bisect.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "diff.h"
   4 #include "revision.h"
   5 #include "refs.h"
   6 #include "list-objects.h"
   7 #include "sha1-lookup.h"
   8 #include "bisect.h"
   9
  10 static unsigned char (*skipped_sha1)[20];
  11 static int skipped_sha1_nr;
  12 static int skipped_sha1_alloc;
  13
  14 static const char **rev_argv;
  15 static int rev_argv_nr;
  16 static int rev_argv_alloc;
  17
  18 /* bits #0-15 in revision.h */
  19
  20 #define COUNTED         (1u<<16)
  21
  22 /*
  23  * This is a truly stupid algorithm, but it's only
  24  * used for bisection, and we just don't care enough.
  25  *
  26  * We care just barely enough to avoid recursing for
  27  * non-merge entries.
  28  */
  29 static int count_distance(struct commit_list *entry)
  30 {
  31         int nr = 0;
  32
  33         while (entry) {
  34                 struct commit *commit = entry->item;
  35                 struct commit_list *p;
  36
  37                 if (commit->object.flags & (UNINTERESTING | COUNTED))
  38                         break;
  39                 if (!(commit->object.flags & TREESAME))
  40                         nr++;
  41                 commit->object.flags |= COUNTED;
  42                 p = commit->parents;
  43                 entry = p;
  44                 if (p) {
  45                         p = p->next;
  46                         while (p) {
  47                                 nr += count_distance(p);
  48                                 p = p->next;
  49                         }
  50                 }
  51         }
  52
  53         return nr;
  54 }
  55
  56 static void clear_distance(struct commit_list *list)
  57 {
  58         while (list) {
  59                 struct commit *commit = list->item;
  60                 commit->object.flags &= ~COUNTED;
  61                 list = list->next;
  62         }
  63 }
  64
  65 #define DEBUG_BISECT 0
  66
  67 static inline int weight(struct commit_list *elem)
  68 {
  69         return *((int*)(elem->item->util));
  70 }
  71
  72 static inline void weight_set(struct commit_list *elem, int weight)
  73 {
  74         *((int*)(elem->item->util)) = weight;
  75 }
  76
  77 static int count_interesting_parents(struct commit *commit)
  78 {
  79         struct commit_list *p;
  80         int count;
  81
  82         for (count = 0, p = commit->parents; p; p = p->next) {
  83                 if (p->item->object.flags & UNINTERESTING)
  84                         continue;
  85                 count++;
  86         }
  87         return count;
  88 }
  89
  90 static inline int halfway(struct commit_list *p, int nr)
  91 {
  92         /*
  93          * Don't short-cut something we are not going to return!
  94          */
  95         if (p->item->object.flags & TREESAME)
  96                 return 0;
  97         if (DEBUG_BISECT)
  98                 return 0;
  99         /*
 100          * 2 and 3 are halfway of 5.
 101          * 3 is halfway of 6 but 2 and 4 are not.
 102          */
 103         switch (2 * weight(p) - nr) {
 104         case -1: case 0: case 1:
 105                 return 1;
 106         default:
 107                 return 0;
 108         }
 109 }
 110
 111 #if !DEBUG_BISECT
 112 #define show_list(a,b,c,d) do { ; } while (0)
 113 #else
 114 static void show_list(const char *debug, int counted, int nr,
 115                       struct commit_list *list)
 116 {
 117         struct commit_list *p;
 118
 119         fprintf(stderr, "%s (%d/%d)\n", debug, counted, nr);
 120
 121         for (p = list; p; p = p->next) {
 122                 struct commit_list *pp;
 123                 struct commit *commit = p->item;
 124                 unsigned flags = commit->object.flags;
 125                 enum object_type type;
 126                 unsigned long size;
 127                 char *buf = read_sha1_file(commit->object.sha1, &type, &size);
 128                 char *ep, *sp;
 129
 130                 fprintf(stderr, "%c%c%c ",
 131                         (flags & TREESAME) ? ' ' : 'T',
 132                         (flags & UNINTERESTING) ? 'U' : ' ',
 133                         (flags & COUNTED) ? 'C' : ' ');
 134                 if (commit->util)
 135                         fprintf(stderr, "%3d", weight(p));
 136                 else
 137                         fprintf(stderr, "---");
 138                 fprintf(stderr, " %.*s", 8, sha1_to_hex(commit->object.sha1));
 139                 for (pp = commit->parents; pp; pp = pp->next)
 140                         fprintf(stderr, " %.*s", 8,
 141                                 sha1_to_hex(pp->item->object.sha1));
 142
 143                 sp = strstr(buf, "\n\n");
 144                 if (sp) {
