Updating branches/google/stable to r176857

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/google/stable@177040 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 686 insertions, 0 deletions

diff --git a/lib/Target/AArch64/AArch64FrameLowering.cpp b/lib/Target/AArch64/AArch64FrameLowering.cpp
new file mode 100644
index 0000000000..cca6d12e16
--- /dev/null
+++ b/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -0,0 +1,686 @@
+//===- AArch64FrameLowering.cpp - AArch64 Frame Information ---------------===//
+//
+//                     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 AArch64 implementation of TargetFrameLowering class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AArch64.h"
+#include "AArch64FrameLowering.h"
+#include "AArch64MachineFunctionInfo.h"
+#include "AArch64InstrInfo.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineMemOperand.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/IR/Function.h"
+#include "llvm/MC/MachineLocation.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+
+using namespace llvm;
+
+void AArch64FrameLowering::splitSPAdjustments(uint64_t Total,
+                                              uint64_t &Initial,
+                                              uint64_t &Residual) const {
+  // 0x1f0 here is a pessimistic (i.e. realistic) boundary: x-register LDP
+  // instructions have a 7-bit signed immediate scaled by 8, giving a reach of
+  // 0x1f8, but stack adjustment should always be a multiple of 16.
+  if (Total <= 0x1f0) {
+    Initial = Total;
+    Residual = 0;
+  } else {
+    Initial = 0x1f0;
+    Residual = Total - Initial;
+  }
+}
+
+void AArch64FrameLowering::emitPrologue(MachineFunction &MF) const {
+  AArch64MachineFunctionInfo *FuncInfo =
+    MF.getInfo<AArch64MachineFunctionInfo>();
+  MachineBasicBlock &MBB = MF.front();
+  MachineBasicBlock::iterator MBBI = MBB.begin();
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
+  DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
+
+  MachineModuleInfo &MMI = MF.getMMI();
+  std::vector<MachineMove> &Moves = MMI.getFrameMoves();
+  bool NeedsFrameMoves = MMI.hasDebugInfo()
+    || MF.getFunction()->needsUnwindTableEntry();
+
+  uint64_t NumInitialBytes, NumResidualBytes;
+
+  // Currently we expect the stack to be laid out by
+  //     sub sp, sp, #initial
+  //     stp x29, x30, [sp, #offset]
+  //     ...
+  //     str xxx, [sp, #offset]
+  //     sub sp, sp, #rest (possibly via extra instructions).
+  if (MFI->getCalleeSavedInfo().size()) {
+    // If there are callee-saved registers, we want to store them efficiently as
+    // a block, and virtual base assignment happens too early to do it for us so
+    // we adjust the stack in two phases: first just for callee-saved fiddling,
+    // then to allocate the rest of the frame.
+    splitSPAdjustments(MFI->getStackSize(), NumInitialBytes, NumResidualBytes);
+  } else {
+    // If there aren't any callee-saved registers, two-phase adjustment is
+    // inefficient. It's more efficient to adjust with NumInitialBytes too
+    // because when we're in a "callee pops argument space" situation, that pop
+    // must be tacked onto Initial for correctness.
+    NumInitialBytes = MFI->getStackSize();
+    NumResidualBytes = 0;
+  }
+
+  // Tell everyone else how much adjustment we're expecting them to use. In
+  // particular if an adjustment is required for a tail call the epilogue could
+  // have a different view of things.
+  FuncInfo->setInitialStackAdjust(NumInitialBytes);
+
+  emitSPUpdate(MBB, MBBI, DL, TII, AArch64::X16, -NumInitialBytes,
+               MachineInstr::FrameSetup);
+
+  if (NeedsFrameMoves && NumInitialBytes) {
+    // We emit this update even if the CFA is set from a frame pointer later so
+    // that the CFA is valid in the interim.
+    MCSymbol *SPLabel = MMI.getContext().CreateTempSymbol();
+    BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
+      .addSym(SPLabel);
+
+    MachineLocation Dst(MachineLocation::VirtualFP);
+    MachineLocation Src(AArch64::XSP, NumInitialBytes);
+    Moves.push_back(MachineMove(SPLabel, Dst, Src));
+  }
+
+  // Otherwise we need to set the frame pointer and/or add a second stack
+  // adjustment.
