Thumb1RegisterInfo.cpp revision 8884148b8e8f19d5484e735618cf188cfa02c626 
1//===- Thumb1RegisterInfo.cpp - Thumb-1 Register Information ----*- C++ -*-===//
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-1 implementation of the TargetRegisterInfo
11// class.
12//
13//===----------------------------------------------------------------------===//
14
15#include "ARM.h"
16#include "ARMBaseInstrInfo.h"
17#include "ARMMachineFunctionInfo.h"
18#include "ARMSubtarget.h"
19#include "Thumb1InstrInfo.h"
20#include "Thumb1RegisterInfo.h"
21#include "MCTargetDesc/ARMAddressingModes.h"
22#include "llvm/Constants.h"
23#include "llvm/DerivedTypes.h"
24#include "llvm/Function.h"
25#include "llvm/LLVMContext.h"
26#include "llvm/CodeGen/MachineConstantPool.h"
27#include "llvm/CodeGen/MachineFrameInfo.h"
28#include "llvm/CodeGen/MachineFunction.h"
29#include "llvm/CodeGen/MachineInstrBuilder.h"
30#include "llvm/CodeGen/MachineRegisterInfo.h"
31#include "llvm/Target/TargetFrameLowering.h"
32#include "llvm/Target/TargetMachine.h"
33#include "llvm/Support/CommandLine.h"
34#include "llvm/Support/ErrorHandling.h"
35#include "llvm/Support/raw_ostream.h"
36
37namespace llvm {
38extern cl::opt<bool> ReuseFrameIndexVals;
39}
40
41using namespace llvm;
42
43Thumb1RegisterInfo::Thumb1RegisterInfo(const ARMBaseInstrInfo &tii,
44                                       const ARMSubtarget &sti)
45  : ARMBaseRegisterInfo(tii, sti) {
46}
47
48const TargetRegisterClass*
49Thumb1RegisterInfo::getLargestLegalSuperClass(const TargetRegisterClass *RC)
50                                                                         const {
51  if (ARM::tGPRRegClass.hasSubClassEq(RC))
52    return ARM::tGPRRegisterClass;
53  return ARMBaseRegisterInfo::getLargestLegalSuperClass(RC);
54}
55
56const TargetRegisterClass *
57Thumb1RegisterInfo::getPointerRegClass(unsigned Kind) const {
58  return ARM::tGPRRegisterClass;
59}
60
61/// emitLoadConstPool - Emits a load from constpool to materialize the
62/// specified immediate.
63void
64Thumb1RegisterInfo::emitLoadConstPool(MachineBasicBlock &MBB,
65                                      MachineBasicBlock::iterator &MBBI,
66                                      DebugLoc dl,
67                                      unsigned DestReg, unsigned SubIdx,
68                                      int Val,
69                                      ARMCC::CondCodes Pred, unsigned PredReg,
70                                      unsigned MIFlags) const {
71  MachineFunction &MF = *MBB.getParent();
72  MachineConstantPool *ConstantPool = MF.getConstantPool();
73  const Constant *C = ConstantInt::get(
74          Type::getInt32Ty(MBB.getParent()->getFunction()->getContext()), Val);
75  unsigned Idx = ConstantPool->getConstantPoolIndex(C, 4);
76
77  BuildMI(MBB, MBBI, dl, TII.get(ARM::tLDRpci))
78    .addReg(DestReg, getDefRegState(true), SubIdx)
79    .addConstantPoolIndex(Idx).addImm(Pred).addReg(PredReg)
80    .setMIFlags(MIFlags);
81}
82
83
84/// emitThumbRegPlusImmInReg - Emits a series of instructions to materialize
85/// a destreg = basereg + immediate in Thumb code. Materialize the immediate
86/// in a register using mov / mvn sequences or load the immediate from a
87/// constpool entry.
