1 //===-- lib/Codegen/MachineRegisterInfo.cpp -------------------------------===//
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 // Implementation of the MachineRegisterInfo class.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/CodeGen/MachineRegisterInfo.h"
15 #include "llvm/CodeGen/MachineInstrBuilder.h"
16 #include "llvm/Target/TargetInstrInfo.h"
17 #include "llvm/Target/TargetMachine.h"
20 MachineRegisterInfo::MachineRegisterInfo(const TargetRegisterInfo &TRI)
21 : TRI(&TRI), IsSSA(true) {
22 VRegInfo.reserve(256);
23 RegAllocHints.reserve(256);
24 UsedPhysRegs.resize(TRI.getNumRegs());
26 // Create the physreg use/def lists.
27 PhysRegUseDefLists = new MachineOperand*[TRI.getNumRegs()];
28 memset(PhysRegUseDefLists, 0, sizeof(MachineOperand*)*TRI.getNumRegs());
31 MachineRegisterInfo::~MachineRegisterInfo() {
33 for (unsigned i = 0, e = getNumVirtRegs(); i != e; ++i)
34 assert(VRegInfo[TargetRegisterInfo::index2VirtReg(i)].second == 0 &&
35 "Vreg use list non-empty still?");
36 for (unsigned i = 0, e = UsedPhysRegs.size(); i != e; ++i)
37 assert(!PhysRegUseDefLists[i] &&
38 "PhysRegUseDefLists has entries after all instructions are deleted");
40 delete [] PhysRegUseDefLists;
43 /// setRegClass - Set the register class of the specified virtual register.
46 MachineRegisterInfo::setRegClass(unsigned Reg, const TargetRegisterClass *RC) {
47 VRegInfo[Reg].first = RC;
50 const TargetRegisterClass *
51 MachineRegisterInfo::constrainRegClass(unsigned Reg,
52 const TargetRegisterClass *RC,
53 unsigned MinNumRegs) {
54 const TargetRegisterClass *OldRC = getRegClass(Reg);
57 const TargetRegisterClass *NewRC = TRI->getCommonSubClass(OldRC, RC);
58 if (!NewRC || NewRC == OldRC)
60 if (NewRC->getNumRegs() < MinNumRegs)
62 setRegClass(Reg, NewRC);
67 MachineRegisterInfo::recomputeRegClass(unsigned Reg, const TargetMachine &TM) {
68 const TargetInstrInfo *TII = TM.getInstrInfo();
69 const TargetRegisterClass *OldRC = getRegClass(Reg);
70 const TargetRegisterClass *NewRC = TRI->getLargestLegalSuperClass(OldRC);
72 // Stop early if there is no room to grow.
76 // Accumulate constraints from all uses.
77 for (reg_nodbg_iterator I = reg_nodbg_begin(Reg), E = reg_nodbg_end(); I != E;
79 // TRI doesn't have accurate enough information to model this yet.
80 if (I.getOperand().getSubReg())
82 // Inline asm instuctions don't remember their constraints.
85 const TargetRegisterClass *OpRC =
86 TII->getRegClass(I->getDesc(), I.getOperandNo(), TRI);
88 NewRC = TRI->getCommonSubClass(NewRC, OpRC);
89 if (!NewRC || NewRC == OldRC)
92 setRegClass(Reg, NewRC);
96 /// createVirtualRegister - Create and return a new virtual register in the
97 /// function with the specified register class.
100 MachineRegisterInfo::createVirtualRegister(const TargetRegisterClass *RegClass){
101 assert(RegClass && "Cannot create register without RegClass!");
102 assert(RegClass->isAllocatable() &&
103 "Virtual register RegClass must be allocatable.");
105 // New virtual register number.
106 unsigned Reg = TargetRegisterInfo::index2VirtReg(getNumVirtRegs());
108 // Add a reg, but keep track of whether the vector reallocated or not.
109 const unsigned FirstVirtReg = TargetRegisterInfo::index2VirtReg(0);
110 void *ArrayBase = getNumVirtRegs() == 0 ? 0 : &VRegInfo[FirstVirtReg];
112 VRegInfo[Reg].first = RegClass;
113 RegAllocHints.grow(Reg);
115 if (ArrayBase && &VRegInfo[FirstVirtReg] != ArrayBase)
116 // The vector reallocated, handle this now.
117 HandleVRegListReallocation();
121 /// HandleVRegListReallocation - We just added a virtual register to the
122 /// VRegInfo info list and it reallocated. Update the use/def lists info
124 void MachineRegisterInfo::HandleVRegListReallocation() {
125 // The back pointers for the vreg lists point into the previous vector.
126 // Update them to point to their correct slots.
127 for (unsigned i = 0, e = getNumVirtRegs(); i != e; ++i) {
128 unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
129 MachineOperand *List = VRegInfo[Reg].second;
131 // Update the back-pointer to be accurate once more.
