1//===-- Thumb2InstrInfo.cpp - Thumb-2 Instruction Information -------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the Thumb-2 implementation of the TargetInstrInfo class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "Thumb2InstrInfo.h"
15#include "ARM.h"
16#include "ARMConstantPoolValue.h"
17#include "ARMMachineFunctionInfo.h"
18#include "MCTargetDesc/ARMAddressingModes.h"
19#include "llvm/CodeGen/MachineFrameInfo.h"
20#include "llvm/CodeGen/MachineInstrBuilder.h"
21#include "llvm/CodeGen/MachineMemOperand.h"
22#include "llvm/CodeGen/MachineRegisterInfo.h"
23#include "llvm/MC/MCInst.h"
24#include "llvm/Support/CommandLine.h"
25
26using namespace llvm;
27
28static cl::opt<bool>
29OldT2IfCvt("old-thumb2-ifcvt", cl::Hidden,
30           cl::desc("Use old-style Thumb2 if-conversion heuristics"),
31           cl::init(false));
32
33Thumb2InstrInfo::Thumb2InstrInfo(const ARMSubtarget &STI)
34  : ARMBaseInstrInfo(STI), RI(STI) {
35}
36
37/// getNoopForMachoTarget - Return the noop instruction to use for a noop.
38void Thumb2InstrInfo::getNoopForMachoTarget(MCInst &NopInst) const {
39  NopInst.setOpcode(ARM::tNOP);
40  NopInst.addOperand(MCOperand::CreateImm(ARMCC::AL));
41  NopInst.addOperand(MCOperand::CreateReg(0));
42}
43
44unsigned Thumb2InstrInfo::getUnindexedOpcode(unsigned Opc) const {
45  // FIXME
46  return 0;
47}
48
49void
50Thumb2InstrInfo::ReplaceTailWithBranchTo(MachineBasicBlock::iterator Tail,
51                                         MachineBasicBlock *NewDest) const {
52  MachineBasicBlock *MBB = Tail->getParent();
53  ARMFunctionInfo *AFI = MBB->getParent()->getInfo<ARMFunctionInfo>();
54  if (!AFI->hasITBlocks()) {
55    TargetInstrInfo::ReplaceTailWithBranchTo(Tail, NewDest);
56    return;
57  }
58
59  // If the first instruction of Tail is predicated, we may have to update
60  // the IT instruction.
61  unsigned PredReg = 0;
62  ARMCC::CondCodes CC = getInstrPredicate(Tail, PredReg);
63  MachineBasicBlock::iterator MBBI = Tail;
64  if (CC != ARMCC::AL)
65    // Expecting at least the t2IT instruction before it.
66    --MBBI;
67
68  // Actually replace the tail.
69  TargetInstrInfo::ReplaceTailWithBranchTo(Tail, NewDest);
70
71  // Fix up IT.
72  if (CC != ARMCC::AL) {
73    MachineBasicBlock::iterator E = MBB->begin();
74    unsigned Count = 4; // At most 4 instructions in an IT block.
75    while (Count && MBBI != E) {
76      if (MBBI->isDebugValue()) {
77        --MBBI;
78        continue;
79      }
80      if (MBBI->getOpcode() == ARM::t2IT) {
81        unsigned Mask = MBBI->getOperand(1).getImm();
82        if (Count == 4)
83          MBBI->eraseFromParent();
84        else {
85          unsigned MaskOn = 1 << Count;
86          unsigned MaskOff = ~(MaskOn - 1);
87          MBBI->getOperand(1).setImm((Mask & MaskOff) | MaskOn);
88        }
89        return;
90      }
91      --MBBI;
92      --Count;
93    }
94
95    // Ctrl flow can reach here if branch folding is run before IT block
96    // formation pass.
97  }
98}
99
100bool
101Thumb2InstrInfo::isLegalToSplitMBBAt(MachineBasicBlock &MBB,
102                                     MachineBasicBlock::iterator MBBI) const {
103  while (MBBI->isDebugValue()) {
104    ++MBBI;
105    if (MBBI == MBB.end())
106      return false;
107  }
108
109  unsigned PredReg = 0;
110  return getITInstrPredicate(MBBI, PredReg) == ARMCC::AL;
111}
112
113void Thumb2InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
114                                  MachineBasicBlock::iterator I, DebugLoc DL,
115                                  unsigned DestReg, unsigned SrcReg,
116                                  bool KillSrc) const {
117  // Handle SPR, DPR, and QPR copies.