88static
89void emitThumbRegPlusImmInReg(MachineBasicBlock &MBB,
90                              MachineBasicBlock::iterator &MBBI,
91                              DebugLoc dl,
92                              unsigned DestReg, unsigned BaseReg,
93                              int NumBytes, bool CanChangeCC,
94                              const TargetInstrInfo &TII,
95                              const ARMBaseRegisterInfo& MRI,
96                              unsigned MIFlags = MachineInstr::NoFlags) {
97    MachineFunction &MF = *MBB.getParent();
98    bool isHigh = !isARMLowRegister(DestReg) ||
99                  (BaseReg != 0 && !isARMLowRegister(BaseReg));
100    bool isSub = false;
101    // Subtract doesn't have high register version. Load the negative value
102    // if either base or dest register is a high register. Also, if do not
103    // issue sub as part of the sequence if condition register is to be
104    // preserved.
105    if (NumBytes < 0 && !isHigh && CanChangeCC) {
106      isSub = true;
107      NumBytes = -NumBytes;
108    }
109    unsigned LdReg = DestReg;
110    if (DestReg == ARM::SP) {
111      assert(BaseReg == ARM::SP && "Unexpected!");
112      LdReg = MF.getRegInfo().createVirtualRegister(ARM::tGPRRegisterClass);
113    }
114
115    if (NumBytes <= 255 && NumBytes >= 0)
116      AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVi8), LdReg))
117        .addImm(NumBytes).setMIFlags(MIFlags);
118    else if (NumBytes < 0 && NumBytes >= -255) {
119      AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVi8), LdReg))
120        .addImm(NumBytes).setMIFlags(MIFlags);
121      AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII.get(ARM::tRSB), LdReg))
122        .addReg(LdReg, RegState::Kill).setMIFlags(MIFlags);
123    } else
124      MRI.emitLoadConstPool(MBB, MBBI, dl, LdReg, 0, NumBytes,
125                            ARMCC::AL, 0, MIFlags);
126
127    // Emit add / sub.
128    int Opc = (isSub) ? ARM::tSUBrr : (isHigh ? ARM::tADDhirr : ARM::tADDrr);
129    MachineInstrBuilder MIB =
130      BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg);
131    if (Opc != ARM::tADDhirr)
132      MIB = AddDefaultT1CC(MIB);
133    if (DestReg == ARM::SP || isSub)
134      MIB.addReg(BaseReg).addReg(LdReg, RegState::Kill);
135    else
136      MIB.addReg(LdReg).addReg(BaseReg, RegState::Kill);
137    AddDefaultPred(MIB);
138}
139
140/// calcNumMI - Returns the number of instructions required to materialize
141/// the specific add / sub r, c instruction.
142static unsigned calcNumMI(int Opc, int ExtraOpc, unsigned Bytes,
143                          unsigned NumBits, unsigned Scale) {
144  unsigned NumMIs = 0;
145  unsigned Chunk = ((1 << NumBits) - 1) * Scale;
146
147  if (Opc == ARM::tADDrSPi) {
148    unsigned ThisVal = (Bytes > Chunk) ? Chunk : Bytes;
149    Bytes -= ThisVal;
150    NumMIs++;
151    NumBits = 8;
152    Scale = 1;  // Followed by a number of tADDi8.
153    Chunk = ((1 << NumBits) - 1) * Scale;
154  }
155
156  NumMIs += Bytes / Chunk;
157  if ((Bytes % Chunk) != 0)
158    NumMIs++;
159  if (ExtraOpc)
160    NumMIs++;
161  return NumMIs;
162}
163
164/// emitThumbRegPlusImmediate - Emits a series of instructions to materialize
165/// a destreg = basereg + immediate in Thumb code.
