[llvm] [VPlan] Construct immutable VPIRBBs for exit blocks at construction(NFC) (PR #128374)

[Florian Hahn via llvm-commits]

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@@ -3559,11 +3564,13 @@ class VPlan {
   /// Return the VPIRBasicBlock wrapping the header of the scalar loop.
   VPIRBasicBlock *getScalarHeader() const { return ScalarHeader; }
 
-  /// Return an iterator range over the VPIRBasicBlock wrapping the exit blocks
-  /// of the VPlan, that is leaf nodes except the scalar header. Defined in
-  /// VPlanHCFG, as the definition of the type needs access to the definitions
-  /// of VPBlockShallowTraversalWrapper.
-  auto getExitBlocks();
+  /// Return an ArrayRef containing VPIRBasicBlocks wrapping the exit blocks of
+  /// the original scalar loop.
+  ArrayRef<VPIRBasicBlock *> getExitBlocks() const { return ExitBlocks; }
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fhahn wrote:

Left as vector for now, as `getExitBlock` should not be needed soonish and be replaced by connecting the blocks during initial VPlan construction.

https://github.com/llvm/llvm-project/pull/128374