ARMBaseRegisterInfo.cpp   [plain text]

//===- ARMBaseRegisterInfo.cpp - ARM Register Information -------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the base ARM implementation of TargetRegisterInfo class.
//
//===----------------------------------------------------------------------===//

#include "ARM.h"
#include "ARMAddressingModes.h"
#include "ARMBaseInstrInfo.h"
#include "ARMBaseRegisterInfo.h"
#include "ARMInstrInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "ARMSubtarget.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/LLVMContext.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineLocation.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetFrameInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/CommandLine.h"

namespace llvm {
static cl::opt<bool>
ForceAllBaseRegAlloc("arm-force-base-reg-alloc", cl::Hidden, cl::init(false),
          cl::desc("Force use of virtual base registers for stack load/store"));
static cl::opt<bool>
EnableLocalStackAlloc("enable-local-stack-alloc", cl::init(true), cl::Hidden,
          cl::desc("Enable pre-regalloc stack frame index allocation"));
}

using namespace llvm;

static cl::opt<bool>
EnableBasePointer("arm-use-base-pointer", cl::Hidden, cl::init(true),
          cl::desc("Enable use of a base pointer for complex stack frames"));


ARMBaseRegisterInfo::ARMBaseRegisterInfo(const ARMBaseInstrInfo &tii,
                                         const ARMSubtarget &sti)
  : ARMGenRegisterInfo(ARM::ADJCALLSTACKDOWN, ARM::ADJCALLSTACKUP),
    TII(tii), STI(sti),
    FramePtr((STI.isTargetDarwin() || STI.isThumb()) ? ARM::R7 : ARM::R11),
    BasePtr(ARM::R6) {
}

const unsigned*
ARMBaseRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
  static const unsigned CalleeSavedRegs[] = {
    ARM::LR, ARM::R11, ARM::R10, ARM::R9, ARM::R8,
    ARM::R7, ARM::R6,  ARM::R5,  ARM::R4,

    ARM::D15, ARM::D14, ARM::D13, ARM::D12,
    ARM::D11, ARM::D10, ARM::D9,  ARM::D8,
    0
  };

  static const unsigned DarwinCalleeSavedRegs[] = {
    // Darwin ABI deviates from ARM standard ABI. R9 is not a callee-saved
    // register.
    ARM::LR,  ARM::R7,  ARM::R6, ARM::R5, ARM::R4,
    ARM::R11, ARM::R10, ARM::R8,

    ARM::D15, ARM::D14, ARM::D13, ARM::D12,
    ARM::D11, ARM::D10, ARM::D9,  ARM::D8,
    0
  };
  return STI.isTargetDarwin() ? DarwinCalleeSavedRegs : CalleeSavedRegs;
}

BitVector ARMBaseRegisterInfo::
getReservedRegs(const MachineFunction &MF) const {
  // FIXME: avoid re-calculating this everytime.
  BitVector Reserved(getNumRegs());
  Reserved.set(ARM::SP);
  Reserved.set(ARM::PC);
  Reserved.set(ARM::FPSCR);
  if (hasFP(MF))
    Reserved.set(FramePtr);
  if (hasBasePointer(MF))
    Reserved.set(BasePtr);
  // Some targets reserve R9.
  if (STI.isR9Reserved())
    Reserved.set(ARM::R9);
  return Reserved;
}

bool ARMBaseRegisterInfo::isReservedReg(const MachineFunction &MF,
                                        unsigned Reg) const {
  switch (Reg) {
  default: break;
  case ARM::SP:
  case ARM::PC:
    return true;
  case ARM::R6:
    if (hasBasePointer(MF))
      return true;
    break;
  case ARM::R7:
  case ARM::R11:
    if (FramePtr == Reg && hasFP(MF))
      return true;
    break;
  case ARM::R9:
    return STI.isR9Reserved();
  }

  return false;
}

const TargetRegisterClass *
ARMBaseRegisterInfo::getMatchingSuperRegClass(const TargetRegisterClass *A,
                                              const TargetRegisterClass *B,
                                              unsigned SubIdx) const {
  switch (SubIdx) {
  default: return 0;
  case ARM::ssub_0:
  case ARM::ssub_1:
  case ARM::ssub_2:
  case ARM::ssub_3: {
    // S sub-registers.
    if (A->getSize() == 8) {
      if (B == &ARM::SPR_8RegClass)
        return &ARM::DPR_8RegClass;
      assert(B == &ARM::SPRRegClass && "Expecting SPR register class!");
      if (A == &ARM::DPR_8RegClass)
        return A;
      return &ARM::DPR_VFP2RegClass;
    }

    if (A->getSize() == 16) {
      if (B == &ARM::SPR_8RegClass)
        return &ARM::QPR_8RegClass;
      return &ARM::QPR_VFP2RegClass;
    }

    if (A->getSize() == 32) {
      if (B == &ARM::SPR_8RegClass)
        return 0;  // Do not allow coalescing!
      return &ARM::QQPR_VFP2RegClass;
    }

    assert(A->getSize() == 64 && "Expecting a QQQQ register class!");
    return 0;  // Do not allow coalescing!
  }
  case ARM::dsub_0:
  case ARM::dsub_1:
  case ARM::dsub_2:
  case ARM::dsub_3: {
    // D sub-registers.
    if (A->getSize() == 16) {
      if (B == &ARM::DPR_VFP2RegClass)
        return &ARM::QPR_VFP2RegClass;
      if (B == &ARM::DPR_8RegClass)
        return 0;  // Do not allow coalescing!
      return A;
    }

    if (A->getSize() == 32) {
      if (B == &ARM::DPR_VFP2RegClass)
        return &ARM::QQPR_VFP2RegClass;
      if (B == &ARM::DPR_8RegClass)
        return 0;  // Do not allow coalescing!
      return A;
    }

    assert(A->getSize() == 64 && "Expecting a QQQQ register class!");
    if (B != &ARM::DPRRegClass)
      return 0;  // Do not allow coalescing!
    return A;
  }
  case ARM::dsub_4:
  case ARM::dsub_5:
  case ARM::dsub_6:
  case ARM::dsub_7: {
    // D sub-registers of QQQQ registers.
    if (A->getSize() == 64 && B == &ARM::DPRRegClass)
      return A;
    return 0;  // Do not allow coalescing!
  }

  case ARM::qsub_0:
  case ARM::qsub_1: {
    // Q sub-registers.
    if (A->getSize() == 32) {
      if (B == &ARM::QPR_VFP2RegClass)
        return &ARM::QQPR_VFP2RegClass;
      if (B == &ARM::QPR_8RegClass)
        return 0;  // Do not allow coalescing!
      return A;
    }

    assert(A->getSize() == 64 && "Expecting a QQQQ register class!");
    if (B == &ARM::QPRRegClass)
      return A;
    return 0;  // Do not allow coalescing!
  }
  case ARM::qsub_2:
  case ARM::qsub_3: {
    // Q sub-registers of QQQQ registers.
    if (A->getSize() == 64 && B == &ARM::QPRRegClass)
      return A;
    return 0;  // Do not allow coalescing!
  }
  }
  return 0;
}

bool
ARMBaseRegisterInfo::canCombineSubRegIndices(const TargetRegisterClass *RC,
                                          SmallVectorImpl<unsigned> &SubIndices,
                                          unsigned &NewSubIdx) const {

  unsigned Size = RC->getSize() * 8;
  if (Size < 6)
    return 0;

  NewSubIdx = 0;  // Whole register.
  unsigned NumRegs = SubIndices.size();
  if (NumRegs == 8) {
    // 8 D registers -> 1 QQQQ register.
    return (Size == 512 &&
            SubIndices[0] == ARM::dsub_0 &&
            SubIndices[1] == ARM::dsub_1 &&
            SubIndices[2] == ARM::dsub_2 &&
            SubIndices[3] == ARM::dsub_3 &&
            SubIndices[4] == ARM::dsub_4 &&
            SubIndices[5] == ARM::dsub_5 &&
            SubIndices[6] == ARM::dsub_6 &&
            SubIndices[7] == ARM::dsub_7);
  } else if (NumRegs == 4) {
    if (SubIndices[0] == ARM::qsub_0) {
      // 4 Q registers -> 1 QQQQ register.
      return (Size == 512 &&
              SubIndices[1] == ARM::qsub_1 &&
              SubIndices[2] == ARM::qsub_2 &&
              SubIndices[3] == ARM::qsub_3);
    } else if (SubIndices[0] == ARM::dsub_0) {
      // 4 D registers -> 1 QQ register.
      if (Size >= 256 &&
          SubIndices[1] == ARM::dsub_1 &&
          SubIndices[2] == ARM::dsub_2 &&
          SubIndices[3] == ARM::dsub_3) {
        if (Size == 512)
          NewSubIdx = ARM::qqsub_0;
        return true;
      }
    } else if (SubIndices[0] == ARM::dsub_4) {
      // 4 D registers -> 1 QQ register (2nd).
      if (Size == 512 &&
          SubIndices[1] == ARM::dsub_5 &&
          SubIndices[2] == ARM::dsub_6 &&
          SubIndices[3] == ARM::dsub_7) {
        NewSubIdx = ARM::qqsub_1;
        return true;
      }
    } else if (SubIndices[0] == ARM::ssub_0) {
      // 4 S registers -> 1 Q register.
      if (Size >= 128 &&
          SubIndices[1] == ARM::ssub_1 &&
          SubIndices[2] == ARM::ssub_2 &&
          SubIndices[3] == ARM::ssub_3) {
        if (Size >= 256)
          NewSubIdx = ARM::qsub_0;
        return true;
      }
    }
  } else if (NumRegs == 2) {
    if (SubIndices[0] == ARM::qsub_0) {
      // 2 Q registers -> 1 QQ register.
      if (Size >= 256 && SubIndices[1] == ARM::qsub_1) {
        if (Size == 512)
          NewSubIdx = ARM::qqsub_0;
        return true;
      }
    } else if (SubIndices[0] == ARM::qsub_2) {
      // 2 Q registers -> 1 QQ register (2nd).
      if (Size == 512 && SubIndices[1] == ARM::qsub_3) {
        NewSubIdx = ARM::qqsub_1;
        return true;
      }
    } else if (SubIndices[0] == ARM::dsub_0) {
      // 2 D registers -> 1 Q register.
      if (Size >= 128 && SubIndices[1] == ARM::dsub_1) {
        if (Size >= 256)
          NewSubIdx = ARM::qsub_0;
        return true;
      }
    } else if (SubIndices[0] == ARM::dsub_2) {
      // 2 D registers -> 1 Q register (2nd).
      if (Size >= 256 && SubIndices[1] == ARM::dsub_3) {
        NewSubIdx = ARM::qsub_1;
        return true;
      }
    } else if (SubIndices[0] == ARM::dsub_4) {
      // 2 D registers -> 1 Q register (3rd).
      if (Size == 512 && SubIndices[1] == ARM::dsub_5) {
        NewSubIdx = ARM::qsub_2;
        return true;
      }
    } else if (SubIndices[0] == ARM::dsub_6) {
      // 2 D registers -> 1 Q register (3rd).
      if (Size == 512 && SubIndices[1] == ARM::dsub_7) {
        NewSubIdx = ARM::qsub_3;
        return true;
      }
    } else if (SubIndices[0] == ARM::ssub_0) {
      // 2 S registers -> 1 D register.
      if (SubIndices[1] == ARM::ssub_1) {
        if (Size >= 128)
          NewSubIdx = ARM::dsub_0;
        return true;
      }
    } else if (SubIndices[0] == ARM::ssub_2) {
      // 2 S registers -> 1 D register (2nd).
      if (Size >= 128 && SubIndices[1] == ARM::ssub_3) {
        NewSubIdx = ARM::dsub_1;
        return true;
      }
    }
  }
  return false;
}