166void llvm::emitThumbRegPlusImmediate(MachineBasicBlock &MBB,
167                                     MachineBasicBlock::iterator &MBBI,
168                                     DebugLoc dl,
169                                     unsigned DestReg, unsigned BaseReg,
170                                     int NumBytes, const TargetInstrInfo &TII,
171                                     const ARMBaseRegisterInfo& MRI,
172                                     unsigned MIFlags) {
173  bool isSub = NumBytes < 0;
174  unsigned Bytes = (unsigned)NumBytes;
175  if (isSub) Bytes = -NumBytes;
176  bool isMul4 = (Bytes & 3) == 0;
177  bool isTwoAddr = false;
178  bool DstNotEqBase = false;
179  unsigned NumBits = 1;
180  unsigned Scale = 1;
181  int Opc = 0;
182  int ExtraOpc = 0;
183  bool NeedCC = false;
184  bool NeedPred = false;
185
186  if (DestReg == BaseReg && BaseReg == ARM::SP) {
187    assert(isMul4 && "Thumb sp inc / dec size must be multiple of 4!");
188    NumBits = 7;
189    Scale = 4;
190    Opc = isSub ? ARM::tSUBspi : ARM::tADDspi;
191    isTwoAddr = true;
192  } else if (!isSub && BaseReg == ARM::SP) {
193    // r1 = add sp, 403
194    // =>
195    // r1 = add sp, 100 * 4
196    // r1 = add r1, 3
197    if (!isMul4) {
198      Bytes &= ~3;
199      ExtraOpc = ARM::tADDi3;
200    }
201    NumBits = 8;
202    Scale = 4;
203    Opc = ARM::tADDrSPi;
204  } else {
205    // sp = sub sp, c
206    // r1 = sub sp, c
207    // r8 = sub sp, c
208    if (DestReg != BaseReg)
209      DstNotEqBase = true;
210    NumBits = 8;
211    if (DestReg == ARM::SP) {
212      Opc = isSub ? ARM::tSUBspi : ARM::tADDspi;
213      assert(isMul4 && "Thumb sp inc / dec size must be multiple of 4!");
214      NumBits = 7;
215      Scale = 4;
216    } else {
217      Opc = isSub ? ARM::tSUBi8 : ARM::tADDi8;
218      NumBits = 8;
219      NeedPred = NeedCC = true;
220    }
221    isTwoAddr = true;
222  }
223
224  unsigned NumMIs = calcNumMI(Opc, ExtraOpc, Bytes, NumBits, Scale);
225  unsigned Threshold = (DestReg == ARM::SP) ? 3 : 2;
226  if (NumMIs > Threshold) {
227    // This will expand into too many instructions. Load the immediate from a
228    // constpool entry.
229    emitThumbRegPlusImmInReg(MBB, MBBI, dl,
230                             DestReg, BaseReg, NumBytes, true,
231                             TII, MRI, MIFlags);
232    return;
233  }
234
235  if (DstNotEqBase) {
236    if (isARMLowRegister(DestReg) && isARMLowRegister(BaseReg)) {
237      // If both are low registers, emit DestReg = add BaseReg, max(Imm, 7)
238      unsigned Chunk = (1 << 3) - 1;
239      unsigned ThisVal = (Bytes > Chunk) ? Chunk : Bytes;
240      Bytes -= ThisVal;
241      const MCInstrDesc &MCID = TII.get(isSub ? ARM::tSUBi3 : ARM::tADDi3);
242      const MachineInstrBuilder MIB =
243        AddDefaultT1CC(BuildMI(MBB, MBBI, dl, MCID, DestReg).setMIFlags(MIFlags));
244      AddDefaultPred(MIB.addReg(BaseReg, RegState::Kill).addImm(ThisVal));
245    } else {
246      AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVr), DestReg)
247        .addReg(BaseReg, RegState::Kill))
248        .setMIFlags(MIFlags);
249    }
250    BaseReg = DestReg;
251  }
252
253  unsigned Chunk = ((1 << NumBits) - 1) * Scale;
254  while (Bytes) {
255    unsigned ThisVal = (Bytes > Chunk) ? Chunk : Bytes;
256    Bytes -= ThisVal;
257    ThisVal /= Scale;
258    // Build the new tADD / tSUB.
