[llvm] [VPlan] Add VPIRBasicBlock, use to model pre-preheader. (PR #93398)

[via llvm-commits]

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@@ -2948,12 +2953,48 @@ class VPBasicBlock : public VPBlockBase {
     return NewBlock;
   }
 
+protected:
+  void executeRecipes(VPTransformState *State, BasicBlock *BB);
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ayalz wrote:

Documentation missing.

https://github.com/llvm/llvm-project/pull/93398