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Do not try and sink a load whose chain result has more than one use, when
trying to create RMW opportunities in the x86 backend. This can cause a cycle to appear in the graph, since the other uses may eventually feed into the TokenFactor we are sinking the load below. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81996 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -364,7 +364,9 @@ static void MoveBelowTokenFactor(SelectionDAG *CurDAG, SDValue Load,
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Store.getOperand(2), Store.getOperand(3));
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}
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/// isRMWLoad - Return true if N is a load that's part of RMW sub-DAG.
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/// isRMWLoad - Return true if N is a load that's part of RMW sub-DAG. The
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/// chain produced by the load must only be used by the store's chain operand,
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/// otherwise this may produce a cycle in the DAG.
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///
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static bool isRMWLoad(SDValue N, SDValue Chain, SDValue Address,
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SDValue &Load) {
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@ -382,8 +384,9 @@ static bool isRMWLoad(SDValue N, SDValue Chain, SDValue Address,
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return false;
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if (N.hasOneUse() &&
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LD->hasNUsesOfValue(1, 1) &&
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N.getOperand(1) == Address &&
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N.getNode()->isOperandOf(Chain.getNode())) {
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LD->isOperandOf(Chain.getNode())) {
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Load = N;
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return true;
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}
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