/// converToCTRLoop - check if the loop is a candidate for
/// converting to a CTR loop. If so, then perform the
/// transformation.
///
/// This function works on innermost loops first. A loop can
/// be converted if it is a counting loop; either a register
/// value or an immediate.
///
/// The code makes several assumptions about the representation
/// of the loop in llvm.
bool PPCCTRLoops::convertToCTRLoop(MachineLoop *L) {
bool Changed = false;
// Process nested loops first.
for (MachineLoop::iterator I = L->begin(), E = L->end(); I != E; ++I) {
Changed |= convertToCTRLoop(*I);
}
// If a nested loop has been converted, then we can't convert this loop.
if (Changed) {
return Changed;
}
SmallVector<MachineInstr *, 2> OldInsts;
// Are we able to determine the trip count for the loop?
CountValue *TripCount = getTripCount(L, OldInsts);
if (TripCount == 0) {
DEBUG(dbgs() << "failed to get trip count!\n");
return false;
}
if (TripCount->isImm()) {
DEBUG(dbgs() << "constant trip count: " << TripCount->getImm() << "\n");
// FIXME: We currently can't form 64-bit constants
// (including 32-bit unsigned constants)
if (!isInt<32>(TripCount->getImm()))
return false;
}
// Does the loop contain any invalid instructions?
if (containsInvalidInstruction(L)) {
return false;
}
MachineBasicBlock *Preheader = L->getLoopPreheader();
// No preheader means there's not place for the loop instr.
if (Preheader == 0) {
return false;
}
MachineBasicBlock::iterator InsertPos = Preheader->getFirstTerminator();
DebugLoc dl;
if (InsertPos != Preheader->end())
dl = InsertPos->getDebugLoc();
MachineBasicBlock *LastMBB = L->getExitingBlock();
// Don't generate CTR loop if the loop has more than one exit.
if (LastMBB == 0) {
return false;
}
MachineBasicBlock::iterator LastI = LastMBB->getFirstTerminator();
// Determine the loop start.
MachineBasicBlock *LoopStart = L->getTopBlock();
if (L->getLoopLatch() != LastMBB) {
// When the exit and latch are not the same, use the latch block as the
// start.
// The loop start address is used only after the 1st iteration, and the loop
// latch may contains instrs. that need to be executed after the 1st iter.
LoopStart = L->getLoopLatch();
// Make sure the latch is a successor of the exit, otherwise it won't work.
if (!LastMBB->isSuccessor(LoopStart)) {
return false;
}
}
// Convert the loop to a CTR loop
DEBUG(dbgs() << "Change to CTR loop at "; L->dump());
MachineFunction *MF = LastMBB->getParent();
const PPCSubtarget &Subtarget = MF->getTarget().getSubtarget<PPCSubtarget>();
bool isPPC64 = Subtarget.isPPC64();
const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
const TargetRegisterClass *RC = isPPC64 ? G8RC : GPRC;
unsigned CountReg;
if (TripCount->isReg()) {
// Create a copy of the loop count register.
const TargetRegisterClass *SrcRC =
MF->getRegInfo().getRegClass(TripCount->getReg());
CountReg = MF->getRegInfo().createVirtualRegister(RC);
unsigned CopyOp = (isPPC64 && GPRC->hasSubClassEq(SrcRC)) ?
(unsigned) PPC::EXTSW_32_64 :
(unsigned) TargetOpcode::COPY;
BuildMI(*Preheader, InsertPos, dl,
TII->get(CopyOp), CountReg).addReg(TripCount->getReg());
if (TripCount->isNeg()) {
unsigned CountReg1 = CountReg;
CountReg = MF->getRegInfo().createVirtualRegister(RC);
BuildMI(*Preheader, InsertPos, dl,
TII->get(isPPC64 ? PPC::NEG8 : PPC::NEG),
CountReg).addReg(CountReg1);
}
} else {
assert(TripCount->isImm() && "Expecting immedate vaule for trip count");
// Put the trip count in a register for transfer into the count register.
int64_t CountImm = TripCount->getImm();
if (TripCount->isNeg())
CountImm = -CountImm;
CountReg = MF->getRegInfo().createVirtualRegister(RC);
if (abs64(CountImm) > 0x7FFF) {
BuildMI(*Preheader, InsertPos, dl,
TII->get(isPPC64 ? PPC::LIS8 : PPC::LIS),
CountReg).addImm((CountImm >> 16) & 0xFFFF);
unsigned CountReg1 = CountReg;
CountReg = MF->getRegInfo().createVirtualRegister(RC);
BuildMI(*Preheader, InsertPos, dl,
TII->get(isPPC64 ? PPC::ORI8 : PPC::ORI),
CountReg).addReg(CountReg1).addImm(CountImm & 0xFFFF);
} else {
/// converToHardwareLoop - check if the loop is a candidate for
/// converting to a hardware loop. If so, then perform the
/// transformation.
