[llvm] Add LoopVectorizer support for `llvm.vector.partial.reduce.fadd` (PR #163975)

[Sander de Smalen via llvm-commits]

================
@@ -5820,6 +5828,9 @@ InstructionCost AArch64TTIImpl::getPartialReductionCost(
   if (VF.getKnownMinValue() <= Ratio)
     return Invalid;
 
+  if (Opcode == Instruction::FAdd && Ratio <= 1)
----------------
sdesmalen-arm wrote:

This seems superfluous.

https://github.com/llvm/llvm-project/pull/163975