[llvm] [PowerPC] Use SelectionDAG::makeEquivalentMemoryOrdering(). NFC (PR #124889)

[Matt Arsenault via llvm-commits]

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@@ -8651,22 +8651,13 @@ bool PPCTargetLowering::canReuseLoadAddress(SDValue Op, EVT MemVT,
 // Given the head of the old chain, ResChain, insert a token factor containing
 // it and NewResChain, and make users of ResChain now be users of that token
 // factor.
-// TODO: Remove and use DAG::makeEquivalentMemoryOrdering() instead.
 void PPCTargetLowering::spliceIntoChain(SDValue ResChain,
                                         SDValue NewResChain,
                                         SelectionDAG &DAG) const {
   if (!ResChain)
     return;
 
-  SDLoc dl(NewResChain);
-
-  SDValue TF = DAG.getNode(ISD::TokenFactor, dl, MVT::Other,
-                           NewResChain, DAG.getUNDEF(MVT::Other));
-  assert(TF.getNode() != NewResChain.getNode() &&
-         "A new TF really is required here");
-
-  DAG.ReplaceAllUsesOfValueWith(ResChain, TF);
-  DAG.UpdateNodeOperands(TF.getNode(), ResChain, NewResChain);
+  DAG.makeEquivalentMemoryOrdering(ResChain, NewResChain);
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arsenm wrote:

Follow the TODO and remove the whole helper function? 

https://github.com/llvm/llvm-project/pull/124889