[llvm] [VPlan] Introduce ExitPhi VPInstruction, use to create phi for FOR. (PR #94760)

[via llvm-commits]

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@@ -729,6 +759,9 @@ void VPInstruction::print(raw_ostream &O, const Twine &Indent,
   case VPInstruction::ActiveLaneMask:
     O << "active lane mask";
     break;
+  case VPInstruction::ResumePhi:
+    O << "exit-phi";
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ayalz wrote:

```suggestion
    O << "resume-phi";
```

https://github.com/llvm/llvm-project/pull/94760