const TargetRegisterClass *
ARMBaseRegisterInfo::getPointerRegClass(unsigned Kind) const {
  return ARM::GPRRegisterClass;
}

/// getAllocationOrder - Returns the register allocation order for a specified
/// register class in the form of a pair of TargetRegisterClass iterators.
std::pair<TargetRegisterClass::iterator,TargetRegisterClass::iterator>
ARMBaseRegisterInfo::getAllocationOrder(const TargetRegisterClass *RC,
                                        unsigned HintType, unsigned HintReg,
                                        const MachineFunction &MF) const {
  // Alternative register allocation orders when favoring even / odd registers
  // of register pairs.

  // No FP, R9 is available.
  static const unsigned GPREven1[] = {
    ARM::R0, ARM::R2, ARM::R4, ARM::R6, ARM::R8, ARM::R10,
    ARM::R1, ARM::R3, ARM::R12,ARM::LR, ARM::R5, ARM::R7,
    ARM::R9, ARM::R11
  };
  static const unsigned GPROdd1[] = {
    ARM::R1, ARM::R3, ARM::R5, ARM::R7, ARM::R9, ARM::R11,
    ARM::R0, ARM::R2, ARM::R12,ARM::LR, ARM::R4, ARM::R6,
    ARM::R8, ARM::R10
  };

  // FP is R7, R9 is available.
  static const unsigned GPREven2[] = {
    ARM::R0, ARM::R2, ARM::R4,          ARM::R8, ARM::R10,
    ARM::R1, ARM::R3, ARM::R12,ARM::LR, ARM::R5, ARM::R6,
    ARM::R9, ARM::R11
  };
  static const unsigned GPROdd2[] = {
    ARM::R1, ARM::R3, ARM::R5,          ARM::R9, ARM::R11,
    ARM::R0, ARM::R2, ARM::R12,ARM::LR, ARM::R4, ARM::R6,
    ARM::R8, ARM::R10
  };

  // FP is R11, R9 is available.
  static const unsigned GPREven3[] = {
    ARM::R0, ARM::R2, ARM::R4, ARM::R6, ARM::R8,
    ARM::R1, ARM::R3, ARM::R10,ARM::R12,ARM::LR, ARM::R5, ARM::R7,
    ARM::R9
  };
  static const unsigned GPROdd3[] = {
    ARM::R1, ARM::R3, ARM::R5, ARM::R6, ARM::R9,
    ARM::R0, ARM::R2, ARM::R10,ARM::R12,ARM::LR, ARM::R4, ARM::R7,
    ARM::R8
  };

  // No FP, R9 is not available.
  static const unsigned GPREven4[] = {
    ARM::R0, ARM::R2, ARM::R4, ARM::R6,          ARM::R10,
    ARM::R1, ARM::R3, ARM::R12,ARM::LR, ARM::R5, ARM::R7, ARM::R8,
    ARM::R11
  };
  static const unsigned GPROdd4[] = {
    ARM::R1, ARM::R3, ARM::R5, ARM::R7,          ARM::R11,
    ARM::R0, ARM::R2, ARM::R12,ARM::LR, ARM::R4, ARM::R6, ARM::R8,
    ARM::R10
  };

  // FP is R7, R9 is not available.
  static const unsigned GPREven5[] = {
    ARM::R0, ARM::R2, ARM::R4,                   ARM::R10,
    ARM::R1, ARM::R3, ARM::R12,ARM::LR, ARM::R5, ARM::R6, ARM::R8,
    ARM::R11
  };
  static const unsigned GPROdd5[] = {
    ARM::R1, ARM::R3, ARM::R5,                   ARM::R11,
    ARM::R0, ARM::R2, ARM::R12,ARM::LR, ARM::R4, ARM::R6, ARM::R8,
    ARM::R10
  };

  // FP is R11, R9 is not available.
  static const unsigned GPREven6[] = {
    ARM::R0, ARM::R2, ARM::R4, ARM::R6,
    ARM::R1, ARM::R3, ARM::R10,ARM::R12,ARM::LR, ARM::R5, ARM::R7, ARM::R8
  };
  static const unsigned GPROdd6[] = {
    ARM::R1, ARM::R3, ARM::R5, ARM::R7,
    ARM::R0, ARM::R2, ARM::R10,ARM::R12,ARM::LR, ARM::R4, ARM::R6, ARM::R8
  };


  if (HintType == ARMRI::RegPairEven) {
    if (isPhysicalRegister(HintReg) && getRegisterPairEven(HintReg, MF) == 0)
      // It's no longer possible to fulfill this hint. Return the default
      // allocation order.
      return std::make_pair(RC->allocation_order_begin(MF),
                            RC->allocation_order_end(MF));

    if (!hasFP(MF)) {
      if (!STI.isR9Reserved())
        return std::make_pair(GPREven1,
                              GPREven1 + (sizeof(GPREven1)/sizeof(unsigned)));
      else
        return std::make_pair(GPREven4,
                              GPREven4 + (sizeof(GPREven4)/sizeof(unsigned)));
    } else if (FramePtr == ARM::R7) {
      if (!STI.isR9Reserved())
        return std::make_pair(GPREven2,
                              GPREven2 + (sizeof(GPREven2)/sizeof(unsigned)));
      else
        return std::make_pair(GPREven5,
                              GPREven5 + (sizeof(GPREven5)/sizeof(unsigned)));
    } else { // FramePtr == ARM::R11
      if (!STI.isR9Reserved())
        return std::make_pair(GPREven3,
                              GPREven3 + (sizeof(GPREven3)/sizeof(unsigned)));
      else
        return std::make_pair(GPREven6,
                              GPREven6 + (sizeof(GPREven6)/sizeof(unsigned)));
    }
  } else if (HintType == ARMRI::RegPairOdd) {
    if (isPhysicalRegister(HintReg) && getRegisterPairOdd(HintReg, MF) == 0)
      // It's no longer possible to fulfill this hint. Return the default
      // allocation order.
      return std::make_pair(RC->allocation_order_begin(MF),
                            RC->allocation_order_end(MF));

    if (!hasFP(MF)) {
      if (!STI.isR9Reserved())
        return std::make_pair(GPROdd1,
                              GPROdd1 + (sizeof(GPROdd1)/sizeof(unsigned)));
      else
        return std::make_pair(GPROdd4,
                              GPROdd4 + (sizeof(GPROdd4)/sizeof(unsigned)));
    } else if (FramePtr == ARM::R7) {
      if (!STI.isR9Reserved())
        return std::make_pair(GPROdd2,
                              GPROdd2 + (sizeof(GPROdd2)/sizeof(unsigned)));
      else
        return std::make_pair(GPROdd5,
                              GPROdd5 + (sizeof(GPROdd5)/sizeof(unsigned)));
    } else { // FramePtr == ARM::R11
      if (!STI.isR9Reserved())
        return std::make_pair(GPROdd3,
                              GPROdd3 + (sizeof(GPROdd3)/sizeof(unsigned)));
      else
        return std::make_pair(GPROdd6,
                              GPROdd6 + (sizeof(GPROdd6)/sizeof(unsigned)));
    }
  }
  return std::make_pair(RC->allocation_order_begin(MF),
                        RC->allocation_order_end(MF));
}

