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

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+//===---- MachineOutliner.h - Outliner data structures ------*- 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Contains all data structures shared between the outliner implemented in
+/// MachineOutliner.cpp and target implementations of the outliner.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_MACHINEOUTLINER_H
+#define LLVM_CODEGEN_MACHINEOUTLINER_H
+
+#include "llvm/CodeGen/LivePhysRegs.h"
+#include "llvm/CodeGen/LiveRegUnits.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+
+namespace llvm {
+namespace outliner {
+
+/// Represents how an instruction should be mapped by the outliner.
+/// \p Legal instructions are those which are safe to outline.
+/// \p LegalTerminator instructions are safe to outline, but only as the
+/// last instruction in a sequence.
+/// \p Illegal instructions are those which cannot be outlined.
+/// \p Invisible instructions are instructions which can be outlined, but
+/// shouldn't actually impact the outlining result.
+enum InstrType { Legal, LegalTerminator, Illegal, Invisible };
+
+/// An individual sequence of instructions to be replaced with a call to
+/// an outlined function.
+struct Candidate {
+private:
+  /// The start index of this \p Candidate in the instruction list.
+  unsigned StartIdx = 0;
+
+  /// The number of instructions in this \p Candidate.
+  unsigned Len = 0;
+
+  // The first instruction in this \p Candidate.
+  MachineBasicBlock::iterator FirstInst;
+
+  // The last instruction in this \p Candidate.
+  MachineBasicBlock::iterator LastInst;
+
+  // The basic block that contains this Candidate.
+  MachineBasicBlock *MBB = nullptr;
+
+  /// Cost of calling an outlined function from this point as defined by the
+  /// target.
+  unsigned CallOverhead = 0;
+
+public:
+  /// The index of this \p Candidate's \p OutlinedFunction in the list of
+  /// \p OutlinedFunctions.
+  unsigned FunctionIdx = 0;
+
+  /// Identifier denoting the instructions to emit to call an outlined function
+  /// from this point. Defined by the target.
+  unsigned CallConstructionID = 0;
+
+  /// Contains physical register liveness information for the MBB containing
+  /// this \p Candidate.
+  ///
+  /// This is optionally used by the target to calculate more fine-grained
+  /// cost model information.
+  LiveRegUnits LRU;
+
+  /// Contains the accumulated register liveness information for the
+  /// instructions in this \p Candidate.
+  ///
+  /// This is optionally used by the target to determine which registers have
+  /// been used across the sequence.
+  LiveRegUnits UsedInSequence;
+
+  /// Target-specific flags for this Candidate's MBB.
+  unsigned Flags = 0x0;
+
+  /// True if initLRU has been called on this Candidate.
+  bool LRUWasSet = false;
+
+  /// Return the number of instructions in this Candidate.
+  unsigned getLength() const { return Len; }
+
+  /// Return the start index of this candidate.
+  unsigned getStartIdx() const { return StartIdx; }
+
+  /// Return the end index of this candidate.
+  unsigned getEndIdx() const { return StartIdx + Len - 1; }
+
+  /// Set the CallConstructionID and CallOverhead of this candidate to CID and
+  /// CO respectively.
+  void setCallInfo(unsigned CID, unsigned CO) {
+    CallConstructionID = CID;
+    CallOverhead = CO;
+  }
+
+  /// Returns the call overhead of this candidate if it is in the list.
+  unsigned getCallOverhead() const { return CallOverhead; }
+
+  MachineBasicBlock::iterator &front() { return FirstInst; }
+  MachineBasicBlock::iterator &back() { return LastInst; }
+  MachineFunction *getMF() const { return MBB->getParent(); }
+  MachineBasicBlock *getMBB() const { return MBB; }
+
+  /// The number of instructions that would be saved by outlining every
+  /// candidate of this type.
+  ///
+  /// This is a fixed value which is not updated during the candidate pruning
+  /// process. It is only used for deciding which candidate to keep if two
+  /// candidates overlap. The true benefit is stored in the OutlinedFunction
+  /// for some given candidate.
