[llvm] [CodeGen][NewPM] Split `MachineDominatorTree` into a concrete analysis result (PR #94571)

[Matt Arsenault via llvm-commits]

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@@ -266,6 +266,7 @@ class MachineDominatorTree : public DomTreeBase<MachineBasicBlock> {
 /// \brief Analysis pass which computes a \c MachineDominatorTree.
 class MachineDominatorTreeWrapperPass : public MachineFunctionPass {
   MachineDominatorTree DT;
+  bool IsDomTreeEmpty = true;
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arsenm wrote:

Either make it std::optional or fix the verifier to not assert on the empty case 

https://github.com/llvm/llvm-project/pull/94571