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When replacing a node in SimplifyDemandedBits, if the old node used any
single-use nodes, they will be dead soon. Make sure to remove them before processing other nodes. This implements CodeGen/X86/shl_elim.ll git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36244 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -182,6 +182,13 @@ namespace {
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// something else needing this node.
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if (TLO.Old.Val->use_empty()) {
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removeFromWorkList(TLO.Old.Val);
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// If the operands of this node are only used by the node, they will now
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// be dead. Make sure to visit them first to delete dead nodes early.
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for (unsigned i = 0, e = TLO.Old.Val->getNumOperands(); i != e; ++i)
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if (TLO.Old.Val->getOperand(i).Val->hasOneUse())
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AddToWorkList(TLO.Old.Val->getOperand(i).Val);
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DAG.DeleteNode(TLO.Old.Val);
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}
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return true;
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@ -1838,6 +1845,7 @@ SDOperand DAGCombiner::visitSRL(SDNode *N) {
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// if (srl x, c) is known to be zero, return 0
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if (N1C && TLI.MaskedValueIsZero(SDOperand(N, 0), ~0ULL >> (64-OpSizeInBits)))
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return DAG.getConstant(0, VT);
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// fold (srl (srl x, c1), c2) -> 0 or (srl x, c1+c2)
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if (N1C && N0.getOpcode() == ISD::SRL &&
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N0.getOperand(1).getOpcode() == ISD::Constant) {
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@ -1899,7 +1907,6 @@ SDOperand DAGCombiner::visitSRL(SDNode *N) {
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return DAG.getNode(ISD::XOR, VT, Op, DAG.getConstant(1, VT));
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}
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}
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return SDOperand();
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}
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