+
+  bool FPNeedsSetting = hasFP(MF);
+  for (; MBBI != MBB.end(); ++MBBI) {
+    // Note that this search makes strong assumptions about the operation used
+    // to store the frame-pointer: it must be "STP x29, x30, ...". This could
+    // change in future, but until then there's no point in implementing
+    // untestable more generic cases.
+    if (FPNeedsSetting && MBBI->getOpcode() == AArch64::LSPair64_STR
+                       && MBBI->getOperand(0).getReg() == AArch64::X29) {
+      int64_t X29FrameIdx = MBBI->getOperand(2).getIndex();
+      FuncInfo->setFramePointerOffset(MFI->getObjectOffset(X29FrameIdx));
+
+      ++MBBI;
+      emitRegUpdate(MBB, MBBI, DL, TII, AArch64::X29, AArch64::XSP,
+                    AArch64::X29,
+                    NumInitialBytes + MFI->getObjectOffset(X29FrameIdx),
+                    MachineInstr::FrameSetup);
+
+      // The offset adjustment used when emitting debugging locations relative
+      // to whatever frame base is set. AArch64 uses the default frame base (FP
+      // or SP) and this adjusts the calculations to be correct.
+      MFI->setOffsetAdjustment(- MFI->getObjectOffset(X29FrameIdx)
+                               - MFI->getStackSize());
+
+      if (NeedsFrameMoves) {
+        MCSymbol *FPLabel = MMI.getContext().CreateTempSymbol();
+        BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
+          .addSym(FPLabel);
+        MachineLocation Dst(MachineLocation::VirtualFP);
+        MachineLocation Src(AArch64::X29, -MFI->getObjectOffset(X29FrameIdx));
+        Moves.push_back(MachineMove(FPLabel, Dst, Src));
+      }
+
+      FPNeedsSetting = false;
+    }
+
+    if (!MBBI->getFlag(MachineInstr::FrameSetup))
+      break;
+  }
+
+  assert(!FPNeedsSetting && "Frame pointer couldn't be set");
+
+  emitSPUpdate(MBB, MBBI, DL, TII, AArch64::X16, -NumResidualBytes,
+               MachineInstr::FrameSetup);
+
+  // Now we emit the rest of the frame setup information, if necessary: we've
+  // already noted the FP and initial SP moves so we're left with the prologue's
+  // final SP update and callee-saved register locations.
+  if (!NeedsFrameMoves)
+    return;
+
+  // Reuse the label if appropriate, so create it in this outer scope.
+  MCSymbol *CSLabel = 0;
+
+  // The rest of the stack adjustment
+  if (!hasFP(MF) && NumResidualBytes) {
+    CSLabel = MMI.getContext().CreateTempSymbol();
+    BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
+      .addSym(CSLabel);
+
+    MachineLocation Dst(MachineLocation::VirtualFP);
+    MachineLocation Src(AArch64::XSP, NumResidualBytes + NumInitialBytes);
+    Moves.push_back(MachineMove(CSLabel, Dst, Src));
+  }
+
+  // And any callee-saved registers (it's fine to leave them to the end here,
+  // because the old values are still valid at this point.
+  const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
+  if (CSI.size()) {
+    if (!CSLabel) {
+      CSLabel = MMI.getContext().CreateTempSymbol();
+      BuildMI(MBB, MBBI, DL, TII.get(TargetOpcode::PROLOG_LABEL))
+        .addSym(CSLabel);
+    }
+
+    for (std::vector<CalleeSavedInfo>::const_iterator I = CSI.begin(),
+           E = CSI.end(); I != E; ++I) {
+      MachineLocation Dst(MachineLocation::VirtualFP,
+                          MFI->getObjectOffset(I->getFrameIdx()));
+      MachineLocation Src(I->getReg());
+      Moves.push_back(MachineMove(CSLabel, Dst, Src));
+    }
+  }
+}
+
+void
+AArch64FrameLowering::emitEpilogue(MachineFunction &MF,
+                                   MachineBasicBlock &MBB) const {
+  AArch64MachineFunctionInfo *FuncInfo =
+    MF.getInfo<AArch64MachineFunctionInfo>();
+
+  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
+  DebugLoc DL = MBBI->getDebugLoc();
+  const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
+  MachineFrameInfo &MFI = *MF.getFrameInfo();
+  unsigned RetOpcode = MBBI->getOpcode();
+
+  // Initial and residual are named for consitency with the prologue. Note that
+  // in the epilogue, the residual adjustment is executed first.
