perf diff: Link same basic blocks among different data

The target is to compare the performance difference (cycles diff) for
the same basic blocks in different data files.

The same basic block means same function, same start address and same
end address. This patch finds the same basic blocks from different data
files and link them together and resort by the cycles diff.

 v3:
 ---
 The block stuffs are maintained by new structure 'block_hist',
 so this patch is update accordingly.

 v2:
 ---
 Since now the basic block hists is changed to per symbol,
 the patch only links the basic block hists for the same
 symbol in different data files.

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1561713784-30533-6-git-send-email-yao.jin@linux.intel.com
[ sym->name is an array, not a pointer, so no need to check it for NULL, fixes de build in some distros ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-diff.c

@@ -641,6 +641,82 @@ static int process_block_per_sym(struct hist_entry *he)
 	return 0;
 }
 
+static int block_pair_cmp(struct hist_entry *a, struct hist_entry *b)
+{
+	struct block_info *bi_a = a->block_info;
+	struct block_info *bi_b = b->block_info;
+	int cmp;
+
+	if (!bi_a->sym || !bi_b->sym)
+		return -1;
+
+	cmp = strcmp(bi_a->sym->name, bi_b->sym->name);
+
+	if ((!cmp) && (bi_a->start == bi_b->start) && (bi_a->end == bi_b->end))
+		return 0;
+
+	return -1;
+}
+
+static struct hist_entry *get_block_pair(struct hist_entry *he,
+					 struct hists *hists_pair)
+{
+	struct rb_root_cached *root = hists_pair->entries_in;
+	struct rb_node *next = rb_first_cached(root);
+	int cmp;
+
+	while (next != NULL) {
+		struct hist_entry *he_pair = rb_entry(next, struct hist_entry,
+						      rb_node_in);
+
+		next = rb_next(&he_pair->rb_node_in);
+
+		cmp = block_pair_cmp(he_pair, he);
+		if (!cmp)
+			return he_pair;
+	}
+
+	return NULL;
+}
+
+static void compute_cycles_diff(struct hist_entry *he,
+				struct hist_entry *pair)
+{
+	pair->diff.computed = true;
+	if (pair->block_info->num && he->block_info->num) {
+		pair->diff.cycles =
+			pair->block_info->cycles_aggr / pair->block_info->num_aggr -
+			he->block_info->cycles_aggr / he->block_info->num_aggr;
+	}
+}
+
+static void block_hists_match(struct hists *hists_base,
+			      struct hists *hists_pair)
+{
+	struct rb_root_cached *root = hists_base->entries_in;
+	struct rb_node *next = rb_first_cached(root);
+
+	while (next != NULL) {
+		struct hist_entry *he = rb_entry(next, struct hist_entry,
+						 rb_node_in);
+		struct hist_entry *pair = get_block_pair(he, hists_pair);
+
+		next = rb_next(&he->rb_node_in);
+
+		if (pair) {
+			hist_entry__add_pair(pair, he);
+			compute_cycles_diff(he, pair);
+		}
+	}
+}
+
+static int filter_cb(struct hist_entry *he, void *arg __maybe_unused)
+{
+	/* Skip the calculation of column length in output_resort */
+	he->filtered = true;
+	return 0;
+}
+
 static void hists__precompute(struct hists *hists)
 {
 	struct rb_root_cached *root;
@@ -653,6 +729,7 @@ static void hists__precompute(struct hists *hists)
 
 	next = rb_first_cached(root);
 	while (next != NULL) {
+		struct block_hist *bh, *pair_bh;
 		struct hist_entry *he, *pair;
 		struct data__file *d;
 		int i;
@@ -681,6 +758,16 @@ static void hists__precompute(struct hists *hists)
 				break;
 			case COMPUTE_CYCLES:
 				process_block_per_sym(pair);
+				bh = container_of(he, struct block_hist, he);
+				pair_bh = container_of(pair, struct block_hist,
+						       he);
+
+				if (bh->valid && pair_bh->valid) {
+					block_hists_match(&bh->block_hists,
+							  &pair_bh->block_hists);
+					hists__output_resort_cb(&pair_bh->block_hists,
+								NULL, filter_cb);
+				}
 				break;
 			default:
 				BUG_ON(1);