1 //===- Thumb2InstrInfo.cpp - Thumb-2 Instruction Information --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the Thumb-2 implementation of the TargetInstrInfo class.
12 //===----------------------------------------------------------------------===//
14 #include "Thumb2InstrInfo.h"
15 #include "ARMMachineFunctionInfo.h"
16 #include "MCTargetDesc/ARMAddressingModes.h"
17 #include "llvm/CodeGen/MachineBasicBlock.h"
18 #include "llvm/CodeGen/MachineFrameInfo.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/CodeGen/MachineInstr.h"
21 #include "llvm/CodeGen/MachineInstrBuilder.h"
22 #include "llvm/CodeGen/MachineMemOperand.h"
23 #include "llvm/CodeGen/MachineOperand.h"
24 #include "llvm/CodeGen/MachineRegisterInfo.h"
25 #include "llvm/CodeGen/TargetRegisterInfo.h"
26 #include "llvm/IR/DebugLoc.h"
27 #include "llvm/MC/MCInst.h"
28 #include "llvm/MC/MCInstrDesc.h"
29 #include "llvm/Support/CommandLine.h"
30 #include "llvm/Support/ErrorHandling.h"
31 #include "llvm/Support/MathExtras.h"
32 #include "llvm/Target/TargetMachine.h"
38 OldT2IfCvt("old-thumb2-ifcvt", cl::Hidden,
39 cl::desc("Use old-style Thumb2 if-conversion heuristics"),
42 Thumb2InstrInfo::Thumb2InstrInfo(const ARMSubtarget &STI)
43 : ARMBaseInstrInfo(STI) {}
45 /// Return the noop instruction to use for a noop.
46 void Thumb2InstrInfo::getNoop(MCInst &NopInst) const {
47 NopInst.setOpcode(ARM::tHINT);
48 NopInst.addOperand(MCOperand::createImm(0));
49 NopInst.addOperand(MCOperand::createImm(ARMCC::AL));
50 NopInst.addOperand(MCOperand::createReg(0));
53 unsigned Thumb2InstrInfo::getUnindexedOpcode(unsigned Opc) const {
59 Thumb2InstrInfo::ReplaceTailWithBranchTo(MachineBasicBlock::iterator Tail,
60 MachineBasicBlock *NewDest) const {
61 MachineBasicBlock *MBB = Tail->getParent();
62 ARMFunctionInfo *AFI = MBB->getParent()->getInfo<ARMFunctionInfo>();
63 if (!AFI->hasITBlocks() || Tail->isBranch()) {
64 TargetInstrInfo::ReplaceTailWithBranchTo(Tail, NewDest);
68 // If the first instruction of Tail is predicated, we may have to update
69 // the IT instruction.
71 ARMCC::CondCodes CC = getInstrPredicate(*Tail, PredReg);
72 MachineBasicBlock::iterator MBBI = Tail;
74 // Expecting at least the t2IT instruction before it.
77 // Actually replace the tail.
78 TargetInstrInfo::ReplaceTailWithBranchTo(Tail, NewDest);
81 if (CC != ARMCC::AL) {
82 MachineBasicBlock::iterator E = MBB->begin();
83 unsigned Count = 4; // At most 4 instructions in an IT block.
84 while (Count && MBBI != E) {
85 if (MBBI->isDebugInstr()) {
89 if (MBBI->getOpcode() == ARM::t2IT) {
90 unsigned Mask = MBBI->getOperand(1).getImm();
92 MBBI->eraseFromParent();
94 unsigned MaskOn = 1 << Count;
95 unsigned MaskOff = ~(MaskOn - 1);
96 MBBI->getOperand(1).setImm((Mask & MaskOff) | MaskOn);
104 // Ctrl flow can reach here if branch folding is run before IT block
110 Thumb2InstrInfo::isLegalToSplitMBBAt(MachineBasicBlock &MBB,
111 MachineBasicBlock::iterator MBBI) const {
112 while (MBBI->isDebugInstr()) {
114 if (MBBI == MBB.end())
118 unsigned PredReg = 0;
119 return getITInstrPredicate(*MBBI, PredReg) == ARMCC::AL;
122 void Thumb2InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
123 MachineBasicBlock::iterator I,
124 const DebugLoc &DL, unsigned DestReg,
125 unsigned SrcReg, bool KillSrc) const {
126 // Handle SPR, DPR, and QPR copies.
