[llvm] [VPlan] Implement VPExtendedReduction, VPMulAccumulateReductionRecipe and correspond vplan transformations. (PR #137746)

[Florian Hahn via llvm-commits]

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@@ -2474,6 +2544,181 @@ class VPReductionEVLRecipe : public VPReductionRecipe {
   }
 };
 
+/// A recipe to represent inloop extended reduction operations, performing a
+/// reduction on a extended vector operand into a scalar value, and adding the
+/// result to a chain. This recipe is abstract and needs to be lowered to
+/// concrete recipes before codegen. The operands are {ChainOp, VecOp,
+/// [Condition]}.
+class VPExtendedReductionRecipe : public VPReductionRecipe {
+  /// Opcode of the extend recipe will be lowered to.
+  Instruction::CastOps ExtOp;
+
+  Type *ResultTy;
+
+  /// For cloning VPExtendedReductionRecipe.
+  VPExtendedReductionRecipe(VPExtendedReductionRecipe *ExtRed)
+      : VPReductionRecipe(
+            VPDef::VPExtendedReductionSC, ExtRed->getRecurrenceKind(),
+            {ExtRed->getChainOp(), ExtRed->getVecOp()}, ExtRed->getCondOp(),
+            ExtRed->isOrdered(), ExtRed->getDebugLoc()),
+        ExtOp(ExtRed->getExtOpcode()), ResultTy(ExtRed->getResultType()) {
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fhahn wrote:

Supported extends are ZExt and SExt at the moment, right? Can we assert?

Same for `VPMulAccumulateReductionRecipe`

https://github.com/llvm/llvm-project/pull/137746