259    if (isTwoAddr) {
260      MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg);
261      if (NeedCC)
262        MIB = AddDefaultT1CC(MIB);
263      MIB.addReg(DestReg).addImm(ThisVal);
264      if (NeedPred)
265        MIB = AddDefaultPred(MIB);
266      MIB.setMIFlags(MIFlags);
267    } else {
268      bool isKill = BaseReg != ARM::SP;
269      MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(Opc), DestReg);
270      if (NeedCC)
271        MIB = AddDefaultT1CC(MIB);
272      MIB.addReg(BaseReg, getKillRegState(isKill)).addImm(ThisVal);
273      if (NeedPred)
274        MIB = AddDefaultPred(MIB);
275      MIB.setMIFlags(MIFlags);
276
277      BaseReg = DestReg;
278      if (Opc == ARM::tADDrSPi) {
279        // r4 = add sp, imm
280        // r4 = add r4, imm
281        // ...
282        NumBits = 8;
283        Scale = 1;
284        Chunk = ((1 << NumBits) - 1) * Scale;
285        Opc = isSub ? ARM::tSUBi8 : ARM::tADDi8;
286        NeedPred = NeedCC = isTwoAddr = true;
287      }
288    }
289  }
290
291  if (ExtraOpc) {
292    const MCInstrDesc &MCID = TII.get(ExtraOpc);
293    AddDefaultPred(AddDefaultT1CC(BuildMI(MBB, MBBI, dl, MCID, DestReg))
294                   .addReg(DestReg, RegState::Kill)
295                   .addImm(((unsigned)NumBytes) & 3)
296                   .setMIFlags(MIFlags));
297  }
298}
299
300static void emitSPUpdate(MachineBasicBlock &MBB,
301                         MachineBasicBlock::iterator &MBBI,
302                         const TargetInstrInfo &TII, DebugLoc dl,
303                         const Thumb1RegisterInfo &MRI,
304                         int NumBytes) {
305  emitThumbRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes, TII,
306                            MRI);
307}
308
309void Thumb1RegisterInfo::
310eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
311                              MachineBasicBlock::iterator I) const {
312  const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering();
313
314  if (!TFI->hasReservedCallFrame(MF)) {
315    // If we have alloca, convert as follows:
316    // ADJCALLSTACKDOWN -> sub, sp, sp, amount
317    // ADJCALLSTACKUP   -> add, sp, sp, amount
318    MachineInstr *Old = I;
319    DebugLoc dl = Old->getDebugLoc();
320    unsigned Amount = Old->getOperand(0).getImm();
321    if (Amount != 0) {
322      // We need to keep the stack aligned properly.  To do this, we round the
323      // amount of space needed for the outgoing arguments up to the next
324      // alignment boundary.
325      unsigned Align = TFI->getStackAlignment();
326      Amount = (Amount+Align-1)/Align*Align;
327
328      // Replace the pseudo instruction with a new instruction...
329      unsigned Opc = Old->getOpcode();
330      if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) {
331        emitSPUpdate(MBB, I, TII, dl, *this, -Amount);
332      } else {
333        assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP);
334        emitSPUpdate(MBB, I, TII, dl, *this, Amount);
335      }
336    }
337  }
338  MBB.erase(I);
339}
340
341/// emitThumbConstant - Emit a series of instructions to materialize a
342/// constant.