118  if (!ARM::GPRRegClass.contains(DestReg, SrcReg))
119    return ARMBaseInstrInfo::copyPhysReg(MBB, I, DL, DestReg, SrcReg, KillSrc);
120
121  AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::tMOVr), DestReg)
122    .addReg(SrcReg, getKillRegState(KillSrc)));
123}
124
125void Thumb2InstrInfo::
126storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
127                    unsigned SrcReg, bool isKill, int FI,
128                    const TargetRegisterClass *RC,
129                    const TargetRegisterInfo *TRI) const {
130  DebugLoc DL;
131  if (I != MBB.end()) DL = I->getDebugLoc();
132
133  MachineFunction &MF = *MBB.getParent();
134  MachineFrameInfo &MFI = *MF.getFrameInfo();
135  MachineMemOperand *MMO =
136    MF.getMachineMemOperand(MachinePointerInfo::getFixedStack(FI),
137                            MachineMemOperand::MOStore,
138                            MFI.getObjectSize(FI),
139                            MFI.getObjectAlignment(FI));
140
141  if (RC == &ARM::GPRRegClass   || RC == &ARM::tGPRRegClass ||
142      RC == &ARM::tcGPRRegClass || RC == &ARM::rGPRRegClass ||
143      RC == &ARM::GPRnopcRegClass) {
144    AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::t2STRi12))
145                   .addReg(SrcReg, getKillRegState(isKill))
146                   .addFrameIndex(FI).addImm(0).addMemOperand(MMO));
147    return;
148  }
149
150  if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
151    // Thumb2 STRD expects its dest-registers to be in rGPR. Not a problem for
152    // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
153    // otherwise).
154    MachineRegisterInfo *MRI = &MF.getRegInfo();
155    MRI->constrainRegClass(SrcReg, &ARM::GPRPair_with_gsub_1_in_rGPRRegClass);
156
157    MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2STRDi8));
158    AddDReg(MIB, SrcReg, ARM::gsub_0, getKillRegState(isKill), TRI);
159    AddDReg(MIB, SrcReg, ARM::gsub_1, 0, TRI);
160    MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO);
161    AddDefaultPred(MIB);
162    return;
163  }
164
165  ARMBaseInstrInfo::storeRegToStackSlot(MBB, I, SrcReg, isKill, FI, RC, TRI);
166}
167
168void Thumb2InstrInfo::
169loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
170                     unsigned DestReg, int FI,
171                     const TargetRegisterClass *RC,
172                     const TargetRegisterInfo *TRI) const {
173  MachineFunction &MF = *MBB.getParent();
174  MachineFrameInfo &MFI = *MF.getFrameInfo();
175  MachineMemOperand *MMO =
176    MF.getMachineMemOperand(MachinePointerInfo::getFixedStack(FI),
177                            MachineMemOperand::MOLoad,
178                            MFI.getObjectSize(FI),
179                            MFI.getObjectAlignment(FI));
180  DebugLoc DL;
181  if (I != MBB.end()) DL = I->getDebugLoc();
182
183  if (RC == &ARM::GPRRegClass   || RC == &ARM::tGPRRegClass ||
184      RC == &ARM::tcGPRRegClass || RC == &ARM::rGPRRegClass ||
185      RC == &ARM::GPRnopcRegClass) {
186    AddDefaultPred(BuildMI(MBB, I, DL, get(ARM::t2LDRi12), DestReg)
187                   .addFrameIndex(FI).addImm(0).addMemOperand(MMO));
188    return;
189  }
190
191  if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
192    // Thumb2 LDRD expects its dest-registers to be in rGPR. Not a problem for
193    // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
194    // otherwise).
