[llvm] [LoopVectorizer] Add support for partial reductions (PR #92418)

[Graham Hunter via llvm-commits]

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@@ -784,6 +784,8 @@ class VPRecipeBase : public ilist_node_with_parent<VPRecipeBase, VPBasicBlock>,
   /// \returns an iterator pointing to the element after the erased one
   iplist<VPRecipeBase>::iterator eraseFromParent();
 
+  virtual void postInsertionOp() {}
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huntergr-arm wrote:

I don't believe this is necessary, or desired. It modifies another VPRecipe (the reduction phi) after all instructions have a defined recipe. If my idea about storing information in the cost model is used, then VPRecipeBuilder will have the necessary information at the time the initial reduction phi recipe is created.

https://github.com/llvm/llvm-project/pull/92418