[PATCH 07/37] perf intel-pt: Ensure never to set 'last_ip' when packet 'count' is zero

Adrian Hunter
2017-05-19T09:08:42Z

Intel PT uses IP compression based on the last IP. For decoding purposes,
'last IP' is not updated when a branch target has been suppressed, which is
indicated by IPBytes == 0. IPBytes is stored in the packet 'count', so
ensure never to set 'last_ip' when packet 'count' is zero.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/util/intel-pt-decoder/intel-pt-decoder.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index f8fada859f12..4359177a0504 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -1450,7 +1450,8 @@ static int intel_pt_walk_psbend(struct intel_pt_decoder *decoder)

case INTEL_PT_FUP:
decoder->pge = true;
- intel_pt_set_last_ip(decoder);
+ if (decoder->packet.count)
+ intel_pt_set_last_ip(decoder);
break;

case INTEL_PT_MODE_TSX:
@@ -1740,8 +1741,9 @@ static int intel_pt_walk_trace(struct intel_pt_decoder *decoder)

static inline bool intel_pt_have_ip(struct intel_pt_decoder *decoder)
{
- return decoder->have_last_ip || decoder->packet.count == 0 ||
- decoder->packet.count == 3 || decoder->packet.count == 6;
+ return decoder->packet.count &&
+ (decoder->have_last_ip || decoder->packet.count == 3 ||
+ decoder->packet.count == 6);
}

/* Walk PSB+ packets to get in sync. */
--
1.9.1