195    MachineRegisterInfo *MRI = &MF.getRegInfo();
196    MRI->constrainRegClass(DestReg, &ARM::GPRPair_with_gsub_1_in_rGPRRegClass);
197
198    MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2LDRDi8));
199    AddDReg(MIB, DestReg, ARM::gsub_0, RegState::DefineNoRead, TRI);
200    AddDReg(MIB, DestReg, ARM::gsub_1, RegState::DefineNoRead, TRI);
201    MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO);
202    AddDefaultPred(MIB);
203
204    if (TargetRegisterInfo::isPhysicalRegister(DestReg))
205      MIB.addReg(DestReg, RegState::ImplicitDefine);
206    return;
207  }
208
209  ARMBaseInstrInfo::loadRegFromStackSlot(MBB, I, DestReg, FI, RC, TRI);
210}
211
212void llvm::emitT2RegPlusImmediate(MachineBasicBlock &MBB,
213                               MachineBasicBlock::iterator &MBBI, DebugLoc dl,
214                               unsigned DestReg, unsigned BaseReg, int NumBytes,
215                               ARMCC::CondCodes Pred, unsigned PredReg,
216                               const ARMBaseInstrInfo &TII, unsigned MIFlags) {
217  bool isSub = NumBytes < 0;
218  if (isSub) NumBytes = -NumBytes;
219
220  // If profitable, use a movw or movt to materialize the offset.
221  // FIXME: Use the scavenger to grab a scratch register.
222  if (DestReg != ARM::SP && DestReg != BaseReg &&
223      NumBytes >= 4096 &&
224      ARM_AM::getT2SOImmVal(NumBytes) == -1) {
225    bool Fits = false;
226    if (NumBytes < 65536) {
227      // Use a movw to materialize the 16-bit constant.
228      BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVi16), DestReg)
229        .addImm(NumBytes)
230        .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
231      Fits = true;
232    } else if ((NumBytes & 0xffff) == 0) {
233      // Use a movt to materialize the 32-bit constant.
234      BuildMI(MBB, MBBI, dl, TII.get(ARM::t2MOVTi16), DestReg)
235        .addReg(DestReg)
236        .addImm(NumBytes >> 16)
237        .addImm((unsigned)Pred).addReg(PredReg).setMIFlags(MIFlags);
238      Fits = true;
239    }
240
241    if (Fits) {
242      if (isSub) {
243        BuildMI(MBB, MBBI, dl, TII.get(ARM::t2SUBrr), DestReg)
244          .addReg(BaseReg, RegState::Kill)
245          .addReg(DestReg, RegState::Kill)
246          .addImm((unsigned)Pred).addReg(PredReg).addReg(0)
247          .setMIFlags(MIFlags);
248      } else {
249        BuildMI(MBB, MBBI, dl, TII.get(ARM::t2ADDrr), DestReg)
250          .addReg(DestReg, RegState::Kill)
251          .addReg(BaseReg, RegState::Kill)
252          .addImm((unsigned)Pred).addReg(PredReg).addReg(0)
253          .setMIFlags(MIFlags);
254      }
255      return;
256    }
257  }
258
259  while (NumBytes) {
260    unsigned ThisVal = NumBytes;
261    unsigned Opc = 0;
262    if (DestReg == ARM::SP && BaseReg != ARM::SP) {
263      // mov sp, rn. Note t2MOVr cannot be used.
264      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr),DestReg)
265        .addReg(BaseReg).setMIFlags(MIFlags));
266      BaseReg = ARM::SP;
267      continue;
268    }
269
270    bool HasCCOut = true;
271    if (BaseReg == ARM::SP) {
272      // sub sp, sp, #imm7
273      if (DestReg == ARM::SP && (ThisVal < ((1 << 7)-1) * 4)) {
274        assert((ThisVal & 3) == 0 && "Stack update is not multiple of 4?");
275        Opc = isSub ? ARM::tSUBspi : ARM::tADDspi;
276        AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg)
277          .addReg(BaseReg).addImm(ThisVal/4).setMIFlags(MIFlags));
278        NumBytes = 0;
279        continue;
280      }
281
282      // sub rd, sp, so_imm
283      Opc = isSub ? ARM::t2SUBri : ARM::t2ADDri;
284      if (ARM_AM::getT2SOImmVal(NumBytes) != -1) {
285        NumBytes = 0;
286      } else {
287        // FIXME: Move this to ARMAddressingModes.h?
288        unsigned RotAmt = countLeadingZeros(ThisVal);
289        ThisVal = ThisVal & ARM_AM::rotr32(0xff000000U, RotAmt);
290        NumBytes &= ~ThisVal;
291        assert(ARM_AM::getT2SOImmVal(ThisVal) != -1 &&
292               "Bit extraction didn't work?");
293      }
294    } else {
295      assert(DestReg != ARM::SP && BaseReg != ARM::SP);
296      Opc = isSub ? ARM::t2SUBri : ARM::t2ADDri;
297      if (ARM_AM::getT2SOImmVal(NumBytes) != -1) {
298        NumBytes = 0;
299      } else if (ThisVal < 4096) {
300        Opc = isSub ? ARM::t2SUBri12 : ARM::t2ADDri12;
301        HasCCOut = false;
302        NumBytes = 0;
303      } else {
304        // FIXME: Move this to ARMAddressingModes.h?
