perf no longer figures out call stacks when debuginfo-level is enabled

[saethlin]

In the past (weeks ago?) I used to often profile a locally built compiler with debuginfo-level = 1 using perf record --call-graph=dwarf cargo +stage1 build. This used to work great, but somewhat recently, the flamegraphs I render with perf script | inferno-collapse-perf | inferno-flamegraph > flamegraph.svg almost look like they are from a built without debuginfo enabled.

I don't have much useful information to share right now. I'm not sure what would be helpful for debugging this. I can provide some demonstration of the flamegraphs I get out of inferno in a few days, but if anyone has specific data they'd like about the builds I'm producing, happy to provide that.

[Enselic]

Triage: is this still a problem? I suspect this is not a problem any longer since there has been no additional complaints for over two years?

[saethlin]

My flamegraphs still seem broken. I can upload some here, they need to be gzipped to prevent GitHub from stripping out the JavaScript that makes them work.

flamegraph-dwarf.svg.gz
flamegraph-fp.svg.gz

These are flamegraphs of the exact same workload, but see how the fp one has much clearer structure than the dwarf one. That's the bug.