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

[Florian Hahn via llvm-commits]

================
@@ -2266,6 +2275,38 @@ class VPReductionPHIRecipe : public VPHeaderPHIRecipe,
   bool isInLoop() const { return IsInLoop; }
 };
 
+/// A recipe for forming partial reductions. In the loop, an accumulator and
+/// vector operand are added together and passed to the next iteration as the
+/// next accumulator. After the loop body, the accumulator is reduced to a
+/// scalar value.
+class VPPartialReductionRecipe : public VPRecipeWithIRFlags {
+  unsigned Opcode;
+  Instruction &Reduction;
----------------
fhahn wrote:

What information is needed from the instruction?

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