[llvm] [Instrumentation] Support MachineFunction in ChangeReporter (PR #80946)

[Arthur Eubanks via llvm-commits]

================
@@ -409,6 +435,10 @@ template <typename T>
 void ChangeReporter<T>::handleInvalidatedPass(StringRef PassID) {
   assert(!BeforeStack.empty() && "Unexpected empty stack encountered.");
 
+  // Prepare to process the next MIR.
+  if (PassID == FreeMachineFunctionPass::name())
----------------
aeubanks wrote:

can you explain why this is necessary?

I think in general I'm not understanding the intent with "InitialIR" in regards to MIR. Previously we'd always start with the entire module as the initial IR right? Why are we handling MachineFunctions differently?

https://github.com/llvm/llvm-project/pull/80946