LLVM  13.0.0git
Localizer.cpp
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1 //===- Localizer.cpp ---------------------- Localize some instrs -*- 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 /// \file
9 /// This file implements the Localizer class.
10 //===----------------------------------------------------------------------===//
11 
13 #include "llvm/ADT/DenseMap.h"
14 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/InitializePasses.h"
19 #include "llvm/Support/Debug.h"
20 
21 #define DEBUG_TYPE "localizer"
22 
23 using namespace llvm;
24 
25 char Localizer::ID = 0;
27  "Move/duplicate certain instructions close to their use",
28  false, false)
31  "Move/duplicate certain instructions close to their use",
33 
35  : MachineFunctionPass(ID), DoNotRunPass(F) {}
36 
38  : Localizer([](const MachineFunction &) { return false; }) {}
39 
40 void Localizer::init(MachineFunction &MF) {
41  MRI = &MF.getRegInfo();
42  TTI = &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(MF.getFunction());
43 }
44 
49 }
50 
51 bool Localizer::isLocalUse(MachineOperand &MOUse, const MachineInstr &Def,
52  MachineBasicBlock *&InsertMBB) {
53  MachineInstr &MIUse = *MOUse.getParent();
54  InsertMBB = MIUse.getParent();
55  if (MIUse.isPHI())
56  InsertMBB = MIUse.getOperand(MIUse.getOperandNo(&MOUse) + 1).getMBB();
57  return InsertMBB == Def.getParent();
58 }
59 
60 bool Localizer::isNonUniquePhiValue(MachineOperand &Op) const {
61  MachineInstr *MI = Op.getParent();
62  if (!MI->isPHI())
63  return false;
64 
65  Register SrcReg = Op.getReg();
66  for (unsigned Idx = 1; Idx < MI->getNumOperands(); Idx += 2) {
67  auto &MO = MI->getOperand(Idx);
68  if (&MO != &Op && MO.isReg() && MO.getReg() == SrcReg)
69  return true;
70  }
71  return false;
72 }
73 
74 bool Localizer::localizeInterBlock(MachineFunction &MF,
75  LocalizedSetVecT &LocalizedInstrs) {
76  bool Changed = false;
77  DenseMap<std::pair<MachineBasicBlock *, unsigned>, unsigned> MBBWithLocalDef;
78 
79  // Since the IRTranslator only emits constants into the entry block, and the
80  // rest of the GISel pipeline generally emits constants close to their users,
81  // we only localize instructions in the entry block here. This might change if
82  // we start doing CSE across blocks.
83  auto &MBB = MF.front();
84  auto &TL = *MF.getSubtarget().getTargetLowering();
85  for (MachineInstr &MI : llvm::reverse(MBB)) {
86  if (!TL.shouldLocalize(MI, TTI))
87  continue;
88  LLVM_DEBUG(dbgs() << "Should localize: " << MI);
89  assert(MI.getDesc().getNumDefs() == 1 &&
90  "More than one definition not supported yet");
91  Register Reg = MI.getOperand(0).getReg();
92  // Check if all the users of MI are local.
93  // We are going to invalidation the list of use operands, so we
94  // can't use range iterator.
95  for (auto MOIt = MRI->use_begin(Reg), MOItEnd = MRI->use_end();
96  MOIt != MOItEnd;) {
97  MachineOperand &MOUse = *MOIt++;
98  // Check if the use is already local.
99  MachineBasicBlock *InsertMBB;
100  LLVM_DEBUG(MachineInstr &MIUse = *MOUse.getParent();
101  dbgs() << "Checking use: " << MIUse
102  << " #Opd: " << MIUse.getOperandNo(&MOUse) << '\n');
103  if (isLocalUse(MOUse, MI, InsertMBB)) {
104  // Even if we're in the same block, if the block is very large we could
105  // still have many long live ranges. Try to do intra-block localization
106  // too.
107  LocalizedInstrs.insert(&MI);
108  continue;
109  }
110 
111  // If the use is a phi operand that's not unique, don't try to localize.
112  // If we do, we can cause unnecessary instruction bloat by duplicating
113  // into each predecessor block, when the existing one is sufficient and
114  // allows for easier optimization later.
