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/MachineFunctionPass.h" |
26 | |
27 | namespace llvm { |
28 | // Forward declarations. |
29 | class AnalysisUsage; |
30 | class MachineBasicBlock; |
31 | class MachineInstr; |
32 | class MachineOperand; |
33 | class MachineRegisterInfo; |
34 | class TargetTransformInfo; |
35 | |
36 | /// This pass implements the localization mechanism described at the |
37 | /// top of this file. One specificity of the implementation is that |
38 | /// it will materialize one and only one instance of a constant per |
39 | /// basic block, thus enabling reuse of that constant within that block. |
40 | /// Moreover, it only materializes constants in blocks where they |
41 | /// are used. PHI uses are considered happening at the end of the |
42 | /// related predecessor. |
43 | class Localizer : public MachineFunctionPass { |
44 | public: |
45 | static char ID; |
46 | |
47 | private: |
48 | /// An input function to decide if the pass should run or not |
49 | /// on the given MachineFunction. |
50 | std::function<bool(const MachineFunction &)> DoNotRunPass; |
51 | |
52 | /// MRI contains all the register class/bank information that this |
53 | /// pass uses and updates. |
54 | MachineRegisterInfo *MRI = nullptr; |
55 | /// TTI used for getting remat costs for instructions. |
56 | TargetTransformInfo *TTI = nullptr; |
57 | |
58 | /// Check if \p MOUse is used in the same basic block as \p Def. |
59 | /// If the use is in the same block, we say it is local. |
60 | /// When the use is not local, \p InsertMBB will contain the basic |
61 | /// block when to insert \p Def to have a local use. |
62 | static bool isLocalUse(MachineOperand &MOUse, const MachineInstr &Def, |
63 | MachineBasicBlock *&InsertMBB); |
64 | |
65 | /// Initialize the field members using \p MF. |
66 | void init(MachineFunction &MF); |
67 | |
68 | typedef SmallSetVector<MachineInstr *, 32> LocalizedSetVecT; |
69 | |
70 | /// If \p Op is a reg operand of a PHI, return the number of total |
71 | /// operands in the PHI that are the same as \p Op, including itself. |
72 | unsigned getNumPhiUses(MachineOperand &Op) const; |
73 | |
74 | /// Do inter-block localization from the entry block. |
75 | bool localizeInterBlock(MachineFunction &MF, |
76 | LocalizedSetVecT &LocalizedInstrs); |
77 | |
78 | /// Do intra-block localization of already localized instructions. |
79 | bool localizeIntraBlock(LocalizedSetVecT &LocalizedInstrs); |
80 | |
81 | public: |
82 | Localizer(); |
83 | Localizer(std::function<bool(const MachineFunction &)>); |
84 | |
85 | StringRef getPassName() const override { return "Localizer" ; } |
86 | |
87 | MachineFunctionProperties getRequiredProperties() const override { |
88 | return MachineFunctionProperties() |
89 | .set(MachineFunctionProperties::Property::IsSSA); |
90 | } |
91 | |
92 | void getAnalysisUsage(AnalysisUsage &AU) const override; |
93 | |
94 | bool runOnMachineFunction(MachineFunction &MF) override; |
95 | }; |
96 | |
97 | } // End namespace llvm. |
98 | |
99 | #endif |
100 | |