343static void emitThumbConstant(MachineBasicBlock &MBB,
344                              MachineBasicBlock::iterator &MBBI,
345                              unsigned DestReg, int Imm,
346                              const TargetInstrInfo &TII,
347                              const Thumb1RegisterInfo& MRI,
348                              DebugLoc dl) {
349  bool isSub = Imm < 0;
350  if (isSub) Imm = -Imm;
351
352  int Chunk = (1 << 8) - 1;
353  int ThisVal = (Imm > Chunk) ? Chunk : Imm;
354  Imm -= ThisVal;
355  AddDefaultPred(AddDefaultT1CC(BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVi8),
356                                        DestReg))
357                 .addImm(ThisVal));
358  if (Imm > 0)
359    emitThumbRegPlusImmediate(MBB, MBBI, dl, DestReg, DestReg, Imm, TII, MRI);
360  if (isSub) {
361    const MCInstrDesc &MCID = TII.get(ARM::tRSB);
362    AddDefaultPred(AddDefaultT1CC(BuildMI(MBB, MBBI, dl, MCID, DestReg))
363                   .addReg(DestReg, RegState::Kill));
364  }
365}
366
367static void removeOperands(MachineInstr &MI, unsigned i) {
368  unsigned Op = i;
369  for (unsigned e = MI.getNumOperands(); i != e; ++i)
370    MI.RemoveOperand(Op);
371}
372
373/// convertToNonSPOpcode - Change the opcode to the non-SP version, because
374/// we're replacing the frame index with a non-SP register.
375static unsigned convertToNonSPOpcode(unsigned Opcode) {
376  switch (Opcode) {
377  case ARM::tLDRspi:
378    return ARM::tLDRi;
379
380  case ARM::tSTRspi:
381    return ARM::tSTRi;
382  }
383
384  return Opcode;
385}
386
387bool Thumb1RegisterInfo::
388rewriteFrameIndex(MachineBasicBlock::iterator II, unsigned FrameRegIdx,
389                  unsigned FrameReg, int &Offset,
390                  const ARMBaseInstrInfo &TII) const {
391  MachineInstr &MI = *II;
392  MachineBasicBlock &MBB = *MI.getParent();
393  DebugLoc dl = MI.getDebugLoc();
394  unsigned Opcode = MI.getOpcode();
395  const MCInstrDesc &Desc = MI.getDesc();
396  unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
397
398  if (Opcode == ARM::tADDrSPi) {
399    Offset += MI.getOperand(FrameRegIdx+1).getImm();
400
401    // Can't use tADDrSPi if it's based off the frame pointer.
402    unsigned NumBits = 0;
403    unsigned Scale = 1;
404    if (FrameReg != ARM::SP) {
405      Opcode = ARM::tADDi3;
406      MI.setDesc(TII.get(Opcode));
407      NumBits = 3;
408    } else {
409      NumBits = 8;
410      Scale = 4;
411      assert((Offset & 3) == 0 &&
412             "Thumb add/sub sp, #imm immediate must be multiple of 4!");
413    }
414
415    unsigned PredReg;
416    if (Offset == 0 && getInstrPredicate(&MI, PredReg) == ARMCC::AL) {
417      // Turn it into a move.
418      MI.setDesc(TII.get(ARM::tMOVr));
419      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
420      // Remove offset and add predicate operands.
421      MI.RemoveOperand(FrameRegIdx+1);
422      MachineInstrBuilder MIB(&MI);
423      AddDefaultPred(MIB);
424      return true;
425    }
426
427    // Common case: small offset, fits into instruction.
428    unsigned Mask = (1 << NumBits) - 1;
429    if (((Offset / Scale) & ~Mask) == 0) {
430      // Replace the FrameIndex with sp / fp
431      if (Opcode == ARM::tADDi3) {
432        removeOperands(MI, FrameRegIdx);
433        MachineInstrBuilder MIB(&MI);
434        AddDefaultPred(AddDefaultT1CC(MIB).addReg(FrameReg)
435                       .addImm(Offset / Scale));
436      } else {
437        MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
438        MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Offset / Scale);
439      }
440      return true;
441    }
442
443    unsigned DestReg = MI.getOperand(0).getReg();
444    unsigned Bytes = (Offset > 0) ? Offset : -Offset;
445    unsigned NumMIs = calcNumMI(Opcode, 0, Bytes, NumBits, Scale);
446    // MI would expand into a large number of instructions. Don't try to
447    // simplify the immediate.
