linux-kernel - [PATCH v1 04/11] perf annotate-data: Improve type comparison from different scopes

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Message-ID: <20260127020617.2804780-5-zli94@ncsu.edu>
Date: Mon, 26 Jan 2026 21:04:57 -0500
From: Zecheng Li <zli94@...u.edu>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	Zecheng Li <zli94@...u.edu>,
	xliuprof@...gle.com,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Zecheng Li <zecheng@...gle.com>
Subject: [PATCH v1 04/11] perf annotate-data: Improve type comparison from different scopes

From: Zecheng Li <zecheng@...gle.com>

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@...gle.com>
Signed-off-by: Zecheng Li <zli94@...u.edu>
---
 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 8ff1972981b7..8ea3e8b024e8 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -1634,7 +1634,9 @@ 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;
-- 
2.52.0