From 644797119d7a3b7a043a51a9cccd8758f8451f91 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Thu, 25 Oct 2007 11:20:56 -0700 Subject: [PATCH] copy vs rename detection: avoid unnecessary O(n*m) loops The core rename detection had some rather stupid code to check if a pathname was used by a later modification or rename, which basically walked the whole pathname space for all renames for each rename, in order to tell whether it was a pure rename (no remaining users) or should be considered a copy (other users of the source file remaining). That's really silly, since we can just keep a count of users around, and replace all those complex and expensive loops with just testing that simple counter (but this all depends on the previous commit that shared the diff_filespec data structure by using a separate reference count). Note that the reference count is not the same as the rename count: they behave otherwise rather similarly, but the reference count is tied to the allocation (and decremented at de-allocation, so that when it turns zero we can get rid of the memory), while the rename count is tied to the renames and is decremented when we find a rename (so that when it turns zero we know that it was a rename, not a copy). Signed-off-by: Linus Torvalds Signed-off-by: Junio C Hamano --- diff.c | 40 ++++++++++++---------------- diffcore-rename.c | 68 ++++++++++++----------------------------------- diffcore.h | 2 +- 3 files changed, 35 insertions(+), 75 deletions(-) diff --git a/diff.c b/diff.c index 0b320f6b9..af85b94d1 100644 --- a/diff.c +++ b/diff.c @@ -2597,9 +2597,9 @@ void diff_debug_filepair(const struct diff_filepair *p, int i) { diff_debug_filespec(p->one, i, "one"); diff_debug_filespec(p->two, i, "two"); - fprintf(stderr, "score %d, status %c stays %d broken %d\n", + fprintf(stderr, "score %d, status %c rename_used %d broken %d\n", p->score, p->status ? p->status : '?', - p->source_stays, p->broken_pair); + p->one->rename_used, p->broken_pair); } void diff_debug_queue(const char *msg, struct diff_queue_struct *q) @@ -2617,8 +2617,8 @@ void diff_debug_queue(const char *msg, struct diff_queue_struct *q) static void diff_resolve_rename_copy(void) { - int i, j; - struct diff_filepair *p, *pp; + int i; + struct diff_filepair *p; struct diff_queue_struct *q = &diff_queued_diff; diff_debug_queue("resolve-rename-copy", q); @@ -2640,27 +2640,21 @@ static void diff_resolve_rename_copy(void) * either in-place edit or rename/copy edit. */ else if (DIFF_PAIR_RENAME(p)) { - if (p->source_stays) { - p->status = DIFF_STATUS_COPIED; - continue; - } - /* See if there is some other filepair that - * copies from the same source as us. If so - * we are a copy. Otherwise we are either a - * copy if the path stays, or a rename if it - * does not, but we already handled "stays" case. + /* + * A rename might have re-connected a broken + * pair up, causing the pathnames to be the + * same again. If so, that's not a rename at + * all, just a modification.. + * + * Otherwise, see if this source was used for + * multiple renames, in which case we decrement + * the count, and call it a copy. */ - for (j = i + 1; j < q->nr; j++) { - pp = q->queue[j]; - if (strcmp(pp->one->path, p->one->path)) - continue; /* not us */ - if (!DIFF_PAIR_RENAME(pp)) - continue; /* not a rename/copy */ - /* pp is a rename/copy from the same source */ + if (!strcmp(p->one->path, p->two->path)) + p->status = DIFF_STATUS_MODIFIED; + else if (--p->one->rename_used > 0) p->status = DIFF_STATUS_COPIED; - break; - } - if (!p->status) + else p->status = DIFF_STATUS_RENAMED; } else if (hashcmp(p->one->sha1, p->two->sha1) || diff --git a/diffcore-rename.c b/diffcore-rename.c index 3da06b702..edb2424d1 100644 --- a/diffcore-rename.c +++ b/diffcore-rename.c @@ -55,12 +55,10 @@ static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two, static struct diff_rename_src { struct diff_filespec *one; unsigned short score; /* to remember the break score */ - unsigned src_path_left : 1; } *rename_src; static int rename_src_nr, rename_src_alloc; static struct diff_rename_src *register_rename_src(struct diff_filespec *one, - int src_path_left, unsigned