132 List->Contents.Reg.Prev = &VRegInfo[Reg].second;
136 /// replaceRegWith - Replace all instances of FromReg with ToReg in the
137 /// machine function. This is like llvm-level X->replaceAllUsesWith(Y),
138 /// except that it also changes any definitions of the register as well.
139 void MachineRegisterInfo::replaceRegWith(unsigned FromReg, unsigned ToReg) {
140 assert(FromReg != ToReg && "Cannot replace a reg with itself");
142 // TODO: This could be more efficient by bulk changing the operands.
143 for (reg_iterator I = reg_begin(FromReg), E = reg_end(); I != E; ) {
144 MachineOperand &O = I.getOperand();
151 /// getVRegDef - Return the machine instr that defines the specified virtual
152 /// register or null if none is found. This assumes that the code is in SSA
153 /// form, so there should only be one definition.
154 MachineInstr *MachineRegisterInfo::getVRegDef(unsigned Reg) const {
155 // Since we are in SSA form, we can use the first definition.
157 return &*def_begin(Reg);
161 bool MachineRegisterInfo::hasOneUse(unsigned RegNo) const {
162 use_iterator UI = use_begin(RegNo);
165 return ++UI == use_end();
168 bool MachineRegisterInfo::hasOneNonDBGUse(unsigned RegNo) const {
169 use_nodbg_iterator UI = use_nodbg_begin(RegNo);
170 if (UI == use_nodbg_end())
172 return ++UI == use_nodbg_end();
175 /// clearKillFlags - Iterate over all the uses of the given register and
176 /// clear the kill flag from the MachineOperand. This function is used by
177 /// optimization passes which extend register lifetimes and need only
178 /// preserve conservative kill flag information.
179 void MachineRegisterInfo::clearKillFlags(unsigned Reg) const {
180 for (use_iterator UI = use_begin(Reg), UE = use_end(); UI != UE; ++UI)
181 UI.getOperand().setIsKill(false);
184 bool MachineRegisterInfo::isLiveIn(unsigned Reg) const {
185 for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
186 if (I->first == Reg || I->second == Reg)
191 bool MachineRegisterInfo::isLiveOut(unsigned Reg) const {
192 for (liveout_iterator I = liveout_begin(), E = liveout_end(); I != E; ++I)
198 /// getLiveInPhysReg - If VReg is a live-in virtual register, return the
199 /// corresponding live-in physical register.
200 unsigned MachineRegisterInfo::getLiveInPhysReg(unsigned VReg) const {
201 for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
202 if (I->second == VReg)
207 /// getLiveInVirtReg - If PReg is a live-in physical register, return the
208 /// corresponding live-in physical register.
209 unsigned MachineRegisterInfo::getLiveInVirtReg(unsigned PReg) const {
210 for (livein_iterator I = livein_begin(), E = livein_end(); I != E; ++I)
211 if (I->first == PReg)
216 /// EmitLiveInCopies - Emit copies to initialize livein virtual registers
217 /// into the given entry block.
219 MachineRegisterInfo::EmitLiveInCopies(MachineBasicBlock *EntryMBB,
220 const TargetRegisterInfo &TRI,
221 const TargetInstrInfo &TII) {
222 // Emit the copies into the top of the block.
223 for (unsigned i = 0, e = LiveIns.size(); i != e; ++i)
224 if (LiveIns[i].second) {
225 if (use_empty(LiveIns[i].second)) {
226 // The livein has no uses. Drop it.
228 // It would be preferable to have isel avoid creating live-in
229 // records for unused arguments in the first place, but it's
230 // complicated by the debug info code for arguments.
231 LiveIns.erase(LiveIns.begin() + i);
235 BuildMI(*EntryMBB, EntryMBB->begin(), DebugLoc(),
236 TII.get(TargetOpcode::COPY), LiveIns[i].second)
237 .addReg(LiveIns[i].first);
239 // Add the register to the entry block live-in set.
240 EntryMBB->addLiveIn(LiveIns[i].first);
243 // Add the register to the entry block live-in set.
244 EntryMBB->addLiveIn(LiveIns[i].first);
248 void MachineRegisterInfo::closePhysRegsUsed(const TargetRegisterInfo &TRI) {
249 for (int i = UsedPhysRegs.find_first(); i >= 0;
250 i = UsedPhysRegs.find_next(i))
251 for (const unsigned *SS = TRI.getSubRegisters(i);
252 unsigned SubReg = *SS; ++SS)
253 if (SubReg > unsigned(i))
254 UsedPhysRegs.set(SubReg);
258 void MachineRegisterInfo::dumpUses(unsigned Reg) const {
259 for (use_iterator I = use_begin(Reg), E = use_end(); I != E; ++I)
260 I.getOperand().getParent()->dump();