305        unsigned RotAmt = countLeadingZeros(ThisVal);
306        ThisVal = ThisVal & ARM_AM::rotr32(0xff000000U, RotAmt);
307        NumBytes &= ~ThisVal;
308        assert(ARM_AM::getT2SOImmVal(ThisVal) != -1 &&
309               "Bit extraction didn't work?");
310      }
311    }
312
313    // Build the new ADD / SUB.
314    MachineInstrBuilder MIB =
315      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg)
316                     .addReg(BaseReg, RegState::Kill)
317                     .addImm(ThisVal)).setMIFlags(MIFlags);
318    if (HasCCOut)
319      AddDefaultCC(MIB);
320
321    BaseReg = DestReg;
322  }
323}
324
325static unsigned
326negativeOffsetOpcode(unsigned opcode)
327{
328  switch (opcode) {
329  case ARM::t2LDRi12:   return ARM::t2LDRi8;
330  case ARM::t2LDRHi12:  return ARM::t2LDRHi8;
331  case ARM::t2LDRBi12:  return ARM::t2LDRBi8;
332  case ARM::t2LDRSHi12: return ARM::t2LDRSHi8;
333  case ARM::t2LDRSBi12: return ARM::t2LDRSBi8;
334  case ARM::t2STRi12:   return ARM::t2STRi8;
335  case ARM::t2STRBi12:  return ARM::t2STRBi8;
336  case ARM::t2STRHi12:  return ARM::t2STRHi8;
337
338  case ARM::t2LDRi8:
339  case ARM::t2LDRHi8:
340  case ARM::t2LDRBi8:
341  case ARM::t2LDRSHi8:
342  case ARM::t2LDRSBi8:
343  case ARM::t2STRi8:
344  case ARM::t2STRBi8:
345  case ARM::t2STRHi8:
346    return opcode;
347
348  default:
349    break;
350  }
351
352  return 0;
353}
354
355static unsigned
356positiveOffsetOpcode(unsigned opcode)
357{
358  switch (opcode) {
359  case ARM::t2LDRi8:   return ARM::t2LDRi12;
360  case ARM::t2LDRHi8:  return ARM::t2LDRHi12;
361  case ARM::t2LDRBi8:  return ARM::t2LDRBi12;
362  case ARM::t2LDRSHi8: return ARM::t2LDRSHi12;
363  case ARM::t2LDRSBi8: return ARM::t2LDRSBi12;
364  case ARM::t2STRi8:   return ARM::t2STRi12;
365  case ARM::t2STRBi8:  return ARM::t2STRBi12;
366  case ARM::t2STRHi8:  return ARM::t2STRHi12;
367
368  case ARM::t2LDRi12:
369  case ARM::t2LDRHi12:
370  case ARM::t2LDRBi12:
371  case ARM::t2LDRSHi12:
372  case ARM::t2LDRSBi12:
373  case ARM::t2STRi12:
374  case ARM::t2STRBi12:
375  case ARM::t2STRHi12:
376    return opcode;
377
378  default:
379    break;
380  }
381
382  return 0;
383}
384
385static unsigned
386immediateOffsetOpcode(unsigned opcode)
387{
388  switch (opcode) {
389  case ARM::t2LDRs:   return ARM::t2LDRi12;
390  case ARM::t2LDRHs:  return ARM::t2LDRHi12;
391  case ARM::t2LDRBs:  return ARM::t2LDRBi12;
392  case ARM::t2LDRSHs: return ARM::t2LDRSHi12;
393  case ARM::t2LDRSBs: return ARM::t2LDRSBi12;
394  case ARM::t2STRs:   return ARM::t2STRi12;
395  case ARM::t2STRBs:  return ARM::t2STRBi12;
396  case ARM::t2STRHs:  return ARM::t2STRHi12;
397
398  case ARM::t2LDRi12:
399  case ARM::t2LDRHi12:
400  case ARM::t2LDRBi12:
401  case ARM::t2LDRSHi12:
402  case ARM::t2LDRSBi12:
403  case ARM::t2STRi12:
404  case ARM::t2STRBi12:
405  case ARM::t2STRHi12:
406  case ARM::t2LDRi8:
407  case ARM::t2LDRHi8:
408  case ARM::t2LDRBi8:
409  case ARM::t2LDRSHi8:
410  case ARM::t2LDRSBi8:
411  case ARM::t2STRi8:
412  case ARM::t2STRBi8:
413  case ARM::t2STRHi8:
414    return opcode;
415
416  default:
417    break;
418  }
419
420  return 0;
421}
422
423bool llvm::rewriteT2FrameIndex(MachineInstr &MI, unsigned FrameRegIdx,
424                               unsigned FrameReg, int &Offset,
425                               const ARMBaseInstrInfo &TII) {
426  unsigned Opcode = MI.getOpcode();
427  const MCInstrDesc &Desc = MI.getDesc();
428  unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
429  bool isSub = false;
430
431  // Memory operands in inline assembly always use AddrModeT2_i12.