127 if (!ARM::GPRRegClass.contains(DestReg, SrcReg))
128 return ARMBaseInstrInfo::copyPhysReg(MBB, I, DL, DestReg, SrcReg, KillSrc);
130 BuildMI(MBB, I, DL, get(ARM::tMOVr), DestReg)
131 .addReg(SrcReg, getKillRegState(KillSrc))
132 .add(predOps(ARMCC::AL));
135 void Thumb2InstrInfo::
136 storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
137 unsigned SrcReg, bool isKill, int FI,
138 const TargetRegisterClass *RC,
139 const TargetRegisterInfo *TRI) const {
141 if (I != MBB.end()) DL = I->getDebugLoc();
143 MachineFunction &MF = *MBB.getParent();
144 MachineFrameInfo &MFI = MF.getFrameInfo();
145 MachineMemOperand *MMO = MF.getMachineMemOperand(
146 MachinePointerInfo::getFixedStack(MF, FI), MachineMemOperand::MOStore,
147 MFI.getObjectSize(FI), MFI.getObjectAlignment(FI));
149 if (ARM::GPRRegClass.hasSubClassEq(RC)) {
150 BuildMI(MBB, I, DL, get(ARM::t2STRi12))
151 .addReg(SrcReg, getKillRegState(isKill))
155 .add(predOps(ARMCC::AL));
159 if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
160 // Thumb2 STRD expects its dest-registers to be in rGPR. Not a problem for
161 // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
163 if (TargetRegisterInfo::isVirtualRegister(SrcReg)) {
164 MachineRegisterInfo *MRI = &MF.getRegInfo();
165 MRI->constrainRegClass(SrcReg, &ARM::GPRPair_with_gsub_1_in_rGPRRegClass);
168 MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2STRDi8));
169 AddDReg(MIB, SrcReg, ARM::gsub_0, getKillRegState(isKill), TRI);
170 AddDReg(MIB, SrcReg, ARM::gsub_1, 0, TRI);
171 MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO).add(predOps(ARMCC::AL));
175 ARMBaseInstrInfo::storeRegToStackSlot(MBB, I, SrcReg, isKill, FI, RC, TRI);
178 void Thumb2InstrInfo::
179 loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
180 unsigned DestReg, int FI,
181 const TargetRegisterClass *RC,
182 const TargetRegisterInfo *TRI) const {
183 MachineFunction &MF = *MBB.getParent();
184 MachineFrameInfo &MFI = MF.getFrameInfo();
185 MachineMemOperand *MMO = MF.getMachineMemOperand(
186 MachinePointerInfo::getFixedStack(MF, FI), MachineMemOperand::MOLoad,
187 MFI.getObjectSize(FI), MFI.getObjectAlignment(FI));
189 if (I != MBB.end()) DL = I->getDebugLoc();
191 if (ARM::GPRRegClass.hasSubClassEq(RC)) {
192 BuildMI(MBB, I, DL, get(ARM::t2LDRi12), DestReg)
196 .add(predOps(ARMCC::AL));
200 if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
201 // Thumb2 LDRD expects its dest-registers to be in rGPR. Not a problem for
202 // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
204 if (TargetRegisterInfo::isVirtualRegister(DestReg)) {
205 MachineRegisterInfo *MRI = &MF.getRegInfo();
206 MRI->constrainRegClass(DestReg,
207 &ARM::GPRPair_with_gsub_1_in_rGPRRegClass);
210 MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2LDRDi8));
211 AddDReg(MIB, DestReg, ARM::gsub_0, RegState::DefineNoRead, TRI);
212 AddDReg(MIB, DestReg, ARM::gsub_1, RegState::DefineNoRead, TRI);
213 MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO).add(predOps(ARMCC::AL));
215 if (TargetRegisterInfo::isPhysicalRegister(DestReg))
216 MIB.addReg(DestReg, RegState::ImplicitDefine);
220 ARMBaseInstrInfo::loadRegFromStackSlot(MBB, I, DestReg, FI, RC, TRI);
223 void Thumb2InstrInfo::expandLoadStackGuard(
224 MachineBasicBlock::iterator MI) const {
225 MachineFunction &MF = *MI->getParent()->getParent();
226 if (MF.getTarget().isPositionIndependent())
227 expandLoadStackGuardBase(MI, ARM::t2MOV_ga_pcrel, ARM::t2LDRi12);
229 expandLoadStackGuardBase(MI, ARM::t2MOVi32imm, ARM::t2LDRi12);
232 void llvm::emitT2RegPlusImmediate(MachineBasicBlock &MBB,
233 MachineBasicBlock::iterator &MBBI,
234 const DebugLoc &dl, unsigned DestReg,
235 unsigned BaseReg, int NumBytes,
236 ARMCC::CondCodes Pred, unsigned PredReg,
237 const ARMBaseInstrInfo &TII,
239 if (NumBytes == 0 && DestReg != BaseReg) {
240 BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), DestReg)
241 .addReg(BaseReg, RegState::Kill)
242 .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
246 bool isSub = NumBytes < 0;
247 if (isSub) NumBytes = -NumBytes;
249 // If profitable, use a movw or movt to materialize the offset.
