[llvm] [RISCV] vfadd.vf + splat (fneg)-> vfsub.vf (PR #173589)

[Luke Lau via llvm-commits]

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@@ -21021,7 +21021,23 @@ SDValue RISCVTargetLowering::PerformDAGCombine(SDNode *N,
       return SDValue();
     return DAG.getNode(RISCVISD::FSGNJX, DL, VT, N1, N0->getOperand(1));
   }
-  case ISD::FADD:
+  case ISD::FADD: {
+    if (SDValue V = combineBinOpToReduce(N, DAG, Subtarget))
+      return V;
+    if (SDValue V = combineBinOpOfExtractToReduceTree(N, DAG, Subtarget))
+      return V;
+    SDValue N1 = N->getOperand(1);
+    if (N1.getOpcode() != ISD::SPLAT_VECTOR)
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lukel97 wrote:

Could you use `DAG.getSplatValue` instead and make this agnostic over fixed/scalable vector types?

https://github.com/llvm/llvm-project/pull/173589