-//===-- RegAllocSolver.h - Heuristic PBQP Solver for reg alloc --*- C++ -*-===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// Heuristic PBQP solver for register allocation problems. This solver uses a
-// graph reduction approach. Nodes of degree 0, 1 and 2 are eliminated with
-// optimality-preserving rules (see ReductionRules.h). When no low-degree (<3)
-// nodes are present, a heuristic derived from Brigg's graph coloring approach
-// is used.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_CODEGEN_PBQP_REGALLOCSOLVER_H
-#define LLVM_CODEGEN_PBQP_REGALLOCSOLVER_H
-
-#include "CostAllocator.h"
-#include "Graph.h"
-#include "ReductionRules.h"
-#include "Solution.h"
-#include "llvm/Support/ErrorHandling.h"
-#include <limits>
-#include <vector>
-
-namespace llvm{
-namespace PBQP {
- namespace RegAlloc {
-
- /// @brief Spill option index.
- inline unsigned getSpillOptionIdx() { return 0; }
-
- /// \brief Metadata to speed allocatability test.
- ///
- /// Keeps track of the number of infinities in each row and column.
- class MatrixMetadata {
- private:
- MatrixMetadata(const MatrixMetadata&);
- void operator=(const MatrixMetadata&);
- public:
- MatrixMetadata(const PBQP::Matrix& M)
- : WorstRow(0), WorstCol(0),
- UnsafeRows(new bool[M.getRows() - 1]()),
- UnsafeCols(new bool[M.getCols() - 1]()) {
-
- unsigned* ColCounts = new unsigned[M.getCols() - 1]();
-
- for (unsigned i = 1; i < M.getRows(); ++i) {
- unsigned RowCount = 0;
- for (unsigned j = 1; j < M.getCols(); ++j) {
- if (M[i][j] == std::numeric_limits<PBQP::PBQPNum>::infinity()) {
- ++RowCount;
- ++ColCounts[j - 1];
- UnsafeRows[i - 1] = true;
- UnsafeCols[j - 1] = true;
- }
- }
- WorstRow = std::max(WorstRow, RowCount);
- }
- unsigned WorstColCountForCurRow =
- *std::max_element(ColCounts, ColCounts + M.getCols() - 1);
- WorstCol = std::max(WorstCol, WorstColCountForCurRow);
- delete[] ColCounts;
- }
-
- ~MatrixMetadata() {
- delete[] UnsafeRows;
- delete[] UnsafeCols;
- }
-
- unsigned getWorstRow() const { return WorstRow; }
- unsigned getWorstCol() const { return WorstCol; }
- const bool* getUnsafeRows() const { return UnsafeRows; }
- const bool* getUnsafeCols() const { return UnsafeCols; }
-
- private:
- unsigned WorstRow, WorstCol;
- bool* UnsafeRows;
- bool* UnsafeCols;
- };
-
- class NodeMetadata {
- public:
- typedef std::vector<unsigned> OptionToRegMap;
-
- typedef enum { Unprocessed,
- OptimallyReducible,
- ConservativelyAllocatable,
- NotProvablyAllocatable } ReductionState;
-
- NodeMetadata() : RS(Unprocessed), DeniedOpts(0), OptUnsafeEdges(nullptr){}
- ~NodeMetadata() { delete[] OptUnsafeEdges; }
-
- void setVReg(unsigned VReg) { this->VReg = VReg; }
- unsigned getVReg() const { return VReg; }
-
- void setOptionRegs(OptionToRegMap OptionRegs) {
- this->OptionRegs = std::move(OptionRegs);
- }
- const OptionToRegMap& getOptionRegs() const { return OptionRegs; }
-
- void setup(const Vector& Costs) {
- NumOpts = Costs.getLength() - 1;
- OptUnsafeEdges = new unsigned[NumOpts]();
- }
-
- ReductionState getReductionState() const { return RS; }
- void setReductionState(ReductionState RS) { this->RS = RS; }
-
