Coverage Report

Created: 2019-02-20 07:29

/Users/buildslave/jenkins/workspace/clang-stage2-coverage-R/llvm/include/llvm/CodeGen/LiveVariables.h
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//===-- llvm/CodeGen/LiveVariables.h - Live Variable Analysis ---*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the LiveVariables analysis pass.  For each machine
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// instruction in the function, this pass calculates the set of registers that
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// are immediately dead after the instruction (i.e., the instruction calculates
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// the value, but it is never used) and the set of registers that are used by
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// the instruction, but are never used after the instruction (i.e., they are
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// killed).
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//
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// This class computes live variables using a sparse implementation based on
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// the machine code SSA form.  This class computes live variable information for
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// each virtual and _register allocatable_ physical register in a function.  It
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// uses the dominance properties of SSA form to efficiently compute live
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// variables for virtual registers, and assumes that physical registers are only
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// live within a single basic block (allowing it to do a single local analysis
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// to resolve physical register lifetimes in each basic block).  If a physical
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// register is not register allocatable, it is not tracked.  This is useful for
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// things like the stack pointer and condition codes.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_LIVEVARIABLES_H
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#define LLVM_CODEGEN_LIVEVARIABLES_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/ADT/IndexedMap.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/ADT/SparseBitVector.h"
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#include "llvm/CodeGen/MachineFunctionPass.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/TargetRegisterInfo.h"
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namespace llvm {
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class MachineBasicBlock;
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class MachineRegisterInfo;
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class LiveVariables : public MachineFunctionPass {
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public:
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  static char ID; // Pass identification, replacement for typeid
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33.3k
  LiveVariables() : MachineFunctionPass(ID) {
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33.3k
    initializeLiveVariablesPass(*PassRegistry::getPassRegistry());
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33.3k
  }
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  /// VarInfo - This represents the regions where a virtual register is live in
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  /// the program.  We represent this with three different pieces of
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  /// information: the set of blocks in which the instruction is live
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  /// throughout, the set of blocks in which the instruction is actually used,
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  /// and the set of non-phi instructions that are the last users of the value.
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  ///
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  /// In the common case where a value is defined and killed in the same block,
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  /// There is one killing instruction, and AliveBlocks is empty.
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  ///
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  /// Otherwise, the value is live out of the block.  If the value is live
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  /// throughout any blocks, these blocks are listed in AliveBlocks.  Blocks
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  /// where the liveness range ends are not included in AliveBlocks, instead
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  /// being captured by the Kills set.  In these blocks, the value is live into
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  /// the block (unless the value is defined and killed in the same block) and
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  /// lives until the specified instruction.  Note that there cannot ever be a
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  /// value whose Kills set contains two instructions from the same basic block.
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  ///
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  /// PHI nodes complicate things a bit.  If a PHI node is the last user of a
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  /// value in one of its predecessor blocks, it is not listed in the kills set,
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  /// but does include the predecessor block in the AliveBlocks set (unless that
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  /// block also defines the value).  This leads to the (perfectly sensical)
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  /// situation where a value is defined in a block, and the last use is a phi
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  /// node in the successor.  In this case, AliveBlocks is empty (the value is
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  /// not live across any  blocks) and Kills is empty (phi nodes are not
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  /// included). This is sensical because the value must be live to the end of
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  /// the block, but is not live in any successor blocks.
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  struct VarInfo {
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    /// AliveBlocks - Set of blocks in which this value is alive completely
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    /// through.  This is a bit set which uses the basic block number as an
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    /// index.
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    ///
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    SparseBitVector<> AliveBlocks;
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    /// Kills - List of MachineInstruction's which are the last use of this
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    /// virtual register (kill it) in their basic block.
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    ///
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    std::vector<MachineInstr*> Kills;
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    /// removeKill - Delete a kill corresponding to the specified
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    /// machine instruction. Returns true if there was a kill
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    /// corresponding to this instruction, false otherwise.
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331k
    bool removeKill(MachineInstr &MI) {
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331k
      std::vector<MachineInstr *>::iterator I = find(Kills, &MI);
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331k
      if (I == Kills.end())
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1.95k
        return false;
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      Kills.erase(I);
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      return true;
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    }
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    /// findKill - Find a kill instruction in MBB. Return NULL if none is found.
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    MachineInstr *findKill(const MachineBasicBlock *MBB) const;
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    /// isLiveIn - Is Reg live in to MBB? This means that Reg is live through
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    /// MBB, or it is killed in MBB. If Reg is only used by PHI instructions in
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    /// MBB, it is not considered live in.
