[llvm-branch-commits] [llvm] [SelectionDAG][X86] Widen <2 x T> vector types for atomic load (PR #120598)

[Matt Arsenault via llvm-branch-commits]

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@@ -6014,6 +6017,85 @@ SDValue DAGTypeLegalizer::WidenVecRes_INSERT_VECTOR_ELT(SDNode *N) {
                      N->getOperand(1), N->getOperand(2));
 }
 
+/// Either return the same load or provide appropriate casts
+/// from the load and return that.
+static SDValue loadElement(SDValue LdOp, EVT FirstVT, EVT WidenVT,
+                           TypeSize LdWidth, TypeSize FirstVTWidth, SDLoc dl,
+                           SelectionDAG &DAG) {
+  assert(TypeSize::isKnownLE(LdWidth, FirstVTWidth));
+  TypeSize WidenWidth = WidenVT.getSizeInBits();
+  if (!FirstVT.isVector()) {
+    unsigned NumElts =
+        WidenWidth.getFixedValue() / FirstVTWidth.getFixedValue();
+    EVT NewVecVT = EVT::getVectorVT(*DAG.getContext(), FirstVT, NumElts);
+    SDValue VecOp = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, NewVecVT, LdOp);
+    return DAG.getNode(ISD::BITCAST, dl, WidenVT, VecOp);
+  } else if (FirstVT == WidenVT)
+    return LdOp;
+  else {
+    // TODO: We don't currently have any tests that exercise this code path.
+    assert(WidenWidth.getFixedValue() % FirstVTWidth.getFixedValue() == 0);
+    unsigned NumConcat =
+        WidenWidth.getFixedValue() / FirstVTWidth.getFixedValue();
+    SmallVector<SDValue, 16> ConcatOps(NumConcat);
+    SDValue UndefVal = DAG.getUNDEF(FirstVT);
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arsenm wrote:

Poison 

https://github.com/llvm/llvm-project/pull/120598