[llvm] [PassManager] Support MachineFunctionProperties (PR #83668)

[Matt Arsenault via llvm-commits]

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@@ -64,6 +64,8 @@ extern llvm::cl::opt<bool> UseNewDbgInfoFormat;
 
 namespace llvm {
 
+class MachineFunction;
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arsenm wrote:

Mostly the API is bad. We have this full set of virtual functions to implement, and then you have to construct an empty MachineFunctionProperties, and set fields in it. It would be much more convenient to have something declarative 

https://github.com/llvm/llvm-project/pull/83668