 145                         sp += 2;
 146                         for (ep = sp; *ep && *ep != '\n'; ep++)
 147                                 ;
 148                         fprintf(stderr, " %.*s", (int)(ep - sp), sp);
 149                 }
 150                 fprintf(stderr, "\n");
 151         }
 152 }
 153 #endif /* DEBUG_BISECT */
 154
 155 static struct commit_list *best_bisection(struct commit_list *list, int nr)
 156 {
 157         struct commit_list *p, *best;
 158         int best_distance = -1;
 159
 160         best = list;
 161         for (p = list; p; p = p->next) {
 162                 int distance;
 163                 unsigned flags = p->item->object.flags;
 164
 165                 if (flags & TREESAME)
 166                         continue;
 167                 distance = weight(p);
 168                 if (nr - distance < distance)
 169                         distance = nr - distance;
 170                 if (distance > best_distance) {
 171                         best = p;
 172                         best_distance = distance;
 173                 }
 174         }
 175
 176         return best;
 177 }
 178
 179 struct commit_dist {
 180         struct commit *commit;
 181         int distance;
 182 };
 183
 184 static int compare_commit_dist(const void *a_, const void *b_)
 185 {
 186         struct commit_dist *a, *b;
 187
 188         a = (struct commit_dist *)a_;
 189         b = (struct commit_dist *)b_;
 190         if (a->distance != b->distance)
 191                 return b->distance - a->distance; /* desc sort */
 192         return hashcmp(a->commit->object.sha1, b->commit->object.sha1);
 193 }
 194
 195 static struct commit_list *best_bisection_sorted(struct commit_list *list, int nr)
 196 {
 197         struct commit_list *p;
 198         struct commit_dist *array = xcalloc(nr, sizeof(*array));
 199         int cnt, i;
 200
 201         for (p = list, cnt = 0; p; p = p->next) {
 202                 int distance;
 203                 unsigned flags = p->item->object.flags;
 204
 205                 if (flags & TREESAME)
 206                         continue;
 207                 distance = weight(p);
 208                 if (nr - distance < distance)
 209                         distance = nr - distance;
 210                 array[cnt].commit = p->item;
 211                 array[cnt].distance = distance;
 212                 cnt++;
 213         }
 214         qsort(array, cnt, sizeof(*array), compare_commit_dist);
 215         for (p = list, i = 0; i < cnt; i++) {
 216                 struct name_decoration *r = xmalloc(sizeof(*r) + 100);
 217                 struct object *obj = &(array[i].commit->object);
 218
 219                 sprintf(r->name, "dist=%d", array[i].distance);
 220                 r->next = add_decoration(&name_decoration, obj, r);
 221                 p->item = array[i].commit;
 222                 p = p->next;
 223         }
 224         if (p)
 225                 p->next = NULL;
 226         free(array);
 227         return list;
 228 }
 229
 230 /*
 231  * zero or positive weight is the number of interesting commits it can
 232  * reach, including itself.  Especially, weight = 0 means it does not
 233  * reach any tree-changing commits (e.g. just above uninteresting one
 234  * but traversal is with pathspec).
 235  *
 236  * weight = -1 means it has one parent and its distance is yet to
 237  * be computed.
 238  *
 239  * weight = -2 means it has more than one parent and its distance is
 240  * unknown.  After running count_distance() first, they will get zero
 241  * or positive distance.
 242  */
 243 static struct commit_list *do_find_bisection(struct commit_list *list,
 244                                              int nr, int *weights,
 245                                              int find_all)
 246 {
 247         int n, counted;
 248         struct commit_list *p;
 249
 250         counted = 0;
 251
 252         for (n = 0, p = list; p; p = p->next) {
 253                 struct commit *commit = p->item;
 254                 unsigned flags = commit->object.flags;
 255
 256                 p->item->util = &weights[n++];
 257                 switch (count_interesting_parents(commit)) {
 258                 case 0:
 259                         if (!(flags & TREESAME)) {
 260                                 weight_set(p, 1);
 261                                 counted++;
 262                                 show_list("bisection 2 count one",
 263                                           counted, nr, list);
 264                         }
 265                         /*
 266                          * otherwise, it is known not to reach any
 267                          * tree-changing commit and gets weight 0.
