[llvm] [DAG] ExpandOp_NormalStore - check for bitcasted value that has legal store instead of splitting (PR #171478)

[Matt Arsenault via llvm-commits]

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@@ -479,15 +479,23 @@ SDValue DAGTypeLegalizer::ExpandOp_NormalStore(SDNode *N, unsigned OpNo) {
 
   StoreSDNode *St = cast<StoreSDNode>(N);
   assert(!St->isAtomic() && "Atomics can not be split");
-  EVT ValueVT = St->getValue().getValueType();
-  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), ValueVT);
   SDValue Chain = St->getChain();
+  SDValue Value = St->getValue();
   SDValue Ptr = St->getBasePtr();
+  EVT ValueVT = Value.getValueType();
+  EVT NVT = TLI.getTypeToTransformTo(*DAG.getContext(), ValueVT);
   AAMDNodes AAInfo = St->getAAInfo();
 
   assert(NVT.isByteSized() && "Expanded type not byte sized!");
   unsigned IncrementSize = NVT.getSizeInBits() / 8;
 
+  // Storing a bitcasted value, see if the original type is a legal store.
+  // TODO: Not necessary if we had proper topological sorting of nodes.
+  if (Value.getOpcode() == ISD::BITCAST &&
+      TLI.isOperationLegal(ISD::STORE, Value.getOperand(0).getValueType()))
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arsenm wrote:

The state of memory instruction legality queries is bad. Does this need to worry about alignment, address space, and everything else? 

https://github.com/llvm/llvm-project/pull/171478