forked from OSchip/llvm-project
Optimize DAGCombiner's worklist processing. Previously it started
its work by putting all nodes in the worklist, requiring a big dynamic allocation. Now, DAGCombiner just iterates over the AllNodes list and maintains a worklist for nodes that are newly created or need to be revisited. This allows the worklist to stay small in most cases, so it can be a SmallVector. This has the side effect of making DAGCombine not miss a folding opportunity in alloca-align-rounding.ll. llvm-svn: 55498
This commit is contained in:
Dan Gohman
parent
17da671922
commit
f27e33baa7
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@ -53,12 +53,31 @@ namespace {
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bool AfterLegalize;
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bool Fast;
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// Create a dummy node (which is not added to allnodes), that adds a reference
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// to the root node, preventing it from being deleted, and tracking any
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// changes of the root.
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HandleSDNode Dummy;
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// Worklist of all of the nodes that need to be simplified.
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std::vector<SDNode*> WorkList;
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SmallVector<SDNode*, 8> WorkList;
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// The current position of our iteration through the allnodes list.
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SelectionDAG::allnodes_iterator CurNode;
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// AA - Used for DAG load/store alias analysis.
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AliasAnalysis &AA;
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/// AdvanceCurNode - Update CurNode to point to the next node to process.
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///
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void AdvanceCurNode() {
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// We start at the end of the list and work towards the front. Setting
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// CurNode to DAG.allnodes_end() indicates that we're done.
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if (CurNode == DAG.allnodes_begin())
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CurNode = DAG.allnodes_end();
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else
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--CurNode;
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}
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/// AddUsersToWorkList - When an instruction is simplified, add all users of
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/// the instruction to the work lists because they might get more simplified
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/// now.
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@ -86,6 +105,10 @@ namespace {
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void removeFromWorkList(SDNode *N) {
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WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), N),
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WorkList.end());
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// If the next node we were planning to process is deleted,
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// skip past it.
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if (N == CurNode)
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AdvanceCurNode();
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}
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SDValue CombineTo(SDNode *N, const SDValue *To, unsigned NumTo,
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@ -243,10 +266,14 @@ public:
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TLI(D.getTargetLoweringInfo()),
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AfterLegalize(false),
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Fast(fast),
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Dummy(D.getRoot()),
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AA(A) {}
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/// Run - runs the dag combiner on all nodes in the work list
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void Run(bool RunningAfterLegalize);
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/// ProcessNode - runs the dag combiner on a node
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void ProcessNode(SDNode *N);
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};
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}
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@ -575,91 +602,89 @@ bool DAGCombiner::SimplifyDemandedBits(SDValue Op, const APInt &Demanded) {
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// Main DAG Combiner implementation
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//===----------------------------------------------------------------------===//
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void DAGCombiner::ProcessNode(SDNode *N) {
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// If N has no uses, it is dead. Make sure to revisit all N's operands once
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// N is deleted from the DAG, since they too may now be dead or may have a
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// reduced number of uses, allowing other xforms.
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if (N->use_empty() && N != &Dummy) {
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for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
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AddToWorkList(N->getOperand(i).Val);
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DAG.DeleteNode(N);
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return;
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}
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SDValue RV = combine(N);
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if (RV.Val == 0)
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return;
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++NodesCombined;
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// If we get back the same node we passed in, rather than a new node or
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// zero, we know that the node must have defined multiple values and
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// CombineTo was used. Since CombineTo takes care of the worklist
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// mechanics for us, we have no work to do in this case.
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if (RV.Val == N)
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return;
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assert(N->getOpcode() != ISD::DELETED_NODE &&
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RV.Val->getOpcode() != ISD::DELETED_NODE &&
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"Node was deleted but visit returned new node!");
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DOUT << "\nReplacing.3 "; DEBUG(N->dump(&DAG));
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DOUT << "\nWith: "; DEBUG(RV.Val->dump(&DAG));
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DOUT << '\n';
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if (N->getNumValues() == RV.Val->getNumValues())
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DAG.ReplaceAllUsesWith(N, RV.Val);
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else {
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assert(N->getValueType(0) == RV.getValueType() &&
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N->getNumValues() == 1 && "Type mismatch");
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SDValue OpV = RV;
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DAG.ReplaceAllUsesWith(N, &OpV);
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}
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// Delete the old node.
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removeFromWorkList(N);
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DAG.DeleteNode(N);
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// Push the new node and any users onto the worklist
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AddToWorkList(RV.Val);
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AddUsersToWorkList(RV.Val);
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}
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void DAGCombiner::Run(bool RunningAfterLegalize) {
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// set the instance variable, so that the various visit routines may use it.
