[PATCH v5] show-branch: convert per-branch flags to commit-slab
- From
- Gatla Vishweshwar Reddy <gatlavishweshwarreddy26@gmail.com>
- Date
- Jul 15, 2026, 12:01 UTC
- Message-ID
- <20260715120156.53025-1-gatlavishweshwarreddy26@gmail.com>
- In-Reply-To
- <xmqqwluwpvme.fsf@gitster.g>
show-branch uses commit->object.flags to store per-branch reachability bits, one bit per branch starting at REV_SHIFT. The flags word has only a fixed number of available bits, limiting the number of branches that can be shown simultaneously to MAX_REVS.
Convert the per-branch bits to a dedicated commit-slab using uint64_t as the element type, initialized with a stride via init_commit_rev_flags_with_stride(). Keep the UNINTERESTING bit in object.flags where it belongs, as it is used for revision walking and does not need to be in the per-branch slab. With UNINTERESTING removed from the slab, REV_SHIFT becomes 0 and all 64 bits of uint64_t are available for branch tracking, lifting MAX_REVS from 27 to 64 branches.
Add helper functions get_rev_flags_ptr(), peek_rev_flags_ptr(), has_any_rev_flags(), or_rev_flag_bit(), test_rev_flag_bit(), has_all_rev_flags(), and has_only_rev_flag_bit() to encapsulate per-bit slab access cleanly. Use has_only_rev_flag_bit() in show_independent() to preserve the original semantics: a commit is independent only if reachable from exactly one tip, not merely if the i-th bit happens to be set. Update all bit operations to use UINT64_C(1) for correct 64-bit shifts. Initialize and clear the slab in cmd_show_branch().
Signed-off-by: Gatla Vishweshwar Reddy <gatlavishweshwarreddy26@gmail.com> ---
Apologies to Patrick for not replying inline to the review before sending v4. For previous review threads I did reply inline; for that round I mistakenly folded the response into the annotation only.
Response to Junio's review of v4:
- Restored the TODO comment above REV_SHIFT since the UNINTERESTING migration to the slab is not yet complete. - Removed the local "#define UNINTERESTING 01" and added #include "revision.h" to use the shared definition instead.
Changes in v5: - Restore TODO comment above REV_SHIFT - Remove local UNINTERESTING define, include revision.h instead
builtin/show-branch.c | 162 +++++++++++++++++++++++++++--------------- 1 file changed, 103 insertions(+), 59 deletions(-)
diff --git a/builtin/show-branch.c b/builtin/show-branch.c index f02831b085..cf037c5814 100644 --- a/builtin/show-branch.c +++ b/builtin/show-branch.c @@ -9,6 +9,7 @@ #include "hex.h" #include "pretty.h" #include "refs.h" +#include "revision.h" #include "color.h" #include "strvec.h" #include "object-name.h" @@ -35,15 +36,12 @@ static enum git_colorbool showbranch_use_color = GIT_COLOR_UNKNOWN; static struct strvec default_args = STRVEC_INIT; /* - * TODO: convert this use of commit->object.flags to commit-slab - * instead to store a pointer to ref name directly. Then use the same - * UNINTERESTING definition from revision.h here. + * TODO: store a pointer to ref name directly in the commit-slab + * instead, and use the UNINTERESTING definition from revision.h + * here once that is done. */ -#define UNINTERESTING 01 - -#define REV_SHIFT 2 -#define MAX_REVS (FLAG_BITS - REV_SHIFT) /* should not exceed bits_per_int - REV_SHIFT */ - +#define REV_SHIFT 0 +#define MAX_REVS (sizeof(uint64_t) * 8) #define DEFAULT_REFLOG 4 static const char *get_color_code(int idx) @@ -79,11 +77,72 @@ struct commit_name { define_commit_slab(commit_name_slab, struct commit_name *); static struct commit_name_slab name_slab; +define_commit_slab(commit_rev_flags, uint64_t); +static struct commit_rev_flags rev_flags_slab; +static int flags_stride; /* number of uint64_t words per commit */ + static struct commit_name *commit_to_name(struct commit *commit) { return *commit_name_slab_at(&name_slab, commit); } +static uint64_t *get_rev_flags_ptr(struct commit *commit) +{ + return commit_rev_flags_at(&rev_flags_slab, commit); +} + +static uint64_t *peek_rev_flags_ptr(struct commit *commit) +{ + return commit_rev_flags_peek(&rev_flags_slab, commit); +} + +static int has_any_rev_flags(struct commit *commit) +{ + uint64_t *f = peek_rev_flags_ptr(commit); + int i; + if (!f) + return 0; + for (i = 0; i < flags_stride; i++) + if (f[i]) + return 1; + return 0; +} + +static void or_rev_flag_bit(struct commit *commit, int branch) +{ + get_rev_flags_ptr(commit)[branch / 64] |= UINT64_C(1) << (branch % 64); +} + +static int test_rev_flag_bit(struct commit *commit, int branch) +{ + uint64_t *f = peek_rev_flags_ptr(commit); + return f && !!