448    if (NumMIs > 2) {
449      emitThumbRegPlusImmediate(MBB, II, dl, DestReg, FrameReg, Offset, TII,
450                                *this);
451      MBB.erase(II);
452      return true;
453    }
454
455    if (Offset > 0) {
456      // Translate r0 = add sp, imm to
457      // r0 = add sp, 255*4
458      // r0 = add r0, (imm - 255*4)
459      if (Opcode == ARM::tADDi3) {
460        removeOperands(MI, FrameRegIdx);
461        MachineInstrBuilder MIB(&MI);
462        AddDefaultPred(AddDefaultT1CC(MIB).addReg(FrameReg).addImm(Mask));
463      } else {
464        MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
465        MI.getOperand(FrameRegIdx+1).ChangeToImmediate(Mask);
466      }
467      Offset = (Offset - Mask * Scale);
468      MachineBasicBlock::iterator NII = llvm::next(II);
469      emitThumbRegPlusImmediate(MBB, NII, dl, DestReg, DestReg, Offset, TII,
470                                *this);
471    } else {
472      // Translate r0 = add sp, -imm to
473      // r0 = -imm (this is then translated into a series of instructons)
474      // r0 = add r0, sp
475      emitThumbConstant(MBB, II, DestReg, Offset, TII, *this, dl);
476
477      MI.setDesc(TII.get(ARM::tADDhirr));
478      MI.getOperand(FrameRegIdx).ChangeToRegister(DestReg, false, false, true);
479      MI.getOperand(FrameRegIdx+1).ChangeToRegister(FrameReg, false);
480      if (Opcode == ARM::tADDi3) {
481        MachineInstrBuilder MIB(&MI);
482        AddDefaultPred(MIB);
483      }
484    }
485    return true;
486  } else {
487    if (AddrMode != ARMII::AddrModeT1_s)
488      llvm_unreachable("Unsupported addressing mode!");
489
490    unsigned ImmIdx = FrameRegIdx + 1;
491    int InstrOffs = MI.getOperand(ImmIdx).getImm();
492    unsigned NumBits = (FrameReg == ARM::SP) ? 8 : 5;
493    unsigned Scale = 4;
494
495    Offset += InstrOffs * Scale;
496    assert((Offset & (Scale - 1)) == 0 && "Can't encode this offset!");
497
498    // Common case: small offset, fits into instruction.
499    MachineOperand &ImmOp = MI.getOperand(ImmIdx);
500    int ImmedOffset = Offset / Scale;
501    unsigned Mask = (1 << NumBits) - 1;
502
503    if ((unsigned)Offset <= Mask * Scale) {
504      // Replace the FrameIndex with the frame register (e.g., sp).
505      MI.getOperand(FrameRegIdx).ChangeToRegister(FrameReg, false);
506      ImmOp.ChangeToImmediate(ImmedOffset);
507
508      // If we're using a register where sp was stored, convert the instruction
509      // to the non-SP version.
510      unsigned NewOpc = convertToNonSPOpcode(Opcode);
511      if (NewOpc != Opcode && FrameReg != ARM::SP)
512        MI.setDesc(TII.get(NewOpc));
513
514      return true;
515    }
516
517    NumBits = 5;
518    Mask = (1 << NumBits) - 1;
519
520    // If this is a thumb spill / restore, we will be using a constpool load to
521    // materialize the offset.
522    if (Opcode == ARM::tLDRspi || Opcode == ARM::tSTRspi) {
523      ImmOp.ChangeToImmediate(0);
524    } else {
525      // Otherwise, it didn't fit. Pull in what we can to simplify the immed.
