[PATCH 2/3] perf cs-etm: Use the packet instruction size for stack events

[Leo Yan <leo.yan@arm.com>]

cs_etm__add_stack_event() uses the last executed instruction of the
previous packet as the branch source. The decoder already records this
instruction's size in last_instr_size, including for T32 instructions.

Use the recorded size directly instead of reading instruction memory
again. This removes an unnecessary read and the dependency on DSO data
when updating the thread stack.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/perf/util/cs-etm.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 25f12bd110934a204d79244f45317085b7a81666..312d4a734e84faa0d24c4ac1fee16f4dae4c2398 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -1626,7 +1626,6 @@ static void cs_etm__add_stack_event(struct cs_etm_queue *etmq,
 {
 	struct cs_etm_auxtrace *etm = etmq->etm;
 	u64 from, to;
-	int size;
 
 	if (!etm->synth_opts.branches && !etm->synth_opts.instructions)
 		return;
@@ -1638,11 +1637,10 @@ static void cs_etm__add_stack_event(struct cs_etm_queue *etmq,
 		from = cs_etm__last_executed_instr(tidq->prev_packet);
 		to = cs_etm__first_executed_instr(tidq->packet);
 
-		size = cs_etm__instr_size(etmq, tidq, tidq->prev_packet, from);
-
 		/* Enable callchain so thread stack entry can be allocated */
 		thread_stack__event(tidq->frontend_thread, tidq->prev_packet->cpu,
-				    tidq->prev_packet->flags, from, to, size,
+				    tidq->prev_packet->flags, from, to,
+				    tidq->prev_packet->last_instr_size,
 				    etmq->buffer->buffer_nr + 1,
 				    etmq->etm->use_callchain,
 				    tidq->br_stack_sz, 0);

-- 
2.34.1