1 //===- Localizer.cpp ---------------------- Localize some instrs -*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// This file implements the Localizer class.
11 //===----------------------------------------------------------------------===//
13 #include "llvm/CodeGen/GlobalISel/Localizer.h"
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/ADT/SmallPtrSet.h"
16 #include "llvm/CodeGen/MachineRegisterInfo.h"
17 #include "llvm/Support/Debug.h"
19 #define DEBUG_TYPE "localizer"
23 char Localizer::ID = 0;
24 INITIALIZE_PASS(Localizer, DEBUG_TYPE,
25 "Move/duplicate certain instructions close to their use", false,
28 Localizer::Localizer() : MachineFunctionPass(ID) {
29 initializeLocalizerPass(*PassRegistry::getPassRegistry());
32 void Localizer::init(MachineFunction &MF) { MRI = &MF.getRegInfo(); }
34 bool Localizer::shouldLocalize(const MachineInstr &MI) {
35 switch (MI.getOpcode()) {
38 // Constants-like instructions should be close to their users.
39 // We don't want long live-ranges for them.
40 case TargetOpcode::G_CONSTANT:
41 case TargetOpcode::G_FCONSTANT:
42 case TargetOpcode::G_FRAME_INDEX:
47 bool Localizer::isLocalUse(MachineOperand &MOUse, const MachineInstr &Def,
48 MachineBasicBlock *&InsertMBB) {
49 MachineInstr &MIUse = *MOUse.getParent();
50 InsertMBB = MIUse.getParent();
52 InsertMBB = MIUse.getOperand(MIUse.getOperandNo(&MOUse) + 1).getMBB();
53 return InsertMBB == Def.getParent();
56 bool Localizer::runOnMachineFunction(MachineFunction &MF) {
57 // If the ISel pipeline failed, do not bother running that pass.
58 if (MF.getProperties().hasProperty(
59 MachineFunctionProperties::Property::FailedISel))
62 DEBUG(dbgs() << "Localize instructions for: " << MF.getName() << '\n');
67 // Keep track of the instructions we localized.
68 // We won't need to process them if we see them later in the CFG.
69 SmallPtrSet<MachineInstr *, 16> LocalizedInstrs;
70 DenseMap<std::pair<MachineBasicBlock *, unsigned>, unsigned> MBBWithLocalDef;
71 // TODO: Do bottom up traversal.
72 for (MachineBasicBlock &MBB : MF) {
73 for (MachineInstr &MI : MBB) {
74 if (LocalizedInstrs.count(&MI) || !shouldLocalize(MI))
76 DEBUG(dbgs() << "Should localize: " << MI);
77 assert(MI.getDesc().getNumDefs() == 1 &&
78 "More than one definition not supported yet");
79 unsigned Reg = MI.getOperand(0).getReg();
80 // Check if all the users of MI are local.
81 // We are going to invalidation the list of use operands, so we
82 // can't use range iterator.
83 for (auto MOIt = MRI->use_begin(Reg), MOItEnd = MRI->use_end();
85 MachineOperand &MOUse = *MOIt++;
86 // Check if the use is already local.
87 MachineBasicBlock *InsertMBB;
88 DEBUG(MachineInstr &MIUse = *MOUse.getParent();
89 dbgs() << "Checking use: " << MIUse
90 << " #Opd: " << MIUse.getOperandNo(&MOUse) << '\n');
91 if (isLocalUse(MOUse, MI, InsertMBB))
93 DEBUG(dbgs() << "Fixing non-local use\n");
95 auto MBBAndReg = std::make_pair(InsertMBB, Reg);
96 auto NewVRegIt = MBBWithLocalDef.find(MBBAndReg);
97 if (NewVRegIt == MBBWithLocalDef.end()) {
98 // Create the localized instruction.
99 MachineInstr *LocalizedMI = MF.CloneMachineInstr(&MI);
100 LocalizedInstrs.insert(LocalizedMI);
101 // Don't try to be smart for the insertion point.
102 // There is no guarantee that the first seen use is the first
104 InsertMBB->insert(InsertMBB->getFirstNonPHI(), LocalizedMI);
106 // Set a new register for the definition.
108 MRI->createGenericVirtualRegister(MRI->getType(Reg));
109 MRI->setRegClassOrRegBank(NewReg, MRI->getRegClassOrRegBank(Reg));
110 LocalizedMI->getOperand(0).setReg(NewReg);
112 MBBWithLocalDef.insert(std::make_pair(MBBAndReg, NewReg)).first;
113 DEBUG(dbgs() << "Inserted: " << *LocalizedMI);
115 DEBUG(dbgs() << "Update use with: " << PrintReg(NewVRegIt->second)
117 // Update the user reg.
118 MOUse.setReg(NewVRegIt->second);