static bool hasRegisterDependency(MachineInstr *MI,
SmallVectorImpl<unsigned> &UsedOpsInCopy,
SmallVectorImpl<unsigned> &DefedRegsInCopy,
LiveRegUnits &ModifiedRegUnits,
LiveRegUnits &UsedRegUnits) {
bool HasRegDependency = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg())
continue;
unsigned Reg = MO.getReg();
if (!Reg)
continue;
if (MO.isDef()) {
if (!ModifiedRegUnits.available(Reg) || !UsedRegUnits.available(Reg)) {
HasRegDependency = true;
break;
}
DefedRegsInCopy.push_back(Reg);
// FIXME: instead of isUse(), readsReg() would be a better fix here,
// For example, we can ignore modifications in reg with undef. However,
// it's not perfectly clear if skipping the internal read is safe in all
// other targets.
} else if (MO.isUse()) {
if (!ModifiedRegUnits.available(Reg)) {
HasRegDependency = true;
break;
}
UsedOpsInCopy.push_back(i);
}
}
return HasRegDependency;
}
static void clearKillFlags(MachineInstr *MI, MachineBasicBlock &CurBB,
SmallVectorImpl<unsigned> &UsedOpsInCopy,
LiveRegUnits &UsedRegUnits,
const TargetRegisterInfo *TRI) {
for (auto U : UsedOpsInCopy) {
MachineOperand &MO = MI->getOperand(U);
unsigned SrcReg = MO.getReg();
if (!UsedRegUnits.available(SrcReg)) {
MachineBasicBlock::iterator NI = std::next(MI->getIterator());
for (MachineInstr &UI : make_range(NI, CurBB.end())) {
if (UI.killsRegister(SrcReg, TRI)) {
UI.clearRegisterKills(SrcReg, TRI);
MO.setIsKill(true);
break;
}
}
}
}
}
/// Add live-in registers of basic block \p MBB to \p LiveUnits.
static void addBlockLiveIns(LiveRegUnits &LiveUnits,
const MachineBasicBlock &MBB) {
for (const auto &LI : MBB.liveins())
LiveUnits.addRegMasked(LI.PhysReg, LI.LaneMask);
}
/// Adds all callee saved registers to \p LiveUnits.
static void addCalleeSavedRegs(LiveRegUnits &LiveUnits,
const MachineFunction &MF) {
const MachineRegisterInfo &MRI = MF.getRegInfo();
for (const MCPhysReg *CSR = MRI.getCalleeSavedRegs(); CSR && *CSR; ++CSR)
LiveUnits.addReg(*CSR);
}
/// Given the bitvector \p Available of free register units at position
/// \p From. Search backwards to find a register that is part of \p
/// Candidates and not used/clobbered until the point \p To. If there is
/// multiple candidates continue searching and pick the one that is not used/
/// clobbered for the longest time.
/// Returns the register and the earliest position we know it to be free or
/// the position MBB.end() if no register is available.
static std::pair<MCPhysReg, MachineBasicBlock::iterator>
findSurvivorBackwards(const MachineRegisterInfo &MRI,
MachineBasicBlock::iterator From, MachineBasicBlock::iterator To,
const LiveRegUnits &LiveOut, ArrayRef<MCPhysReg> AllocationOrder) {
bool FoundTo = false;
MCPhysReg Survivor = 0;
MachineBasicBlock::iterator Pos;
MachineBasicBlock &MBB = *From->getParent();
unsigned InstrLimit = 25;
unsigned InstrCountDown = InstrLimit;
const TargetRegisterInfo &TRI = *MRI.getTargetRegisterInfo();
LiveRegUnits Used(TRI);
for (MachineBasicBlock::iterator I = From;; --I) {
const MachineInstr &MI = *I;
Used.accumulateBackward(MI);
if (I == To) {
// See if one of the registers in RC wasn't used so far.
for (MCPhysReg Reg : AllocationOrder) {
if (!MRI.isReserved(Reg) && Used.available(Reg) &&
LiveOut.available(Reg))
return std::make_pair(Reg, MBB.end());
}
// Otherwise we will continue up to InstrLimit instructions to find
// the register which is not defined/used for the longest time.
FoundTo = true;
Pos = To;
}
if (FoundTo) {
if (Survivor == 0 || !Used.available(Survivor)) {
MCPhysReg AvilableReg = 0;
for (MCPhysReg Reg : AllocationOrder) {
if (!MRI.isReserved(Reg) && Used.available(Reg)) {
AvilableReg = Reg;
break;
}
}
if (AvilableReg == 0)
break;
Survivor = AvilableReg;
}
if (--InstrCountDown == 0)
break;
// Keep searching when we find a vreg since the spilled register will
// be usefull for this other vreg as well later.
bool FoundVReg = false;
for (const MachineOperand &MO : MI.operands()) {
if (MO.isReg() && TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
FoundVReg = true;
break;
}
}
if (FoundVReg) {
InstrCountDown = InstrLimit;
Pos = I;
}
if (I == MBB.begin())
break;
}
}
return std::make_pair(Survivor, Pos);
}