/// ResolveRegAllocHint - Resolves the specified register allocation hint
/// to a physical register. Returns the physical register if it is successful.
unsigned
ARMBaseRegisterInfo::ResolveRegAllocHint(unsigned Type, unsigned Reg,
                                         const MachineFunction &MF) const {
  if (Reg == 0 || !isPhysicalRegister(Reg))
    return 0;
  if (Type == 0)
    return Reg;
  else if (Type == (unsigned)ARMRI::RegPairOdd)
    // Odd register.
    return getRegisterPairOdd(Reg, MF);
  else if (Type == (unsigned)ARMRI::RegPairEven)
    // Even register.
    return getRegisterPairEven(Reg, MF);
  return 0;
}

void
ARMBaseRegisterInfo::UpdateRegAllocHint(unsigned Reg, unsigned NewReg,
                                        MachineFunction &MF) const {
  MachineRegisterInfo *MRI = &MF.getRegInfo();
  std::pair<unsigned, unsigned> Hint = MRI->getRegAllocationHint(Reg);
  if ((Hint.first == (unsigned)ARMRI::RegPairOdd ||
       Hint.first == (unsigned)ARMRI::RegPairEven) &&
      Hint.second && TargetRegisterInfo::isVirtualRegister(Hint.second)) {
    // If 'Reg' is one of the even / odd register pair and it's now changed
    // (e.g. coalesced) into a different register. The other register of the
    // pair allocation hint must be updated to reflect the relationship
    // change.
    unsigned OtherReg = Hint.second;
    Hint = MRI->getRegAllocationHint(OtherReg);
    if (Hint.second == Reg)
      // Make sure the pair has not already divorced.
      MRI->setRegAllocationHint(OtherReg, Hint.first, NewReg);
  }
}

/// hasFP - Return true if the specified function should have a dedicated frame
/// pointer register.  This is true if the function has variable sized allocas
/// or if frame pointer elimination is disabled.
///
bool ARMBaseRegisterInfo::hasFP(const MachineFunction &MF) const {
  // Mac OS X requires FP not to be clobbered for backtracing purpose.
  if (STI.isTargetDarwin())
    return true;

  const MachineFrameInfo *MFI = MF.getFrameInfo();
  // Always eliminate non-leaf frame pointers.
  return ((DisableFramePointerElim(MF) && MFI->hasCalls()) ||
          needsStackRealignment(MF) ||
          MFI->hasVarSizedObjects() ||
          MFI->isFrameAddressTaken());
}

bool ARMBaseRegisterInfo::hasBasePointer(const MachineFunction &MF) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();

  if (!EnableBasePointer)
    return false;

  if (needsStackRealignment(MF) && MFI->hasVarSizedObjects())
    return true;

  // Thumb has trouble with negative offsets from the FP. Thumb2 has a limited
  // negative range for ldr/str (255), and thumb1 is positive offsets only.
  // It's going to be better to use the SP or Base Pointer instead. When there
  // are variable sized objects, we can't reference off of the SP, so we
  // reserve a Base Pointer.
  if (AFI->isThumbFunction() && MFI->hasVarSizedObjects()) {
    // Conservatively estimate whether the negative offset from the frame
    // pointer will be sufficient to reach. If a function has a smallish
    // frame, it's less likely to have lots of spills and callee saved
    // space, so it's all more likely to be within range of the frame pointer.
    // If it's wrong, the scavenger will still enable access to work, it just
    // won't be optimal.
    if (AFI->isThumb2Function() && MFI->getLocalFrameSize() < 128)
      return false;
    return true;
  }

  return false;
}

bool ARMBaseRegisterInfo::canRealignStack(const MachineFunction &MF) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  // We can't realign the stack if:
  // 1. Dynamic stack realignment is explicitly disabled,
  // 2. This is a Thumb1 function (it's not useful, so we don't bother), or
  // 3. There are VLAs in the function and the base pointer is disabled.
  return (RealignStack && !AFI->isThumb1OnlyFunction() &&
          (!MFI->hasVarSizedObjects() || EnableBasePointer));
}

bool ARMBaseRegisterInfo::
needsStackRealignment(const MachineFunction &MF) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  const Function *F = MF.getFunction();
  unsigned StackAlign = MF.getTarget().getFrameInfo()->getStackAlignment();
  bool requiresRealignment = ((MFI->getLocalFrameMaxAlign() > StackAlign) ||
                               F->hasFnAttr(Attribute::StackAlignment));

  return requiresRealignment && canRealignStack(MF);
}

bool ARMBaseRegisterInfo::
cannotEliminateFrame(const MachineFunction &MF) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  if (DisableFramePointerElim(MF) && MFI->adjustsStack())
    return true;
  return MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken()
    || needsStackRealignment(MF);
}

/// estimateStackSize - Estimate and return the size of the frame.
static unsigned estimateStackSize(MachineFunction &MF) {
  const MachineFrameInfo *FFI = MF.getFrameInfo();
  int Offset = 0;
  for (int i = FFI->getObjectIndexBegin(); i != 0; ++i) {
    int FixedOff = -FFI->getObjectOffset(i);
    if (FixedOff > Offset) Offset = FixedOff;
  }
  for (unsigned i = 0, e = FFI->getObjectIndexEnd(); i != e; ++i) {
    if (FFI->isDeadObjectIndex(i))
      continue;
    Offset += FFI->getObjectSize(i);
    unsigned Align = FFI->getObjectAlignment(i);
    // Adjust to alignment boundary
    Offset = (Offset+Align-1)/Align*Align;
  }
  return (unsigned)Offset;
}

/// estimateRSStackSizeLimit - Look at each instruction that references stack
/// frames and return the stack size limit beyond which some of these
/// instructions will require a scratch register during their expansion later.
unsigned
ARMBaseRegisterInfo::estimateRSStackSizeLimit(MachineFunction &MF) const {
  const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  unsigned Limit = (1 << 12) - 1;
  for (MachineFunction::iterator BB = MF.begin(),E = MF.end(); BB != E; ++BB) {
    for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
         I != E; ++I) {
      for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
        if (!I->getOperand(i).isFI()) continue;

        // When using ADDri to get the address of a stack object, 255 is the
        // largest offset guaranteed to fit in the immediate offset.
        if (I->getOpcode() == ARM::ADDri) {
          Limit = std::min(Limit, (1U << 8) - 1);
          break;
        }

        // Otherwise check the addressing mode.
        switch (I->getDesc().TSFlags & ARMII::AddrModeMask) {
        case ARMII::AddrMode3:
        case ARMII::AddrModeT2_i8:
          Limit = std::min(Limit, (1U << 8) - 1);
          break;
        case ARMII::AddrMode5:
        case ARMII::AddrModeT2_i8s4:
          Limit = std::min(Limit, ((1U << 8) - 1) * 4);
          break;
        case ARMII::AddrModeT2_i12:
          // i12 supports only positive offset so these will be converted to
          // i8 opcodes. See llvm::rewriteT2FrameIndex.
          if (hasFP(MF) && AFI->hasStackFrame())
            Limit = std::min(Limit, (1U << 8) - 1);
          break;
        case ARMII::AddrMode4:
        case ARMII::AddrMode6:
          // Addressing modes 4 & 6 (load/store) instructions can't encode an
          // immediate offset for stack references.
          return 0;
        default:
          break;
        }
        break; // At most one FI per instruction
      }
    }
  }

  return Limit;
}

static unsigned GetFunctionSizeInBytes(const MachineFunction &MF,
                                       const ARMBaseInstrInfo &TII) {
  unsigned FnSize = 0;
  for (MachineFunction::const_iterator MBBI = MF.begin(), E = MF.end();
       MBBI != E; ++MBBI) {
    const MachineBasicBlock &MBB = *MBBI;
    for (MachineBasicBlock::const_iterator I = MBB.begin(),E = MBB.end();
         I != E; ++I)
      FnSize += TII.GetInstSizeInBytes(I);
  }
  return FnSize;
}

void
ARMBaseRegisterInfo::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                                       RegScavenger *RS) const {
  // This tells PEI to spill the FP as if it is any other callee-save register
  // to take advantage the eliminateFrameIndex machinery. This also ensures it
  // is spilled in the order specified by getCalleeSavedRegs() to make it easier
  // to combine multiple loads / stores.
  bool CanEliminateFrame = true;
  bool CS1Spilled = false;
  bool LRSpilled = false;
  unsigned NumGPRSpills = 0;
  SmallVector<unsigned, 4> UnspilledCS1GPRs;
  SmallVector<unsigned, 4> UnspilledCS2GPRs;
  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  MachineFrameInfo *MFI = MF.getFrameInfo();

  // Spill R4 if Thumb2 function requires stack realignment - it will be used as
  // scratch register. Also spill R4 if Thumb2 function has varsized objects,
  // since it's not always possible to restore sp from fp in a single
  // instruction.
  // FIXME: It will be better just to find spare register here.
  if (AFI->isThumb2Function() &&
      (MFI->hasVarSizedObjects() || needsStackRealignment(MF)))
    MF.getRegInfo().setPhysRegUsed(ARM::R4);

  // Spill LR if Thumb1 function uses variable length argument lists.
  if (AFI->isThumb1OnlyFunction() && AFI->getVarArgsRegSaveSize() > 0)
    MF.getRegInfo().setPhysRegUsed(ARM::LR);

  // Spill the BasePtr if it's used.
  if (hasBasePointer(MF))
    MF.getRegInfo().setPhysRegUsed(BasePtr);

  // Don't spill FP if the frame can be eliminated. This is determined
  // by scanning the callee-save registers to see if any is used.
  const unsigned *CSRegs = getCalleeSavedRegs();
  for (unsigned i = 0; CSRegs[i]; ++i) {
    unsigned Reg = CSRegs[i];
    bool Spilled = false;
    if (MF.getRegInfo().isPhysRegUsed(Reg)) {
      AFI->setCSRegisterIsSpilled(Reg);
      Spilled = true;
      CanEliminateFrame = false;
    } else {
      // Check alias registers too.
      for (const unsigned *Aliases = getAliasSet(Reg); *Aliases; ++Aliases) {
        if (MF.getRegInfo().isPhysRegUsed(*Aliases)) {
          Spilled = true;
          CanEliminateFrame = false;
        }
      }
    }

    if (!ARM::GPRRegisterClass->contains(Reg))
      continue;

    if (Spilled) {
      NumGPRSpills++;

      if (!STI.isTargetDarwin()) {
        if (Reg == ARM::LR)
          LRSpilled = true;
        CS1Spilled = true;
        continue;
      }