- void handleAddEdge(const MatrixMetadata& MD, bool Transpose) {
- DeniedOpts += Transpose ? MD.getWorstCol() : MD.getWorstRow();
- const bool* UnsafeOpts =
- Transpose ? MD.getUnsafeCols() : MD.getUnsafeRows();
- for (unsigned i = 0; i < NumOpts; ++i)
- OptUnsafeEdges[i] += UnsafeOpts[i];
- }
-
- void handleRemoveEdge(const MatrixMetadata& MD, bool Transpose) {
- DeniedOpts -= Transpose ? MD.getWorstCol() : MD.getWorstRow();
- const bool* UnsafeOpts =
- Transpose ? MD.getUnsafeCols() : MD.getUnsafeRows();
- for (unsigned i = 0; i < NumOpts; ++i)
- OptUnsafeEdges[i] -= UnsafeOpts[i];
- }
-
- bool isConservativelyAllocatable() const {
- return (DeniedOpts < NumOpts) ||
- (std::find(OptUnsafeEdges, OptUnsafeEdges + NumOpts, 0) !=
- OptUnsafeEdges + NumOpts);
- }
-
- private:
- ReductionState RS;
- unsigned NumOpts;
- unsigned DeniedOpts;
- unsigned* OptUnsafeEdges;
- unsigned VReg;
- OptionToRegMap OptionRegs;
- };
-
- class RegAllocSolverImpl {
- private:
- typedef PBQP::MDMatrix<MatrixMetadata> RAMatrix;
- public:
- typedef PBQP::Vector RawVector;
- typedef PBQP::Matrix RawMatrix;
- typedef PBQP::Vector Vector;
- typedef RAMatrix Matrix;
- typedef PBQP::PoolCostAllocator<
- Vector, PBQP::VectorComparator,
- Matrix, PBQP::MatrixComparator> CostAllocator;
-
- typedef PBQP::GraphBase::NodeId NodeId;
- typedef PBQP::GraphBase::EdgeId EdgeId;
-
- typedef RegAlloc::NodeMetadata NodeMetadata;
-
- struct EdgeMetadata { };
-
- class GraphMetadata {
- public:
- GraphMetadata(MachineFunction &MF,
- LiveIntervals &LIS,
- MachineBlockFrequencyInfo &MBFI)
- : MF(MF), LIS(LIS), MBFI(MBFI) {}
-
- MachineFunction &MF;
- LiveIntervals &LIS;
- MachineBlockFrequencyInfo &MBFI;
-
- void setNodeIdForVReg(unsigned VReg, GraphBase::NodeId NId) {
- VRegToNodeId[VReg] = NId;
- }
-
- GraphBase::NodeId getNodeIdForVReg(unsigned VReg) const {
- auto VRegItr = VRegToNodeId.find(VReg);
- if (VRegItr == VRegToNodeId.end())
- return GraphBase::invalidNodeId();
- return VRegItr->second;
- }
-
- void eraseNodeIdForVReg(unsigned VReg) {
- VRegToNodeId.erase(VReg);
- }
-
- private:
- DenseMap<unsigned, NodeId> VRegToNodeId;
- };
-
- typedef PBQP::Graph<RegAllocSolverImpl> Graph;
-
- RegAllocSolverImpl(Graph &G) : G(G) {}
-
- Solution solve() {
- G.setSolver(*this);
- Solution S;
- setup();
- S = backpropagate(G, reduce());
- G.unsetSolver();
- return S;
- }
-
- void handleAddNode(NodeId NId) {
- G.getNodeMetadata(NId).setup(G.getNodeCosts(NId));
- }
- void handleRemoveNode(NodeId NId) {}
- void handleSetNodeCosts(NodeId NId, const Vector& newCosts) {}
-
- void handleAddEdge(EdgeId EId) {
- handleReconnectEdge(EId, G.getEdgeNode1Id(EId));
- handleReconnectEdge(EId, G.getEdgeNode2Id(EId));
- }
-
- void handleRemoveEdge(EdgeId EId) {
- handleDisconnectEdge(EId, G.getEdgeNode1Id(EId));
- handleDisconnectEdge(EId, G.getEdgeNode2Id(EId));
- }
-
- void handleDisconnectEdge(EdgeId EId, NodeId NId) {
- NodeMetadata& NMd = G.getNodeMetadata(NId);
- const MatrixMetadata& MMd = G.getEdgeCosts(EId).getMetadata();
- NMd.handleRemoveEdge(MMd, NId == G.getEdgeNode2Id(EId));
- if (G.getNodeDegree(NId) == 3) {
- // This node is becoming optimally reducible.