+  uint64_t NumInitialBytes = FuncInfo->getInitialStackAdjust();
+  uint64_t NumResidualBytes = MFI.getStackSize() - NumInitialBytes;
+  uint64_t ArgumentPopSize = 0;
+  if (RetOpcode == AArch64::TC_RETURNdi ||
+      RetOpcode == AArch64::TC_RETURNxi) {
+    MachineOperand &JumpTarget = MBBI->getOperand(0);
+    MachineOperand &StackAdjust = MBBI->getOperand(1);
+
+    MachineInstrBuilder MIB;
+    if (RetOpcode == AArch64::TC_RETURNdi) {
+      MIB = BuildMI(MBB, MBBI, DL, TII.get(AArch64::TAIL_Bimm));
+      if (JumpTarget.isGlobal()) {
+        MIB.addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset(),
+                             JumpTarget.getTargetFlags());
+      } else {
+        assert(JumpTarget.isSymbol() && "unexpected tail call destination");
+        MIB.addExternalSymbol(JumpTarget.getSymbolName(),
+                              JumpTarget.getTargetFlags());
+      }
+    } else {
+      assert(RetOpcode == AArch64::TC_RETURNxi && JumpTarget.isReg()
+             && "Unexpected tail call");
+
+      MIB = BuildMI(MBB, MBBI, DL, TII.get(AArch64::TAIL_BRx));
+      MIB.addReg(JumpTarget.getReg(), RegState::Kill);
+    }
+
+    // Add the extra operands onto the new tail call instruction even though
+    // they're not used directly (so that liveness is tracked properly etc).
+    for (unsigned i = 2, e = MBBI->getNumOperands(); i != e; ++i)
+        MIB->addOperand(MBBI->getOperand(i));
+
+
+    // Delete the pseudo instruction TC_RETURN.
+    MachineInstr *NewMI = prior(MBBI);
+    MBB.erase(MBBI);
+    MBBI = NewMI;
+
+    // For a tail-call in a callee-pops-arguments environment, some or all of
+    // the stack may actually be in use for the call's arguments, this is
+    // calculated during LowerCall and consumed here...
+    ArgumentPopSize = StackAdjust.getImm();
+  } else {
+    // ... otherwise the amount to pop is *all* of the argument space,
+    // conveniently stored in the MachineFunctionInfo by
+    // LowerFormalArguments. This will, of course, be zero for the C calling
+    // convention.
+    ArgumentPopSize = FuncInfo->getArgumentStackToRestore();
+  }
+
+  assert(NumInitialBytes % 16 == 0 && NumResidualBytes % 16 == 0
+         && "refusing to adjust stack by misaligned amt");
+
+  // We may need to address callee-saved registers differently, so find out the
+  // bound on the frame indices.
+  const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
+  int MinCSFI = 0;
+  int MaxCSFI = -1;
+
+  if (CSI.size()) {
+    MinCSFI = CSI[0].getFrameIdx();
+    MaxCSFI = CSI[CSI.size() - 1].getFrameIdx();
+  }
+
+  // The "residual" stack update comes first from this direction and guarantees
+  // that SP is NumInitialBytes below its value on function entry, either by a
+  // direct update or restoring it from the frame pointer.
+  if (NumInitialBytes + ArgumentPopSize != 0) {
+    emitSPUpdate(MBB, MBBI, DL, TII, AArch64::X16,
+                 NumInitialBytes + ArgumentPopSize);
+    --MBBI;
+  }
+
+
+  // MBBI now points to the instruction just past the last callee-saved
+  // restoration (either RET/B if NumInitialBytes == 0, or the "ADD sp, sp"
+  // otherwise).
+
+  // Now we need to find out where to put the bulk of the stack adjustment
+  MachineBasicBlock::iterator FirstEpilogue = MBBI;
+  while (MBBI != MBB.begin()) {
+    --MBBI;
+
+    unsigned FrameOp;
+    for (FrameOp = 0; FrameOp < MBBI->getNumOperands(); ++FrameOp) {
+      if (MBBI->getOperand(FrameOp).isFI())
+        break;
+    }
+
+    // If this instruction doesn't have a frame index we've reached the end of
+    // the callee-save restoration.
