[clang-tools-extra] [lld] [clang] [llvm] [llvm-exegesis] Add support for validation counters (PR #76653)

[Aiden Grossman via cfe-commits]

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@@ -112,9 +116,11 @@ class Counter {
   PerfEvent Event;
   int FileDescriptor = -1;
   bool IsDummyEvent;
+  std::vector<PerfEvent> ValidationEvents;
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boomanaiden154 wrote:

My understanding is that `Counter` was an abstraction over a specific event that we want to measure (like uops through a specific port or cycles) rather than over an individual performance counter created with `perf_event_open`.

It is a little weird (maybe renaming it to something like `CounterGroup` would make this better?), but I think this still makes the most sense given the tight coupling between the validation counters and the actual event counter both conceptually and in regards to how everything is set up in the perf subsystem (as an individual group).

https://github.com/llvm/llvm-project/pull/76653