Make it easy to add diffing of output of arbitrary profilers (demonstrate for dep-graph)

[oli-obk]

I did some cleanups beforehand which, while not strictly necessary, were distracting me 😆

[Kobzol]

Thanks, this makes sense! The cleanup is also nice.

Left a few nits.

[Kobzol]

There is also profiler diffing for runtime benchmarks (

rustc-perf/collector/src/bin/collector.rs

Line 799 in 700be8c

RuntimeProfiler::Cachegrind => {

), which could be moved to the new "API". But I don't think that it's super important, I can do it later.

[oli-obk]

Yea, I wanted to do that, but the enums RuntimeProfiler and Profiler are different, so I didn't do that yet. I think figuring out deduplication for those later is better

[Kobzol]

Agreed. Thanks!