      // Keep track if LR and any of R4, R5, R6, and R7 is spilled.
      switch (Reg) {
      case ARM::LR:
        LRSpilled = true;
        // Fallthrough
      case ARM::R4:
      case ARM::R5:
      case ARM::R6:
      case ARM::R7:
        CS1Spilled = true;
        break;
      default:
        break;
      }
    } else {
      if (!STI.isTargetDarwin()) {
        UnspilledCS1GPRs.push_back(Reg);
        continue;
      }

      switch (Reg) {
      case ARM::R4:
      case ARM::R5:
      case ARM::R6:
      case ARM::R7:
      case ARM::LR:
        UnspilledCS1GPRs.push_back(Reg);
        break;
      default:
        UnspilledCS2GPRs.push_back(Reg);
        break;
      }
    }
  }

  bool ForceLRSpill = false;
  if (!LRSpilled && AFI->isThumb1OnlyFunction()) {
    unsigned FnSize = GetFunctionSizeInBytes(MF, TII);
    // Force LR to be spilled if the Thumb function size is > 2048. This enables
    // use of BL to implement far jump. If it turns out that it's not needed
    // then the branch fix up path will undo it.
    if (FnSize >= (1 << 11)) {
      CanEliminateFrame = false;
      ForceLRSpill = true;
    }
  }

  // If any of the stack slot references may be out of range of an immediate
  // offset, make sure a register (or a spill slot) is available for the
  // register scavenger. Note that if we're indexing off the frame pointer, the
  // effective stack size is 4 bytes larger since the FP points to the stack
  // slot of the previous FP. Also, if we have variable sized objects in the
  // function, stack slot references will often be negative, and some of
  // our instructions are positive-offset only, so conservatively consider
  // that case to want a spill slot (or register) as well. Similarly, if
  // the function adjusts the stack pointer during execution and the
  // adjustments aren't already part of our stack size estimate, our offset
  // calculations may be off, so be conservative.
  // FIXME: We could add logic to be more precise about negative offsets
  //        and which instructions will need a scratch register for them. Is it
  //        worth the effort and added fragility?
  bool BigStack =
    (RS &&
     (estimateStackSize(MF) + ((hasFP(MF) && AFI->hasStackFrame()) ? 4:0) >=
      estimateRSStackSizeLimit(MF)))
    || MFI->hasVarSizedObjects()
    || (MFI->adjustsStack() && !canSimplifyCallFramePseudos(MF));

  bool ExtraCSSpill = false;
  if (BigStack || !CanEliminateFrame || cannotEliminateFrame(MF)) {
    AFI->setHasStackFrame(true);

    // If LR is not spilled, but at least one of R4, R5, R6, and R7 is spilled.
    // Spill LR as well so we can fold BX_RET to the registers restore (LDM).
    if (!LRSpilled && CS1Spilled) {
      MF.getRegInfo().setPhysRegUsed(ARM::LR);
      AFI->setCSRegisterIsSpilled(ARM::LR);
      NumGPRSpills++;
      UnspilledCS1GPRs.erase(std::find(UnspilledCS1GPRs.begin(),
                                    UnspilledCS1GPRs.end(), (unsigned)ARM::LR));
      ForceLRSpill = false;
      ExtraCSSpill = true;
    }

    if (hasFP(MF)) {
      MF.getRegInfo().setPhysRegUsed(FramePtr);
      NumGPRSpills++;
    }

    // If stack and double are 8-byte aligned and we are spilling an odd number
    // of GPRs, spill one extra callee save GPR so we won't have to pad between
    // the integer and double callee save areas.
    unsigned TargetAlign = MF.getTarget().getFrameInfo()->getStackAlignment();
    if (TargetAlign == 8 && (NumGPRSpills & 1)) {
      if (CS1Spilled && !UnspilledCS1GPRs.empty()) {
        for (unsigned i = 0, e = UnspilledCS1GPRs.size(); i != e; ++i) {
          unsigned Reg = UnspilledCS1GPRs[i];
          // Don't spill high register if the function is thumb1
          if (!AFI->isThumb1OnlyFunction() ||
              isARMLowRegister(Reg) || Reg == ARM::LR) {
            MF.getRegInfo().setPhysRegUsed(Reg);
            AFI->setCSRegisterIsSpilled(Reg);
            if (!isReservedReg(MF, Reg))
              ExtraCSSpill = true;
            break;
          }
        }
      } else if (!UnspilledCS2GPRs.empty() &&
                 !AFI->isThumb1OnlyFunction()) {
        unsigned Reg = UnspilledCS2GPRs.front();
        MF.getRegInfo().setPhysRegUsed(Reg);
        AFI->setCSRegisterIsSpilled(Reg);
        if (!isReservedReg(MF, Reg))
          ExtraCSSpill = true;
      }
    }

    // Estimate if we might need to scavenge a register at some point in order
    // to materialize a stack offset. If so, either spill one additional
    // callee-saved register or reserve a special spill slot to facilitate
    // register scavenging. Thumb1 needs a spill slot for stack pointer
    // adjustments also, even when the frame itself is small.
    if (BigStack && !ExtraCSSpill) {
      // If any non-reserved CS register isn't spilled, just spill one or two
      // extra. That should take care of it!
      unsigned NumExtras = TargetAlign / 4;
      SmallVector<unsigned, 2> Extras;
      while (NumExtras && !UnspilledCS1GPRs.empty()) {
        unsigned Reg = UnspilledCS1GPRs.back();
        UnspilledCS1GPRs.pop_back();
        if (!isReservedReg(MF, Reg) &&
            (!AFI->isThumb1OnlyFunction() || isARMLowRegister(Reg) ||
             Reg == ARM::LR)) {
          Extras.push_back(Reg);
          NumExtras--;
        }
      }
      // For non-Thumb1 functions, also check for hi-reg CS registers
      if (!AFI->isThumb1OnlyFunction()) {
        while (NumExtras && !UnspilledCS2GPRs.empty()) {
          unsigned Reg = UnspilledCS2GPRs.back();
          UnspilledCS2GPRs.pop_back();
          if (!isReservedReg(MF, Reg)) {
            Extras.push_back(Reg);
            NumExtras--;
          }
        }
      }
      if (Extras.size() && NumExtras == 0) {
        for (unsigned i = 0, e = Extras.size(); i != e; ++i) {
          MF.getRegInfo().setPhysRegUsed(Extras[i]);
          AFI->setCSRegisterIsSpilled(Extras[i]);
        }
      } else if (!AFI->isThumb1OnlyFunction()) {
        // note: Thumb1 functions spill to R12, not the stack.  Reserve a slot
        // closest to SP or frame pointer.
        const TargetRegisterClass *RC = ARM::GPRRegisterClass;
        RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
                                                           RC->getAlignment(),
                                                           false));
      }
    }
  }

  if (ForceLRSpill) {
    MF.getRegInfo().setPhysRegUsed(ARM::LR);
    AFI->setCSRegisterIsSpilled(ARM::LR);
    AFI->setLRIsSpilledForFarJump(true);
  }
}

unsigned ARMBaseRegisterInfo::getRARegister() const {
  return ARM::LR;
}

unsigned
ARMBaseRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
  if (hasFP(MF))
    return FramePtr;
  return ARM::SP;
}

// Provide a base+offset reference to an FI slot for debug info. It's the
// same as what we use for resolving the code-gen references for now.
// FIXME: This can go wrong when references are SP-relative and simple call
//        frames aren't used.
int
ARMBaseRegisterInfo::getFrameIndexReference(const MachineFunction &MF, int FI,
                                            unsigned &FrameReg) const {
  return ResolveFrameIndexReference(MF, FI, FrameReg, 0);
}

int
ARMBaseRegisterInfo::ResolveFrameIndexReference(const MachineFunction &MF,
                                                int FI,
                                                unsigned &FrameReg,
                                                int SPAdj) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  const ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  int Offset = MFI->getObjectOffset(FI) + MFI->getStackSize();
  int FPOffset = Offset - AFI->getFramePtrSpillOffset();
  bool isFixed = MFI->isFixedObjectIndex(FI);

  FrameReg = ARM::SP;
  Offset += SPAdj;
  if (AFI->isGPRCalleeSavedArea1Frame(FI))
    return Offset - AFI->getGPRCalleeSavedArea1Offset();
  else if (AFI->isGPRCalleeSavedArea2Frame(FI))
    return Offset - AFI->getGPRCalleeSavedArea2Offset();
  else if (AFI->isDPRCalleeSavedAreaFrame(FI))
    return Offset - AFI->getDPRCalleeSavedAreaOffset();

  // When dynamically realigning the stack, use the frame pointer for
  // parameters, and the stack/base pointer for locals.
  if (needsStackRealignment(MF)) {
    assert (hasFP(MF) && "dynamic stack realignment without a FP!");
    if (isFixed) {
      FrameReg = getFrameRegister(MF);
      Offset = FPOffset;
    } else if (MFI->hasVarSizedObjects()) {
      assert(hasBasePointer(MF) &&
             "VLAs and dynamic stack alignment, but missing base pointer!");
      FrameReg = BasePtr;
    }
    return Offset;
  }

