-bool
-Thumb2ITBlockPass::MoveCPSRUseUp(MachineBasicBlock &MBB,
- MachineBasicBlock::iterator MBBI,
- MachineBasicBlock::iterator E,
- unsigned PredReg,
- ARMCC::CondCodes CC, ARMCC::CondCodes OCC,
- bool &Done) {
- SmallSet<unsigned, 4> Defs, Uses;
- MachineBasicBlock::iterator I = MBBI;
- // Look for next CPSR use by scanning up to 4 instructions.
- for (unsigned i = 0; i < 4; ++i) {
- MachineInstr *MI = &*I;
- unsigned MPredReg = 0;
- ARMCC::CondCodes MCC = llvm::getITInstrPredicate(MI, MPredReg);
- if (MCC != ARMCC::AL) {
- if (MPredReg != PredReg || (MCC != CC && MCC != OCC))
- return false;
-
- // Check if the instruction is using any register that's defined
- // below the previous predicated instruction. Also return false if
- // it defines any register which is used in between.
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg())
- continue;
- unsigned Reg = MO.getReg();
- if (!Reg)
- continue;
- if (MO.isDef()) {
- if (Reg == PredReg || Uses.count(Reg))
- return false;
- } else {
- if (Defs.count(Reg))
- return false;
- }
- }
-
- Done = (I == E);
- MBB.remove(MI);
- MBB.insert(MBBI, MI);
- ++NumMovedInsts;
- return true;
- }
-
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- const MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg())
- continue;
- unsigned Reg = MO.getReg();
- if (!Reg)
- continue;
- if (MO.isDef()) {
- if (Reg == PredReg)
- return false;
- Defs.insert(Reg);
- } else
- Uses.insert(Reg);
- }
-
- if (I == E)
- break;
- ++I;
- }
- return false;
-}
-
-static bool isCPSRLiveout(MachineBasicBlock &MBB) {
- for (MachineBasicBlock::succ_iterator I = MBB.succ_begin(),
- E = MBB.succ_end(); I != E; ++I) {
- if ((*I)->isLiveIn(ARM::CPSR))
- return true;
- }
- return false;
-}
-
-void Thumb2ITBlockPass::FindITBlockRanges(MachineBasicBlock &MBB,
- SmallVector<MachineInstr*,4> &FirstUses,
- SmallVector<MachineInstr*,4> &LastUses) {
- bool SeenUse = false;
- MachineOperand *LastUse = 0;
- MachineBasicBlock::iterator MBBI = MBB.begin(), E = MBB.end();
- while (MBBI != E) {
- MachineInstr *MI = &*MBBI;
- ++MBBI;
-
- MachineOperand *Def = 0;
- MachineOperand *Use = 0;
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg() || MO.getReg() != ARM::CPSR)
- continue;
- if (MO.isDef()) {
- assert(Def == 0 && "Multiple defs of CPSR?");
- Def = &MO;
- } else {
- assert(Use == 0 && "Multiple uses of CPSR?");
- Use = &MO;
- }
- }
-
- if (Use) {
- LastUse = Use;
- if (!SeenUse) {
- FirstUses.push_back(MI);
- SeenUse = true;
- }
- }
- if (Def) {
- if (LastUse) {
- LastUses.push_back(LastUse->getParent());
- LastUse = 0;
- }
- SeenUse = false;
- }
- }
-
- if (LastUse) {
- // Is the last use a kill?
- if (isCPSRLiveout(MBB))
- LastUses.push_back(0);
- else
- LastUses.push_back(LastUse->getParent());
- }
-}
-
-bool Thumb2ITBlockPass::InsertITBlock(MachineInstr *First, MachineInstr *Last) {
- if (First == Last)
- return false;
-
- bool Modified = false;
- MachineBasicBlock *MBB = First->getParent();
- MachineBasicBlock::iterator MBBI = First;
- MachineBasicBlock::iterator E = Last;
-
- if (First->getDesc().isBranch() || First->getDesc().isReturn())
- return false;
-
- unsigned PredReg = 0;
- ARMCC::CondCodes CC = llvm::getITInstrPredicate(First, PredReg);
- if (CC == ARMCC::AL)
- return Modified;
-
- // Move uses of the CPSR together if possible.
- ARMCC::CondCodes OCC = ARMCC::getOppositeCondition(CC);
-
- do {
- ++MBBI;
- if (MBBI->getDesc().isBranch() || MBBI->getDesc().isReturn())
- return Modified;
- MachineInstr *NMI = &*MBBI;
- unsigned NPredReg = 0;
- ARMCC::CondCodes NCC = llvm::getITInstrPredicate(NMI, NPredReg);
- if (NCC != CC && NCC != OCC) {
- if (NCC != ARMCC::AL)
- return Modified;
- assert(MBBI != E);
- bool Done = false;
- if (!MoveCPSRUseUp(*MBB, MBBI, E, PredReg, CC, OCC, Done))
- return Modified;
- Modified = true;
- if (Done)
- MBBI = E;
- }
- } while (MBBI != E);
- return true;
-}
-
-bool Thumb2ITBlockPass::InsertITBlocks(MachineBasicBlock &MBB) {
- SmallVector<MachineInstr*, 4> FirstUses;
- SmallVector<MachineInstr*, 4> LastUses;
- FindITBlockRanges(MBB, FirstUses, LastUses);
- assert(FirstUses.size() == LastUses.size() && "Incorrect range information!");
-
- bool Modified = false;
- for (unsigned i = 0, e = FirstUses.size(); i != e; ++i) {
- if (LastUses[i] == 0)
- // Must be the last pair where CPSR is live out of the block.
- return Modified;
- Modified |= InsertITBlock(FirstUses[i], LastUses[i]);
- }
- return Modified;
-}
-