654 return NULL;
655 case ADDRL: case ADDRF:
656 return p->u.sym;
657 case RIGHT: case ASGN:
658 if (p->kids[1])
659 return localaddr(p->kids[1]);
660 return localaddr(p->kids[0]);
661 case COND: {
662 Symbol q;
663 assert(p->kids[1] && p->kids[1]->op == RIGHT);
664 if ((q = localaddr(p->kids[1]->kids[0])) != NULL)
665 return q;
666 return localaddr(p->kids[1]->kids[1]);
667 }
668 default: {
669 Symbol q;
670 if (p->kids[0] && (q = localaddr(p->kids[0])) != NULL)
671 return q;
672 return localaddr(p->kids[1]);
673 }
674 }
675 }
676
677 /* whilestmt - while ( expression ) statement */
whilestmt(int lab,Swtch swp,int lev)678 static void whilestmt(int lab, Swtch swp, int lev) {
679 Coordinate pt;
680 Tree e;
681
682 refinc *= 10.0;
683 t = gettok();
684 expect('(');
685 walk(NULL, 0, 0);
686 pt = src;
687 e = texpr(conditional, ')', FUNC);
688 branch(lab + 1);
689 definelab(lab);
690 statement(lab, swp, lev);
691 definelab(lab + 1);
692 definept(&pt);
693 walk(e, lab, 0);
694 if (findlabel(lab + 2)->ref)
695 definelab(lab + 2);
696 }
697