  // If there is a frame pointer, use it when we can.
  if (hasFP(MF) && AFI->hasStackFrame()) {
    // Use frame pointer to reference fixed objects. Use it for locals if
    // there are VLAs (and thus the SP isn't reliable as a base).
    if (isFixed || (MFI->hasVarSizedObjects() && !hasBasePointer(MF))) {
      FrameReg = getFrameRegister(MF);
      return FPOffset;
    } else if (MFI->hasVarSizedObjects()) {
      assert(hasBasePointer(MF) && "missing base pointer!");
      // Try to use the frame pointer if we can, else use the base pointer
      // since it's available. This is handy for the emergency spill slot, in
      // particular.
      if (AFI->isThumb2Function()) {
        if (FPOffset >= -255 && FPOffset < 0) {
          FrameReg = getFrameRegister(MF);
          return FPOffset;
        }
      } else
        FrameReg = BasePtr;
    } else if (AFI->isThumb2Function()) {
      // In Thumb2 mode, the negative offset is very limited. Try to avoid
      // out of range references.
      if (FPOffset >= -255 && FPOffset < 0) {
        FrameReg = getFrameRegister(MF);
        return FPOffset;
      }
    } else if (Offset > (FPOffset < 0 ? -FPOffset : FPOffset)) {
      // Otherwise, use SP or FP, whichever is closer to the stack slot.
      FrameReg = getFrameRegister(MF);
      return FPOffset;
    }
  }
  // Use the base pointer if we have one.
  if (hasBasePointer(MF))
    FrameReg = BasePtr;
  return Offset;
}

int
ARMBaseRegisterInfo::getFrameIndexOffset(const MachineFunction &MF,
                                         int FI) const {
  unsigned FrameReg;
  return getFrameIndexReference(MF, FI, FrameReg);
}

unsigned ARMBaseRegisterInfo::getEHExceptionRegister() const {
  llvm_unreachable("What is the exception register");
  return 0;
}

unsigned ARMBaseRegisterInfo::getEHHandlerRegister() const {
  llvm_unreachable("What is the exception handler register");
  return 0;
}

int ARMBaseRegisterInfo::getDwarfRegNum(unsigned RegNum, bool isEH) const {
  return ARMGenRegisterInfo::getDwarfRegNumFull(RegNum, 0);
}

unsigned ARMBaseRegisterInfo::getRegisterPairEven(unsigned Reg,
                                              const MachineFunction &MF) const {
  switch (Reg) {
  default: break;
  // Return 0 if either register of the pair is a special register.
  // So no R12, etc.
  case ARM::R1:
    return ARM::R0;
  case ARM::R3:
    return ARM::R2;
  case ARM::R5:
    return ARM::R4;
  case ARM::R7:
    return (isReservedReg(MF, ARM::R7) || isReservedReg(MF, ARM::R6))
      ? 0 : ARM::R6;
  case ARM::R9:
    return isReservedReg(MF, ARM::R9)  ? 0 :ARM::R8;
  case ARM::R11:
    return isReservedReg(MF, ARM::R11) ? 0 : ARM::R10;

  case ARM::S1:
    return ARM::S0;
  case ARM::S3:
    return ARM::S2;
  case ARM::S5:
    return ARM::S4;
  case ARM::S7:
    return ARM::S6;
  case ARM::S9:
    return ARM::S8;
  case ARM::S11:
    return ARM::S10;
  case ARM::S13:
    return ARM::S12;
  case ARM::S15:
    return ARM::S14;
  case ARM::S17:
    return ARM::S16;
  case ARM::S19:
    return ARM::S18;
  case ARM::S21:
    return ARM::S20;
  case ARM::S23:
    return ARM::S22;
  case ARM::S25:
    return ARM::S24;
  case ARM::S27:
    return ARM::S26;
  case ARM::S29:
    return ARM::S28;
  case ARM::S31:
    return ARM::S30;

  case ARM::D1:
    return ARM::D0;
  case ARM::D3:
    return ARM::D2;
  case ARM::D5:
    return ARM::D4;
  case ARM::D7:
    return ARM::D6;
  case ARM::D9:
    return ARM::D8;
  case ARM::D11:
    return ARM::D10;
  case ARM::D13:
    return ARM::D12;
  case ARM::D15:
    return ARM::D14;
  case ARM::D17:
    return ARM::D16;
  case ARM::D19:
    return ARM::D18;
  case ARM::D21:
    return ARM::D20;
  case ARM::D23:
    return ARM::D22;
  case ARM::D25:
    return ARM::D24;
  case ARM::D27:
    return ARM::D26;
  case ARM::D29:
    return ARM::D28;
  case ARM::D31:
    return ARM::D30;
  }

  return 0;
}

unsigned ARMBaseRegisterInfo::getRegisterPairOdd(unsigned Reg,
                                             const MachineFunction &MF) const {
  switch (Reg) {
  default: break;
  // Return 0 if either register of the pair is a special register.
  // So no R12, etc.
  case ARM::R0:
    return ARM::R1;
  case ARM::R2:
    return ARM::R3;
  case ARM::R4:
    return ARM::R5;
  case ARM::R6:
    return (isReservedReg(MF, ARM::R7) || isReservedReg(MF, ARM::R6))
      ? 0 : ARM::R7;
  case ARM::R8:
    return isReservedReg(MF, ARM::R9)  ? 0 :ARM::R9;
  case ARM::R10:
    return isReservedReg(MF, ARM::R11) ? 0 : ARM::R11;

  case ARM::S0:
    return ARM::S1;
  case ARM::S2:
    return ARM::S3;
  case ARM::S4:
    return ARM::S5;
  case ARM::S6:
    return ARM::S7;
  case ARM::S8:
    return ARM::S9;
  case ARM::S10:
    return ARM::S11;
  case ARM::S12:
    return ARM::S13;
  case ARM::S14:
    return ARM::S15;
  case ARM::S16:
    return ARM::S17;
  case ARM::S18:
    return ARM::S19;
  case ARM::S20:
    return ARM::S21;
  case ARM::S22:
    return ARM::S23;
  case ARM::S24:
    return ARM::S25;
  case ARM::S26:
    return ARM::S27;
  case ARM::S28:
    return ARM::S29;
  case ARM::S30:
    return ARM::S31;

  case ARM::D0:
    return ARM::D1;
  case ARM::D2:
    return ARM::D3;
  case ARM::D4:
    return ARM::D5;
  case ARM::D6:
    return ARM::D7;
  case ARM::D8:
    return ARM::D9;
  case ARM::D10:
    return ARM::D11;
  case ARM::D12:
    return ARM::D13;
  case ARM::D14:
    return ARM::D15;
  case ARM::D16:
    return ARM::D17;
  case ARM::D18:
    return ARM::D19;
  case ARM::D20:
    return ARM::D21;
  case ARM::D22:
    return ARM::D23;
  case ARM::D24:
    return ARM::D25;
  case ARM::D26:
    return ARM::D27;
  case ARM::D28:
    return ARM::D29;
  case ARM::D30:
    return ARM::D31;
  }

  return 0;
}

/// emitLoadConstPool - Emits a load from constpool to materialize the
/// specified immediate.
void ARMBaseRegisterInfo::
emitLoadConstPool(MachineBasicBlock &MBB,
                  MachineBasicBlock::iterator &MBBI,
                  DebugLoc dl,
                  unsigned DestReg, unsigned SubIdx, int Val,
                  ARMCC::CondCodes Pred,
                  unsigned PredReg) const {
  MachineFunction &MF = *MBB.getParent();
  MachineConstantPool *ConstantPool = MF.getConstantPool();
  const Constant *C =
        ConstantInt::get(Type::getInt32Ty(MF.getFunction()->getContext()), Val);
  unsigned Idx = ConstantPool->getConstantPoolIndex(C, 4);

  BuildMI(MBB, MBBI, dl, TII.get(ARM::LDRcp))
    .addReg(DestReg, getDefRegState(true), SubIdx)
    .addConstantPoolIndex(Idx)
    .addImm(0).addImm(Pred).addReg(PredReg);
}

bool ARMBaseRegisterInfo::
requiresRegisterScavenging(const MachineFunction &MF) const {
  return true;
}

bool ARMBaseRegisterInfo::
requiresFrameIndexScavenging(const MachineFunction &MF) const {
  return true;
}

bool ARMBaseRegisterInfo::
requiresVirtualBaseRegisters(const MachineFunction &MF) const {
  return EnableLocalStackAlloc;
}

// hasReservedCallFrame - Under normal circumstances, when a frame pointer is
// not required, we reserve argument space for call sites in the function
// immediately on entry to the current function. This eliminates the need for
// add/sub sp brackets around call sites. Returns true if the call frame is
// included as part of the stack frame.
bool ARMBaseRegisterInfo::
hasReservedCallFrame(const MachineFunction &MF) const {
  const MachineFrameInfo *FFI = MF.getFrameInfo();
  unsigned CFSize = FFI->getMaxCallFrameSize();
  // It's not always a good idea to include the call frame as part of the
  // stack frame. ARM (especially Thumb) has small immediate offset to
  // address the stack frame. So a large call frame can cause poor codegen
  // and may even makes it impossible to scavenge a register.
  if (CFSize >= ((1 << 12) - 1) / 2)  // Half of imm12
    return false;

  return !MF.getFrameInfo()->hasVarSizedObjects();
}

// canSimplifyCallFramePseudos - If there is a reserved call frame, the
// call frame pseudos can be simplified. Unlike most targets, having a FP
// is not sufficient here since we still may reference some objects via SP
// even when FP is available in Thumb2 mode.
bool ARMBaseRegisterInfo::
canSimplifyCallFramePseudos(const MachineFunction &MF) const {
  return hasReservedCallFrame(MF) || MF.getFrameInfo()->hasVarSizedObjects();
}

static void
emitSPUpdate(bool isARM,
             MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
             DebugLoc dl, const ARMBaseInstrInfo &TII,
             int NumBytes,
             ARMCC::CondCodes Pred = ARMCC::AL, unsigned PredReg = 0) {
  if (isARM)
    emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
                            Pred, PredReg, TII);
  else
    emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::SP, ARM::SP, NumBytes,
                           Pred, PredReg, TII);
}


void ARMBaseRegisterInfo::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator I) const {
  if (!hasReservedCallFrame(MF)) {
    // If we have alloca, convert as follows:
    // ADJCALLSTACKDOWN -> sub, sp, sp, amount
    // ADJCALLSTACKUP   -> add, sp, sp, amount
    MachineInstr *Old = I;
    DebugLoc dl = Old->getDebugLoc();
    unsigned Amount = Old->getOperand(0).getImm();
    if (Amount != 0) {
      // We need to keep the stack aligned properly.  To do this, we round the
      // amount of space needed for the outgoing arguments up to the next
      // alignment boundary.
      unsigned Align = MF.getTarget().getFrameInfo()->getStackAlignment();
      Amount = (Amount+Align-1)/Align*Align;

      ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
      assert(!AFI->isThumb1OnlyFunction() &&
             "This eliminateCallFramePseudoInstr does not support Thumb1!");
      bool isARM = !AFI->isThumbFunction();

      // Replace the pseudo instruction with a new instruction...
      unsigned Opc = Old->getOpcode();
      int PIdx = Old->findFirstPredOperandIdx();
      ARMCC::CondCodes Pred = (PIdx == -1)
        ? ARMCC::AL : (ARMCC::CondCodes)Old->getOperand(PIdx).getImm();
      if (Opc == ARM::ADJCALLSTACKDOWN || Opc == ARM::tADJCALLSTACKDOWN) {
        // Note: PredReg is operand 2 for ADJCALLSTACKDOWN.
        unsigned PredReg = Old->getOperand(2).getReg();
        emitSPUpdate(isARM, MBB, I, dl, TII, -Amount, Pred, PredReg);
      } else {
        // Note: PredReg is operand 3 for ADJCALLSTACKUP.
        unsigned PredReg = Old->getOperand(3).getReg();
        assert(Opc == ARM::ADJCALLSTACKUP || Opc == ARM::tADJCALLSTACKUP);
        emitSPUpdate(isARM, MBB, I, dl, TII, Amount, Pred, PredReg);
      }
    }
  }
  MBB.erase(I);
}

int64_t ARMBaseRegisterInfo::
getFrameIndexInstrOffset(const MachineInstr *MI, int Idx) const {
  const TargetInstrDesc &Desc = MI->getDesc();
  unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
  int64_t InstrOffs = 0;;
  int Scale = 1;
  unsigned ImmIdx = 0;
  switch (AddrMode) {
  case ARMII::AddrModeT2_i8:
  case ARMII::AddrModeT2_i12:
  case ARMII::AddrMode_i12:
    InstrOffs = MI->getOperand(Idx+1).getImm();
    Scale = 1;
    break;
  case ARMII::AddrMode5: {
    // VFP address mode.
    const MachineOperand &OffOp = MI->getOperand(Idx+1);
    InstrOffs = ARM_AM::getAM5Offset(OffOp.getImm());
    if (ARM_AM::getAM5Op(OffOp.getImm()) == ARM_AM::sub)
      InstrOffs = -InstrOffs;
    Scale = 4;
    break;
  }
  case ARMII::AddrMode2: {
    ImmIdx = Idx+2;
    InstrOffs = ARM_AM::getAM2Offset(MI->getOperand(ImmIdx).getImm());
    if (ARM_AM::getAM2Op(MI->getOperand(ImmIdx).getImm()) == ARM_AM::sub)
      InstrOffs = -InstrOffs;
    break;
  }
  case ARMII::AddrMode3: {
    ImmIdx = Idx+2;
    InstrOffs = ARM_AM::getAM3Offset(MI->getOperand(ImmIdx).getImm());
    if (ARM_AM::getAM3Op(MI->getOperand(ImmIdx).getImm()) == ARM_AM::sub)
      InstrOffs = -InstrOffs;
    break;
  }
  case ARMII::AddrModeT1_s: {
    ImmIdx = Idx+1;
    InstrOffs = MI->getOperand(ImmIdx).getImm();
    Scale = 4;
    break;
  }
  default:
    llvm_unreachable("Unsupported addressing mode!");
    break;
  }

  return InstrOffs * Scale;
}

/// needsFrameBaseReg - Returns true if the instruction's frame index
/// reference would be better served by a base register other than FP
/// or SP. Used by LocalStackFrameAllocation to determine which frame index
/// references it should create new base registers for.
bool ARMBaseRegisterInfo::
needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const {
  for (unsigned i = 0; !MI->getOperand(i).isFI(); ++i) {
    assert(i < MI->getNumOperands() &&"Instr doesn't have FrameIndex operand!");
  }

  // It's the load/store FI references that cause issues, as it can be difficult
  // to materialize the offset if it won't fit in the literal field. Estimate
  // based on the size of the local frame and some conservative assumptions
  // about the rest of the stack frame (note, this is pre-regalloc, so
  // we don't know everything for certain yet) whether this offset is likely
  // to be out of range of the immediate. Return true if so.

  // We only generate virtual base registers for loads and stores, so
  // return false for everything else.
  unsigned Opc = MI->getOpcode();
  switch (Opc) {
  case ARM::LDRi12: case ARM::LDRH: case ARM::LDRBi12:
  case ARM::STRi12: case ARM::STRH: case ARM::STRBi12:
  case ARM::t2LDRi12: case ARM::t2LDRi8:
  case ARM::t2STRi12: case ARM::t2STRi8:
  case ARM::VLDRS: case ARM::VLDRD:
  case ARM::VSTRS: case ARM::VSTRD:
  case ARM::tSTRspi: case ARM::tLDRspi:
    if (ForceAllBaseRegAlloc)
      return true;
    break;
  default:
    return false;
  }

  // Without a virtual base register, if the function has variable sized
  // objects, all fixed-size local references will be via the frame pointer,
  // Approximate the offset and see if it's legal for the instruction.
  // Note that the incoming offset is based on the SP value at function entry,
  // so it'll be negative.
  MachineFunction &MF = *MI->getParent()->getParent();
  MachineFrameInfo *MFI = MF.getFrameInfo();
  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();

  // Estimate an offset from the frame pointer.
  // Conservatively assume all callee-saved registers get pushed. R4-R6
  // will be earlier than the FP, so we ignore those.
  // R7, LR
  int64_t FPOffset = Offset - 8;
  // ARM and Thumb2 functions also need to consider R8-R11 and D8-D15
  if (!AFI->isThumbFunction() || !AFI->isThumb1OnlyFunction())
    FPOffset -= 80;
  // Estimate an offset from the stack pointer.
  // The incoming offset is relating to the SP at the start of the function,
  // but when we access the local it'll be relative to the SP after local
  // allocation, so adjust our SP-relative offset by that allocation size.
  Offset = -Offset;
  Offset += MFI->getLocalFrameSize();
  // Assume that we'll have at least some spill slots allocated.
  // FIXME: This is a total SWAG number. We should run some statistics
  //        and pick a real one.
  Offset += 128; // 128 bytes of spill slots

  // If there is a frame pointer, try using it.
  // The FP is only available if there is no dynamic realignment. We
  // don't know for sure yet whether we'll need that, so we guess based
  // on whether there are any local variables that would trigger it.
  unsigned StackAlign = MF.getTarget().getFrameInfo()->getStackAlignment();
  if (hasFP(MF) &&
      !((MFI->getLocalFrameMaxAlign() > StackAlign) && canRealignStack(MF))) {
    if (isFrameOffsetLegal(MI, FPOffset))
      return false;
  }
  // If we can reference via the stack pointer, try that.
  // FIXME: This (and the code that resolves the references) can be improved
  //        to only disallow SP relative references in the live range of
  //        the VLA(s). In practice, it's unclear how much difference that
  //        would make, but it may be worth doing.
  if (!MFI->hasVarSizedObjects() && isFrameOffsetLegal(MI, Offset))
    return false;

  // The offset likely isn't legal, we want to allocate a virtual base register.
  return true;
}

/// materializeFrameBaseRegister - Insert defining instruction(s) for BaseReg to
/// be a pointer to FrameIdx at the beginning of the basic block.
void ARMBaseRegisterInfo::
materializeFrameBaseRegister(MachineBasicBlock *MBB,
                             unsigned BaseReg, int FrameIdx,
                             int64_t Offset) const {
  ARMFunctionInfo *AFI = MBB->getParent()->getInfo<ARMFunctionInfo>();
  unsigned ADDriOpc = !AFI->isThumbFunction() ? ARM::ADDri :
    (AFI->isThumb1OnlyFunction() ? ARM::tADDrSPi : ARM::t2ADDri);

  MachineBasicBlock::iterator Ins = MBB->begin();
  DebugLoc DL;                  // Defaults to "unknown"
  if (Ins != MBB->end())
    DL = Ins->getDebugLoc();

  MachineInstrBuilder MIB =
    BuildMI(*MBB, Ins, DL, TII.get(ADDriOpc), BaseReg)
    .addFrameIndex(FrameIdx).addImm(Offset);

  if (!AFI->isThumb1OnlyFunction())
    AddDefaultCC(AddDefaultPred(MIB));
}

void
ARMBaseRegisterInfo::resolveFrameIndex(MachineBasicBlock::iterator I,
                                       unsigned BaseReg, int64_t Offset) const {
  MachineInstr &MI = *I;
  MachineBasicBlock &MBB = *MI.getParent();
  MachineFunction &MF = *MBB.getParent();
  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  int Off = Offset; // ARM doesn't need the general 64-bit offsets
  unsigned i = 0;

  assert(!AFI->isThumb1OnlyFunction() &&
         "This resolveFrameIndex does not support Thumb1!");

  while (!MI.getOperand(i).isFI()) {
    ++i;
    assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
  }
  bool Done = false;
  if (!AFI->isThumbFunction())
    Done = rewriteARMFrameIndex(MI, i, BaseReg, Off, TII);
  else {
    assert(AFI->isThumb2Function());
    Done = rewriteT2FrameIndex(MI, i, BaseReg, Off, TII);
  }
  assert (Done && "Unable to resolve frame index!");
}

bool ARMBaseRegisterInfo::isFrameOffsetLegal(const MachineInstr *MI,
                                             int64_t Offset) const {
  const TargetInstrDesc &Desc = MI->getDesc();
  unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
  unsigned i = 0;

  while (!MI->getOperand(i).isFI()) {
    ++i;
    assert(i < MI->getNumOperands() &&"Instr doesn't have FrameIndex operand!");
  }

