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 93