432  if (Opcode == ARM::INLINEASM)
433    AddrMode = ARMII::AddrModeT2_i12; // FIXME. mode for thumb2?
434
435  if (Opcode == ARM::t2ADDri || Opcode == ARM::t2ADDri12) {
436    Offset += MI.getOperand(FrameRegIdx+1).getImm();
437
438    unsigned PredReg;
439    if (Offset == 0 && getInstrPredicate(&MI, PredReg) == ARMCC::AL) {
440      // Turn it into a move.
441      MI.setDesc(TII.get(ARM::tMOVr));
442      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
443      // Remove offset and remaining explicit predicate operands.
444      do MI.RemoveOperand(FrameRegIdx+1);
445      while (MI.getNumOperands() > FrameRegIdx+1);
446      MachineInstrBuilder MIB(*MI.getParent()->getParent(), &MI);
447      AddDefaultPred(MIB);
448      return true;
449    }
450
451    bool HasCCOut = Opcode != ARM::t2ADDri12;
452
453    if (Offset < 0) {
454      Offset = -Offset;
455      isSub = true;
456      MI.setDesc(TII.get(ARM::t2SUBri));
457    } else {
458      MI.setDesc(TII.get(ARM::t2ADDri));
459    }
460
461    // Common case: small offset, fits into instruction.
462    if (ARM_AM::getT2SOImmVal(Offset) != -1) {
463      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
464      MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
465      // Add cc_out operand if the original instruction did not have one.
466      if (!HasCCOut)
467        MI.addOperand(MachineOperand::CreateReg(0, false));
468      Offset = 0;
469      return true;
470    }
471    // Another common case: imm12.
472    if (Offset < 4096 &&
473        (!HasCCOut || MI.getOperand(MI.getNumOperands()-1).getReg() == 0)) {
474      unsigned NewOpc = isSub ? ARM::t2SUBri12 : ARM::t2ADDri12;
475      MI.setDesc(TII.get(NewOpc));
476      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
477      MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset);
478      // Remove the cc_out operand.
479      if (HasCCOut)
480        MI.RemoveOperand(MI.getNumOperands()-1);
481      Offset = 0;
482      return true;
483    }
484
485    // Otherwise, extract 8 adjacent bits from the immediate into this
486    // t2ADDri/t2SUBri.
487    unsigned RotAmt = countLeadingZeros<unsigned>(Offset);
488    unsigned ThisImmVal = Offset & ARM_AM::rotr32(0xff000000U, RotAmt);
489
490    // We will handle these bits from offset, clear them.
491    Offset &= ~ThisImmVal;
492
493    assert(ARM_AM::getT2SOImmVal(ThisImmVal) != -1 &&
494           "Bit extraction didn't work?");
495    MI.getOperand(FrameRegIdx+1).ChangeToImmediate(ThisImmVal);
496    // Add cc_out operand if the original instruction did not have one.
497    if (!HasCCOut)
498      MI.addOperand(MachineOperand::CreateReg(0, false));
499
500  } else {
501
502    // AddrMode4 and AddrMode6 cannot handle any offset.
503    if (AddrMode == ARMII::AddrMode4 || AddrMode == ARMII::AddrMode6)
504      return false;
505
506    // AddrModeT2_so cannot handle any offset. If there is no offset
507    // register then we change to an immediate version.