+  unsigned Benefit = 0;
+
+  Candidate(unsigned StartIdx, unsigned Len,
+            MachineBasicBlock::iterator &FirstInst,
+            MachineBasicBlock::iterator &LastInst, MachineBasicBlock *MBB,
+            unsigned FunctionIdx, unsigned Flags)
+      : StartIdx(StartIdx), Len(Len), FirstInst(FirstInst), LastInst(LastInst),
+        MBB(MBB), FunctionIdx(FunctionIdx), Flags(Flags) {}
+  Candidate() = default;
+
+  /// Used to ensure that \p Candidates are outlined in an order that
+  /// preserves the start and end indices of other \p Candidates.
+  bool operator<(const Candidate &RHS) const {
+    return getStartIdx() > RHS.getStartIdx();
+  }
+
+  /// Compute the registers that are live across this Candidate.
+  /// Used by targets that need this information for cost model calculation.
+  /// If a target does not need this information, then this should not be
+  /// called.
+  void initLRU(const TargetRegisterInfo &TRI) {
+    assert(MBB->getParent()->getRegInfo().tracksLiveness() &&
+           "Candidate's Machine Function must track liveness");
+    // Only initialize once.
+    if (LRUWasSet)
+      return;
+    LRUWasSet = true;
+    LRU.init(TRI);
+    LRU.addLiveOuts(*MBB);
+
+    // Compute liveness from the end of the block up to the beginning of the
+    // outlining candidate.
+    std::for_each(MBB->rbegin(), (MachineBasicBlock::reverse_iterator)front(),
+                  [this](MachineInstr &MI) { LRU.stepBackward(MI); });
+
+    // Walk over the sequence itself and figure out which registers were used
+    // in the sequence.
+    UsedInSequence.init(TRI);
+    std::for_each(front(), std::next(back()),
+                  [this](MachineInstr &MI) { UsedInSequence.accumulate(MI); });
+  }
+};
+
+/// The information necessary to create an outlined function for some
+/// class of candidate.
+struct OutlinedFunction {
+
+public:
+  std::vector<Candidate> Candidates;
+
+  /// The actual outlined function created.
+  /// This is initialized after we go through and create the actual function.
+  MachineFunction *MF = nullptr;
+
+  /// Represents the size of a sequence in bytes. (Some instructions vary
+  /// widely in size, so just counting the instructions isn't very useful.)
+  unsigned SequenceSize = 0;
+
+  /// Target-defined overhead of constructing a frame for this function.
+  unsigned FrameOverhead = 0;
+
+  /// Target-defined identifier for constructing a frame for this function.
+  unsigned FrameConstructionID = 0;
+
+  /// Return the number of candidates for this \p OutlinedFunction.
+  unsigned getOccurrenceCount() const { return Candidates.size(); }
+
+  /// Return the number of bytes it would take to outline this
+  /// function.
+  unsigned getOutliningCost() const {
+    unsigned CallOverhead = 0;
+    for (const Candidate &C : Candidates)
+      CallOverhead += C.getCallOverhead();
+    return CallOverhead + SequenceSize + FrameOverhead;
+  }
+
+  /// Return the size in bytes of the unoutlined sequences.
+  unsigned getNotOutlinedCost() const {
+    return getOccurrenceCount() * SequenceSize;
+  }
+
+  /// Return the number of instructions that would be saved by outlining
+  /// this function.
+  unsigned getBenefit() const {
+    unsigned NotOutlinedCost = getNotOutlinedCost();
+    unsigned OutlinedCost = getOutliningCost();
+    return (NotOutlinedCost < OutlinedCost) ? 0
+                                            : NotOutlinedCost - OutlinedCost;
+  }
+
+  /// Return the number of instructions in this sequence.
+  unsigned getNumInstrs() const { return Candidates[0].getLength(); }
+
+  OutlinedFunction(std::vector<Candidate> &Candidates, unsigned SequenceSize,
+                   unsigned FrameOverhead, unsigned FrameConstructionID)
+      : Candidates(Candidates), SequenceSize(SequenceSize),
+        FrameOverhead(FrameOverhead), FrameConstructionID(FrameConstructionID) {
+    const unsigned B = getBenefit();
+    for (Candidate &C : Candidates)
+      C.Benefit = B;
+  }
+
+  OutlinedFunction() = default;
+};
+} // namespace outliner
+} // namespace llvm
+
+#endif