115  if (isNonUniquePhiValue(MOUse))
116  continue;
117 
118  LLVM_DEBUG(dbgs() << "Fixing non-local use\n");
119  Changed = true;
120  auto MBBAndReg = std::make_pair(InsertMBB, Reg);
121  auto NewVRegIt = MBBWithLocalDef.find(MBBAndReg);
122  if (NewVRegIt == MBBWithLocalDef.end()) {
123  // Create the localized instruction.
124  MachineInstr *LocalizedMI = MF.CloneMachineInstr(&MI);
125  LocalizedInstrs.insert(LocalizedMI);
126  MachineInstr &UseMI = *MOUse.getParent();
127  if (MRI->hasOneUse(Reg) && !UseMI.isPHI())
128  InsertMBB->insert(InsertMBB->SkipPHIsAndLabels(UseMI), LocalizedMI);
129  else
130  InsertMBB->insert(InsertMBB->SkipPHIsAndLabels(InsertMBB->begin()),
131  LocalizedMI);
132 
133  // Set a new register for the definition.
134  Register NewReg = MRI->createGenericVirtualRegister(MRI->getType(Reg));
135  MRI->setRegClassOrRegBank(NewReg, MRI->getRegClassOrRegBank(Reg));
136  LocalizedMI->getOperand(0).setReg(NewReg);
137  NewVRegIt =
138  MBBWithLocalDef.insert(std::make_pair(MBBAndReg, NewReg)).first;
139  LLVM_DEBUG(dbgs() << "Inserted: " << *LocalizedMI);
140  }
141  LLVM_DEBUG(dbgs() << "Update use with: " << printReg(NewVRegIt->second)
142  << '\n');
143  // Update the user reg.
144  MOUse.setReg(NewVRegIt->second);
145  }
146  }
147  return Changed;
148 }
149 
150 bool Localizer::localizeIntraBlock(LocalizedSetVecT &LocalizedInstrs) {
151  bool Changed = false;
152 
153  // For each already-localized instruction which has multiple users, then we
154  // scan the block top down from the current position until we hit one of them.
155 
156  // FIXME: Consider doing inst duplication if live ranges are very long due to
157  // many users, but this case may be better served by regalloc improvements.
158 
159  for (MachineInstr *MI : LocalizedInstrs) {
160  Register Reg = MI->getOperand(0).getReg();
161  MachineBasicBlock &MBB = *MI->getParent();
162  // All of the user MIs of this reg.
165  if (!UseMI.isPHI())
166  Users.insert(&UseMI);
167  }
168  // If all the users were PHIs then they're not going to be in our block,
169  // don't try to move this instruction.
170  if (Users.empty())
171  continue;
172 
174  ++II;
175  while (II != MBB.end() && !Users.count(&*II))
176  ++II;
177 
178  LLVM_DEBUG(dbgs() << "Intra-block: moving " << *MI << " before " << *&*II
179  << "\n");
180  assert(II != MBB.end() && "Didn't find the user in the MBB");
181  MI->removeFromParent();
182  MBB.insert(II, MI);
183  Changed = true;
184  }
185  return Changed;
186 }
187 
189  // If the ISel pipeline failed, do not bother running that pass.
190  if (MF.getProperties().hasProperty(
192  return false;
193 
194  // Don't run the pass if the target asked so.
195  if (DoNotRunPass(MF))
196  return false;
197 
198  LLVM_DEBUG(dbgs() << "Localize instructions for: " << MF.getName() << '\n');
199 
200  init(MF);
201 
202  // Keep track of the instructions we localized. We'll do a second pass of
203  // intra-block localization to further reduce live ranges.
204  LocalizedSetVecT LocalizedInstrs;
205 
206  bool Changed = localizeInterBlock(MF, LocalizedInstrs);
207  Changed |= localizeIntraBlock(LocalizedInstrs);
208  return Changed;
209 }
use
Move duplicate certain instructions close to their use
Definition: Localizer.cpp:31
llvm::MachineFunctionProperties::hasProperty
bool hasProperty(Property P) const
Definition: MachineFunction.h:165
MI
IRTranslator LLVM IR MI
Definition: IRTranslator.cpp:100
llvm::MachineInstr::getOperandNo
unsigned getOperandNo(const_mop_iterator I) const
Returns the number of the operand iterator I points to.
