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/Support/Debug.h"
21 #include "llvm/Support/raw_ostream.h"
25 /// \brief Remove all registers from the set that get clobbered by the register
27 /// The clobbers set will be the list of live registers clobbered
29 void LivePhysRegs::removeRegsInMask(const MachineOperand &MO,
30 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers) {
31 SparseSet<unsigned>::iterator LRI = LiveRegs.begin();
32 while (LRI != LiveRegs.end()) {
33 if (MO.clobbersPhysReg(*LRI)) {
35 Clobbers->push_back(std::make_pair(*LRI, &MO));
36 LRI = LiveRegs.erase(LRI);
42 /// Simulates liveness when stepping backwards over an instruction(bundle):
43 /// Remove Defs, add uses. This is the recommended way of calculating liveness.
44 void LivePhysRegs::stepBackward(const MachineInstr &MI) {
45 // Remove defined registers and regmask kills from the set.
46 for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
50 unsigned Reg = O->getReg();
54 } else if (O->isRegMask())
55 removeRegsInMask(*O, nullptr);
58 // Add uses to the set.
59 for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
60 if (!O->isReg() || !O->readsReg() || O->isUndef())
62 unsigned Reg = O->getReg();
69 /// Simulates liveness when stepping forward over an instruction(bundle): Remove
70 /// killed-uses, add defs. This is the not recommended way, because it depends
71 /// on accurate kill flags. If possible use stepBackward() instead of this
73 void LivePhysRegs::stepForward(const MachineInstr &MI,
74 SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers) {
75 // Remove killed registers from the set.
76 for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
78 unsigned Reg = O->getReg();
82 // Note, dead defs are still recorded. The caller should decide how to
84 Clobbers.push_back(std::make_pair(Reg, &*O));
91 } else if (O->isRegMask())
92 removeRegsInMask(*O, &Clobbers);
95 // Add defs to the set.
96 for (auto Reg : Clobbers) {
97 // Skip dead defs. They shouldn't be added to the set.
98 if (Reg.second->isReg() && Reg.second->isDead())
104 /// Prin the currently live registers to OS.
105 void LivePhysRegs::print(raw_ostream &OS) const {
106 OS << "Live Registers:";
108 OS << " (uninitialized)\n";
117 for (const_iterator I = begin(), E = end(); I != E; ++I)
118 OS << " " << PrintReg(*I, TRI);
122 /// Dumps the currently live registers to the debug output.
123 void LivePhysRegs::dump() const {
124 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
125 dbgs() << " " << *this;
129 /// Add live-in registers of basic block \p MBB to \p LiveRegs.
130 static void addLiveIns(LivePhysRegs &LiveRegs, const MachineBasicBlock &MBB) {
131 for (const auto &LI : MBB.liveins())
132 LiveRegs.addReg(LI.PhysReg);
135 /// Add pristine registers to the given \p LiveRegs. This function removes
136 /// actually saved callee save registers when \p InPrologueEpilogue is false.
137 static void addPristines(LivePhysRegs &LiveRegs, const MachineFunction &MF,
138 const TargetRegisterInfo &TRI) {
139 const MachineFrameInfo &MFI = *MF.getFrameInfo();
140 if (!MFI.isCalleeSavedInfoValid())
143 for (const MCPhysReg *CSR = TRI.getCalleeSavedRegs(&MF); CSR && *CSR; ++CSR)
144 LiveRegs.addReg(*CSR);
145 for (const CalleeSavedInfo &Info : MFI.getCalleeSavedInfo())
146 LiveRegs.removeReg(Info.getReg());
149 void LivePhysRegs::addLiveOuts(const MachineBasicBlock *MBB,
150 bool AddPristinesAndCSRs) {
151 if (AddPristinesAndCSRs) {
152 const MachineFunction &MF = *MBB->getParent();
153 addPristines(*this, MF, *TRI);
154 if (!MBB->isReturnBlock()) {
155 // The return block has no successors whose live-ins we could merge
156 // below. So instead we add the callee saved registers manually.
157 for (const MCPhysReg *I = TRI->getCalleeSavedRegs(&MF); *I; ++I)
162 // To get the live-outs we simply merge the live-ins of all successors.
163 for (const MachineBasicBlock *Succ : MBB->successors())
164 ::addLiveIns(*this, *Succ);
167 void LivePhysRegs::addLiveIns(const MachineBasicBlock *MBB,
170 const MachineFunction &MF = *MBB->getParent();
171 addPristines(*this, MF, *TRI);
173 ::addLiveIns(*this, *MBB);