250 // FIXME: Use the scavenger to grab a scratch register.
251 if (DestReg != ARM::SP && DestReg != BaseReg &&
253 ARM_AM::getT2SOImmVal(NumBytes) == -1) {
255 if (NumBytes < 65536) {
256 // Use a movw to materialize the 16-bit constant.
257 BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), DestReg)
259 .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
261 } else if ((NumBytes & 0xffff) == 0) {
262 // Use a movt to materialize the 32-bit constant.
263 BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVTi16), DestReg)
265 .addImm(NumBytes >> 16)
266 .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
272 BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr), DestReg)
274 .addReg(DestReg, RegState::Kill)
275 .add(predOps(Pred, PredReg))
277 .setMIFlags(MIFlags);
279 // Here we know that DestReg is not SP but we do not
280 // know anything about BaseReg. t2ADDrr is an invalid
281 // instruction is SP is used as the second argument, but
282 // is fine if SP is the first argument. To be sure we
283 // do not generate invalid encoding, put BaseReg first.
284 BuildMI(MBB, MBBI, dl, TII.get(ARM::t2ADDrr), DestReg)
286 .addReg(DestReg, RegState::Kill)
287 .add(predOps(Pred, PredReg))
289 .setMIFlags(MIFlags);
296 unsigned ThisVal = NumBytes;
298 if (DestReg == ARM::SP && BaseReg != ARM::SP) {
299 // mov sp, rn. Note t2MOVr cannot be used.
300 BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), DestReg)
303 .add(predOps(ARMCC::AL));
308 bool HasCCOut = true;
309 if (BaseReg == ARM::SP) {
311 if (DestReg == ARM::SP && (ThisVal < ((1 << 7)-1) * 4)) {
312 assert((ThisVal & 3) == 0 && "Stack update is not multiple of 4?");
313 Opc = isSub ? ARM::tSUBspi : ARM::tADDspi;
314 BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg)
318 .add(predOps(ARMCC::AL));
323 // sub rd, sp, so_imm
324 Opc = isSub ? ARM::t2SUBri : ARM::t2ADDri;
325 if (ARM_AM::getT2SOImmVal(NumBytes) != -1) {
328 // FIXME: Move this to ARMAddressingModes.h?
329 unsigned RotAmt = countLeadingZeros(ThisVal);
330 ThisVal = ThisVal & ARM_AM::rotr32(0xff000000U, RotAmt);
331 NumBytes &= ~ThisVal;
332 assert(ARM_AM::getT2SOImmVal(ThisVal) != -1 &&
333 "Bit extraction didn't work?");
336 assert(DestReg != ARM::SP && BaseReg != ARM::SP);
337 Opc = isSub ? ARM::t2SUBri : ARM::t2ADDri;
338 if (ARM_AM::getT2SOImmVal(NumBytes) != -1) {
340 } else if (ThisVal < 4096) {
341 Opc = isSub ? ARM::t2SUBri12 : ARM::t2ADDri12;
345 // FIXME: Move this to ARMAddressingModes.h?
346 unsigned RotAmt = countLeadingZeros(ThisVal);
347 ThisVal = ThisVal & ARM_AM::rotr32(0xff000000U, RotAmt);
348 NumBytes &= ~ThisVal;
349 assert(ARM_AM::getT2SOImmVal(ThisVal) != -1 &&
350 "Bit extraction didn't work?");
354 // Build the new ADD / SUB.
