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