Definition: MachineInstr.h:672
llvm
Definition: AllocatorList.h:23
llvm::tgtok::Def
@ Def
Definition: TGLexer.h:50
Reg
unsigned Reg
Definition: MachineSink.cpp:1566
UseMI
MachineInstrBuilder & UseMI
Definition: AArch64ExpandPseudoInsts.cpp:100
llvm::TargetTransformInfo
This pass provides access to the codegen interfaces that are needed for IR-level transformations.
Definition: TargetTransformInfo.h:167
llvm::MachineFunctionPass
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
Definition: MachineFunctionPass.h:30
llvm::MachineRegisterInfo::use_nodbg_instructions
iterator_range< use_instr_nodbg_iterator > use_nodbg_instructions(Register Reg) const
Definition: MachineRegisterInfo.h:543
to
Should compile to
Definition: README.txt:449
llvm::Localizer::getAnalysisUsage
void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - This function should be overriden by passes that need analysis information to do t...
Definition: Localizer.cpp:45
DenseMap.h
llvm::reverse
auto reverse(ContainerTy &&C, std::enable_if_t< has_rbegin< ContainerTy >::value > *=nullptr)
Definition: STLExtras.h:329
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SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements.
Definition: SmallPtrSet.h:449
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void getSelectionDAGFallbackAnalysisUsage(AnalysisUsage &AU)
Modify analysis usage so it preserves passes required for the SelectionDAG fallback.
Definition: Utils.cpp:749
STLExtras.h
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void getAnalysisUsage(AnalysisUsage &AU) const override
getAnalysisUsage - Subclasses that override getAnalysisUsage must call this.
Definition: MachineFunctionPass.cpp:102
LLVM_DEBUG
#define LLVM_DEBUG(X)
Definition: Debug.h:122
F
#define F(x, y, z)
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MachineRegisterInfo.h
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raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
TargetLowering.h
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const MachineBasicBlock & front() const
Definition: MachineFunction.h:752
llvm::MachineFunction::getRegInfo
MachineRegisterInfo & getRegInfo()
getRegInfo - Return information about the registers currently in use.
Definition: MachineFunction.h:568
llvm::MachineRegisterInfo::setRegClassOrRegBank
void setRegClassOrRegBank(Register Reg, const RegClassOrRegBank &RCOrRB)
Definition: MachineRegisterInfo.h:678
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const MachineOperand & getOperand(unsigned i) const
Definition: MachineInstr.h:488
llvm::AnalysisUsage
Represent the analysis usage information of a pass.
Definition: PassAnalysisSupport.h:47
llvm::MachineFunction::getProperties
const MachineFunctionProperties & getProperties() const
Get the function properties.
Definition: MachineFunction.h:649
false
Definition: StackSlotColoring.cpp:142
llvm::MachineOperand
MachineOperand class - Representation of each machine instruction operand.
Definition: MachineOperand.h:49
llvm::MachineOperand::getParent
MachineInstr * getParent()
getParent - Return the instruction that this operand belongs to.
Definition: MachineOperand.h:238
llvm::Localizer::runOnMachineFunction
bool runOnMachineFunction(MachineFunction &MF) override
runOnMachineFunction - This method must be overloaded to perform the desired machine code transformat...
Definition: Localizer.cpp:188
llvm::MachineBasicBlock
Definition: MachineBasicBlock.h:95
INITIALIZE_PASS_END
#define INITIALIZE_PASS_END(passName, arg, name, cfg, analysis)
Definition: PassSupport.h:58
llvm::Localizer::Localizer
Localizer()
Definition: Localizer.cpp:37
llvm::MachineFunction::getSubtarget
const TargetSubtargetInfo & getSubtarget() const
getSubtarget - Return the subtarget for which this machine code is being compiled.
Definition: MachineFunction.h:558
llvm::instructions
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Definition: InstIterator.h:133
llvm::MachineInstr
Representation of each machine instruction.
Definition: MachineInstr.h:64
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Wrapper pass for TargetTransformInfo.