  // AddrMode4 and AddrMode6 cannot handle any offset.
  if (AddrMode == ARMII::AddrMode4 || AddrMode == ARMII::AddrMode6)
    return Offset == 0;

  unsigned NumBits = 0;
  unsigned Scale = 1;
  bool isSigned = true;
  switch (AddrMode) {
  case ARMII::AddrModeT2_i8:
  case ARMII::AddrModeT2_i12:
    // i8 supports only negative, and i12 supports only positive, so
    // based on Offset sign, consider the appropriate instruction
    Scale = 1;
    if (Offset < 0) {
      NumBits = 8;
      Offset = -Offset;
    } else {
      NumBits = 12;
    }
    break;
  case ARMII::AddrMode5:
    // VFP address mode.
    NumBits = 8;
    Scale = 4;
    break;
  case ARMII::AddrMode_i12:
  case ARMII::AddrMode2:
    NumBits = 12;
    break;
  case ARMII::AddrMode3:
    NumBits = 8;
    break;
  case ARMII::AddrModeT1_s:
    NumBits = 5;
    Scale = 4;
    isSigned = false;
    break;
  default:
    llvm_unreachable("Unsupported addressing mode!");
    break;
  }

  Offset += getFrameIndexInstrOffset(MI, i);
  // Make sure the offset is encodable for instructions that scale the
  // immediate.
  if ((Offset & (Scale-1)) != 0)
    return false;

  if (isSigned && Offset < 0)
    Offset = -Offset;

  unsigned Mask = (1 << NumBits) - 1;
  if ((unsigned)Offset <= Mask * Scale)
    return true;

  return false;
}

void
ARMBaseRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
                                         int SPAdj, RegScavenger *RS) const {
  unsigned i = 0;
  MachineInstr &MI = *II;
  MachineBasicBlock &MBB = *MI.getParent();
  MachineFunction &MF = *MBB.getParent();
  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  assert(!AFI->isThumb1OnlyFunction() &&
         "This eliminateFrameIndex does not support Thumb1!");

  while (!MI.getOperand(i).isFI()) {
    ++i;
    assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
  }

  int FrameIndex = MI.getOperand(i).getIndex();
  unsigned FrameReg;

  int Offset = ResolveFrameIndexReference(MF, FrameIndex, FrameReg, SPAdj);

  // Special handling of dbg_value instructions.
  if (MI.isDebugValue()) {
    MI.getOperand(i).  ChangeToRegister(FrameReg, false /*isDef*/);
    MI.getOperand(i+1).ChangeToImmediate(Offset);
    return;
  }

  // Modify MI as necessary to handle as much of 'Offset' as possible
  bool Done = false;
  if (!AFI->isThumbFunction())
    Done = rewriteARMFrameIndex(MI, i, FrameReg, Offset, TII);
  else {
    assert(AFI->isThumb2Function());
    Done = rewriteT2FrameIndex(MI, i, FrameReg, Offset, TII);
  }
  if (Done)
    return;

  // If we get here, the immediate doesn't fit into the instruction.  We folded
  // as much as possible above, handle the rest, providing a register that is
  // SP+LargeImm.
  assert((Offset ||
          (MI.getDesc().TSFlags & ARMII::AddrModeMask) == ARMII::AddrMode4 ||
          (MI.getDesc().TSFlags & ARMII::AddrModeMask) == ARMII::AddrMode6) &&
         "This code isn't needed if offset already handled!");

  unsigned ScratchReg = 0;
  int PIdx = MI.findFirstPredOperandIdx();
  ARMCC::CondCodes Pred = (PIdx == -1)
    ? ARMCC::AL : (ARMCC::CondCodes)MI.getOperand(PIdx).getImm();
  unsigned PredReg = (PIdx == -1) ? 0 : MI.getOperand(PIdx+1).getReg();
  if (Offset == 0)
    // Must be addrmode4/6.
    MI.getOperand(i).ChangeToRegister(FrameReg, false, false, false);
  else {
    ScratchReg = MF.getRegInfo().createVirtualRegister(ARM::GPRRegisterClass);
    if (!AFI->isThumbFunction())
      emitARMRegPlusImmediate(MBB, II, MI.getDebugLoc(), ScratchReg, FrameReg,
                              Offset, Pred, PredReg, TII);
    else {
      assert(AFI->isThumb2Function());
      emitT2RegPlusImmediate(MBB, II, MI.getDebugLoc(), ScratchReg, FrameReg,
                             Offset, Pred, PredReg, TII);
    }
    MI.getOperand(i).ChangeToRegister(ScratchReg, false, false, true);
  }
}

/// Move iterator past the next bunch of callee save load / store ops for
/// the particular spill area (1: integer area 1, 2: integer area 2,
/// 3: fp area, 0: don't care).
static void movePastCSLoadStoreOps(MachineBasicBlock &MBB,
                                   MachineBasicBlock::iterator &MBBI,
                                   int Opc1, int Opc2, unsigned Area,
                                   const ARMSubtarget &STI) {
  while (MBBI != MBB.end() &&
         ((MBBI->getOpcode() == Opc1) || (MBBI->getOpcode() == Opc2)) &&
         MBBI->getOperand(1).isFI()) {
    if (Area != 0) {
      bool Done = false;
      unsigned Category = 0;
      switch (MBBI->getOperand(0).getReg()) {
      case ARM::R4:  case ARM::R5:  case ARM::R6: case ARM::R7:
      case ARM::LR:
        Category = 1;
        break;
      case ARM::R8:  case ARM::R9:  case ARM::R10: case ARM::R11:
        Category = STI.isTargetDarwin() ? 2 : 1;
        break;
      case ARM::D8:  case ARM::D9:  case ARM::D10: case ARM::D11:
      case ARM::D12: case ARM::D13: case ARM::D14: case ARM::D15:
        Category = 3;
        break;
      default:
        Done = true;
        break;
      }
      if (Done || Category != Area)
        break;
    }

    ++MBBI;
  }
}

void ARMBaseRegisterInfo::
emitPrologue(MachineFunction &MF) const {
  MachineBasicBlock &MBB = MF.front();
  MachineBasicBlock::iterator MBBI = MBB.begin();
  MachineFrameInfo  *MFI = MF.getFrameInfo();
  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  assert(!AFI->isThumb1OnlyFunction() &&
         "This emitPrologue does not support Thumb1!");
  bool isARM = !AFI->isThumbFunction();
  unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize();
  unsigned NumBytes = MFI->getStackSize();
  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
  DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

  // Determine the sizes of each callee-save spill areas and record which frame
  // belongs to which callee-save spill areas.
  unsigned GPRCS1Size = 0, GPRCS2Size = 0, DPRCSSize = 0;
  int FramePtrSpillFI = 0;

  // Allocate the vararg register save area. This is not counted in NumBytes.
  if (VARegSaveSize)
    emitSPUpdate(isARM, MBB, MBBI, dl, TII, -VARegSaveSize);

  if (!AFI->hasStackFrame()) {
    if (NumBytes != 0)
      emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes);
    return;
  }

  for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
    unsigned Reg = CSI[i].getReg();
    int FI = CSI[i].getFrameIdx();
    switch (Reg) {
    case ARM::R4:
    case ARM::R5:
    case ARM::R6:
    case ARM::R7:
    case ARM::LR:
      if (Reg == FramePtr)
        FramePtrSpillFI = FI;
      AFI->addGPRCalleeSavedArea1Frame(FI);
      GPRCS1Size += 4;
      break;
    case ARM::R8:
    case ARM::R9:
    case ARM::R10:
    case ARM::R11:
      if (Reg == FramePtr)
        FramePtrSpillFI = FI;
      if (STI.isTargetDarwin()) {
        AFI->addGPRCalleeSavedArea2Frame(FI);
        GPRCS2Size += 4;
      } else {
        AFI->addGPRCalleeSavedArea1Frame(FI);
        GPRCS1Size += 4;
      }
      break;
    default:
      AFI->addDPRCalleeSavedAreaFrame(FI);
      DPRCSSize += 8;
    }
  }

  // Build the new SUBri to adjust SP for integer callee-save spill area 1.
  emitSPUpdate(isARM, MBB, MBBI, dl, TII, -GPRCS1Size);
  movePastCSLoadStoreOps(MBB, MBBI, ARM::STRi12, ARM::t2STRi12, 1, STI);

  // Set FP to point to the stack slot that contains the previous FP.
  // For Darwin, FP is R7, which has now been stored in spill area 1.
  // Otherwise, if this is not Darwin, all the callee-saved registers go
  // into spill area 1, including the FP in R11.  In either case, it is
  // now safe to emit this assignment.
  bool HasFP = hasFP(MF);
  if (HasFP) {
    unsigned ADDriOpc = !AFI->isThumbFunction() ? ARM::ADDri : ARM::t2ADDri;
    MachineInstrBuilder MIB =
      BuildMI(MBB, MBBI, dl, TII.get(ADDriOpc), FramePtr)
      .addFrameIndex(FramePtrSpillFI).addImm(0);
    AddDefaultCC(AddDefaultPred(MIB));
  }

  // Build the new SUBri to adjust SP for integer callee-save spill area 2.
  emitSPUpdate(isARM, MBB, MBBI, dl, TII, -GPRCS2Size);

  // Build the new SUBri to adjust SP for FP callee-save spill area.
  movePastCSLoadStoreOps(MBB, MBBI, ARM::STRi12, ARM::t2STRi12, 2, STI);
  emitSPUpdate(isARM, MBB, MBBI, dl, TII, -DPRCSSize);

