include/llvm/CodeGen/GlobalISel/Localizer.h

   1 //== llvm/CodeGen/GlobalISel/Localizer.h - Localizer -------------*- C++ -*-==//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 /// \file This file describes the interface of the Localizer pass.
  10 /// This pass moves/duplicates constant-like instructions close to their uses.
  11 /// Its primarily goal is to workaround the deficiencies of the fast register
  12 /// allocator.
  13 /// With GlobalISel constants are all materialized in the entry block of
  14 /// a function. However, the fast allocator cannot rematerialize constants and
  15 /// has a lot more live-ranges to deal with and will most likely end up
  16 /// spilling a lot.
  17 /// By pushing the constants close to their use, we only create small
  18 /// live-ranges.
  19 //===----------------------------------------------------------------------===//
  20
  21 #ifndef LLVM_CODEGEN_GLOBALISEL_LOCALIZER_H
  22 #define LLVM_CODEGEN_GLOBALISEL_LOCALIZER_H
  23
  24 #include "llvm/ADT/SetVector.h"
  25 #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
  26 #include "llvm/CodeGen/MachineFunctionPass.h"
  27
  28 namespace llvm {
  29 // Forward declarations.
  30 class MachineRegisterInfo;
  31 class TargetTransformInfo;
  32
  33 /// This pass implements the localization mechanism described at the
  34 /// top of this file. One specificity of the implementation is that
  35 /// it will materialize one and only one instance of a constant per
  36 /// basic block, thus enabling reuse of that constant within that block.
  37 /// Moreover, it only materializes constants in blocks where they
  38 /// are used. PHI uses are considered happening at the end of the
  39 /// related predecessor.
  40 class Localizer : public MachineFunctionPass {
  41 public:
  42   static char ID;
  43
  44 private:
  45   /// MRI contains all the register class/bank information that this
  46   /// pass uses and updates.
  47   MachineRegisterInfo *MRI;
  48   /// TTI used for getting remat costs for instructions.
  49   TargetTransformInfo *TTI;
  50
  51   /// Check whether or not \p MI needs to be moved close to its uses.
  52   bool shouldLocalize(const MachineInstr &MI);
  53
  54   /// Check if \p MOUse is used in the same basic block as \p Def.
  55   /// If the use is in the same block, we say it is local.
  56   /// When the use is not local, \p InsertMBB will contain the basic
  57   /// block when to insert \p Def to have a local use.
  58   static bool isLocalUse(MachineOperand &MOUse, const MachineInstr &Def,
  59                          MachineBasicBlock *&InsertMBB);
  60
  61   /// Initialize the field members using \p MF.
  62   void init(MachineFunction &MF);
  63
  64   typedef SmallSetVector<MachineInstr *, 32> LocalizedSetVecT;
  65
  66   /// Do inter-block localization from the entry block.
  67   bool localizeInterBlock(MachineFunction &MF,
  68                           LocalizedSetVecT &LocalizedInstrs);
  69
  70   /// Do intra-block localization of already localized instructions.
  71   bool localizeIntraBlock(LocalizedSetVecT &LocalizedInstrs);
  72
  73 public:
  74   Localizer();
  75
  76   StringRef getPassName() const override { return "Localizer"; }
  77
  78   MachineFunctionProperties getRequiredProperties() const override {
  79     return MachineFunctionProperties()
  80         .set(MachineFunctionProperties::Property::IsSSA)
  81         .set(MachineFunctionProperties::Property::Legalized)
  82         .set(MachineFunctionProperties::Property::RegBankSelected);
  83   }
  84
  85   void getAnalysisUsage(AnalysisUsage &AU) const override;
  86
  87   bool runOnMachineFunction(MachineFunction &MF) override;
  88 };
  89
  90 } // End namespace llvm.
  91
  92 #endif