(f[branch / 64] & (UINT64_C(1) << (branch % 64))); +} + +static int has_all_rev_flags(struct commit *commit, int num_rev) +{ + int i; + for (i = 0; i < num_rev; i++) + if (!test_rev_flag_bit(commit, i)) + return 0; + return 1; +} + +static int has_only_rev_flag_bit(struct commit *commit, int branch) +{ + uint64_t *f = peek_rev_flags_ptr(commit); + int i; + if (!f) + return 0; + for (i = 0; i < flags_stride; i++) { + uint64_t expected = (i == branch / 64) + ? (UINT64_C(1) << (branch % 64)) + : 0; + if (f[i] != expected) + return 0; + } + return 1; +} /* Name the commit as nth generation ancestor of head_name; * we count only the first-parent relationship for naming purposes. @@ -215,7 +274,7 @@ static void name_commits(struct commit_list *list, static int mark_seen(struct commit *commit, struct commit_list **seen_p) { - if (!commit->object.flags) { + if (!has_any_rev_flags(commit)) { commit_list_insert(commit, seen_p); return 1; } @@ -226,34 +285,34 @@ static void join_revs(struct prio_queue *queue, struct commit_list **seen_p, int num_rev, int extra) { - int all_mask = ((1u << (REV_SHIFT + num_rev)) - 1); - int all_revs = all_mask & ~((1u << REV_SHIFT) - 1); - while (queue->nr) { struct commit_list *parents; int still_interesting = !!interesting(queue); struct commit *commit = prio_queue_peek(queue); bool get_pending = true; - int flags = commit->object.flags & all_mask; if (!still_interesting && extra <= 0) break; mark_seen(commit, seen_p); - if ((flags & all_revs) == all_revs) - flags |= UNINTERESTING; + if (has_all_rev_flags(commit, num_rev)) + commit->object.flags |= UNINTERESTING; parents = commit->parents; while (parents) { struct commit *p = parents->item; - int this_flag = p->object.flags; parents = parents->next; - if ((this_flag & flags) == flags) + if (has_all_rev_flags(p, num_rev)) continue; repo_parse_commit(the_repository, p); if (mark_seen(p, seen_p) && !still_interesting) extra--; - p->object.flags |= flags; + { + int _b; + for (_b = 0; _b < num_rev; _b++) + if (test_rev_flag_bit(commit, _b)) + or_rev_flag_bit(p, _b); + } if (get_pending) prio_queue_replace(queue, p); else @@ -263,7 +322,6 @@ static void join_revs(struct prio_queue *queue, if (get_pending) prio_queue_get(queue); } - /* * Postprocess to complete well-poisoning. * @@ -278,7 +336,7 @@ static void join_revs(struct prio_queue *queue, struct commit *c = s->item; struct commit_list *parents; - if (((c->object.flags & all_revs) != all_revs) && + if (!has_all_rev_flags(c, num_rev) && !(c->object.flags & UNINTERESTING)) continue; @@ -410,8 +468,8 @@ static int append_ref(const char *refname, const struct object_id *oid, return 0; } if (MAX_REVS <= ref_name_cnt) { - warning(Q_("ignoring %s; cannot handle more than %d ref", - "ignoring %s; cannot handle more than %d refs", + warning(Q_("ignoring %s; cannot handle more than %zu ref", + "ignoring %s; cannot handle more than %zu refs", MAX_REVS), refname, MAX_REVS); return 0; } @@ -511,15 +569,12 @@ static int rev_is_head(const char *head, const char *name) static int show_merge_base(const struct commit_list *seen, int num_rev) { - int all_mask = ((1u << (REV_SHIFT + num_rev)) - 1); - int all_revs = all_mask & ~((1u << REV_SHIFT) - 1); int exit_status = 1; for (const struct commit_list *s = seen; s; s = s->next) { struct commit *commit = s->item; - int flags = commit->object.flags & all_mask; - if (!(flags & UNINTERESTING) && - ((flags & all_revs) == all_revs)) { + if (!