+    if (FrameOp == MBBI->getNumOperands())
+      break;
+
+    // Likewise if it *is* a local reference, but not to a callee-saved object.
+    int FrameIdx = MBBI->getOperand(FrameOp).getIndex();
+    if (FrameIdx < MinCSFI || FrameIdx > MaxCSFI)
+      break;
+
+    FirstEpilogue = MBBI;
+  }
+
+  if (MF.getFrameInfo()->hasVarSizedObjects()) {
+    int64_t StaticFrameBase;
+    StaticFrameBase = -(NumInitialBytes + FuncInfo->getFramePointerOffset());
+    emitRegUpdate(MBB, FirstEpilogue, DL, TII,
+                  AArch64::XSP, AArch64::X29, AArch64::NoRegister,
+                  StaticFrameBase);
+  } else {
+    emitSPUpdate(MBB, FirstEpilogue, DL,TII, AArch64::X16, NumResidualBytes);
+  }
+}
+
+int64_t
+AArch64FrameLowering::resolveFrameIndexReference(MachineFunction &MF,
+                                                 int FrameIndex,
+                                                 unsigned &FrameReg,
+                                                 int SPAdj,
+                                                 bool IsCalleeSaveOp) const {
+  AArch64MachineFunctionInfo *FuncInfo =
+    MF.getInfo<AArch64MachineFunctionInfo>();
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+
+  int64_t TopOfFrameOffset = MFI->getObjectOffset(FrameIndex);
+
+  assert(!(IsCalleeSaveOp && FuncInfo->getInitialStackAdjust() == 0)
+         && "callee-saved register in unexpected place");
+
+  // If the frame for this function is particularly large, we adjust the stack
+  // in two phases which means the callee-save related operations see a
+  // different (intermediate) stack size.
+  int64_t FrameRegPos;
+  if (IsCalleeSaveOp) {
+    FrameReg = AArch64::XSP;
+    FrameRegPos = -static_cast<int64_t>(FuncInfo->getInitialStackAdjust());
+  } else if (useFPForAddressing(MF)) {
+    // Have to use the frame pointer since we have no idea where SP is.
+    FrameReg = AArch64::X29;
+    FrameRegPos = FuncInfo->getFramePointerOffset();
+  } else {
+    FrameReg = AArch64::XSP;
+    FrameRegPos = -static_cast<int64_t>(MFI->getStackSize()) + SPAdj;
+  }
+
+  return TopOfFrameOffset - FrameRegPos;
+}
+
+/// Estimate and return the size of the frame.
+static unsigned estimateStackSize(MachineFunction &MF) {
+  // FIXME: Make generic? Really consider after upstreaming.  This code is now
+  // shared between PEI, ARM *and* here.
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering();
+  const TargetRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
+  unsigned MaxAlign = MFI->getMaxAlignment();
+  int Offset = 0;
+
+  // This code is very, very similar to PEI::calculateFrameObjectOffsets().
+  // It really should be refactored to share code. Until then, changes
+  // should keep in mind that there's tight coupling between the two.
+
+  for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
+    int FixedOff = -MFI->getObjectOffset(i);
+    if (FixedOff > Offset) Offset = FixedOff;
+  }
+  for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+    if (MFI->isDeadObjectIndex(i))
+      continue;
+    Offset += MFI->getObjectSize(i);
+    unsigned Align = MFI->getObjectAlignment(i);
+    // Adjust to alignment boundary
+    Offset = (Offset+Align-1)/Align*Align;
+
+    MaxAlign = std::max(Align, MaxAlign);
+  }
+
+  if (MFI->adjustsStack() && TFI->hasReservedCallFrame(MF))
+    Offset += MFI->getMaxCallFrameSize();
+
+  // Round up the size to a multiple of the alignment.  If the function has
+  // any calls or alloca's, align to the target's StackAlignment value to
+  // ensure that the callee's frame or the alloca data is suitably aligned;
+  // otherwise, for leaf functions, align to the TransientStackAlignment
+  // value.
+  unsigned StackAlign;
+  if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
+      (RegInfo->needsStackRealignment(MF) && MFI->getObjectIndexEnd() != 0))
+    StackAlign = TFI->getStackAlignment();
+  else
+    StackAlign = TFI->getTransientStackAlignment();
+
+  // If the frame pointer is eliminated, all frame offsets will be relative to
+  // SP not FP. Align to MaxAlign so this works.
