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[X86] narrowBitOpRMW - allow additional uses of the BTC/R/S result #166376

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Merged
merged 3 commits into from
Nov 5, 2025
Merged

[X86] narrowBitOpRMW - allow additional uses of the BTC/R/S result #166376

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4616866
[X86] narrowBitOpRMW - allow additional uses of the BTC/R/S result
RKSimon Nov 4, 2025
0615b7d
Merge branch 'upstream' into x86-bittest-multistore
RKSimon Nov 5, 2025
9e7207e
Drop extra store-load-store chain splicing
RKSimon Nov 5, 2025
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17 changes: 13 additions & 4 deletions llvm/lib/Target/X86/X86ISelLowering.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -53370,8 +53370,7 @@ static SDValue narrowBitOpRMW(StoreSDNode *St, const SDLoc &DL,
//
// BitInsert: (X & ~(1 << ShAmt)) | (InsertBit << ShAmt)
SDValue SrcVal, InsertBit, ShAmt;
if (!StoredVal.hasOneUse() ||
!(sd_match(StoredVal, m_And(m_Value(SrcVal),
if (!(sd_match(StoredVal, m_And(m_Value(SrcVal),
m_Not(m_Shl(m_One(), m_Value(ShAmt))))) ||
sd_match(StoredVal,
m_Or(m_Value(SrcVal), m_Shl(m_One(), m_Value(ShAmt)))) ||
Expand Down Expand Up @@ -53442,8 +53441,18 @@ static SDValue narrowBitOpRMW(StoreSDNode *St, const SDLoc &DL,
Res = DAG.getNode(StoredVal.getOpcode(), DL, MVT::i32, X, Mask);
}

return DAG.getStore(St->getChain(), DL, Res, NewPtr, St->getPointerInfo(),
Align(), St->getMemOperand()->getFlags());
SDValue NewStore =
DAG.getStore(St->getChain(), DL, Res, NewPtr, St->getPointerInfo(),
Align(), St->getMemOperand()->getFlags());

// If there are other uses of StoredVal, replace with a new load of the
// whole (updated) value.
if (!StoredVal.hasOneUse()) {
SDValue NewLoad =
DAG.getLoad(VT, DL, NewStore, Ld->getBasePtr(), Ld->getMemOperand());
DAG.ReplaceAllUsesWith(StoredVal, NewLoad);
}
return NewStore;
}

static SDValue combineStore(SDNode *N, SelectionDAG &DAG,
Expand Down
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