526      ImmedOffset = ImmedOffset & Mask;
527      ImmOp.ChangeToImmediate(ImmedOffset);
528      Offset &= ~(Mask * Scale);
529    }
530  }
531
532  return Offset == 0;
533}
534
535void
536Thumb1RegisterInfo::resolveFrameIndex(MachineBasicBlock::iterator I,
537                                      unsigned BaseReg, int64_t Offset) const {
538  MachineInstr &MI = *I;
539  int Off = Offset; // ARM doesn't need the general 64-bit offsets
540  unsigned i = 0;
541
542  while (!MI.getOperand(i).isFI()) {
543    ++i;
544    assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
545  }
546  bool Done = rewriteFrameIndex(MI, i, BaseReg, Off, TII);
547  assert (Done && "Unable to resolve frame index!");
548  (void)Done;
549}
550
551/// saveScavengerRegister - Spill the register so it can be used by the
552/// register scavenger. Return true.
553bool
554Thumb1RegisterInfo::saveScavengerRegister(MachineBasicBlock &MBB,
555                                          MachineBasicBlock::iterator I,
556                                          MachineBasicBlock::iterator &UseMI,
557                                          const TargetRegisterClass *RC,
558                                          unsigned Reg) const {
559  // Thumb1 can't use the emergency spill slot on the stack because
560  // ldr/str immediate offsets must be positive, and if we're referencing
561  // off the frame pointer (if, for example, there are alloca() calls in
562  // the function, the offset will be negative. Use R12 instead since that's
563  // a call clobbered register that we know won't be used in Thumb1 mode.
564  DebugLoc DL;
565  AddDefaultPred(BuildMI(MBB, I, DL, TII.get(ARM::tMOVr))
566    .addReg(ARM::R12, RegState::Define)
567    .addReg(Reg, RegState::Kill));
568
569  // The UseMI is where we would like to restore the register. If there's
570  // interference with R12 before then, however, we'll need to restore it
571  // before that instead and adjust the UseMI.
572  bool done = false;
573  for (MachineBasicBlock::iterator II = I; !done && II != UseMI ; ++II) {
574    if (II->isDebugValue())
575      continue;
576    // If this instruction affects R12, adjust our restore point.
577    for (unsigned i = 0, e = II->getNumOperands(); i != e; ++i) {
578      const MachineOperand &MO = II->getOperand(i);
579      if (!MO.isReg() || MO.isUndef() || !MO.getReg() ||
580          TargetRegisterInfo::isVirtualRegister(MO.getReg()))
581        continue;
582      if (MO.getReg() == ARM::R12) {
583        UseMI = II;
584        done = true;
585        break;
586      }
587    }
588  }
589  // Restore the register from R12
590  AddDefaultPred(BuildMI(MBB, UseMI, DL, TII.get(ARM::tMOVr)).
591    addReg(Reg, RegState::Define).addReg(ARM::R12, RegState::Kill));
592
593  return true;
594}
595
596void
597Thumb1RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
598                                        int SPAdj, RegScavenger *RS) const {
599  unsigned VReg = 0;
600  unsigned i = 0;
601  MachineInstr &MI = *II;
602  MachineBasicBlock &MBB = *MI.getParent();
603  MachineFunction &MF = *MBB.getParent();
604  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
605  DebugLoc dl = MI.getDebugLoc();
606
607  while (!MI.getOperand(i).isFI()) {
608    ++i;
609    assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
610  }
611
612  unsigned FrameReg = ARM::SP;
613  int FrameIndex = MI.getOperand(i).getIndex();
614  int Offset = MF.getFrameInfo()->getObjectOffset(FrameIndex) +
615               MF.getFrameInfo()->getStackSize() + SPAdj;
616
617  if (AFI->isGPRCalleeSavedArea1Frame(FrameIndex))
618    Offset -= AFI->getGPRCalleeSavedArea1Offset();
619  else if (AFI->isGPRCalleeSavedArea2Frame(FrameIndex))
620    Offset -= AFI->getGPRCalleeSavedArea2Offset();
621  else if (MF.getFrameInfo()->hasVarSizedObjects()) {
622    assert(SPAdj == 0 && MF.getTarget().getFrameLowering()->hasFP(MF) &&
623           "Unexpected");
624    // There are alloca()'s in this function, must reference off the frame
625    // pointer or base pointer instead.