+  StackAlign = std::max(StackAlign, MaxAlign);
+  unsigned AlignMask = StackAlign - 1;
+  Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
+
+  return (unsigned)Offset;
+}
+
+void
+AArch64FrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
+                                                       RegScavenger *RS) const {
+  const AArch64RegisterInfo *RegInfo =
+    static_cast<const AArch64RegisterInfo *>(MF.getTarget().getRegisterInfo());
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  const AArch64InstrInfo &TII =
+    *static_cast<const AArch64InstrInfo *>(MF.getTarget().getInstrInfo());
+
+  if (hasFP(MF)) {
+    MF.getRegInfo().setPhysRegUsed(AArch64::X29);
+    MF.getRegInfo().setPhysRegUsed(AArch64::X30);
+  }
+
+  // If addressing of local variables is going to be more complicated than
+  // shoving a base register and an offset into the instruction then we may well
+  // need to scavenge registers. We should either specifically add an
+  // callee-save register for this purpose or allocate an extra spill slot.
+
+  bool BigStack =
+    (RS && estimateStackSize(MF) >= TII.estimateRSStackLimit(MF))
+    || MFI->hasVarSizedObjects() // Access will be from X29: messes things up
+    || (MFI->adjustsStack() && !hasReservedCallFrame(MF));
+
+  if (!BigStack)
+    return;
+
+  // We certainly need some slack space for the scavenger, preferably an extra
+  // register.
+  const uint16_t *CSRegs = RegInfo->getCalleeSavedRegs();
+  uint16_t ExtraReg = AArch64::NoRegister;
+
+  for (unsigned i = 0; CSRegs[i]; ++i) {
+    if (AArch64::GPR64RegClass.contains(CSRegs[i]) &&
+        !MF.getRegInfo().isPhysRegUsed(CSRegs[i])) {
+      ExtraReg = CSRegs[i];
+      break;
+    }
+  }
+
+  if (ExtraReg != 0) {
+    MF.getRegInfo().setPhysRegUsed(ExtraReg);
+  } else {
+    // Create a stack slot for scavenging purposes. PrologEpilogInserter
+    // helpfully places it near either SP or FP for us to avoid
+    // infinitely-regression during scavenging.
+    const TargetRegisterClass *RC = &AArch64::GPR64RegClass;
+    RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+                                                       RC->getAlignment(),
+                                                       false));
+  }
+}
+
+bool AArch64FrameLowering::determinePrologueDeath(MachineBasicBlock &MBB,
+                                                  unsigned Reg) const {
+  // If @llvm.returnaddress is called then it will refer to X30 by some means;
+  // the prologue store does not kill the register.
+  if (Reg == AArch64::X30) {
+    if (MBB.getParent()->getFrameInfo()->isReturnAddressTaken()
+        && MBB.getParent()->getRegInfo().isLiveIn(Reg))
+    return false;
+  }
+
+  // In all other cases, physical registers are dead after they've been saved
+  // but live at the beginning of the prologue block.
+  MBB.addLiveIn(Reg);
+  return true;
+}
+
+void
+AArch64FrameLowering::emitFrameMemOps(bool isPrologue, MachineBasicBlock &MBB,
+                                      MachineBasicBlock::iterator MBBI,
+                                      const std::vector<CalleeSavedInfo> &CSI,
+                                      const TargetRegisterInfo *TRI,
+                                      LoadStoreMethod PossClasses[],
+                                      unsigned NumClasses) const {
+  DebugLoc DL = MBB.findDebugLoc(MBBI);
+  MachineFunction &MF = *MBB.getParent();
+  MachineFrameInfo &MFI = *MF.getFrameInfo();
+  const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
+
+  // A certain amount of implicit contract is present here. The actual stack
+  // offsets haven't been allocated officially yet, so for strictly correct code
+  // we rely on the fact that the elements of CSI are allocated in order
+  // starting at SP, purely as dictated by size and alignment. In practice since
+  // this function handles the only accesses to those slots it's not quite so
+  // important.
