[llvm] [Pass] Support start/stop in instrumentation (PR #70912)

[Arthur Eubanks via llvm-commits]

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@@ -28,6 +28,14 @@ PassInstrumentationCallbacks::getPassNameForClassName(StringRef ClassName) {
   return ClassToPassName[ClassName];
 }
 
+StringRef
+PassInstrumentationCallbacks::getClassNameForPassName(StringRef PassName) {
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aeubanks wrote:

rather than adding this reverse map, let's be consistent with existing instrumentation like [here](https://github.com/llvm/llvm-project/blob/b53628a52d1947c51e250d6fa4ff5dd12b737aa0/llvm/lib/Passes/StandardInstrumentations.cpp#L920) where we check the pass name against `PIC->getPassNameForClassName(PassID)` in the callbacks. even if this is slower it doesn't really matter since this is just used for testing iiuc

https://github.com/llvm/llvm-project/pull/70912