626    if (!hasBasePointer(MF)) {
627      FrameReg = getFrameRegister(MF);
628      Offset -= AFI->getFramePtrSpillOffset();
629    } else
630      FrameReg = BasePtr;
631  }
632
633  // Special handling of dbg_value instructions.
634  if (MI.isDebugValue()) {
635    MI.getOperand(i).  ChangeToRegister(FrameReg, false /*isDef*/);
636    MI.getOperand(i+1).ChangeToImmediate(Offset);
637    return;
638  }
639
640  // Modify MI as necessary to handle as much of 'Offset' as possible
641  assert(AFI->isThumbFunction() &&
642         "This eliminateFrameIndex only supports Thumb1!");
643  if (rewriteFrameIndex(MI, i, FrameReg, Offset, TII))
644    return;
645
646  // If we get here, the immediate doesn't fit into the instruction.  We folded
647  // as much as possible above, handle the rest, providing a register that is
648  // SP+LargeImm.
649  assert(Offset && "This code isn't needed if offset already handled!");
650
651  unsigned Opcode = MI.getOpcode();
652  const MCInstrDesc &Desc = MI.getDesc();
653
654  // Remove predicate first.
655  int PIdx = MI.findFirstPredOperandIdx();
656  if (PIdx != -1)
657    removeOperands(MI, PIdx);
658
659  if (Desc.mayLoad()) {
660    // Use the destination register to materialize sp + offset.
661    unsigned TmpReg = MI.getOperand(0).getReg();
662    bool UseRR = false;
663    if (Opcode == ARM::tLDRspi) {
664      if (FrameReg == ARM::SP)
665        emitThumbRegPlusImmInReg(MBB, II, dl, TmpReg, FrameReg,
666                                 Offset, false, TII, *this);
667      else {
668        emitLoadConstPool(MBB, II, dl, TmpReg, 0, Offset);
669        UseRR = true;
670      }
671    } else {
672      emitThumbRegPlusImmediate(MBB, II, dl, TmpReg, FrameReg, Offset, TII,
673                                *this);
674    }
675
676    MI.setDesc(TII.get(UseRR ? ARM::tLDRr : ARM::tLDRi));
677    MI.getOperand(i).ChangeToRegister(TmpReg, false, false, true);
678    if (UseRR)
679      // Use [reg, reg] addrmode. Replace the immediate operand w/ the frame
680      // register. The offset is already handled in the vreg value.
681      MI.getOperand(i+1).ChangeToRegister(FrameReg, false, false, false);
682  } else if (Desc.mayStore()) {
683      VReg = MF.getRegInfo().createVirtualRegister(ARM::tGPRRegisterClass);
684      bool UseRR = false;
685
686      if (Opcode == ARM::tSTRspi) {
687        if (FrameReg == ARM::SP)
688          emitThumbRegPlusImmInReg(MBB, II, dl, VReg, FrameReg,
689                                   Offset, false, TII, *this);
690        else {
691          emitLoadConstPool(MBB, II, dl, VReg, 0, Offset);
692          UseRR = true;
693        }
694      } else
695        emitThumbRegPlusImmediate(MBB, II, dl, VReg, FrameReg, Offset, TII,
696                                  *this);
697      MI.setDesc(TII.get(UseRR ? ARM::tSTRr : ARM::tSTRi));
698      MI.getOperand(i).ChangeToRegister(VReg, false, false, true);
699      if (UseRR)
700        // Use [reg, reg] addrmode. Replace the immediate operand w/ the frame
701        // register. The offset is already handled in the vreg value.
702        MI.getOperand(i+1).ChangeToRegister(FrameReg, false, false, false);
703  } else {
704    assert(false && "Unexpected opcode!");
705  }
706
707  // Add predicate back if it's needed.
708  if (MI.getDesc().isPredicable()) {
709    MachineInstrBuilder MIB(&MI);
710    AddDefaultPred(MIB);
711  }
712}
713