///
/// This function works on innermost loops first. A loop can
/// be converted if it is a counting loop; either a register
/// value or an immediate.
///
/// The code makes several assumptions about the representation
/// of the loop in llvm.
bool HexagonHardwareLoops::convertToHardwareLoop(MachineLoop *L) {
bool Changed = false;
// Process nested loops first.
for (MachineLoop::iterator I = L->begin(), E = L->end(); I != E; ++I) {
Changed |= convertToHardwareLoop(*I);
}
// If a nested loop has been converted, then we can't convert this loop.
if (Changed) {
return Changed;
}
// Are we able to determine the trip count for the loop?
CountValue *TripCount = getTripCount(L);
if (TripCount == 0) {
return false;
}
// Does the loop contain any invalid instructions?
if (containsInvalidInstruction(L)) {
return false;
}
MachineBasicBlock *Preheader = L->getLoopPreheader();
// No preheader means there's not place for the loop instr.
if (Preheader == 0) {
return false;
}
MachineBasicBlock::iterator InsertPos = Preheader->getFirstTerminator();
MachineBasicBlock *LastMBB = L->getExitingBlock();
// Don't generate hw loop if the loop has more than one exit.
if (LastMBB == 0) {
return false;
}
MachineBasicBlock::iterator LastI = LastMBB->getFirstTerminator();
// Determine the loop start.
MachineBasicBlock *LoopStart = L->getTopBlock();
if (L->getLoopLatch() != LastMBB) {
// When the exit and latch are not the same, use the latch block as the
// start.
// The loop start address is used only after the 1st iteration, and the loop
// latch may contains instrs. that need to be executed after the 1st iter.
LoopStart = L->getLoopLatch();
// Make sure the latch is a successor of the exit, otherwise it won't work.
if (!LastMBB->isSuccessor(LoopStart)) {
return false;
}
}
// Convert the loop to a hardware loop
DEBUG(dbgs() << "Change to hardware loop at "; L->dump());
if (TripCount->isReg()) {
// Create a copy of the loop count register.
MachineFunction *MF = LastMBB->getParent();
const TargetRegisterClass *RC =
MF->getRegInfo().getRegClass(TripCount->getReg());
unsigned CountReg = MF->getRegInfo().createVirtualRegister(RC);
BuildMI(*Preheader, InsertPos, InsertPos->getDebugLoc(),
TII->get(TargetOpcode::COPY), CountReg).addReg(TripCount->getReg());
if (TripCount->isNeg()) {
unsigned CountReg1 = CountReg;
CountReg = MF->getRegInfo().createVirtualRegister(RC);
BuildMI(*Preheader, InsertPos, InsertPos->getDebugLoc(),
TII->get(Hexagon::NEG), CountReg).addReg(CountReg1);
}
// Add the Loop instruction to the begining of the loop.
BuildMI(*Preheader, InsertPos, InsertPos->getDebugLoc(),
TII->get(Hexagon::LOOP0_r)).addMBB(LoopStart).addReg(CountReg);
} else {
assert(TripCount->isImm() && "Expecting immedate vaule for trip count");
// Add the Loop immediate instruction to the beginning of the loop.
int64_t CountImm = TripCount->getImm();
BuildMI(*Preheader, InsertPos, InsertPos->getDebugLoc(),
TII->get(Hexagon::LOOP0_i)).addMBB(LoopStart).addImm(CountImm);
}
// Make sure the loop start always has a reference in the CFG. We need to
// create a BlockAddress operand to get this mechanism to work both the
// MachineBasicBlock and BasicBlock objects need the flag set.
LoopStart->setHasAddressTaken();
// This line is needed to set the hasAddressTaken flag on the BasicBlock
// object
BlockAddress::get(const_cast<BasicBlock *>(LoopStart->getBasicBlock()));
// Replace the loop branch with an endloop instruction.
DebugLoc dl = LastI->getDebugLoc();
BuildMI(*LastMBB, LastI, dl, TII->get(Hexagon::ENDLOOP0)).addMBB(LoopStart);
// The loop ends with either:
// - a conditional branch followed by an unconditional branch, or
// - a conditional branch to the loop start.
if (LastI->getOpcode() == Hexagon::JMP_c ||
LastI->getOpcode() == Hexagon::JMP_cNot) {
// delete one and change/add an uncond. branch to out of the loop
MachineBasicBlock *BranchTarget = LastI->getOperand(1).getMBB();
LastI = LastMBB->erase(LastI);
if (!L->contains(BranchTarget)) {
if (LastI != LastMBB->end()) {
TII->RemoveBranch(*LastMBB);
}
SmallVector<MachineOperand, 0> Cond;
TII->InsertBranch(*LastMBB, BranchTarget, 0, Cond, dl);
}
} else {
// Conditional branch to loop start; just delete it.
LastMBB->erase(LastI);
}
delete TripCount;
++NumHWLoops;
return true;
}
