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thirdparty/capstone/suite/synctools/tablegen/include/llvm/CodeGen/RegAllocPBQP.h

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+//===- RegAllocPBQP.h -------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the PBQPBuilder interface, for classes which build PBQP
+// instances to represent register allocation problems, and the RegAllocPBQP
+// interface.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_REGALLOCPBQP_H
+#define LLVM_CODEGEN_REGALLOCPBQP_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/Hashing.h"
+#include "llvm/CodeGen/PBQP/CostAllocator.h"
+#include "llvm/CodeGen/PBQP/Graph.h"
+#include "llvm/CodeGen/PBQP/Math.h"
+#include "llvm/CodeGen/PBQP/ReductionRules.h"
+#include "llvm/CodeGen/PBQP/Solution.h"
+#include "llvm/CodeGen/Register.h"
+#include "llvm/MC/MCRegister.h"
+#include "llvm/Support/ErrorHandling.h"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <limits>
+#include <memory>
+#include <set>
+#include <vector>
+
+namespace llvm {
+
+class FunctionPass;
+class LiveIntervals;
+class MachineBlockFrequencyInfo;
+class MachineFunction;
+class raw_ostream;
+
+namespace PBQP {
+namespace RegAlloc {
+
+/// Spill option index.
+inline unsigned getSpillOptionIdx() { return 0; }
+
+/// Metadata to speed allocatability test.
+///
+/// Keeps track of the number of infinities in each row and column.
+class MatrixMetadata {
+public:
+  MatrixMetadata(const Matrix& M)
+    : 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<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(const MatrixMetadata &) = delete;
+  MatrixMetadata &operator=(const MatrixMetadata &) = delete;
+
+  unsigned getWorstRow() const { return WorstRow; }
+  unsigned getWorstCol() const { return WorstCol; }
+  const bool* getUnsafeRows() const { return UnsafeRows.get(); }
+  const bool* getUnsafeCols() const { return UnsafeCols.get(); }
+
+private:
+  unsigned WorstRow = 0;
+  unsigned WorstCol = 0;
+  std::unique_ptr<bool[]> UnsafeRows;
+  std::unique_ptr<bool[]> UnsafeCols;
+};
+
+/// Holds a vector of the allowed physical regs for a vreg.
+class AllowedRegVector {
+  friend hash_code hash_value(const AllowedRegVector &);
+
+public:
+  AllowedRegVector() = default;
+  AllowedRegVector(AllowedRegVector &&) = default;
+
+  AllowedRegVector(const std::vector<MCRegister> &OptVec)
+      : NumOpts(OptVec.size()), Opts(new MCRegister[NumOpts]) {
+    std::copy(OptVec.begin(), OptVec.end(), Opts.get());
+  }
+
+  unsigned size() const { return NumOpts; }
+  MCRegister operator[](size_t I) const { return Opts[I]; }
+
+  bool operator==(const AllowedRegVector &Other) const {
+    if (NumOpts != Other.NumOpts)
+      return false;
+    return std::equal(Opts.get(), Opts.get() + NumOpts, Other.Opts.get());
+  }
+
+  bool operator!=(const AllowedRegVector &Other) const {
+    return !(*this == Other);
+  }
+
+private:
+  unsigned NumOpts = 0;
+  std::unique_ptr<MCRegister[]> Opts;
+};
+
+inline hash_code hash_value(const AllowedRegVector &OptRegs) {
+  MCRegister *OStart = OptRegs.Opts.get();
+  MCRegister *OEnd = OptRegs.Opts.get() + OptRegs.NumOpts;
+  return hash_combine(OptRegs.NumOpts,
+                      hash_combine_range(OStart, OEnd));
+}
+
+/// Holds graph-level metadata relevant to PBQP RA problems.