  // Determine starting offsets of spill areas.
  unsigned DPRCSOffset  = NumBytes - (GPRCS1Size + GPRCS2Size + DPRCSSize);
  unsigned GPRCS2Offset = DPRCSOffset + DPRCSSize;
  unsigned GPRCS1Offset = GPRCS2Offset + GPRCS2Size;
  if (HasFP)
    AFI->setFramePtrSpillOffset(MFI->getObjectOffset(FramePtrSpillFI) +
                                NumBytes);
  AFI->setGPRCalleeSavedArea1Offset(GPRCS1Offset);
  AFI->setGPRCalleeSavedArea2Offset(GPRCS2Offset);
  AFI->setDPRCalleeSavedAreaOffset(DPRCSOffset);

  movePastCSLoadStoreOps(MBB, MBBI, ARM::VSTRD, 0, 3, STI);
  NumBytes = DPRCSOffset;
  if (NumBytes) {
    // Adjust SP after all the callee-save spills.
    emitSPUpdate(isARM, MBB, MBBI, dl, TII, -NumBytes);
    if (HasFP && isARM)
      // Restore from fp only in ARM mode: e.g. sub sp, r7, #24
      // Note it's not safe to do this in Thumb2 mode because it would have
      // taken two instructions:
      // mov sp, r7
      // sub sp, #24
      // If an interrupt is taken between the two instructions, then sp is in
      // an inconsistent state (pointing to the middle of callee-saved area).
      // The interrupt handler can end up clobbering the registers.
      AFI->setShouldRestoreSPFromFP(true);
  }

  if (STI.isTargetELF() && hasFP(MF))
    MFI->setOffsetAdjustment(MFI->getOffsetAdjustment() -
                             AFI->getFramePtrSpillOffset());

  AFI->setGPRCalleeSavedArea1Size(GPRCS1Size);
  AFI->setGPRCalleeSavedArea2Size(GPRCS2Size);
  AFI->setDPRCalleeSavedAreaSize(DPRCSSize);

  // If we need dynamic stack realignment, do it here. Be paranoid and make
  // sure if we also have VLAs, we have a base pointer for frame access.
  if (needsStackRealignment(MF)) {
    unsigned MaxAlign = MFI->getMaxAlignment();
    assert (!AFI->isThumb1OnlyFunction());
    if (!AFI->isThumbFunction()) {
      // Emit bic sp, sp, MaxAlign
      AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
                                          TII.get(ARM::BICri), ARM::SP)
                                  .addReg(ARM::SP, RegState::Kill)
                                  .addImm(MaxAlign-1)));
    } else {
      // We cannot use sp as source/dest register here, thus we're emitting the
      // following sequence:
      // mov r4, sp
      // bic r4, r4, MaxAlign
      // mov sp, r4
      // FIXME: It will be better just to find spare register here.
      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2tgpr), ARM::R4)
        .addReg(ARM::SP, RegState::Kill);
      AddDefaultCC(AddDefaultPred(BuildMI(MBB, MBBI, dl,
                                          TII.get(ARM::t2BICri), ARM::R4)
                                  .addReg(ARM::R4, RegState::Kill)
                                  .addImm(MaxAlign-1)));
      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVtgpr2gpr), ARM::SP)
        .addReg(ARM::R4, RegState::Kill);
    }

    AFI->setShouldRestoreSPFromFP(true);
  }

  // If we need a base pointer, set it up here. It's whatever the value
  // of the stack pointer is at this point. Any variable size objects
  // will be allocated after this, so we can still use the base pointer
  // to reference locals.
  if (hasBasePointer(MF)) {
    if (isARM)
      BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), BasePtr)
        .addReg(ARM::SP)
        .addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
    else
      BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), BasePtr)
        .addReg(ARM::SP);
  }

  // If the frame has variable sized objects then the epilogue must restore
  // the sp from fp.
  if (MFI->hasVarSizedObjects())
    AFI->setShouldRestoreSPFromFP(true);
}

static bool isCalleeSavedRegister(unsigned Reg, const unsigned *CSRegs) {
  for (unsigned i = 0; CSRegs[i]; ++i)
    if (Reg == CSRegs[i])
      return true;
  return false;
}

static bool isCSRestore(MachineInstr *MI,
                        const ARMBaseInstrInfo &TII,
                        const unsigned *CSRegs) {
  return ((MI->getOpcode() == (int)ARM::VLDRD ||
           MI->getOpcode() == (int)ARM::LDRi12 ||
           MI->getOpcode() == (int)ARM::t2LDRi12) &&
          MI->getOperand(1).isFI() &&
          isCalleeSavedRegister(MI->getOperand(0).getReg(), CSRegs));
}

void ARMBaseRegisterInfo::
emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const {
  MachineBasicBlock::iterator MBBI = prior(MBB.end());
  assert(MBBI->getDesc().isReturn() &&
         "Can only insert epilog into returning blocks");
  unsigned RetOpcode = MBBI->getOpcode();
  DebugLoc dl = MBBI->getDebugLoc();
  MachineFrameInfo *MFI = MF.getFrameInfo();
  ARMFunctionInfo *AFI = MF.getInfo<ARMFunctionInfo>();
  assert(!AFI->isThumb1OnlyFunction() &&
         "This emitEpilogue does not support Thumb1!");
  bool isARM = !AFI->isThumbFunction();

  unsigned VARegSaveSize = AFI->getVarArgsRegSaveSize();
  int NumBytes = (int)MFI->getStackSize();

  if (!AFI->hasStackFrame()) {
    if (NumBytes != 0)
      emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);
  } else {
    // Unwind MBBI to point to first LDR / VLDRD.
    const unsigned *CSRegs = getCalleeSavedRegs();
    if (MBBI != MBB.begin()) {
      do
        --MBBI;
      while (MBBI != MBB.begin() && isCSRestore(MBBI, TII, CSRegs));
      if (!isCSRestore(MBBI, TII, CSRegs))
        ++MBBI;
    }

    // Move SP to start of FP callee save spill area.
    NumBytes -= (AFI->getGPRCalleeSavedArea1Size() +
                 AFI->getGPRCalleeSavedArea2Size() +
                 AFI->getDPRCalleeSavedAreaSize());

    // Reset SP based on frame pointer only if the stack frame extends beyond
    // frame pointer stack slot or target is ELF and the function has FP.
    if (AFI->shouldRestoreSPFromFP()) {
      NumBytes = AFI->getFramePtrSpillOffset() - NumBytes;
      if (NumBytes) {
        if (isARM)
          emitARMRegPlusImmediate(MBB, MBBI, dl, ARM::SP, FramePtr, -NumBytes,
                                  ARMCC::AL, 0, TII);
        else {
          // It's not possible to restore SP from FP in a single instruction.
          // For Darwin, this looks like:
          // mov sp, r7
          // sub sp, #24
          // This is bad, if an interrupt is taken after the mov, sp is in an
          // inconsistent state.
          // Use the first callee-saved register as a scratch register.
          assert(MF.getRegInfo().isPhysRegUsed(ARM::R4) &&
                 "No scratch register to restore SP from FP!");
          emitT2RegPlusImmediate(MBB, MBBI, dl, ARM::R4, FramePtr, -NumBytes,
                                 ARMCC::AL, 0, TII);
          BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), ARM::SP)
            .addReg(ARM::R4);
        }
      } else {
        // Thumb2 or ARM.
        if (isARM)
          BuildMI(MBB, MBBI, dl, TII.get(ARM::MOVr), ARM::SP)
            .addReg(FramePtr).addImm((unsigned)ARMCC::AL).addReg(0).addReg(0);
        else
          BuildMI(MBB, MBBI, dl, TII.get(ARM::tMOVgpr2gpr), ARM::SP)
            .addReg(FramePtr);
      }
    } else if (NumBytes)
      emitSPUpdate(isARM, MBB, MBBI, dl, TII, NumBytes);

    // Move SP to start of integer callee save spill area 2.
    movePastCSLoadStoreOps(MBB, MBBI, ARM::VLDRD, 0, 3, STI);
    emitSPUpdate(isARM, MBB, MBBI, dl, TII, AFI->getDPRCalleeSavedAreaSize());

    // Move SP to start of integer callee save spill area 1.
    movePastCSLoadStoreOps(MBB, MBBI, ARM::LDRi12, ARM::t2LDRi12, 2, STI);
    emitSPUpdate(isARM, MBB, MBBI, dl, TII, AFI->getGPRCalleeSavedArea2Size());

    // Move SP to SP upon entry to the function.
    movePastCSLoadStoreOps(MBB, MBBI, ARM::LDRi12, ARM::t2LDRi12, 1, STI);
    emitSPUpdate(isARM, MBB, MBBI, dl, TII, AFI->getGPRCalleeSavedArea1Size());
  }

  if (RetOpcode == ARM::TCRETURNdi || RetOpcode == ARM::TCRETURNdiND ||
      RetOpcode == ARM::TCRETURNri || RetOpcode == ARM::TCRETURNriND) {
    // Tail call return: adjust the stack pointer and jump to callee.
    MBBI = prior(MBB.end());
    MachineOperand &JumpTarget = MBBI->getOperand(0);

    // Jump to label or value in register.
    if (RetOpcode == ARM::TCRETURNdi) {
      BuildMI(MBB, MBBI, dl,
            TII.get(STI.isThumb() ? ARM::TAILJMPdt : ARM::TAILJMPd)).
        addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
                         JumpTarget.getTargetFlags());
    } else if (RetOpcode == ARM::TCRETURNdiND) {
      BuildMI(MBB, MBBI, dl,
            TII.get(STI.isThumb() ? ARM::TAILJMPdNDt : ARM::TAILJMPdND)).
        addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
                         JumpTarget.getTargetFlags());
    } else if (RetOpcode == ARM::TCRETURNri) {
      BuildMI(MBB, MBBI, dl, TII.get(ARM::TAILJMPr)).
        addReg(JumpTarget.getReg(), RegState::Kill);
    } else if (RetOpcode == ARM::TCRETURNriND) {
      BuildMI(MBB, MBBI, dl, TII.get(ARM::TAILJMPrND)).
        addReg(JumpTarget.getReg(), RegState::Kill);
    }

    MachineInstr *NewMI = prior(MBBI);
    for (unsigned i = 1, e = MBBI->getNumOperands(); i != e; ++i)
      NewMI->addOperand(MBBI->getOperand(i));

    // Delete the pseudo instruction TCRETURN.
    MBB.erase(MBBI);
  }

  if (VARegSaveSize)
    emitSPUpdate(isARM, MBB, MBBI, dl, TII, VARegSaveSize);
}

#include "ARMGenRegisterInfo.inc"