[llvm] [AArch64] Combine vector FNEG+FMA into `FNML[A|S]` (PR #167900)

[Benjamin Maxwell via llvm-commits]

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@@ -20435,6 +20437,52 @@ static SDValue performFADDCombine(SDNode *N,
   return SDValue();
 }
 
+static SDValue performFMACombine(SDNode *N,
+                                 TargetLowering::DAGCombinerInfo &DCI,
+                                 const AArch64Subtarget *Subtarget) {
+  SelectionDAG &DAG = DCI.DAG;
+  SDValue Op1 = N->getOperand(0);
+  SDValue Op2 = N->getOperand(1);
+  SDValue Op3 = N->getOperand(2);
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MacDue wrote:

Maybe rename these `OpA`/`OpB`/`OpC` to be consistent with the examples below? 

https://github.com/llvm/llvm-project/pull/167900