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

[Matt Arsenault via llvm-branch-commits]

================
@@ -6003,6 +6006,74 @@ 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 coerceLoadedValue(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);
+  }
+  assert(FirstVT == WidenVT);
+  return LdOp;
+}
+
+static std::optional<EVT> findMemType(SelectionDAG &DAG,
+                                      const TargetLowering &TLI, unsigned Width,
+                                      EVT WidenVT, unsigned Align,
+                                      unsigned WidenEx);
+
+SDValue DAGTypeLegalizer::WidenVecRes_ATOMIC_LOAD(AtomicSDNode *LD) {
+  EVT WidenVT =
+      TLI.getTypeToTransformTo(*DAG.getContext(), LD->getValueType(0));
+  EVT LdVT = LD->getMemoryVT();
+  SDLoc dl(LD);
+  assert(LdVT.isVector() && WidenVT.isVector() && "Expected vectors");
+  assert(LdVT.isScalableVector() == WidenVT.isScalableVector() &&
+         "Must be scalable");
+  assert(LdVT.getVectorElementType() == WidenVT.getVectorElementType() &&
+         "Expected equivalent element types");
+
+  // Load information
+  SDValue Chain = LD->getChain();
+  SDValue BasePtr = LD->getBasePtr();
+  MachineMemOperand::Flags MMOFlags = LD->getMemOperand()->getFlags();
+  AAMDNodes AAInfo = LD->getAAInfo();
+
+  TypeSize LdWidth = LdVT.getSizeInBits();
+  TypeSize WidenWidth = WidenVT.getSizeInBits();
+  TypeSize WidthDiff = WidenWidth - LdWidth;
+
+  // Find the vector type that can load from.
+  std::optional<EVT> FirstVT =
+      findMemType(DAG, TLI, LdWidth.getKnownMinValue(), WidenVT, /*LdAlign=*/0,
----------------
arsenm wrote:

Why is this using 0 for the sign instead of passing in the alignment of the load?

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