 268                          */
 269                         break;
 270                 case 1:
 271                         weight_set(p, -1);
 272                         break;
 273                 default:
 274                         weight_set(p, -2);
 275                         break;
 276                 }
 277         }
 278
 279         show_list("bisection 2 initialize", counted, nr, list);
 280
 281         /*
 282          * If you have only one parent in the resulting set
 283          * then you can reach one commit more than that parent
 284          * can reach.  So we do not have to run the expensive
 285          * count_distance() for single strand of pearls.
 286          *
 287          * However, if you have more than one parents, you cannot
 288          * just add their distance and one for yourself, since
 289          * they usually reach the same ancestor and you would
 290          * end up counting them twice that way.
 291          *
 292          * So we will first count distance of merges the usual
 293          * way, and then fill the blanks using cheaper algorithm.
 294          */
 295         for (p = list; p; p = p->next) {
 296                 if (p->item->object.flags & UNINTERESTING)
 297                         continue;
 298                 if (weight(p) != -2)
 299                         continue;
 300                 weight_set(p, count_distance(p));
 301                 clear_distance(list);
 302
 303                 /* Does it happen to be at exactly half-way? */
 304                 if (!find_all && halfway(p, nr))
 305                         return p;
 306                 counted++;
 307         }
 308
 309         show_list("bisection 2 count_distance", counted, nr, list);
 310
 311         while (counted < nr) {
 312                 for (p = list; p; p = p->next) {
 313                         struct commit_list *q;
 314                         unsigned flags = p->item->object.flags;
 315
 316                         if (0 <= weight(p))
 317                                 continue;
 318                         for (q = p->item->parents; q; q = q->next) {
 319                                 if (q->item->object.flags & UNINTERESTING)
 320                                         continue;
 321                                 if (0 <= weight(q))
 322                                         break;
 323                         }
 324                         if (!q)
 325                                 continue;
 326
 327                         /*
 328                          * weight for p is unknown but q is known.
 329                          * add one for p itself if p is to be counted,
 330                          * otherwise inherit it from q directly.
 331                          */
 332                         if (!(flags & TREESAME)) {
 333                                 weight_set(p, weight(q)+1);
 334                                 counted++;
 335                                 show_list("bisection 2 count one",
 336                                           counted, nr, list);
 337                         }
 338                         else
 339                                 weight_set(p, weight(q));
 340
 341                         /* Does it happen to be at exactly half-way? */
 342                         if (!find_all && halfway(p, nr))
 343                                 return p;
 344                 }
 345         }
 346
 347         show_list("bisection 2 counted all", counted, nr, list);
 348
 349         if (!find_all)
 350                 return best_bisection(list, nr);
 351         else
 352                 return best_bisection_sorted(list, nr);
 353 }
 354
 355 struct commit_list *find_bisection(struct commit_list *list,
 356                                           int *reaches, int *all,
 357                                           int find_all)
 358 {
 359         int nr, on_list;
 360         struct commit_list *p, *best, *next, *last;
 361         int *weights;
 362
 363         show_list("bisection 2 entry", 0, 0, list);
 364
 365         /*
 366          * Count the number of total and tree-changing items on the
 367          * list, while reversing the list.
