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

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RKSimon wants to merge 1 commit into from
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[DAG] ExpandOp_NormalStore - check for bitcasted value that has legal store instead of splitting #171478

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12 changes: 10 additions & 2 deletions llvm/lib/CodeGen/SelectionDAG/LegalizeTypesGeneric.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -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 arsenm Dec 9, 2025

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

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@RKSimon RKSimon Dec 9, 2025

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We can add a isStoreBitCastBeneficial check as well similar to what DAGCombiner::visitSTORE does - which should do a allowsMemoryAccess check?

return DAG.getStore(Chain, dl, Value.getOperand(0), Ptr,
St->getMemOperand());

SDValue Lo, Hi;
GetExpandedOp(St->getValue(), Lo, Hi);

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