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    bool isLiveIn(const MachineBasicBlock &MBB,
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                  unsigned Reg,
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                  MachineRegisterInfo &MRI);
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    void dump() const;
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  };
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private:
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  /// VirtRegInfo - This list is a mapping from virtual register number to
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  /// variable information.
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  ///
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  IndexedMap<VarInfo, VirtReg2IndexFunctor> VirtRegInfo;
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  /// PHIJoins - list of virtual registers that are PHI joins. These registers
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  /// may have multiple definitions, and they require special handling when
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  /// building live intervals.
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  SparseBitVector<> PHIJoins;
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private:   // Intermediate data structures
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  MachineFunction *MF;
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  MachineRegisterInfo* MRI;
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  const TargetRegisterInfo *TRI;
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  // PhysRegInfo - Keep track of which instruction was the last def of a
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  // physical register. This is a purely local property, because all physical
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  // register references are presumed dead across basic blocks.
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  std::vector<MachineInstr *> PhysRegDef;
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  // PhysRegInfo - Keep track of which instruction was the last use of a
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  // physical register. This is a purely local property, because all physical
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  // register references are presumed dead across basic blocks.
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  std::vector<MachineInstr *> PhysRegUse;
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  std::vector<SmallVector<unsigned, 4>> PHIVarInfo;
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  // DistanceMap - Keep track the distance of a MI from the start of the
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  // current basic block.
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  DenseMap<MachineInstr*, unsigned> DistanceMap;
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  /// HandlePhysRegKill - Add kills of Reg and its sub-registers to the
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  /// uses. Pay special attention to the sub-register uses which may come below
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  /// the last use of the whole register.
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  bool HandlePhysRegKill(unsigned Reg, MachineInstr *MI);
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  /// HandleRegMask - Call HandlePhysRegKill for all registers clobbered by Mask.
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  void HandleRegMask(const MachineOperand&);
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  void HandlePhysRegUse(unsigned Reg, MachineInstr &MI);
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  void HandlePhysRegDef(unsigned Reg, MachineInstr *MI,
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                        SmallVectorImpl<unsigned> &Defs);
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  void UpdatePhysRegDefs(MachineInstr &MI, SmallVectorImpl<unsigned> &Defs);
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  /// FindLastRefOrPartRef - Return the last reference or partial reference of
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  /// the specified register.
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  MachineInstr *FindLastRefOrPartRef(unsigned Reg);
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  /// FindLastPartialDef - Return the last partial def of the specified
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  /// register. Also returns the sub-registers that're defined by the
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  /// instruction.
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  MachineInstr *FindLastPartialDef(unsigned Reg,
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                                   SmallSet<unsigned,4> &PartDefRegs);
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  /// analyzePHINodes - Gather information about the PHI nodes in here. In
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  /// particular, we want to map the variable information of a virtual
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  /// register which is used in a PHI node. We map that to the BB the vreg
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  /// is coming from.
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  void analyzePHINodes(const MachineFunction& Fn);
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  void runOnInstr(MachineInstr &MI, SmallVectorImpl<unsigned> &Defs);
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  void runOnBlock(MachineBasicBlock *MBB, unsigned NumRegs);
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public:
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  bool runOnMachineFunction(MachineFunction &MF) override;
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  /// RegisterDefIsDead - Return true if the specified instruction defines the
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  /// specified register, but that definition is dead.
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  bool RegisterDefIsDead(MachineInstr &MI, unsigned Reg) const;
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  //===--------------------------------------------------------------------===//
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  //  API to update live variable information
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  /// replaceKillInstruction - Update register kill info by replacing a kill
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  /// instruction with a new one.
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  void replaceKillInstruction(unsigned Reg, MachineInstr &OldMI,
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                              MachineInstr &NewMI);
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  /// addVirtualRegisterKilled - Add information about the fact that the
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  /// specified register is killed after being used by the specified
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  /// instruction. If AddIfNotFound is true, add a implicit operand if it's
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  /// not found.
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  void addVirtualRegisterKilled(unsigned IncomingReg, MachineInstr &MI,
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2.21M
                                bool AddIfNotFound = false) {
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2.21M
    if (MI.addRegisterKilled(IncomingReg, TRI, AddIfNotFound))
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2.21M
      getVarInfo(IncomingReg).Kills.push_back(&MI);
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2.21M
  }
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  /// removeVirtualRegisterKilled - Remove the specified kill of the virtual
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  /// register from the live variable information. Returns true if the
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  /// variable was marked as killed by the specified instruction,
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  /// false otherwise.
