[llvm] [NFC][EarlyIfConverter] Turn SSAIfConv into a local variable (PR #107390)

[Matt Arsenault via llvm-commits]

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@@ -163,8 +163,7 @@ class SSAIfConv {
   void rewritePHIOperands();
 
 public:
-  /// runOnMachineFunction - Initialize per-function data structures.
-  void runOnMachineFunction(MachineFunction &MF) {
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arsenm wrote:

runOnMachineFunction was a deceptive name for something that's not a pass 

https://github.com/llvm/llvm-project/pull/107390