1 //===--- LivePhysRegs.cpp - Live Physical Register Set --------------------===//
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 LivePhysRegs utility for tracking liveness of
11 // physical registers across machine instructions in forward or backward order.
12 // A more detailed description can be found in the corresponding header file.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/CodeGen/LivePhysRegs.h"
17 #include "llvm/CodeGen/MachineFrameInfo.h"
18 #include "llvm/CodeGen/MachineFunction.h"
19 #include "llvm/CodeGen/MachineInstrBundle.h"
20 #include "llvm/CodeGen/MachineRegisterInfo.h"
21 #include "llvm/Support/Debug.h"
22 #include "llvm/Support/raw_ostream.h"
26 /// \brief Remove all registers from the set that get clobbered by the register
28 /// The clobbers set will be the list of live registers clobbered
30 void LivePhysRegs::removeRegsInMask(const MachineOperand &MO,
31 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers) {
32 SparseSet<unsigned>::iterator LRI = LiveRegs.begin();
33 while (LRI != LiveRegs.end()) {
34 if (MO.clobbersPhysReg(*LRI)) {
36 Clobbers->push_back(std::make_pair(*LRI, &MO));
37 LRI = LiveRegs.erase(LRI);
43 /// Simulates liveness when stepping backwards over an instruction(bundle):
44 /// Remove Defs, add uses. This is the recommended way of calculating liveness.
45 void LivePhysRegs::stepBackward(const MachineInstr &MI) {
46 // Remove defined registers and regmask kills from the set.
47 for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
51 unsigned Reg = O->getReg();
55 } else if (O->isRegMask())
56 removeRegsInMask(*O, nullptr);
59 // Add uses to the set.
60 for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
61 if (!O->isReg() || !O->readsReg())
63 unsigned Reg = O->getReg();
70 /// Simulates liveness when stepping forward over an instruction(bundle): Remove
71 /// killed-uses, add defs. This is the not recommended way, because it depends
72 /// on accurate kill flags. If possible use stepBackward() instead of this
74 void LivePhysRegs::stepForward(const MachineInstr &MI,
75 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers) {
76 // Remove killed registers from the set.
77 for (ConstMIBundleOperands O(MI); O.isValid(); ++O) {
79 unsigned Reg = O->getReg();
83 // Note, dead defs are still recorded. The caller should decide how to
85 Clobbers.push_back(std::make_pair(Reg, &*O));
92 } else if (O->isRegMask())
93 removeRegsInMask(*O, &Clobbers);
96 // Add defs to the set.
97 for (auto Reg : Clobbers) {
98 // Skip dead defs. They shouldn't be added to the set.
99 if (Reg.second->isReg() && Reg.second->isDead())
105 /// Prin the currently live registers to OS.
106 void LivePhysRegs::print(raw_ostream &OS) const {
107 OS << "Live Registers:";
109 OS << " (uninitialized)\n";
118 for (const_iterator I = begin(), E = end(); I != E; ++I)
119 OS << " " << PrintReg(*I, TRI);
123 /// Dumps the currently live registers to the debug output.
124 LLVM_DUMP_METHOD void LivePhysRegs::dump() const {
125 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
126 dbgs() << " " << *this;
130 bool LivePhysRegs::available(const MachineRegisterInfo &MRI,
131 unsigned Reg) const {
132 if (LiveRegs.count(Reg))
134 if (MRI.isReserved(Reg))
136 for (MCRegAliasIterator R(Reg, TRI, false); R.isValid(); ++R) {
137 if (LiveRegs.count(*R))
143 /// Add live-in registers of basic block \p MBB to \p LiveRegs.
144 static void addLiveIns(LivePhysRegs &LiveRegs, const MachineBasicBlock &MBB) {
145 for (const auto &LI : MBB.liveins())
146 LiveRegs.addReg(LI.PhysReg);
149 /// Add pristine registers to the given \p LiveRegs. This function removes
150 /// actually saved callee save registers when \p InPrologueEpilogue is false.
151 static void addPristines(LivePhysRegs &LiveRegs, const MachineFunction &MF,
152 const MachineFrameInfo &MFI,
153 const TargetRegisterInfo &TRI) {
154 for (const MCPhysReg *CSR = TRI.getCalleeSavedRegs(&MF); CSR && *CSR; ++CSR)
155 LiveRegs.addReg(*CSR);
156 for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo())
157 LiveRegs.removeReg(Info.getReg());
160 void LivePhysRegs::addLiveOutsNoPristines(const MachineBasicBlock &MBB) {
161 // To get the live-outs we simply merge the live-ins of all successors.
162 for (const MachineBasicBlock *Succ : MBB.successors())
163 ::addLiveIns(*this, *Succ);
166 void LivePhysRegs::addLiveOuts(const MachineBasicBlock &MBB) {
167 const MachineFunction &MF = *MBB.getParent();
168 const MachineFrameInfo &MFI = *MF.getFrameInfo();
169 if (MFI.isCalleeSavedInfoValid()) {
170 if (MBB.isReturnBlock()) {
171 // The return block has no successors whose live-ins we could merge
172 // below. So instead we add the callee saved registers manually.
173 for (const MCPhysReg *I = TRI->getCalleeSavedRegs(&MF); *I; ++I)
176 addPristines(*this, MF, MFI, *TRI);
180 addLiveOutsNoPristines(MBB);
183 void LivePhysRegs::addLiveIns(const MachineBasicBlock &MBB) {
184 const MachineFunction &MF = *MBB.getParent();
185 const MachineFrameInfo &MFI = *MF.getFrameInfo();
186 if (MFI.isCalleeSavedInfoValid())
187 addPristines(*this, MF, MFI, *TRI);
188 ::addLiveIns(*this, MBB);