+  //
+  // We have also ordered the Callee-saved register list in AArch64CallingConv
+  // so that the above scheme puts registers in order: in particular we want
+  // &X30 to be &X29+8 for an ABI-correct frame record (PCS 5.2.2)
+  for (unsigned i = 0, e = CSI.size(); i < e; ++i) {
+    unsigned Reg = CSI[i].getReg();
+
+    // First we need to find out which register class the register belongs to so
+    // that we can use the correct load/store instrucitons.
+    unsigned ClassIdx;
+    for (ClassIdx = 0; ClassIdx < NumClasses; ++ClassIdx) {
+      if (PossClasses[ClassIdx].RegClass->contains(Reg))
+        break;
+    }
+    assert(ClassIdx != NumClasses
+           && "Asked to store register in unexpected class");
+    const TargetRegisterClass &TheClass = *PossClasses[ClassIdx].RegClass;
+
+    // Now we need to decide whether it's possible to emit a paired instruction:
+    // for this we want the next register to be in the same class.
+    MachineInstrBuilder NewMI;
+    bool Pair = false;
+    if (i + 1 < CSI.size() && TheClass.contains(CSI[i+1].getReg())) {
+      Pair = true;
+      unsigned StLow = 0, StHigh = 0;
+      if (isPrologue) {
+        // Most of these registers will be live-in to the MBB and killed by our
+        // store, though there are exceptions (see determinePrologueDeath).
+        StLow = getKillRegState(determinePrologueDeath(MBB, CSI[i+1].getReg()));
+        StHigh = getKillRegState(determinePrologueDeath(MBB, CSI[i].getReg()));
+      } else {
+        StLow = RegState::Define;
+        StHigh = RegState::Define;
+      }
+
+      NewMI = BuildMI(MBB, MBBI, DL, TII.get(PossClasses[ClassIdx].PairOpcode))
+                .addReg(CSI[i+1].getReg(), StLow)
+                .addReg(CSI[i].getReg(), StHigh);
+
+      // If it's a paired op, we've consumed two registers
+      ++i;
+    } else {
+      unsigned State;
+      if (isPrologue) {
+        State = getKillRegState(determinePrologueDeath(MBB, CSI[i].getReg()));
+      } else {
+        State = RegState::Define;
+      }
+
+      NewMI = BuildMI(MBB, MBBI, DL,
+                      TII.get(PossClasses[ClassIdx].SingleOpcode))
+                .addReg(CSI[i].getReg(), State);
+    }
+
+    // Note that the FrameIdx refers to the second register in a pair: it will
+    // be allocated the smaller numeric address and so is the one an LDP/STP
+    // address must use.
+    int FrameIdx = CSI[i].getFrameIdx();
+    MachineMemOperand::MemOperandFlags Flags;
+    Flags = isPrologue ? MachineMemOperand::MOStore : MachineMemOperand::MOLoad;
+    MachineMemOperand *MMO =
+      MF.getMachineMemOperand(MachinePointerInfo::getFixedStack(FrameIdx),
+                             Flags,
+                             Pair ? TheClass.getSize() * 2 : TheClass.getSize(),
+                             MFI.getObjectAlignment(FrameIdx));
+
+    NewMI.addFrameIndex(FrameIdx)
+      .addImm(0)                  // address-register offset
+      .addMemOperand(MMO);
+
+    if (isPrologue)
+      NewMI.setMIFlags(MachineInstr::FrameSetup);
+
+    // For aesthetic reasons, during an epilogue we want to emit complementary
+    // operations to the prologue, but in the opposite order. So we still
+    // iterate through the CalleeSavedInfo list in order, but we put the
+    // instructions successively earlier in the MBB.
