Looks good except for the typo.

One more const-comment, otherwise looks good.

In D85254#2305179, @hliao wrote:

This change is reverted as, on hosts without LBR supported but with LIBPFM installed and used, this change makes llvm/test/tools/llvm-exegesis/X86/lbr/mov-add.s failed. On that host, perf_event_open fails with EOPNOTSUPP on LBR config. That change's basic assumption

If this is run on a non-supported hardware, it will produce all zeroes for latency.

could not stand as perf_event_open system call will fail if the underlying hardware really doesn't have LBR supported.

Thanks Vy!

Thanks Vy for working on this!

Looks good overall.

One last comment, but otherwise this looks good. I'll leave the approval to Clement.

I've added a couple of style comment + one bigger comment on the aggregation of results from multiple runs/counter buffer.

This looks good in general, but we should be careful about aggregating the values from the measurements (and aggregation when the counter returns multiple values). In particular for the LBR, we'd be losing interesting and potentially useful information by aggregating all the values into a single number.