[llvm] Add a pass to collect dropped variable statistics (PR #102233)

[Adrian Prantl via llvm-commits]

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@@ -578,6 +579,74 @@ class PrintCrashIRInstrumentation {
   static void SignalHandler(void *);
 };
 
+class DroppedVariableStats {
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adrian-prantl wrote:

Can you add a Doxygen comment for this?

https://github.com/llvm/llvm-project/pull/102233