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 //== llvm/CodeGen/GlobalISel/Localizer.h - Localizer -------------*- 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 This file describes the interface of the Localizer pass.
 /// This pass moves/duplicates constant-like instructions close to their uses.
 /// Its primarily goal is to workaround the deficiencies of the fast register
 /// allocator.
 /// With GlobalISel constants are all materialized in the entry block of
 /// a function. However, the fast allocator cannot rematerialize constants and
 /// has a lot more live-ranges to deal with and will most likely end up
 /// spilling a lot.
 /// By pushing the constants close to their use, we only create small
 /// live-ranges.
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CODEGEN_GLOBALISEL_LOCALIZER_H
 #define LLVM_CODEGEN_GLOBALISEL_LOCALIZER_H
 
 #include "llvm/ADT/SetVector.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 
 namespace llvm {
 // Forward declarations.
 class AnalysisUsage;
 class MachineBasicBlock;
 class MachineInstr;
 class MachineOperand;
 class MachineRegisterInfo;
 class TargetTransformInfo;
 
 /// This pass implements the localization mechanism described at the
 /// top of this file. One specificity of the implementation is that
 /// it will materialize one and only one instance of a constant per
 /// basic block, thus enabling reuse of that constant within that block.
 /// Moreover, it only materializes constants in blocks where they
 /// are used. PHI uses are considered happening at the end of the
 /// related predecessor.
 class Localizer : public MachineFunctionPass {
 public:
   static char ID;
 
 private:
   /// An input function to decide if the pass should run or not
   /// on the given MachineFunction.
   std::function<bool(const MachineFunction &)> DoNotRunPass;
 
   /// MRI contains all the register class/bank information that this
   /// pass uses and updates.
   MachineRegisterInfo *MRI = nullptr;
   /// TTI used for getting remat costs for instructions.
   TargetTransformInfo *TTI = nullptr;
 
   /// Check if \p MOUse is used in the same basic block as \p Def.
   /// If the use is in the same block, we say it is local.
   /// When the use is not local, \p InsertMBB will contain the basic
   /// block when to insert \p Def to have a local use.
   static bool isLocalUse(MachineOperand &MOUse, const MachineInstr &Def,
                          MachineBasicBlock *&InsertMBB);
 
   /// Initialize the field members using \p MF.
   void init(MachineFunction &MF);
 
   typedef SmallSetVector<MachineInstr *, 32> LocalizedSetVecT;
 
   /// If \p Op is a reg operand of a PHI, return the number of total
   /// operands in the PHI that are the same as \p Op, including itself.
   unsigned getNumPhiUses(MachineOperand &Op) const;
 
   /// Do inter-block localization from the entry block.
   bool localizeInterBlock(MachineFunction &MF,
                           LocalizedSetVecT &LocalizedInstrs);
 
   /// Do intra-block localization of already localized instructions.
   bool localizeIntraBlock(LocalizedSetVecT &LocalizedInstrs);
 
 public:
   Localizer();
   Localizer(std::function<bool(const MachineFunction &)>);
 
   StringRef getPassName() const override { return "Localizer"; }
 
   MachineFunctionProperties getRequiredProperties() const override {
     return MachineFunctionProperties()
         .set(MachineFunctionProperties::Property::IsSSA);
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override;
 
   bool runOnMachineFunction(MachineFunction &MF) override;
 };
 
 } // End namespace llvm.
 
 #endif

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