+    if (!isPrologue)
+      --MBBI;
+  }
+}
+
+bool
+AArch64FrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
+                                        MachineBasicBlock::iterator MBBI,
+                                        const std::vector<CalleeSavedInfo> &CSI,
+                                        const TargetRegisterInfo *TRI) const {
+  if (CSI.empty())
+    return false;
+
+  static LoadStoreMethod PossibleClasses[] = {
+    {&AArch64::GPR64RegClass, AArch64::LSPair64_STR, AArch64::LS64_STR},
+    {&AArch64::FPR64RegClass, AArch64::LSFPPair64_STR, AArch64::LSFP64_STR},
+  };
+  unsigned NumClasses = llvm::array_lengthof(PossibleClasses);
+
+  emitFrameMemOps(/* isPrologue = */ true, MBB, MBBI, CSI, TRI,
+                  PossibleClasses, NumClasses);
+
+  return true;
+}
+
+bool
+AArch64FrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
+                                        MachineBasicBlock::iterator MBBI,
+                                        const std::vector<CalleeSavedInfo> &CSI,
+                                        const TargetRegisterInfo *TRI) const {
+
+  if (CSI.empty())
+    return false;
+
+  static LoadStoreMethod PossibleClasses[] = {
+    {&AArch64::GPR64RegClass, AArch64::LSPair64_LDR, AArch64::LS64_LDR},
+    {&AArch64::FPR64RegClass, AArch64::LSFPPair64_LDR, AArch64::LSFP64_LDR},
+  };
+  unsigned NumClasses = llvm::array_lengthof(PossibleClasses);
+
+  emitFrameMemOps(/* isPrologue = */ false, MBB, MBBI, CSI, TRI,
+                  PossibleClasses, NumClasses);
+
+  return true;
+}
+
+bool
+AArch64FrameLowering::hasFP(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  const TargetRegisterInfo *RI = MF.getTarget().getRegisterInfo();
+
+  // This is a decision of ABI compliance. The AArch64 PCS gives various options
+  // for conformance, and even at the most stringent level more or less permits
+  // elimination for leaf functions because there's no loss of functionality
+  // (for debugging etc)..
+  if (MF.getTarget().Options.DisableFramePointerElim(MF) && MFI->hasCalls())
+    return true;
+
+  // The following are hard-limits: incorrect code will be generated if we try
+  // to omit the frame.
+  return (RI->needsStackRealignment(MF) ||
+          MFI->hasVarSizedObjects() ||
+          MFI->isFrameAddressTaken());
+}
+
+bool
+AArch64FrameLowering::useFPForAddressing(const MachineFunction &MF) const {
+  return MF.getFrameInfo()->hasVarSizedObjects();
+}
+
+bool
+AArch64FrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+
+  // Of the various reasons for having a frame pointer, it's actually only
+  // variable-sized objects that prevent reservation of a call frame.
+  return !(hasFP(MF) && MFI->hasVarSizedObjects());
+}
+
+void
+AArch64FrameLowering::eliminateCallFramePseudoInstr(
+                                MachineFunction &MF,
+                                MachineBasicBlock &MBB,
+                                MachineBasicBlock::iterator MI) const {
+  const AArch64InstrInfo &TII =
+    *static_cast<const AArch64InstrInfo *>(MF.getTarget().getInstrInfo());
+  DebugLoc dl = MI->getDebugLoc();
+  int Opcode = MI->getOpcode();
+  bool IsDestroy = Opcode == TII.getCallFrameDestroyOpcode();
+  uint64_t CalleePopAmount = IsDestroy ? MI->getOperand(1).getImm() : 0;
+
+  if (!hasReservedCallFrame(MF)) {
+    unsigned Align = getStackAlignment();
+
+    int64_t Amount = MI->getOperand(0).getImm();
+    Amount = RoundUpToAlignment(Amount, Align);
+    if (!IsDestroy) Amount = -Amount;
+
+    // N.b. if CalleePopAmount is valid but zero (i.e. callee would pop, but it
+    // doesn't have to pop anything), then the first operand will be zero too so
+    // this adjustment is a no-op.
+    if (CalleePopAmount == 0) {
+      // FIXME: in-function stack adjustment for calls is limited to 12-bits
+      // because there's no guaranteed temporary register available. Mostly call
+      // frames will be allocated at the start of a function so this is OK, but
+      // it is a limitation that needs dealing with.
+      assert(Amount > -0xfff && Amount < 0xfff && "call frame too large");
+      emitSPUpdate(MBB, MI, dl, TII, AArch64::NoRegister, Amount);
+    }
+  } else if (CalleePopAmount != 0) {
+    // If the calling convention demands that the callee pops arguments from the
+    // stack, we want to add it back if we have a reserved call frame.
+    assert(CalleePopAmount < 0xfff && "call frame too large");
+    emitSPUpdate(MBB, MI, dl, TII, AArch64::NoRegister, -CalleePopAmount);
+  }
+
+  MBB.erase(MI);
+}