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DAG: Simplify demanded bits for truncating atomic_store #90113

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Merged
merged 1 commit into from
Apr 26, 2024
Merged

DAG: Simplify demanded bits for truncating atomic_store #90113

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20 changes: 20 additions & 0 deletions llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -530,6 +530,7 @@ namespace {
bool refineExtractVectorEltIntoMultipleNarrowExtractVectorElts(SDNode *N);

SDValue visitSTORE(SDNode *N);
SDValue visitATOMIC_STORE(SDNode *N);
SDValue visitLIFETIME_END(SDNode *N);
SDValue visitINSERT_VECTOR_ELT(SDNode *N);
SDValue visitEXTRACT_VECTOR_ELT(SDNode *N);
Expand Down Expand Up @@ -1909,6 +1910,7 @@ SDValue DAGCombiner::visit(SDNode *N) {
case ISD::BR_CC: return visitBR_CC(N);
case ISD::LOAD: return visitLOAD(N);
case ISD::STORE: return visitSTORE(N);
case ISD::ATOMIC_STORE: return visitATOMIC_STORE(N);
case ISD::INSERT_VECTOR_ELT: return visitINSERT_VECTOR_ELT(N);
case ISD::EXTRACT_VECTOR_ELT: return visitEXTRACT_VECTOR_ELT(N);
case ISD::BUILD_VECTOR: return visitBUILD_VECTOR(N);
Expand Down Expand Up @@ -21096,6 +21098,24 @@ SDValue DAGCombiner::replaceStoreOfInsertLoad(StoreSDNode *ST) {
ST->getMemOperand()->getFlags());
}

SDValue DAGCombiner::visitATOMIC_STORE(SDNode *N) {
AtomicSDNode *ST = cast<AtomicSDNode>(N);
SDValue Val = ST->getVal();
EVT VT = Val.getValueType();
EVT MemVT = ST->getMemoryVT();

if (MemVT.bitsLT(VT)) { // Is truncating store
APInt TruncDemandedBits = APInt::getLowBitsSet(VT.getScalarSizeInBits(),
MemVT.getScalarSizeInBits());
// See if we can simplify the operation with SimplifyDemandedBits, which
// only works if the value has a single use.
if (SimplifyDemandedBits(Val, TruncDemandedBits))
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Do you need any of the worklist fiddling that the corresponding code in visitSTORE does?

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The comments there suggest it's due to merge optimizations triggering, which I assumed don't apply for the atomic case. It's probably not important to revisit these aggressively in any case

return SDValue(N, 0);
}

return SDValue();
}

SDValue DAGCombiner::visitSTORE(SDNode *N) {
StoreSDNode *ST = cast<StoreSDNode>(N);
SDValue Chain = ST->getChain();
Expand Down
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