355 MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg)
356 .addReg(BaseReg, RegState::Kill)
358 .add(predOps(ARMCC::AL))
359 .setMIFlags(MIFlags);
361 MIB.add(condCodeOp());
368 negativeOffsetOpcode(unsigned opcode)
371 case ARM::t2LDRi12: return ARM::t2LDRi8;
372 case ARM::t2LDRHi12: return ARM::t2LDRHi8;
373 case ARM::t2LDRBi12: return ARM::t2LDRBi8;
374 case ARM::t2LDRSHi12: return ARM::t2LDRSHi8;
375 case ARM::t2LDRSBi12: return ARM::t2LDRSBi8;
376 case ARM::t2STRi12: return ARM::t2STRi8;
377 case ARM::t2STRBi12: return ARM::t2STRBi8;
378 case ARM::t2STRHi12: return ARM::t2STRHi8;
379 case ARM::t2PLDi12: return ARM::t2PLDi8;
400 positiveOffsetOpcode(unsigned opcode)
403 case ARM::t2LDRi8: return ARM::t2LDRi12;
404 case ARM::t2LDRHi8: return ARM::t2LDRHi12;
405 case ARM::t2LDRBi8: return ARM::t2LDRBi12;
406 case ARM::t2LDRSHi8: return ARM::t2LDRSHi12;
407 case ARM::t2LDRSBi8: return ARM::t2LDRSBi12;
408 case ARM::t2STRi8: return ARM::t2STRi12;
409 case ARM::t2STRBi8: return ARM::t2STRBi12;
410 case ARM::t2STRHi8: return ARM::t2STRHi12;
411 case ARM::t2PLDi8: return ARM::t2PLDi12;
416 case ARM::t2LDRSHi12:
417 case ARM::t2LDRSBi12:
432 immediateOffsetOpcode(unsigned opcode)
435 case ARM::t2LDRs: return ARM::t2LDRi12;
436 case ARM::t2LDRHs: return ARM::t2LDRHi12;
437 case ARM::t2LDRBs: return ARM::t2LDRBi12;
438 case ARM::t2LDRSHs: return ARM::t2LDRSHi12;
439 case ARM::t2LDRSBs: return ARM::t2LDRSBi12;
440 case ARM::t2STRs: return ARM::t2STRi12;
441 case ARM::t2STRBs: return ARM::t2STRBi12;
442 case ARM::t2STRHs: return ARM::t2STRHi12;
443 case ARM::t2PLDs: return ARM::t2PLDi12;
448 case ARM::t2LDRSHi12:
449 case ARM::t2LDRSBi12:
472 bool llvm::rewriteT2FrameIndex(MachineInstr &MI, unsigned FrameRegIdx,
473 unsigned FrameReg, int &Offset,
474 const ARMBaseInstrInfo &TII) {
475 unsigned Opcode = MI.getOpcode();
476 const MCInstrDesc &Desc = MI.getDesc();
477 unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
480 // Memory operands in inline assembly always use AddrModeT2_i12.
481 if (Opcode == ARM::INLINEASM)
482 AddrMode = ARMII::AddrModeT2_i12; // FIXME. mode for thumb2?
484 if (Opcode == ARM::t2ADDri || Opcode == ARM::t2ADDri12) {
485 Offset += MI.getOperand(FrameRegIdx+1).getImm();
488 if (Offset == 0 && getInstrPredicate(MI, PredReg) == ARMCC::AL &&
489 !MI.definesRegister(ARM::CPSR)) {
490 // Turn it into a move.
491 MI.setDesc(TII.get(ARM::tMOVr));
492 MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
493 // Remove offset and remaining explicit predicate operands.
494 do MI.RemoveOperand(FrameRegIdx+1);
495 while (MI.getNumOperands() > FrameRegIdx+1);
496 MachineInstrBuilder MIB(*MI.getParent()->getParent(), &MI);
497 MIB.add(predOps(ARMCC::AL));
501 bool HasCCOut = Opcode != ARM::t2ADDri12;
506 MI.setDesc(TII.get(ARM::t2SUBri));
508 MI.setDesc(TII.get(ARM::t2ADDri));
511 // Common case: small offset, fits into instruction.
512 if (ARM_AM::getT2SOImmVal(Offset) != -1) {
513 MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
514 MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
515 // Add cc_out operand if the original instruction did not have one.
517 MI.addOperand(MachineOperand::CreateReg(0, false));
521 // Another common case: imm12.
523 (!HasCCOut || MI.getOperand(MI.getNumOperands()-1).getReg() == 0)) {
524 unsigned NewOpc = isSub ? ARM::t2SUBri12 : ARM::t2ADDri12;
525 MI.setDesc(TII.get(NewOpc));
526 MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
527 MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
528 // Remove the cc_out operand.
530 MI.RemoveOperand(MI.getNumOperands()-1);
535 // Otherwise, extract 8 adjacent bits from the immediate into this
537 unsigned RotAmt = countLeadingZeros<unsigned>(Offset);
538 unsigned ThisImmVal = Offset & ARM_AM::rotr32(0xff000000U, RotAmt);
540 // We will handle these bits from offset, clear them.
541 Offset &= ~ThisImmVal;
543 assert(ARM_AM::getT2SOImmVal(ThisImmVal) != -1 &&
544 "Bit extraction didn't work?");
545 MI.getOperand(FrameRegIdx+1).ChangeToImmediate(ThisImmVal);
546 // Add cc_out operand if the original instruction did not have one.