+class GraphMetadata {
+private:
+  using AllowedRegVecPool = ValuePool<AllowedRegVector>;
+
+public:
+  using AllowedRegVecRef = AllowedRegVecPool::PoolRef;
+
+  GraphMetadata(MachineFunction &MF,
+                LiveIntervals &LIS,
+                MachineBlockFrequencyInfo &MBFI)
+    : MF(MF), LIS(LIS), MBFI(MBFI) {}
+
+  MachineFunction &MF;
+  LiveIntervals &LIS;
+  MachineBlockFrequencyInfo &MBFI;
+
+  void setNodeIdForVReg(Register VReg, GraphBase::NodeId NId) {
+    VRegToNodeId[VReg.id()] = NId;
+  }
+
+  GraphBase::NodeId getNodeIdForVReg(Register VReg) const {
+    auto VRegItr = VRegToNodeId.find(VReg);
+    if (VRegItr == VRegToNodeId.end())
+      return GraphBase::invalidNodeId();
+    return VRegItr->second;
+  }
+
+  AllowedRegVecRef getAllowedRegs(AllowedRegVector Allowed) {
+    return AllowedRegVecs.getValue(std::move(Allowed));
+  }
+
+private:
+  DenseMap<Register, GraphBase::NodeId> VRegToNodeId;
+  AllowedRegVecPool AllowedRegVecs;
+};
+
+/// Holds solver state and other metadata relevant to each PBQP RA node.
+class NodeMetadata {
+public:
+  using AllowedRegVector = RegAlloc::AllowedRegVector;
+
+  // The node's reduction state. The order in this enum is important,
+  // as it is assumed nodes can only progress up (i.e. towards being
+  // optimally reducible) when reducing the graph.
+  using ReductionState = enum {
+    Unprocessed,
+    NotProvablyAllocatable,
+    ConservativelyAllocatable,
+    OptimallyReducible
+  };
+
+  NodeMetadata() = default;
+
+  NodeMetadata(const NodeMetadata &Other)
+    : RS(Other.RS), NumOpts(Other.NumOpts), DeniedOpts(Other.DeniedOpts),
+      OptUnsafeEdges(new unsigned[NumOpts]), VReg(Other.VReg),
+      AllowedRegs(Other.AllowedRegs)
+#ifndef NDEBUG
+      , everConservativelyAllocatable(Other.everConservativelyAllocatable)
+#endif
+  {
+    if (NumOpts > 0) {
+      std::copy(&Other.OptUnsafeEdges[0], &Other.OptUnsafeEdges[NumOpts],
+                &OptUnsafeEdges[0]);
+    }
+  }
+
+  NodeMetadata(NodeMetadata &&) = default;
+  NodeMetadata& operator=(NodeMetadata &&) = default;
+
+  void setVReg(Register VReg) { this->VReg = VReg; }
+  Register getVReg() const { return VReg; }
+
+  void setAllowedRegs(GraphMetadata::AllowedRegVecRef AllowedRegs) {
+    this->AllowedRegs = std::move(AllowedRegs);
+  }
+  const AllowedRegVector& getAllowedRegs() const { return *AllowedRegs; }
+
+  void setup(const Vector& Costs) {
+    NumOpts = Costs.getLength() - 1;
+    OptUnsafeEdges = std::unique_ptr<unsigned[]>(new unsigned[NumOpts]());
+  }
+
+  ReductionState getReductionState() const { return RS; }
+  void setReductionState(ReductionState RS) {
+    assert(RS >= this->RS && "A node's reduction state can not be downgraded");
+    this->RS = RS;
+
+#ifndef NDEBUG
+    // Remember this state to assert later that a non-infinite register
+    // option was available.
