1 //===-- LiveInterval.cpp - Live Interval Representation -------------------===// 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 // 10 // This file implements the LiveRegUnits utility for tracking liveness of 11 // physical register units across machine instructions in forward or backward 12 // order. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/CodeGen/LiveRegUnits.h" 17 #include "llvm/CodeGen/MachineInstrBundle.h" 18 using namespace llvm; 19 20 /// We assume the high bits of a physical super register are not preserved 21 /// unless the instruction has an implicit-use operand reading the 22 /// super-register or a register unit for the upper bits is available. 23 void LiveRegUnits::removeRegsInMask(const MachineOperand &Op, 24 const MCRegisterInfo &MCRI) { 25 const uint32_t *Mask = Op.getRegMask(); 26 unsigned Bit = 0; 27 for (unsigned R = 0; R < MCRI.getNumRegs(); ++R) { 28 if ((*Mask & (1u << Bit)) == 0) 29 removeReg(R, MCRI); 30 ++Bit; 31 if (Bit >= 32) { 32 Bit = 0; 33 ++Mask; 34 } 35 } 36 } 37 38 void LiveRegUnits::stepBackward(const MachineInstr &MI, 39 const MCRegisterInfo &MCRI) { 40 // Remove defined registers and regmask kills from the set. 41 for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) { 42 if (O->isReg()) { 43 if (!O->isDef()) 44 continue; 45 unsigned Reg = O->getReg(); 46 if (Reg == 0) 47 continue; 48 removeReg(Reg, MCRI); 49 } else if (O->isRegMask()) { 50 removeRegsInMask(*O, MCRI); 51 } 52 } 53 // Add uses to the set. 54 for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) { 55 if (!O->isReg() || !O->readsReg() || O->isUndef()) 56 continue; 57 unsigned Reg = O->getReg(); 58 if (Reg == 0) 59 continue; 60 addReg(Reg, MCRI); 61 } 62 } 63 64 /// Uses with kill flag get removed from the set, defs added. If possible 65 /// use StepBackward() instead of this function because some kill flags may 66 /// be missing. 67 void LiveRegUnits::stepForward(const MachineInstr &MI, 68 const MCRegisterInfo &MCRI) { 69 SmallVector<unsigned, 4> Defs; 70 // Remove killed registers from the set. 71 for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) { 72 if (O->isReg()) { 73 unsigned Reg = O->getReg(); 74 if (Reg == 0) 75 continue; 76 if (O->isDef()) { 77 if (!O->isDead()) 78 Defs.push_back(Reg); 79 } else { 80 if (!O->isKill()) 81 continue; 82 assert(O->isUse()); 83 removeReg(Reg, MCRI); 84 } 85 } else if (O->isRegMask()) { 86 removeRegsInMask(*O, MCRI); 87 } 88 } 89 // Add defs to the set. 90 for (unsigned i = 0, e = Defs.size(); i != e; ++i) { 91 addReg(Defs[i], MCRI); 92 } 93 } 94 95 /// Adds all registers in the live-in list of block @p BB. 96 void LiveRegUnits::addLiveIns(const MachineBasicBlock &BB, 97 const MCRegisterInfo &MCRI) { 98 for (MachineBasicBlock::livein_iterator L = BB.livein_begin(), 99 LE = BB.livein_end(); L != LE; ++L) { 100 addReg(*L, MCRI); 101 } 102 } 103