- moveToOptimallyReducibleNodes(NId);
- } else if (NMd.getReductionState() ==
- NodeMetadata::NotProvablyAllocatable &&
- NMd.isConservativelyAllocatable()) {
- // This node just became conservatively allocatable.
- moveToConservativelyAllocatableNodes(NId);
- }
- }
-
- void handleReconnectEdge(EdgeId EId, NodeId NId) {
- NodeMetadata& NMd = G.getNodeMetadata(NId);
- const MatrixMetadata& MMd = G.getEdgeCosts(EId).getMetadata();
- NMd.handleAddEdge(MMd, NId == G.getEdgeNode2Id(EId));
- }
-
- void handleSetEdgeCosts(EdgeId EId, const Matrix& NewCosts) {
- handleRemoveEdge(EId);
-
- NodeId N1Id = G.getEdgeNode1Id(EId);
- NodeId N2Id = G.getEdgeNode2Id(EId);
- NodeMetadata& N1Md = G.getNodeMetadata(N1Id);
- NodeMetadata& N2Md = G.getNodeMetadata(N2Id);
- const MatrixMetadata& MMd = NewCosts.getMetadata();
- N1Md.handleAddEdge(MMd, N1Id != G.getEdgeNode1Id(EId));
- N2Md.handleAddEdge(MMd, N2Id != G.getEdgeNode1Id(EId));
- }
-
- private:
-
- void removeFromCurrentSet(NodeId NId) {
- switch (G.getNodeMetadata(NId).getReductionState()) {
- case NodeMetadata::Unprocessed: break;
- case NodeMetadata::OptimallyReducible:
- assert(OptimallyReducibleNodes.find(NId) !=
- OptimallyReducibleNodes.end() &&
- "Node not in optimally reducible set.");
- OptimallyReducibleNodes.erase(NId);
- break;
- case NodeMetadata::ConservativelyAllocatable:
- assert(ConservativelyAllocatableNodes.find(NId) !=
- ConservativelyAllocatableNodes.end() &&
- "Node not in conservatively allocatable set.");
- ConservativelyAllocatableNodes.erase(NId);
- break;
- case NodeMetadata::NotProvablyAllocatable:
- assert(NotProvablyAllocatableNodes.find(NId) !=
- NotProvablyAllocatableNodes.end() &&
- "Node not in not-provably-allocatable set.");
- NotProvablyAllocatableNodes.erase(NId);
- break;
- }
- }
-
- void moveToOptimallyReducibleNodes(NodeId NId) {
- removeFromCurrentSet(NId);
- OptimallyReducibleNodes.insert(NId);
- G.getNodeMetadata(NId).setReductionState(
- NodeMetadata::OptimallyReducible);
- }
-
- void moveToConservativelyAllocatableNodes(NodeId NId) {
- removeFromCurrentSet(NId);
- ConservativelyAllocatableNodes.insert(NId);
- G.getNodeMetadata(NId).setReductionState(
- NodeMetadata::ConservativelyAllocatable);
- }
-
- void moveToNotProvablyAllocatableNodes(NodeId NId) {
- removeFromCurrentSet(NId);
- NotProvablyAllocatableNodes.insert(NId);
- G.getNodeMetadata(NId).setReductionState(
- NodeMetadata::NotProvablyAllocatable);
- }
-
- void setup() {
- // Set up worklists.