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6.16k
  bool removeVirtualRegisterKilled(unsigned reg, MachineInstr &MI) {
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6.16k
    if (!getVarInfo(reg).removeKill(MI))
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      return false;
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6.16k
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6.16k
    bool Removed = false;
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14.8k
    for (unsigned i = 0, e = MI.getNumOperands(); i != e; 
++i8.73k
) {
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      MachineOperand &MO = MI.getOperand(i);
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14.8k
      if (MO.isReg() && 
MO.isKill()14.5k
&&
MO.getReg() == reg8.15k
) {
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6.16k
        MO.setIsKill(false);
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6.16k
        Removed = true;
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        break;
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      }
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14.8k
    }
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6.16k
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    assert(Removed && "Register is not used by this instruction!");
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    (void)Removed;
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    return true;
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  }
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  /// removeVirtualRegistersKilled - Remove all killed info for the specified
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  /// instruction.
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  void removeVirtualRegistersKilled(MachineInstr &MI);
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  /// addVirtualRegisterDead - Add information about the fact that the specified
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  /// register is dead after being used by the specified instruction. If
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  /// AddIfNotFound is true, add a implicit operand if it's not found.
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  void addVirtualRegisterDead(unsigned IncomingReg, MachineInstr &MI,
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                              bool AddIfNotFound = false) {
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    if (MI.addRegisterDead(IncomingReg, TRI, AddIfNotFound))
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      getVarInfo(IncomingReg).Kills.push_back(&MI);
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  }
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  /// removeVirtualRegisterDead - Remove the specified kill of the virtual
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  /// register from the live variable information. Returns true if the
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  /// variable was marked dead at the specified instruction, false
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  /// otherwise.
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1.95k
  bool removeVirtualRegisterDead(unsigned reg, MachineInstr &MI) {
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1.95k
    if (!getVarInfo(reg).removeKill(MI))
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1.95k
      return false;
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    bool Removed = false;
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    for (unsigned i = 0, e = MI.getNumOperands(); i != e; 
++i0
) {
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      MachineOperand &MO = MI.getOperand(i);
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      if (MO.isReg() && MO.isDef() && MO.getReg() == reg) {
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        MO.setIsDead(false);
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        Removed = true;
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        break;
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      }
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    }
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    assert(Removed && "Register is not defined by this instruction!");
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    (void)Removed;
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    return true;
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  }
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  void getAnalysisUsage(AnalysisUsage &AU) const override;
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471k
  void releaseMemory() override {
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471k
    VirtRegInfo.clear();
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471k
  }
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  /// getVarInfo - Return the VarInfo structure for the specified VIRTUAL
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  /// register.
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  VarInfo &getVarInfo(unsigned RegIdx);
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  void MarkVirtRegAliveInBlock(VarInfo& VRInfo, MachineBasicBlock* DefBlock,
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                               MachineBasicBlock *BB);
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  void MarkVirtRegAliveInBlock(VarInfo& VRInfo, MachineBasicBlock* DefBlock,
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                               MachineBasicBlock *BB,
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                               std::vector<MachineBasicBlock*> &WorkList);
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  void HandleVirtRegDef(unsigned reg, MachineInstr &MI);
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  void HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB, MachineInstr &MI);
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182k
  bool isLiveIn(unsigned Reg, const MachineBasicBlock &MBB) {
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182k
    return getVarInfo(Reg).isLiveIn(MBB, Reg, *MRI);
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182k
  }
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  /// isLiveOut - Determine if Reg is live out from MBB, when not considering
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  /// PHI nodes. This means that Reg is either killed by a successor block or
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  /// passed through one.
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  bool isLiveOut(unsigned Reg, const MachineBasicBlock &MBB);
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  /// addNewBlock - Add a new basic block BB between DomBB and SuccBB. All
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  /// variables that are live out of DomBB and live into SuccBB will be marked
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  /// as passing live through BB. This method assumes that the machine code is
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  /// still in SSA form.
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  void addNewBlock(MachineBasicBlock *BB,
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                   MachineBasicBlock *DomBB,
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                   MachineBasicBlock *SuccBB);
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  /// isPHIJoin - Return true if Reg is a phi join register.
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0
  bool isPHIJoin(unsigned Reg) { return PHIJoins.test(Reg); }
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  /// setPHIJoin - Mark Reg as a phi join register.
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614k
  void setPHIJoin(unsigned Reg) { PHIJoins.set(Reg); }
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};
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} // End llvm namespace
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#endif