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Add a new HandleNode class, which is used to handle (haha) cases in the

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dead node elim and dag combiner passes where the root is potentially updated.
This fixes a fixme in the dag combiner.

llvm-svn: 23634
This commit is contained in:
Chris Lattner 2005-10-05 06:35:28 +00:00
parent bc5ae03dea
commit 697fdaba58
2 changed files with 17 additions and 11 deletions
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17
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -274,6 +274,11 @@ void DAGCombiner::Run(bool RunningAfterLegalize) {
// Add all the dag nodes to the worklist.
WorkList.insert(WorkList.end(), DAG.allnodes_begin(), DAG.allnodes_end());
// Create a dummy node (which is not added to allnodes), that adds a reference
// to the root node, preventing it from being deleted, and tracking any
// changes of the root.
HandleSDNode Dummy(DAG.getRoot());
// while the worklist isn't empty, inspect the node on the end of it and
// try and combine it.
while (!WorkList.empty()) {
@ -281,15 +286,14 @@ void DAGCombiner::Run(bool RunningAfterLegalize) {
WorkList.pop_back();
// If N has no uses, it is dead. Make sure to revisit all N's operands once
// N is deleted from the DAG, since they too may now be dead.
// FIXME: is there a better way to keep from deleting the dag root because
// we think it has no uses? This works for now...
if (N->use_empty() && N != DAG.getRoot().Val) {
// N is deleted from the DAG, since they too may now be dead or may have a
// reduced number of uses, allowing other xforms.
if (N->use_empty() && N != &Dummy) {
for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
WorkList.push_back(N->getOperand(i).Val);
DAG.DeleteNode(N);
removeFromWorkList(N);
DAG.DeleteNode(N);
continue;
}
@ -319,6 +323,9 @@ void DAGCombiner::Run(bool RunningAfterLegalize) {
}
}
}
// If the root changed (e.g. it was a dead load, update the root).
DAG.setRoot(Dummy.getValue());
}
SDOperand DAGCombiner::visit(SDNode *N) {

11
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
View File

@ -176,7 +176,7 @@ void SelectionDAG::RemoveDeadNodes(SDNode *N) {
// Create a dummy node (which is not added to allnodes), that adds a reference
// to the root node, preventing it from being deleted.
SDNode *DummyNode = new SDNode(ISD::EntryToken, getRoot());
HandleSDNode Dummy(getRoot());
// If we have a hint to start from, use it.
if (N) DeleteNodeIfDead(N, &AllNodeSet);
@ -199,11 +199,7 @@ void SelectionDAG::RemoveDeadNodes(SDNode *N) {
AllNodes.assign(AllNodeSet.begin(), AllNodeSet.end());
// If the root changed (e.g. it was a dead load, update the root).
setRoot(DummyNode->getOperand(0));
// Now that we are done with the dummy node, delete it.
DummyNode->getOperand(0).Val->removeUser(DummyNode);
delete DummyNode;
setRoot(Dummy.getValue());
}
@ -276,6 +272,7 @@ void SelectionDAG::DeleteNodeNotInCSEMaps(SDNode *N) {
void SelectionDAG::RemoveNodeFromCSEMaps(SDNode *N) {
bool Erased = false;
switch (N->getOpcode()) {
case ISD::HANDLENODE: return; // noop.
case ISD::Constant:
Erased = Constants.erase(std::make_pair(cast<ConstantSDNode>(N)->getValue(),
N->getValueType(0)));
@ -397,6 +394,8 @@ SDNode *SelectionDAG::AddNonLeafNodeToCSEMaps(SDNode *N) {
N->getValueType(0)))];
if (L) return L;
L = N;
} else if (N->getOpcode() == ISD::HANDLENODE) {
return 0; // never add it.
} else if (N->getNumOperands() == 1) {
SDNode *&U = UnaryOps[std::make_pair(N->getOpcode(),
std::make_pair(N->getOperand(0),