[llvm] [BOLT] Gadget scanner: reformulate the state for data-flow analysis (PR #131898)

[Kristof Beyls via llvm-commits]

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@@ -169,16 +186,26 @@ struct State {
   std::vector<SmallPtrSet<const MCInst *, 4>> LastInstWritingReg;
   State() {}
   State(unsigned NumRegs, unsigned NumRegsToTrack)
-      : NonAutClobRegs(NumRegs), LastInstWritingReg(NumRegsToTrack) {}
-  State &operator|=(const State &StateIn) {
-    NonAutClobRegs |= StateIn.NonAutClobRegs;
+      : SafeToDerefRegs(NumRegs), LastInstWritingReg(NumRegsToTrack) {}
+
+  /// Returns S, so that S.merge(S1) == S1.merge(S) == S1.
+  static State getMergeNeutralElement(unsigned NumRegs,
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kbeyls wrote:

I wasn't fully sure what `getMergeNeutralElement` meant when I first read this code linearly.
Reading further, I see this method is used to initialize the state object in the dataflow analysis.
I'm wondering if it would be easier to understand for most readers of this code if the name instead were something like `createInitialState` or something similar?

https://github.com/llvm/llvm-project/pull/131898