short score) { int first, last; @@ -92,7 +90,6 @@ static struct diff_rename_src *register_rename_src(struct diff_filespec *one, (rename_src_nr - first - 1) * sizeof(*rename_src)); rename_src[first].one = one; rename_src[first].score = score; - rename_src[first].src_path_left = src_path_left; return &(rename_src[first]); } @@ -216,6 +213,7 @@ static void record_rename_pair(int dst_index, int src_index, int score) die("internal error: dst already matched."); src = rename_src[src_index].one; + src->rename_used++; src->count++; dst = rename_dst[dst_index].two; @@ -227,7 +225,6 @@ static void record_rename_pair(int dst_index, int src_index, int score) dp->score = rename_src[src_index].score; else dp->score = score; - dp->source_stays = rename_src[src_index].src_path_left; rename_dst[dst_index].pair = dp; } @@ -245,21 +242,6 @@ static int score_compare(const void *a_, const void *b_) return b->score - a->score; } -static int compute_stays(struct diff_queue_struct *q, - struct diff_filespec *one) -{ - int i; - for (i = 0; i < q->nr; i++) { - struct diff_filepair *p = q->queue[i]; - if (strcmp(one->path, p->two->path)) - continue; - if (DIFF_PAIR_RENAME(p)) { - return 0; /* something else is renamed into this */ - } - } - return 1; -} - /* * Find exact renames first. * @@ -338,15 +320,25 @@ void diffcore_rename(struct diff_options *options) locate_rename_dst(p->two, 1); } else if (!DIFF_FILE_VALID(p->two)) { - /* If the source is a broken "delete", and + /* + * If the source is a broken "delete", and * they did not really want to get broken, * that means the source actually stays. + * So we increment the "rename_used" score + * by one, to indicate ourselves as a user + */ + if (p->broken_pair && !p->score) + p->one->rename_used++; + register_rename_src(p->one, p->score); + } + else if (detect_rename == DIFF_DETECT_COPY) { + /* + * Increment the "rename_used" score by + * one, to indicate ourselves as a user. */ - int stays = (p->broken_pair && !p->score); - register_rename_src(p->one, stays, p->score); + p->one->rename_used++; + register_rename_src(p->one, p->score); } - else if (detect_rename == DIFF_DETECT_COPY) - register_rename_src(p->one, 1, p->score); } if (rename_dst_nr == 0 || rename_src_nr == 0) goto cleanup; /* nothing to do */ @@ -472,16 +464,7 @@ void diffcore_rename(struct diff_options *options) pair_to_free = p; } else { - for (j = 0; j < rename_dst_nr; j++) { - if (!rename_dst[j].pair) - continue; - if (strcmp(rename_dst[j].pair-> - one->path, - p->one->path)) - continue; - break; - } - if (j < rename_dst_nr) + if (p->one->rename_used) /* this path remains */ pair_to_free = p; } @@ -507,23 +490,6 @@ void diffcore_rename(struct diff_options *options) *q = outq; diff_debug_queue("done collapsing", q); - /* We need to see which rename source really stays here; - * earlier we only checked if the path is left in the result, - * but even if a path remains in the result, if that is coming - * from copying something else on top of it, then the original - * source is lost and does not stay. - */ - for (i = 0; i < q->nr; i++) { - struct diff_filepair *p = q->queue[i]; - if (DIFF_PAIR_RENAME(p) && p->source_stays) { - /* If one appears as the target of a rename-copy, - * then mark p->source_stays = 0; otherwise - * leave it as is. - */ - p->source_stays = compute_stays(q, p->one); - } - } - for (i = 0; i < rename_dst_nr; i++) free_filespec(rename_dst[i].two); diff --git a/diffcore.h b/diffcore.h index 30055ac5a..cc96c2073 100644 --- a/diffcore.h +++ b/diffcore.h @@ -31,6 +31,7 @@ struct diff_filespec { unsigned long size; int count; /* Reference count */ int xfrm_flags; /* for use by the xfrm */ + int rename_used; /* Count of rename users */ unsigned short mode; /* file mode */ unsigned sha1_valid : 1; /* if true, use sha1 and trust mode; * if false, use the name and read from @@ -58,7 +59,6 @@ struct diff_filepair { struct diff_filespec *two; unsigned short int score; char status; /* M C R N D U (see Documentation/diff-format.txt) */ - unsigned source_stays : 1; /* all of R/C are copies */ unsigned broken_pair : 1; unsigned renamed_pair : 1; unsigned is_unmerged : 1; -- 2.26.2