548 MI.addOperand(MachineOperand::CreateReg(0, false));
550 // AddrMode4 and AddrMode6 cannot handle any offset.
551 if (AddrMode == ARMII::AddrMode4 || AddrMode == ARMII::AddrMode6)
554 // AddrModeT2_so cannot handle any offset. If there is no offset
555 // register then we change to an immediate version.
556 unsigned NewOpc = Opcode;
557 if (AddrMode == ARMII::AddrModeT2_so) {
558 unsigned OffsetReg = MI.getOperand(FrameRegIdx+1).getReg();
559 if (OffsetReg != 0) {
560 MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
564 MI.RemoveOperand(FrameRegIdx+1);
565 MI.getOperand(FrameRegIdx+1).ChangeToImmediate(0);
566 NewOpc = immediateOffsetOpcode(Opcode);
567 AddrMode = ARMII::AddrModeT2_i12;
570 unsigned NumBits = 0;
572 if (AddrMode == ARMII::AddrModeT2_i8 || AddrMode == ARMII::AddrModeT2_i12) {
573 // i8 supports only negative, and i12 supports only positive, so
574 // based on Offset sign convert Opcode to the appropriate
576 Offset += MI.getOperand(FrameRegIdx+1).getImm();
578 NewOpc = negativeOffsetOpcode(Opcode);
583 NewOpc = positiveOffsetOpcode(Opcode);
586 } else if (AddrMode == ARMII::AddrMode5) {
588 const MachineOperand &OffOp = MI.getOperand(FrameRegIdx+1);
589 int InstrOffs = ARM_AM::getAM5Offset(OffOp.getImm());
590 if (ARM_AM::getAM5Op(OffOp.getImm()) == ARM_AM::sub)
594 Offset += InstrOffs * 4;
595 assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
600 } else if (AddrMode == ARMII::AddrMode5FP16) {
602 const MachineOperand &OffOp = MI.getOperand(FrameRegIdx+1);
603 int InstrOffs = ARM_AM::getAM5FP16Offset(OffOp.getImm());
604 if (ARM_AM::getAM5FP16Op(OffOp.getImm()) == ARM_AM::sub)
608 Offset += InstrOffs * 2;
609 assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
614 } else if (AddrMode == ARMII::AddrModeT2_i8s4) {
615 Offset += MI.getOperand(FrameRegIdx + 1).getImm() * 4;
616 NumBits = 10; // 8 bits scaled by 4
617 // MCInst operand expects already scaled value.
619 assert((Offset & 3) == 0 && "Can't encode this offset!");
620 } else if (AddrMode == ARMII::AddrModeT2_ldrex) {
621 Offset += MI.getOperand(FrameRegIdx + 1).getImm() * 4;
622 NumBits = 8; // 8 bits scaled by 4
624 assert((Offset & 3) == 0 && "Can't encode this offset!");
626 llvm_unreachable("Unsupported addressing mode!");
629 if (NewOpc != Opcode)
630 MI.setDesc(TII.get(NewOpc));
632 MachineOperand &ImmOp = MI.getOperand(FrameRegIdx+1);
634 // Attempt to fold address computation
635 // Common case: small offset, fits into instruction.
636 int ImmedOffset = Offset / Scale;
637 unsigned Mask = (1 << NumBits) - 1;
638 if ((unsigned)Offset <= Mask * Scale) {
639 // Replace the FrameIndex with fp/sp
640 MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
642 if (AddrMode == ARMII::AddrMode5)
643 // FIXME: Not consistent.
644 ImmedOffset |= 1 << NumBits;
646 ImmedOffset = -ImmedOffset;
648 ImmOp.ChangeToImmediate(ImmedOffset);
653 // Otherwise, offset doesn't fit. Pull in what we can to simplify
654 ImmedOffset = ImmedOffset & Mask;
656 if (AddrMode == ARMII::AddrMode5)
657 // FIXME: Not consistent.
658 ImmedOffset |= 1 << NumBits;
660 ImmedOffset = -ImmedOffset;
661 if (ImmedOffset == 0)
662 // Change the opcode back if the encoded offset is zero.
663 MI.setDesc(TII.get(positiveOffsetOpcode(NewOpc)));
666 ImmOp.ChangeToImmediate(ImmedOffset);
667 Offset &= ~(Mask*Scale);
670 Offset = (isSub) ? -Offset : Offset;
674 ARMCC::CondCodes llvm::getITInstrPredicate(const MachineInstr &MI,
676 unsigned Opc = MI.getOpcode();
677 if (Opc == ARM::tBcc || Opc == ARM::t2Bcc)
679 return getInstrPredicate(MI, PredReg);