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AfterLegalize = RunningAfterLegalize;
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// Add all the dag nodes to the worklist.
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WorkList.reserve(DAG.allnodes_size());
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for (SelectionDAG::allnodes_iterator I = DAG.allnodes_begin(),
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E = DAG.allnodes_end(); I != E; ++I)
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WorkList.push_back(I);
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// Create a dummy node (which is not added to allnodes), that adds a reference
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// to the root node, preventing it from being deleted, and tracking any
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// changes of the root.
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HandleSDNode Dummy(DAG.getRoot());
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// The root of the dag may dangle to deleted nodes until the dag combiner is
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// done. Set it to null to avoid confusion.
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DAG.setRoot(SDValue());
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// while the worklist isn't empty, inspect the node on the end of it and
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// try and combine it.
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while (!WorkList.empty()) {
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SDNode *N = WorkList.back();
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WorkList.pop_back();
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// If N has no uses, it is dead. Make sure to revisit all N's operands once
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// N is deleted from the DAG, since they too may now be dead or may have a
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// reduced number of uses, allowing other xforms.
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if (N->use_empty() && N != &Dummy) {
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for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
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AddToWorkList(N->getOperand(i).Val);
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DAG.DeleteNode(N);
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continue;
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// Process all the original dag nodes. We process starting from the
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// end of the list and working forward, which is in roughly topological
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// order. Starting at the end and working forward means we won't
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// accidentally revisit nodes created during the dagcombine process.
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CurNode = prior(DAG.allnodes_end());
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do {
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SDNode *N = &*CurNode;
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AdvanceCurNode();
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ProcessNode(N);
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// Processing the node may have resulted in nodes being added to the
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// worklist, because the were newly created or because one of their
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// operands changed or some other reason they should be revisited.
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// While the worklist isn't empty, inspect the node on the end of it
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// and try and combine it.
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while (!WorkList.empty()) {
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SDNode *N = WorkList.back();
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WorkList.pop_back();
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if (N == CurNode)
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AdvanceCurNode();
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ProcessNode(N);
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}
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SDValue RV = combine(N);
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if (RV.Val == 0)
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continue;
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++NodesCombined;
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// If we get back the same node we passed in, rather than a new node or
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// zero, we know that the node must have defined multiple values and
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// CombineTo was used. Since CombineTo takes care of the worklist
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// mechanics for us, we have no work to do in this case.
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if (RV.Val == N)
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continue;
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assert(N->getOpcode() != ISD::DELETED_NODE &&
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RV.Val->getOpcode() != ISD::DELETED_NODE &&
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"Node was deleted but visit returned new node!");
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} while (CurNode != DAG.allnodes_end());
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DOUT << "\nReplacing.3 "; DEBUG(N->dump(&DAG));
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DOUT << "\nWith: "; DEBUG(RV.Val->dump(&DAG));
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DOUT << '\n';
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WorkListRemover DeadNodes(*this);
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if (N->getNumValues() == RV.Val->getNumValues())
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DAG.ReplaceAllUsesWith(N, RV.Val, &DeadNodes);
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else {
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assert(N->getValueType(0) == RV.getValueType() &&
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N->getNumValues() == 1 && "Type mismatch");
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SDValue OpV = RV;
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DAG.ReplaceAllUsesWith(N, &OpV, &DeadNodes);
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}
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// Push the new node and any users onto the worklist
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AddToWorkList(RV.Val);
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AddUsersToWorkList(RV.Val);
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// Add any uses of the old node to the worklist in case this node is the
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// last one that uses them. They may become dead after this node is
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// deleted.
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for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
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AddToWorkList(N->getOperand(i).Val);
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// Nodes can be reintroduced into the worklist. Make sure we do not
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// process a node that has been replaced.
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removeFromWorkList(N);
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// Finally, since the node is now dead, remove it from the graph.
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DAG.DeleteNode(N);
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}
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// If the root changed (e.g. it was a dead load, update the root).
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DAG.setRoot(Dummy.getValue());
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}
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@ -1,5 +1,5 @@
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; RUN: llvm-as < %s | llc -march=x86 -mtriple=i686-apple-darwin | grep and | count 1
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; RUN: llvm-as < %s | llc -march=x86-64 -mtriple=i686-pc-linux | grep and | count 3
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; RUN: llvm-as < %s | llc -march=x86-64 -mtriple=i686-pc-linux | grep and | count 1
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declare void @bar(<2 x i64>* %n)
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