- for (auto NId : G.nodeIds()) {
- if (G.getNodeDegree(NId) < 3)
- moveToOptimallyReducibleNodes(NId);
- else if (G.getNodeMetadata(NId).isConservativelyAllocatable())
- moveToConservativelyAllocatableNodes(NId);
- else
- moveToNotProvablyAllocatableNodes(NId);
- }
- }
-
- // Compute a reduction order for the graph by iteratively applying PBQP
- // reduction rules. Locally optimal rules are applied whenever possible (R0,
- // R1, R2). If no locally-optimal rules apply then any conservatively
- // allocatable node is reduced. Finally, if no conservatively allocatable
- // node exists then the node with the lowest spill-cost:degree ratio is
- // selected.
- std::vector<GraphBase::NodeId> reduce() {
- assert(!G.empty() && "Cannot reduce empty graph.");
-
- typedef GraphBase::NodeId NodeId;
- std::vector<NodeId> NodeStack;
-
- // Consume worklists.
- while (true) {
- if (!OptimallyReducibleNodes.empty()) {
- NodeSet::iterator NItr = OptimallyReducibleNodes.begin();
- NodeId NId = *NItr;
- OptimallyReducibleNodes.erase(NItr);
- NodeStack.push_back(NId);
- switch (G.getNodeDegree(NId)) {
- case 0:
- break;
- case 1:
- applyR1(G, NId);
- break;
- case 2:
- applyR2(G, NId);
- break;
- default: llvm_unreachable("Not an optimally reducible node.");
- }
- } else if (!ConservativelyAllocatableNodes.empty()) {
- // Conservatively allocatable nodes will never spill. For now just
- // take the first node in the set and push it on the stack. When we
- // start optimizing more heavily for register preferencing, it may
- // would be better to push nodes with lower 'expected' or worst-case
- // register costs first (since early nodes are the most
- // constrained).
- NodeSet::iterator NItr = ConservativelyAllocatableNodes.begin();
- NodeId NId = *NItr;
- ConservativelyAllocatableNodes.erase(NItr);
- NodeStack.push_back(NId);
- G.disconnectAllNeighborsFromNode(NId);
-
- } else if (!NotProvablyAllocatableNodes.empty()) {
- NodeSet::iterator NItr =
- std::min_element(NotProvablyAllocatableNodes.begin(),
- NotProvablyAllocatableNodes.end(),
- SpillCostComparator(G));
- NodeId NId = *NItr;
- NotProvablyAllocatableNodes.erase(NItr);
- NodeStack.push_back(NId);
- G.disconnectAllNeighborsFromNode(NId);
- } else
- break;
- }
-
- return NodeStack;
- }
-
- class SpillCostComparator {
- public:
- SpillCostComparator(const Graph& G) : G(G) {}
- bool operator()(NodeId N1Id, NodeId N2Id) {
- PBQPNum N1SC = G.getNodeCosts(N1Id)[0] / G.getNodeDegree(N1Id);
- PBQPNum N2SC = G.getNodeCosts(N2Id)[0] / G.getNodeDegree(N2Id);
- return N1SC < N2SC;
- }
- private:
- const Graph& G;
- };
-
- Graph& G;
- typedef std::set<NodeId> NodeSet;
- NodeSet OptimallyReducibleNodes;
- NodeSet ConservativelyAllocatableNodes;
- NodeSet NotProvablyAllocatableNodes;
- };
-
- class PBQPRAGraph : public PBQP::Graph<RegAllocSolverImpl> {
- private:
- typedef PBQP::Graph<RegAllocSolverImpl> BaseT;
- public:
- PBQPRAGraph(GraphMetadata Metadata) : BaseT(Metadata) {}
- };
-
- inline Solution solve(PBQPRAGraph& G) {
- if (G.empty())
- return Solution();
- RegAllocSolverImpl RegAllocSolver(G);
- return RegAllocSolver.solve();
- }
- } // namespace RegAlloc
-} // namespace PBQP
-} // namespace llvm
-
-#endif // LLVM_CODEGEN_PBQP_REGALLOCSOLVER_H
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