Definition: TargetTransformInfo.h:2375
const
aarch64 promote const
Definition: AArch64PromoteConstant.cpp:232
llvm::MachineFunction::CloneMachineInstr
MachineInstr * CloneMachineInstr(const MachineInstr *Orig)
Create a new MachineInstr which is a copy of Orig, identical in all ways except the instruction has n...
Definition: MachineFunction.cpp:358
INITIALIZE_PASS_DEPENDENCY
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
llvm::MachineBasicBlock::SkipPHIsAndLabels
iterator SkipPHIsAndLabels(iterator I)
Return the first instruction in MBB after I that is not a PHI or a label.
Definition: MachineBasicBlock.cpp:209
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Definition: DenseMap.h:714
Localizer.h
llvm::DenseMapBase< DenseMap< KeyT, ValueT, DenseMapInfo< KeyT >, llvm::detail::DenseMapPair< KeyT, ValueT > >, KeyT, ValueT, DenseMapInfo< KeyT >, llvm::detail::DenseMapPair< KeyT, ValueT > >::find
iterator find(const_arg_type_t< KeyT > Val)
Definition: DenseMap.h:150
llvm::MachineFunction::getName
StringRef getName() const
getName - Return the name of the corresponding LLVM function.
Definition: MachineFunction.cpp:522
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DEBUG_TYPE
#define DEBUG_TYPE
Definition: Localizer.cpp:21
function
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Definition: MemDepPrinter.cpp:83
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bool isPHI() const
Definition: MachineInstr.h:1243
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Register createGenericVirtualRegister(LLT Ty, StringRef Name="")
Create and return a new generic virtual register with low-level type Ty.
Definition: MachineRegisterInfo.cpp:188
llvm::MachineRegisterInfo::getRegClassOrRegBank
const RegClassOrRegBank & getRegClassOrRegBank(Register Reg) const
Return the register bank or register class of Reg.
Definition: MachineRegisterInfo.h:668
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Definition: MachineFunction.h:230
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MachineBasicBlock * getMBB() const
Definition: MachineOperand.h:552
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use_iterator use_begin(Register RegNo) const
Definition: MachineRegisterInfo.h:464
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const MachineBasicBlock * getParent() const
Definition: MachineInstr.h:286
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std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:207
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Definition: Register.h:19
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Definition: AArch64SLSHardening.cpp:74
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@ FailedISel
std
Definition: BitVector.h:838
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Return the LLVM function that this machine code represents.
Definition: MachineFunction.h:524
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Definition: DenseMap.h:83
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Definition: SIDefines.h:314
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Definition: MachineBasicBlock.cpp:1337
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static char ID
Definition: Localizer.h:42
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INITIALIZE_PASS_BEGIN(Localizer, DEBUG_TYPE, "Move/duplicate certain instructions close to their use", false, false) INITIALIZE_PASS_END(Localizer
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static use_iterator use_end()
Definition: MachineRegisterInfo.h:467
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virtual const TargetLowering * getTargetLowering() const
Definition: TargetSubtargetInfo.h:96
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bool hasOneUse(Register RegNo) const
hasOneUse - Return true if there is exactly one instruction using the specified register.
Definition: MachineRegisterInfo.h:510
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Definition: MachineBasicBlock.h:268
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LLT getType(Register Reg) const
Get the low-level type of Reg or LLT{} if Reg is not a generic (target independent) virtual register.
Definition: MachineRegisterInfo.h:732
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void setReg(Register Reg)
Change the register this operand corresponds to.
Definition: MachineOperand.cpp:55
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iv Induction Variable Users
Definition: IVUsers.cpp:52
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A SetVector that performs no allocations if smaller than a certain size.
Definition: SetVector.h:307
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AnalysisUsage & addRequired()
Definition: PassAnalysisSupport.h:75
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Printable printReg(Register Reg, const TargetRegisterInfo *TRI=nullptr, unsigned SubIdx=0, const MachineRegisterInfo *MRI=nullptr)
Prints virtual and physical registers with or without a TRI instance.
Definition: TargetRegisterInfo.cpp:110
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InitializePasses.h
Debug.h
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Definition: MachineBasicBlock.h:270
llvm::Localizer
This pass implements the localization mechanism described at the top of this file.
Definition: Localizer.h:40
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Definition: TargetTransformInfo.h:38