[llvm] [RISCV] Initial ISel support for the experimental zacas extension (PR #67918)

[Craig Topper via llvm-commits]

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@@ -10451,13 +10460,73 @@ static SDValue customLegalizeToWOpWithSExt(SDNode *N, SelectionDAG &DAG) {
   return DAG.getNode(ISD::TRUNCATE, DL, MVT::i32, NewRes);
 }
 
+// Create an even/odd pair of X registers holding integer value V.
+static SDValue createGPRPairNode(SelectionDAG &DAG, SDValue V, MVT VT,
+                                 MVT SubRegVT) {
+  SDLoc DL(V.getNode());
+  SDValue VLo = DAG.getAnyExtOrTrunc(V, DL, SubRegVT);
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topperc wrote:

Can we use DAG.getSplitScalar?

https://github.com/llvm/llvm-project/pull/67918