LLVM  6.0.0svn
Localizer.cpp
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1 //===- Localizer.cpp ---------------------- Localize some instrs -*- 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 /// \file
10 /// This file implements the Localizer class.
11 //===----------------------------------------------------------------------===//
12 
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/ADT/SmallPtrSet.h"
17 #include "llvm/Support/Debug.h"
18 
19 #define DEBUG_TYPE "localizer"
20 
21 using namespace llvm;
22 
23 char Localizer::ID = 0;
25  "Move/duplicate certain instructions close to their use", false,
26  false)
27 
30 }
31 
32 void Localizer::init(MachineFunction &MF) { MRI = &MF.getRegInfo(); }
33 
34 bool Localizer::shouldLocalize(const MachineInstr &MI) {
35  switch (MI.getOpcode()) {
36  default:
37  return false;
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:
43  return true;
44  }
45 }
46 
47 bool Localizer::isLocalUse(MachineOperand &MOUse, const MachineInstr &Def,
48  MachineBasicBlock *&InsertMBB) {
49  MachineInstr &MIUse = *MOUse.getParent();
50  InsertMBB = MIUse.getParent();
51  if (MIUse.isPHI())
52  InsertMBB = MIUse.getOperand(MIUse.getOperandNo(&MOUse) + 1).getMBB();
53  return InsertMBB == Def.getParent();
54 }
55 
57  // If the ISel pipeline failed, do not bother running that pass.
58  if (MF.getProperties().hasProperty(
60  return false;
61 
62  DEBUG(dbgs() << "Localize instructions for: " << MF.getName() << '\n');
63 
64  init(MF);
65 
66  bool Changed = false;
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))
75  continue;
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();
84  MOIt != MOItEnd;) {
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))
92  continue;
93  DEBUG(dbgs() << "Fixing non-local use\n");
94  Changed = true;
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
103  // use in the block.
104  InsertMBB->insert(InsertMBB->SkipPHIsAndLabels(InsertMBB->begin()),
105  LocalizedMI);
106 
107  // Set a new register for the definition.
108  unsigned NewReg =
109  MRI->createGenericVirtualRegister(MRI->getType(Reg));
110  MRI->setRegClassOrRegBank(NewReg, MRI->getRegClassOrRegBank(Reg));
111  LocalizedMI->getOperand(0).setReg(NewReg);
112  NewVRegIt =
113  MBBWithLocalDef.insert(std::make_pair(MBBAndReg, NewReg)).first;
114  DEBUG(dbgs() << "Inserted: " << *LocalizedMI);
115  }
116  DEBUG(dbgs() << "Update use with: " << PrintReg(NewVRegIt->second)
117  << '\n');
118  // Update the user reg.
119  MOUse.setReg(NewVRegIt->second);
120  }
121  }
122  }
123  return Changed;
124 }
MachineInstr * getParent()
getParent - Return the instruction that this operand belongs to.
static PassRegistry * getPassRegistry()
getPassRegistry - Access the global registry object, which is automatically initialized at applicatio...
static char ID
Definition: Localizer.h:41
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
const MachineFunctionProperties & getProperties() const
Get the function properties.
This pass implements the localization mechanism described at the top of this file.
Definition: Localizer.h:39
unsigned getReg() const
getReg - Returns the register number.
unsigned getOperandNo(const_mop_iterator I) const
Returns the number of the operand iterator I points to.
Definition: MachineInstr.h:384
unsigned createGenericVirtualRegister(LLT Ty)
Create and return a new generic virtual register with low-level type Ty.
bool isPHI() const
Definition: MachineInstr.h:826
std::pair< iterator, bool > insert(const std::pair< KeyT, ValueT > &KV)
Definition: DenseMap.h:191
static use_iterator use_end()
MachineFunctionPass - This class adapts the FunctionPass interface to allow convenient creation of pa...
void initializeLocalizerPass(PassRegistry &)
Reg
All possible values of the reg field in the ModR/M byte.
unsigned getOpcode() const
Returns the opcode of this MachineInstr.
Definition: MachineInstr.h:290
bool runOnMachineFunction(MachineFunction &MF) override
runOnMachineFunction - This method must be overloaded to perform the desired machine code transformat...
Definition: Localizer.cpp:56
const MCInstrDesc & getDesc() const
Returns the target instruction descriptor of this MachineInstr.
Definition: MachineInstr.h:287
const RegClassOrRegBank & getRegClassOrRegBank(unsigned Reg) const
Return the register bank or register class of Reg.
instr_iterator insert(instr_iterator I, MachineInstr *M)
Insert MI into the instruction list before I, possibly inside a bundle.
Printable PrintReg(unsigned Reg, const TargetRegisterInfo *TRI=nullptr, unsigned SubRegIdx=0)
Prints virtual and physical registers with or without a TRI instance.
StringRef getName() const
getName - Return the name of the corresponding LLVM function.
INITIALIZE_PASS(Localizer, DEBUG_TYPE, "Move/duplicate certain instructions close to their use", false, false) Localizer
Definition: Localizer.cpp:24
iterator SkipPHIsAndLabels(iterator I)
Return the first instruction in MBB after I that is not a PHI or a label.
std::pair< iterator, bool > insert(PtrType Ptr)
Inserts Ptr if and only if there is no element in the container equal to Ptr.
Definition: SmallPtrSet.h:371
size_type count(ConstPtrType Ptr) const
count - Return 1 if the specified pointer is in the set, 0 otherwise.
Definition: SmallPtrSet.h:382
#define DEBUG_TYPE
Definition: Localizer.cpp:19
SmallPtrSet - This class implements a set which is optimized for holding SmallSize or less elements...
Definition: SmallPtrSet.h:418
MachineOperand class - Representation of each machine instruction operand.
unsigned getNumDefs() const
Return the number of MachineOperands that are register definitions.
Definition: MCInstrDesc.h:225
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
const MachineBasicBlock * getParent() const
Definition: MachineInstr.h:139
Representation of each machine instruction.
Definition: MachineInstr.h:59
MachineRegisterInfo & getRegInfo()
getRegInfo - Return information about the registers currently in use.
use_iterator use_begin(unsigned RegNo) const
void setReg(unsigned Reg)
Change the register this operand corresponds to.
LLT getType(unsigned VReg) const
Get the low-level type of VReg or LLT{} if VReg is not a generic (target independent) virtual registe...
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
bool hasProperty(Property P) const
#define DEBUG(X)
Definition: Debug.h:118
IRTranslator LLVM IR MI
void setRegClassOrRegBank(unsigned Reg, const RegClassOrRegBank &RCOrRB)
const MachineOperand & getOperand(unsigned i) const
Definition: MachineInstr.h:295