 368          */
 369         for (nr = on_list = 0, last = NULL, p = list;
 370              p;
 371              p = next) {
 372                 unsigned flags = p->item->object.flags;
 373
 374                 next = p->next;
 375                 if (flags & UNINTERESTING)
 376                         continue;
 377                 p->next = last;
 378                 last = p;
 379                 if (!(flags & TREESAME))
 380                         nr++;
 381                 on_list++;
 382         }
 383         list = last;
 384         show_list("bisection 2 sorted", 0, nr, list);
 385
 386         *all = nr;
 387         weights = xcalloc(on_list, sizeof(*weights));
 388
 389         /* Do the real work of finding bisection commit. */
 390         best = do_find_bisection(list, nr, weights, find_all);
 391         if (best) {
 392                 if (!find_all)
 393                         best->next = NULL;
 394                 *reaches = weight(best);
 395         }
 396         free(weights);
 397         return best;
 398 }
 399
 400 static int register_ref(const char *refname, const unsigned char *sha1,
 401                         int flags, void *cb_data)
 402 {
 403         if (!strcmp(refname, "bad")) {
 404                 ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 405                 rev_argv[rev_argv_nr++] = xstrdup(sha1_to_hex(sha1));
 406         } else if (!prefixcmp(refname, "good-")) {
 407                 const char *hex = sha1_to_hex(sha1);
 408                 char *good = xmalloc(strlen(hex) + 2);
 409                 *good = '^';
 410                 memcpy(good + 1, hex, strlen(hex) + 1);
 411                 ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 412                 rev_argv[rev_argv_nr++] = good;
 413         } else if (!prefixcmp(refname, "skip-")) {
 414                 ALLOC_GROW(skipped_sha1, skipped_sha1_nr + 1,
 415                            skipped_sha1_alloc);
 416                 hashcpy(skipped_sha1[skipped_sha1_nr++], sha1);
 417         }
 418
 419         return 0;
 420 }
 421
 422 static int read_bisect_refs(void)
 423 {
 424         return for_each_ref_in("refs/bisect/", register_ref, NULL);
 425 }
 426
 427 static int skipcmp(const void *a, const void *b)
 428 {
 429         return hashcmp(a, b);
 430 }
 431
 432 static void prepare_skipped(void)
 433 {
 434         qsort(skipped_sha1, skipped_sha1_nr, sizeof(*skipped_sha1), skipcmp);
 435 }
 436
 437 static const unsigned char *skipped_sha1_access(size_t index, void *table)
 438 {
 439         unsigned char (*skipped)[20] = table;
 440         return skipped[index];
 441 }
 442
 443 static int lookup_skipped(unsigned char *sha1)
 444 {
 445         return sha1_pos(sha1, skipped_sha1, skipped_sha1_nr,
 446                         skipped_sha1_access);
 447 }
 448
 449 struct commit_list *filter_skipped(struct commit_list *list,
 450                                    struct commit_list **tried,
 451                                    int show_all)
 452 {
 453         struct commit_list *filtered = NULL, **f = &filtered;
 454
 455         *tried = NULL;
 456
 457         if (!skipped_sha1_nr)
 458                 return list;
 459
 460         prepare_skipped();
 461
 462         while (list) {
 463                 struct commit_list *next = list->next;
 464                 list->next = NULL;
 465                 if (0 <= lookup_skipped(list->item->object.sha1)) {
 466                         /* Move current to tried list */
 467                         *tried = list;
 468                         tried = &list->next;
 469                 } else {
 470                         if (!show_all)
 471                                 return list;
 472                         /* Move current to filtered list */
 473                         *f = list;
 474                         f = &list->next;
 475                 }
 476                 list = next;
 477         }
 478
 479         return filtered;
 480 }
 481
 482 int bisect_next_vars(const char *prefix)
 483 {
 484         struct rev_info revs;
 485         int reaches = 0, all = 0;
 486
 487         init_revisions(&revs, prefix);
 488         revs.abbrev = 0;
 489         revs.commit_format = CMIT_FMT_UNSPECIFIED;
 490
 491         /* argv[0] will be ignored by setup_revisions */
 492         ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 493         rev_argv[rev_argv_nr++] = xstrdup("bisect_rev_setup");
 494
 495         if (read_bisect_refs())
 496                 die("reading bisect refs failed");
 497
 498         ALLOC_GROW(rev_argv, rev_argv_nr + 1, rev_argv_alloc);
 499         rev_argv[rev_argv_nr++] = xstrdup("--");
 500
 501         setup_revisions(rev_argv_nr, rev_argv, &revs, NULL);
 502
 503         revs.limited = 1;
 504
 505         if (prepare_revision_walk(&revs))
 506                 die("revision walk setup failed");
 507         if (revs.tree_objects)
 508                 mark_edges_uninteresting(revs.commits, &revs, NULL);
 509
 510         revs.commits = find_bisection(revs.commits, &reaches, &all,
 511                                       !!skipped_sha1_nr);
 512
 513         return show_bisect_vars(&revs, reaches, all, 0, 1);
 514 }