merge-ort: store filepairs and filespecs in our mem_pool

For the testcases mentioned in commit 557ac03 ("merge-ort: begin
performance work; instrument with trace2_region_* calls", 2020-10-28),
this change improves the performance as follows:

                            Before                  After
    no-renames:       198.1 ms ±  2.6 ms     198.5 ms ±  3.4 ms
    mega-renames:     715.8 ms ±  4.0 ms     679.1 ms ±  5.6 ms
    just-one-mega:    276.8 ms ±  4.2 ms     271.9 ms ±  2.8 ms

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

diffcore-rename.c

@@ -1334,7 +1334,6 @@ static void free_filespec_data(struct diff_filespec *spec)
 		diff_free_filespec_data(spec);
 }
 
-MAYBE_UNUSED
 static void pool_free_filespec(struct mem_pool *pool,
 			       struct diff_filespec *spec)
 {
@@ -1351,7 +1350,6 @@ static void pool_free_filespec(struct mem_pool *pool,
 	free_filespec_data(spec);
 }
 
-MAYBE_UNUSED
 void pool_diff_free_filepair(struct mem_pool *pool,
 			     struct diff_filepair *p)
 {
@@ -1370,6 +1368,7 @@ void pool_diff_free_filepair(struct mem_pool *pool,
 }
 
 void diffcore_rename_extended(struct diff_options *options,
+			      struct mem_pool *pool,
 			      struct strintmap *relevant_sources,
 			      struct strintmap *dirs_removed,
 			      struct strmap *dir_rename_count,
@@ -1683,7 +1682,7 @@ void diffcore_rename_extended(struct diff_options *options,
 			pair_to_free = p;
 
 		if (pair_to_free)
-			diff_free_filepair(pair_to_free);
+			pool_diff_free_filepair(pool, pair_to_free);
 	}
 	diff_debug_queue("done copying original", &outq);
 
@@ -1693,7 +1692,7 @@ void diffcore_rename_extended(struct diff_options *options,
 
 	for (i = 0; i < rename_dst_nr; i++)
 		if (rename_dst[i].filespec_to_free)
-			free_filespec(rename_dst[i].filespec_to_free);
+			pool_free_filespec(pool, rename_dst[i].filespec_to_free);
 
 	cleanup_dir_rename_info(&info, dirs_removed, dir_rename_count != NULL);
 	FREE_AND_NULL(rename_dst);
@@ -1710,5 +1709,5 @@ void diffcore_rename_extended(struct diff_options *options,
 
 void diffcore_rename(struct diff_options *options)
 {
-	diffcore_rename_extended(options, NULL, NULL, NULL, NULL);
+	diffcore_rename_extended(options, NULL, NULL, NULL, NULL, NULL);
 }

diffcore.h

@@ -181,6 +181,7 @@ void partial_clear_dir_rename_count(struct strmap *dir_rename_count);
 void diffcore_break(struct repository *, int);
 void diffcore_rename(struct diff_options *);
 void diffcore_rename_extended(struct diff_options *options,
+			      struct mem_pool *pool,
 			      struct strintmap *relevant_sources,
 			      struct strintmap *dirs_removed,
 			      struct strmap *dir_rename_count,

merge-ort.c

@@ -690,7 +690,6 @@ static void path_msg(struct merge_options *opt,
 	strbuf_addch(sb, '\n');
 }
 
-MAYBE_UNUSED
 static struct diff_filespec *pool_alloc_filespec(struct mem_pool *pool,
 						 const char *path)
 {
@@ -712,7 +711,6 @@ static struct diff_filespec *pool_alloc_filespec(struct mem_pool *pool,
 	return spec;
 }
 
-MAYBE_UNUSED
 static struct diff_filepair *pool_diff_queue(struct mem_pool *pool,
 					     struct diff_queue_struct *queue,
 					     struct diff_filespec *one,
@@ -930,6 +928,7 @@ static void add_pair(struct merge_options *opt,
 		     unsigned dir_rename_mask)
 {
 	struct diff_filespec *one, *two;
+	struct mem_pool *pool = opt->priv->pool;
 	struct rename_info *renames = &opt->priv->renames;
 	int names_idx = is_add ? side : 0;
 
@@ -980,11 +979,11 @@ static void add_pair(struct merge_options *opt,
 			return;
 	}
 
-	one = alloc_filespec(pathname);
-	two = alloc_filespec(pathname);
+	one = pool_alloc_filespec(pool, pathname);
+	two = pool_alloc_filespec(pool, pathname);
 	fill_filespec(is_add ? two : one,
 		      &names[names_idx].oid, 1, names[names_idx].mode);
-	diff_queue(&renames->pairs[side], one, two);
+	pool_diff_queue(pool, &renames->pairs[side], one, two);
 }
 
 static void collect_rename_info(struct merge_options *opt,
@@ -2893,6 +2892,7 @@ static void use_cached_pairs(struct merge_options *opt,
 {
 	struct hashmap_iter iter;
 	struct strmap_entry *entry;
+	struct mem_pool *pool = opt->priv->pool;
 
 	/*
 	 * Add to side_pairs all entries from renames->cached_pairs[side_index].
@@ -2906,9 +2906,9 @@ static void use_cached_pairs(struct merge_options *opt,
 			new_name = old_name;
 
 		/* We don't care about oid/mode, only filenames and status */
-		one = alloc_filespec(old_name);
-		two = alloc_filespec(new_name);
-		diff_queue(pairs, one, two);
+		one = pool_alloc_filespec(pool, old_name);
+		two = pool_alloc_filespec(pool, new_name);
+		pool_diff_queue(pool, pairs, one, two);
 		pairs->queue[pairs->nr-1]->status = entry->value ? 'R' : 'D';
 	}
 }
@@ -3016,6 +3016,7 @@ static int detect_regular_renames(struct merge_options *opt,
 	diff_queued_diff = renames->pairs[side_index];
 	trace2_region_enter("diff", "diffcore_rename", opt->repo);
 	diffcore_rename_extended(&diff_opts,
+				 opt->priv->pool,
 				 &renames->relevant_sources[side_index],
 				 &renames->dirs_removed[side_index],
 				 &renames->dir_rename_count[side_index],
@@ -3066,7 +3067,7 @@ static int collect_renames(struct merge_options *opt,
 
 		if (p->status != 'A' && p->status != 'R') {
 			possibly_cache_new_pair(renames, p, side_index, NULL);
-			diff_free_filepair(p);
+			pool_diff_free_filepair(opt->priv->pool, p);
 			continue;
 		}
 
@@ -3079,7 +3080,7 @@ static int collect_renames(struct merge_options *opt,
 
 		possibly_cache_new_pair(renames, p, side_index, new_path);
 		if (p->status != 'R' && !new_path) {
-			diff_free_filepair(p);
+			pool_diff_free_filepair(opt->priv->pool, p);
 			continue;
 		}
 
@@ -3197,7 +3198,7 @@ static int detect_and_process_renames(struct merge_options *opt,
 		side_pairs = &renames->pairs[s];
 		for (i = 0; i < side_pairs->nr; ++i) {
 			struct diff_filepair *p = side_pairs->queue[i];
-			diff_free_filepair(p);
+			pool_diff_free_filepair(opt->priv->pool, p);
 		}
 	}
 
@@ -3210,7 +3211,8 @@ static int detect_and_process_renames(struct merge_options *opt,
 	if (combined.nr) {
 		int i;
 		for (i = 0; i < combined.nr; i++)
-			diff_free_filepair(combined.queue[i]);
+			pool_diff_free_filepair(opt->priv->pool,
+						combined.queue[i]);
 		free(combined.queue);
 	}