+    if (RS == ConservativelyAllocatable)
+      everConservativelyAllocatable = true;
+#endif
+  }
+
+  void handleAddEdge(const MatrixMetadata& MD, bool Transpose) {
+    DeniedOpts += Transpose ? MD.getWorstRow() : MD.getWorstCol();
+    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.getWorstRow() : MD.getWorstCol();
+    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[0], &OptUnsafeEdges[NumOpts], 0) !=
+       &OptUnsafeEdges[NumOpts]);
+  }
+
+#ifndef NDEBUG
+  bool wasConservativelyAllocatable() const {
+    return everConservativelyAllocatable;
+  }
+#endif
+
+private:
+  ReductionState RS = Unprocessed;
+  unsigned NumOpts = 0;
+  unsigned DeniedOpts = 0;
+  std::unique_ptr<unsigned[]> OptUnsafeEdges;
+  Register VReg;
+  GraphMetadata::AllowedRegVecRef AllowedRegs;
+
+#ifndef NDEBUG
+  bool everConservativelyAllocatable = false;
+#endif
+};
+
+class RegAllocSolverImpl {
+private:
+  using RAMatrix = MDMatrix<MatrixMetadata>;
+
+public:
+  using RawVector = PBQP::Vector;
+  using RawMatrix = PBQP::Matrix;
+  using Vector = PBQP::Vector;
+  using Matrix = RAMatrix;
+  using CostAllocator = PBQP::PoolCostAllocator<Vector, Matrix>;
+
+  using NodeId = GraphBase::NodeId;
+  using EdgeId = GraphBase::EdgeId;
+
+  using NodeMetadata = RegAlloc::NodeMetadata;
+  struct EdgeMetadata {};
+  using GraphMetadata = RegAlloc::GraphMetadata;
+
+  using Graph = PBQP::Graph<RegAllocSolverImpl>;
+
+  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) {
+    assert(G.getNodeCosts(NId).getLength() > 1 &&
+           "PBQP Graph should not contain single or zero-option nodes");
+    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 handleDisconnectEdge(EdgeId EId, NodeId NId) {
+    NodeMetadata& NMd = G.getNodeMetadata(NId);
+    const MatrixMetadata& MMd = G.getEdgeCosts(EId).getMetadata();
+    NMd.handleRemoveEdge(MMd, NId == G.getEdgeNode2Id(EId));
+    promote(NId, NMd);
+  }
+
+  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 handleUpdateCosts(EdgeId EId, const Matrix& NewCosts) {
+    NodeId N1Id = G.getEdgeNode1Id(EId);
+    NodeId N2Id = G.getEdgeNode2Id(EId);
+    NodeMetadata& N1Md = G.getNodeMetadata(N1Id);
+    NodeMetadata& N2Md = G.getNodeMetadata(N2Id);
+    bool Transpose = N1Id != G.getEdgeNode1Id(EId);
+
+    // Metadata are computed incrementally. First, update them
+    // by removing the old cost.
+    const MatrixMetadata& OldMMd = G.getEdgeCosts(EId).getMetadata();
+    N1Md.handleRemoveEdge(OldMMd, Transpose);
+    N2Md.handleRemoveEdge(OldMMd, !Transpose);
+
+    // And update now the metadata with the new cost.
+    const MatrixMetadata& MMd = NewCosts.getMetadata();
+    N1Md.handleAddEdge(MMd, Transpose);
+    N2Md.handleAddEdge(MMd, !Transpose);
+
+    // As the metadata may have changed with the update, the nodes may have
+    // become ConservativelyAllocatable or OptimallyReducible.
+    promote(N1Id, N1Md);
+    promote(N2Id, N2Md);
+  }
+
+private:
+  void promote(NodeId NId, NodeMetadata& NMd) {
+    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 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.");
+
+    using NodeId = GraphBase::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];
+      PBQPNum N2SC = G.getNodeCosts(N2Id)[0];
+      if (N1SC == N2SC)
+        return G.getNodeDegree(N1Id) < G.getNodeDegree(N2Id);
+      return N1SC < N2SC;
+    }
+
+  private:
+    const Graph& G;
+  };
+
+  Graph& G;
+  using NodeSet = std::set<NodeId>;
+  NodeSet OptimallyReducibleNodes;
+  NodeSet ConservativelyAllocatableNodes;
+  NodeSet NotProvablyAllocatableNodes;
+};
+
+class PBQPRAGraph : public PBQP::Graph<RegAllocSolverImpl> {
+private:
+  using BaseT = PBQP::Graph<RegAllocSolverImpl>;
+
+public:
+  PBQPRAGraph(GraphMetadata Metadata) : BaseT(std::move(Metadata)) {}
+
+  /// Dump this graph to dbgs().
+  void dump() const;
+
+  /// Dump this graph to an output stream.
+  /// @param OS Output stream to print on.
+  void dump(raw_ostream &OS) const;
+
+  /// Print a representation of this graph in DOT format.
+  /// @param OS Output stream to print on.
+  void printDot(raw_ostream &OS) const;
+};
+
+inline Solution solve(PBQPRAGraph& G) {
+  if (G.empty())
+    return Solution();
+  RegAllocSolverImpl RegAllocSolver(G);
+  return RegAllocSolver.solve();
+}
+
+} // end namespace RegAlloc
+} // end namespace PBQP
+
+/// Create a PBQP register allocator instance.
+FunctionPass *
+createPBQPRegisterAllocator(char *customPassID = nullptr);
+
+} // end namespace llvm
+
+#endif // LLVM_CODEGEN_REGALLOCPBQP_H