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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

llvm-svn: 36244
This commit is contained in:
Chris Lattner 2007-04-18 03:05:22 +00:00
parent 1af7b8451e
commit bf14f20632
1 changed files with 8 additions and 1 deletions
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9
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -182,6 +182,13 @@ namespace {
// something else needing this node.
if (TLO.Old.Val->use_empty()) {
removeFromWorkList(TLO.Old.Val);
// If the operands of this node are only used by the node, they will now
// be dead. Make sure to visit them first to delete dead nodes early.
for (unsigned i = 0, e = TLO.Old.Val->getNumOperands(); i != e; ++i)
if (TLO.Old.Val->getOperand(i).Val->hasOneUse())
AddToWorkList(TLO.Old.Val->getOperand(i).Val);
DAG.DeleteNode(TLO.Old.Val);
}
return true;
@ -1838,6 +1845,7 @@ SDOperand DAGCombiner::visitSRL(SDNode *N) {
// if (srl x, c) is known to be zero, return 0
if (N1C && TLI.MaskedValueIsZero(SDOperand(N, 0), ~0ULL >> (64-OpSizeInBits)))
return DAG.getConstant(0, VT);
// fold (srl (srl x, c1), c2) -> 0 or (srl x, c1+c2)
if (N1C && N0.getOpcode() == ISD::SRL &&
N0.getOperand(1).getOpcode() == ISD::Constant) {
@ -1899,7 +1907,6 @@ SDOperand DAGCombiner::visitSRL(SDNode *N) {
return DAG.getNode(ISD::XOR, VT, Op, DAG.getConstant(1, VT));
}
}
return SDOperand();
}