[PATCH v2 04/11] perf annotate-data: Improve type comparison from different scopes

[Zecheng Li]

From: Zecheng Li <zecheng@xxxxxxxxxx>

When comparing types from different scopes, first compare their type
offsets. A larger offset means the field belongs to an outer (enclosing)
struct. This helps resolve cases where a pointer is found in an inner
scope, but a struct containing that pointer exists in an outer scope.
Previously, is_better_type would prefer the pointer type, but the struct
type is actually more complete and should be chosen.

Prefer types from outer scopes when is_better_type cannot determine a
better type. This is a heuristic for the case `struct A { struct B; }`
where A and B have the same size but I think in most cases A is in the
outer scope and should be preferred.

Signed-off-by: Zecheng Li <zecheng@xxxxxxxxxx>
Signed-off-by: Zecheng Li <zli94@xxxxxxxx>
---
 tools/perf/util/annotate-data.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 23a09bf58f86..6fe2efd48a83 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -1629,7 +1629,9 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die)
 			pr_debug_dtp("type_offset=%#x\n", type_offset);
 		}
 
-		if (!found || is_better_type(type_die, &mem_die)) {
+		if (!found || dloc->type_offset < type_offset ||
+		    (dloc->type_offset == type_offset &&
+		     !is_better_type(&mem_die, type_die))) {
 			*type_die = mem_die;
 			dloc->type_offset = type_offset;
 			found = true;
-- 
2.53.0