(commit->object.flags & UNINTERESTING) && + has_all_rev_flags(commit, num_rev)) { puts(oid_to_hex(&commit->object.oid)); exit_status = 0; commit->object.flags |= UNINTERESTING; @@ -528,17 +583,13 @@ static int show_merge_base(const struct commit_list *seen, int num_rev) return exit_status; } -static int show_independent(struct commit **rev, - int num_rev, - unsigned int *rev_mask) +static int show_independent(struct commit **rev, int num_rev) { int i; for (i = 0; i < num_rev; i++) { struct commit *commit = rev[i]; - unsigned int flag = rev_mask[i]; - - if (commit->object.flags == flag) + if (has_only_rev_flag_bit(commit, i)) puts(oid_to_hex(&commit->object.oid)); commit->object.flags |= UNINTERESTING; } @@ -603,13 +654,12 @@ static int omit_in_dense(struct commit *commit, struct commit **rev, int n) * Otherwise, if it is a merge that is reachable from only one * tip, it is not that interesting. */ - int i, flag, count; + int i, count; for (i = 0; i < n; i++) if (rev[i] == commit) return 0; - flag = commit->object.flags; for (i = count = 0; i < n; i++) { - if (flag & (1u << (i + REV_SHIFT))) + if (test_rev_flag_bit(commit, i)) count++; } if (count == 1) @@ -648,10 +698,8 @@ int cmd_show_branch(int ac, char *reflog_msg[MAX_REVS] = {0}; struct commit_list *seen = NULL; struct prio_queue queue = { compare_commits_by_commit_date }; - unsigned int rev_mask[MAX_REVS]; int num_rev, i, extra = 0; int all_heads = 0, all_remotes = 0; - int all_mask, all_revs; enum rev_sort_order sort_order = REV_SORT_IN_GRAPH_ORDER; char *head; struct object_id head_oid; @@ -713,7 +761,8 @@ int cmd_show_branch(int ac, const char **args_copy = NULL; int ret; - init_commit_name_slab(&name_slab); + flags_stride = (MAX_REVS + 63) / 64; + init_commit_rev_flags_with_stride(&rev_flags_slab, flags_stride); repo_config(the_repository, git_show_branch_config, NULL); @@ -779,8 +828,8 @@ int cmd_show_branch(int ac, die(_("--reflog option needs one branch name")); if (MAX_REVS < reflog) - die(Q_("only %d entry can be shown at one time.", - "only %d entries can be shown at one time.", + die(Q_("only %zu entry can be shown at one time.", + "only %zu entries can be shown at one time.", MAX_REVS), MAX_REVS); if (!repo_dwim_ref(the_repository, *av, strlen(*av), &oid, &ref, 0)) @@ -870,11 +919,11 @@ int cmd_show_branch(int ac, for (num_rev = 0; ref_name[num_rev]; num_rev++) { struct object_id revkey; - unsigned int flag = 1u << (num_rev + REV_SHIFT); + int first_seen; if (MAX_REVS <= num_rev) - die(Q_("cannot handle more than %d rev.", - "cannot handle more than %d revs.", + die(Q_("cannot handle more than %zu rev.", + "cannot handle more than %zu revs.", MAX_REVS), MAX_REVS); if (repo_get_oid(the_repository, ref_name[num_rev], &revkey)) die(_("'%s' is not a valid ref."), ref_name[num_rev]); @@ -885,17 +934,15 @@ int cmd_show_branch(int ac, repo_parse_commit(the_repository, commit); mark_seen(commit, &seen); - /* rev#0 uses bit REV_SHIFT, rev#1 uses bit REV_SHIFT+1, - * and so on. REV_SHIFT bits from bit 0 are used for - * internal bookkeeping. + /* rev#0 uses bit 0, rev#1 uses bit 1, + * and so on. All bits are available for branch tracking. */ - commit->object.flags |= flag; - if (commit->object.flags == flag) + first_seen = !has_any_rev_flags(commit); + or_rev_flag_bit(commit, num_rev); + if (first_seen) prio_queue_put(&queue, commit); rev[num_rev] = commit; } - for (i = 0; i < num_rev; i++) - rev_mask[i] = rev[i]->object.flags; if (0 <= extra) join_revs(&queue, &seen, num_rev, extra); @@ -908,7 +955,7 @@ int cmd_show_branch(int ac, } if (independent) { - ret = show_independent(rev, num_rev, rev_mask); + ret = show_independent(rev, num_rev); goto out; } @@ -958,13 +1005,9 @@ int cmd_show_branch(int ac, if (!sha1_name && !no_name) name_commits(seen, rev, ref_name, num_rev); - all_mask = ((1u << (REV_SHIFT + num_rev)) - 1); - all_revs = all_mask & ~((1u << REV_SHIFT) - 1); - for (struct commit_list *l = seen; l; l = l->next) { struct commit *commit = l->item; - int this_flag = commit->object.flags; - int is_merge_point = ((this_flag & all_revs) == all_revs); + int is_merge_point = has_all_rev_flags(commit, num_rev); shown_merge_point |= is_merge_point; @@ -973,14 +1016,14 @@ int cmd_show_branch(int ac, commit->parents->next); if (topics && !is_merge_point && - (this_flag & (1u << REV_SHIFT))) + test_rev_flag_bit(commit, 0)) continue; if (!sparse && is_merge && omit_in_dense(commit, rev, num_rev)) continue; for (i = 0; i < num_rev; i++) { int mark; - if (!(this_flag & (1u << (i + REV_SHIFT)))) + if (!test_rev_flag_bit(commit, i)) mark = ' '; else if (is_merge) mark = '-'; @@ -1010,6 +1053,7 @@ int cmd_show_branch(int ac, free(reflog_msg[i]); commit_list_free(seen); clear_prio_queue(&queue); + clear_commit_rev_flags(&rev_flags_slab); free(args_copy); free(head); return ret;
-- 2.54.0