bool Filler::findDelayInstr(MachineBasicBlock &MBB,
MachineBasicBlock::instr_iterator Slot,
MachineBasicBlock::instr_iterator &Filler) {
SmallSet<unsigned, 32> RegDefs;
SmallSet<unsigned, 32> RegUses;
insertDefsUses(Slot, RegDefs, RegUses);
bool SawLoad = false;
bool SawStore = false;
for (MachineBasicBlock::reverse_instr_iterator I = ++Slot.getReverse();
I != MBB.instr_rend(); ++I) {
// skip debug value
if (I->isDebugValue())
continue;
// Convert to forward iterator.
MachineBasicBlock::instr_iterator FI = I.getReverse();
if (I->hasUnmodeledSideEffects() || I->isInlineAsm() || I->isLabel() ||
FI == LastFiller || I->isPseudo())
break;
if (delayHasHazard(FI, SawLoad, SawStore, RegDefs, RegUses)) {
insertDefsUses(FI, RegDefs, RegUses);
continue;
}
Filler = FI;
return true;
}
return false;
}
// runOnMachineBasicBlock - Fill in delay slots for the given basic block.
// There is one or two delay slot per delayed instruction.
bool Filler::runOnMachineBasicBlock(MachineBasicBlock &MBB) {
bool Changed = false;
LastFiller = MBB.instr_end();
for (MachineBasicBlock::instr_iterator I = MBB.instr_begin();
I != MBB.instr_end(); ++I) {
if (I->getDesc().hasDelaySlot()) {
MachineBasicBlock::instr_iterator InstrWithSlot = I;
MachineBasicBlock::instr_iterator J = I;
// Treat RET specially as it is only instruction with 2 delay slots
// generated while all others generated have 1 delay slot.
if (I->getOpcode() == Lanai::RET) {
// RET is generated as part of epilogue generation and hence we know
// what the two instructions preceding it are and that it is safe to
// insert RET above them.
MachineBasicBlock::reverse_instr_iterator RI = ++I.getReverse();
assert(RI->getOpcode() == Lanai::LDW_RI && RI->getOperand(0).isReg() &&
RI->getOperand(0).getReg() == Lanai::FP &&
RI->getOperand(1).isReg() &&
RI->getOperand(1).getReg() == Lanai::FP &&
RI->getOperand(2).isImm() && RI->getOperand(2).getImm() == -8);
++RI;
assert(RI->getOpcode() == Lanai::ADD_I_LO &&
RI->getOperand(0).isReg() &&
RI->getOperand(0).getReg() == Lanai::SP &&
RI->getOperand(1).isReg() &&
RI->getOperand(1).getReg() == Lanai::FP);
MachineBasicBlock::instr_iterator FI = RI.getReverse();
MBB.splice(std::next(I), &MBB, FI, I);
FilledSlots += 2;
} else {
if (!NopDelaySlotFiller && findDelayInstr(MBB, I, J)) {
MBB.splice(std::next(I), &MBB, J);
} else {
BuildMI(MBB, std::next(I), DebugLoc(), TII->get(Lanai::NOP));
}
++FilledSlots;
}
Changed = true;
// Record the filler instruction that filled the delay slot.
// The instruction after it will be visited in the next iteration.
LastFiller = ++I;
// Bundle the delay slot filler to InstrWithSlot so that the machine
// verifier doesn't expect this instruction to be a terminator.
MIBundleBuilder(MBB, InstrWithSlot, std::next(LastFiller));
}
}
return Changed;
}