508    unsigned NewOpc = Opcode;
509    if (AddrMode == ARMII::AddrModeT2_so) {
510      unsigned OffsetReg = MI.getOperand(FrameRegIdx+1).getReg();
511      if (OffsetReg != 0) {
512        MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
513        return Offset == 0;
514      }
515
516      MI.RemoveOperand(FrameRegIdx+1);
517      MI.getOperand(FrameRegIdx+1).ChangeToImmediate(0);
518      NewOpc = immediateOffsetOpcode(Opcode);
519      AddrMode = ARMII::AddrModeT2_i12;
520    }
521
522    unsigned NumBits = 0;
523    unsigned Scale = 1;
524    if (AddrMode == ARMII::AddrModeT2_i8 || AddrMode == ARMII::AddrModeT2_i12) {
525      // i8 supports only negative, and i12 supports only positive, so
526      // based on Offset sign convert Opcode to the appropriate
527      // instruction
528      Offset += MI.getOperand(FrameRegIdx+1).getImm();
529      if (Offset < 0) {
530        NewOpc = negativeOffsetOpcode(Opcode);
531        NumBits = 8;
532        isSub = true;
533        Offset = -Offset;
534      } else {
535        NewOpc = positiveOffsetOpcode(Opcode);
536        NumBits = 12;
537      }
538    } else if (AddrMode == ARMII::AddrMode5) {
539      // VFP address mode.
540      const MachineOperand &OffOp = MI.getOperand(FrameRegIdx+1);
541      int InstrOffs = ARM_AM::getAM5Offset(OffOp.getImm());
542      if (ARM_AM::getAM5Op(OffOp.getImm()) == ARM_AM::sub)
543        InstrOffs *= -1;
544      NumBits = 8;
545      Scale = 4;
546      Offset += InstrOffs * 4;
547      assert((Offset & (Scale-1)) == 0 && "Can't encode this offset!");
548      if (Offset < 0) {
549        Offset = -Offset;
550        isSub = true;
551      }
552    } else if (AddrMode == ARMII::AddrModeT2_i8s4) {
553      Offset += MI.getOperand(FrameRegIdx + 1).getImm() * 4;
554      NumBits = 8;
555      // MCInst operand has already scaled value.
556      Scale = 1;
557      if (Offset < 0) {
558        isSub = true;
559        Offset = -Offset;
560      }
561    } else {
562      llvm_unreachable("Unsupported addressing mode!");
563    }
564
565    if (NewOpc != Opcode)
566      MI.setDesc(TII.get(NewOpc));
567
568    MachineOperand &ImmOp = MI.getOperand(FrameRegIdx+1);
569
570    // Attempt to fold address computation
571    // Common case: small offset, fits into instruction.
572    int ImmedOffset = Offset / Scale;
573    unsigned Mask = (1 << NumBits) - 1;
574    if ((unsigned)Offset <= Mask * Scale) {
575      // Replace the FrameIndex with fp/sp
576      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
577      if (isSub) {
578        if (AddrMode == ARMII::AddrMode5)
579          // FIXME: Not consistent.
580          ImmedOffset |= 1 << NumBits;
581        else
582          ImmedOffset = -ImmedOffset;
583      }
584      ImmOp.ChangeToImmediate(ImmedOffset);
585      Offset = 0;
586      return true;
587    }
588
589    // Otherwise, offset doesn't fit. Pull in what we can to simplify
590    ImmedOffset = ImmedOffset & Mask;
591    if (isSub) {
592      if (AddrMode == ARMII::AddrMode5)
593        // FIXME: Not consistent.
594        ImmedOffset |= 1 << NumBits;
595      else {
596        ImmedOffset = -ImmedOffset;
597        if (ImmedOffset == 0)
598          // Change the opcode back if the encoded offset is zero.
599          MI.setDesc(TII.get(positiveOffsetOpcode(NewOpc)));
600      }
601    }
602    ImmOp.ChangeToImmediate(ImmedOffset);
603    Offset &= ~(Mask*Scale);
604  }
605
606  Offset = (isSub) ? -Offset : Offset;
607  return Offset == 0;
608}
609
610ARMCC::CondCodes
611llvm::getITInstrPredicate(const MachineInstr *MI, unsigned &PredReg) {
612  unsigned Opc = MI->getOpcode();
613  if (Opc == ARM::tBcc || Opc == ARM::t2Bcc)
614    return ARMCC::AL;
615  return getInstrPredicate(MI, PredReg);
616}
617