Use the space freed up by sparc and zaurus to import LLVM.

ok hackroom@

1 files changed, 591 insertions, 0 deletions

diff --git a/gnu/llvm/lib/Target/XCore/XCoreFrameLowering.cpp b/gnu/llvm/lib/Target/XCore/XCoreFrameLowering.cpp
new file mode 100644
index 00000000000..ae493de083b
--- /dev/null
+++ b/gnu/llvm/lib/Target/XCore/XCoreFrameLowering.cpp
@@ -0,0 +1,591 @@
+//===-- XCoreFrameLowering.cpp - Frame info for XCore Target --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains XCore frame information that doesn't fit anywhere else
+// cleanly...
+//
+//===----------------------------------------------------------------------===//
+
+#include "XCoreFrameLowering.h"
+#include "XCore.h"
+#include "XCoreInstrInfo.h"
+#include "XCoreMachineFunctionInfo.h"
+#include "XCoreSubtarget.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineModuleInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/RegisterScavenging.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Function.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetOptions.h"
+#include <algorithm>    // std::sort
+
+using namespace llvm;
+
+static const unsigned FramePtr = XCore::R10;
+static const int MaxImmU16 = (1<<16) - 1;
+
+// helper functions. FIXME: Eliminate.
+static inline bool isImmU6(unsigned val) {
+  return val < (1 << 6);
+}
+
+static inline bool isImmU16(unsigned val) {
+  return val < (1 << 16);
+}
+
+// Helper structure with compare function for handling stack slots.
+namespace {
+struct StackSlotInfo {
+  int FI;
+  int Offset;
+  unsigned Reg;
+  StackSlotInfo(int f, int o, int r) : FI(f), Offset(o), Reg(r){};
+};
+}  // end anonymous namespace
+
+static bool CompareSSIOffset(const StackSlotInfo& a, const StackSlotInfo& b) {
+  return a.Offset < b.Offset;
+}
+
+
+static void EmitDefCfaRegister(MachineBasicBlock &MBB,
+                               MachineBasicBlock::iterator MBBI, DebugLoc dl,
+                               const TargetInstrInfo &TII,
+                               MachineModuleInfo *MMI, unsigned DRegNum) {
+  unsigned CFIIndex = MMI->addFrameInst(
+      MCCFIInstruction::createDefCfaRegister(nullptr, DRegNum));
+  BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+      .addCFIIndex(CFIIndex);
+}
+
+static void EmitDefCfaOffset(MachineBasicBlock &MBB,
+                             MachineBasicBlock::iterator MBBI, DebugLoc dl,
+                             const TargetInstrInfo &TII,
+                             MachineModuleInfo *MMI, int Offset) {
+  unsigned CFIIndex =
+      MMI->addFrameInst(MCCFIInstruction::createDefCfaOffset(nullptr, -Offset));
+  BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+      .addCFIIndex(CFIIndex);
+}
+
+static void EmitCfiOffset(MachineBasicBlock &MBB,
+                          MachineBasicBlock::iterator MBBI, DebugLoc dl,
+                          const TargetInstrInfo &TII, MachineModuleInfo *MMI,
+                          unsigned DRegNum, int Offset) {
+  unsigned CFIIndex = MMI->addFrameInst(
+      MCCFIInstruction::createOffset(nullptr, DRegNum, Offset));
+  BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
+      .addCFIIndex(CFIIndex);
+}
+
+/// The SP register is moved in steps of 'MaxImmU16' towards the bottom of the
+/// frame. During these steps, it may be necessary to spill registers.
+/// IfNeededExtSP emits the necessary EXTSP instructions to move the SP only
+/// as far as to make 'OffsetFromBottom' reachable using an STWSP_lru6.
+/// \param OffsetFromTop the spill offset from the top of the frame.
+/// \param [in,out] Adjusted the current SP offset from the top of the frame.
+static void IfNeededExtSP(MachineBasicBlock &MBB,
+                          MachineBasicBlock::iterator MBBI, DebugLoc dl,
+                          const TargetInstrInfo &TII, MachineModuleInfo *MMI,
+                          int OffsetFromTop, int &Adjusted, int FrameSize,
+                          bool emitFrameMoves) {
+  while (OffsetFromTop > Adjusted) {
+    assert(Adjusted < FrameSize && "OffsetFromTop is beyond FrameSize");
+    int remaining = FrameSize - Adjusted;
+    int OpImm = (remaining > MaxImmU16) ? MaxImmU16 : remaining;
+    int Opcode = isImmU6(OpImm) ? XCore::EXTSP_u6 : XCore::EXTSP_lu6;
+    BuildMI(MBB, MBBI, dl, TII.get(Opcode)).addImm(OpImm);
+    Adjusted += OpImm;
+    if (emitFrameMoves)
+      EmitDefCfaOffset(MBB, MBBI, dl, TII, MMI, Adjusted*4);
+  }
+}
+
+/// The SP register is moved in steps of 'MaxImmU16' towards the top of the
+/// frame. During these steps, it may be necessary to re-load registers.
+/// IfNeededLDAWSP emits the necessary LDAWSP instructions to move the SP only
+/// as far as to make 'OffsetFromTop' reachable using an LDAWSP_lru6.
+/// \param OffsetFromTop the spill offset from the top of the frame.
+/// \param [in,out] RemainingAdj the current SP offset from the top of the
+/// frame.
+static void IfNeededLDAWSP(MachineBasicBlock &MBB,
+                           MachineBasicBlock::iterator MBBI, DebugLoc dl,
+                           const TargetInstrInfo &TII, int OffsetFromTop,
+                           int &RemainingAdj) {
+  while (OffsetFromTop < RemainingAdj - MaxImmU16) {
+    assert(RemainingAdj && "OffsetFromTop is beyond FrameSize");
+    int OpImm = (RemainingAdj > MaxImmU16) ? MaxImmU16 : RemainingAdj;
+    int Opcode = isImmU6(OpImm) ? XCore::LDAWSP_ru6 : XCore::LDAWSP_lru6;
+    BuildMI(MBB, MBBI, dl, TII.get(Opcode), XCore::SP).addImm(OpImm);
+    RemainingAdj -= OpImm;
+  }
+}
+
+/// Creates an ordered list of registers that are spilled
+/// during the emitPrologue/emitEpilogue.
+/// Registers are ordered according to their frame offset.
+/// As offsets are negative, the largest offsets will be first.
+static void GetSpillList(SmallVectorImpl<StackSlotInfo> &SpillList,
+                         MachineFrameInfo *MFI, XCoreFunctionInfo *XFI,
+                         bool fetchLR, bool fetchFP) {
+  if (fetchLR) {
+    int Offset = MFI->getObjectOffset(XFI->getLRSpillSlot());
+    SpillList.push_back(StackSlotInfo(XFI->getLRSpillSlot(),
+                                      Offset,
+                                      XCore::LR));
+  }
+  if (fetchFP) {
+    int Offset = MFI->getObjectOffset(XFI->getFPSpillSlot());
+    SpillList.push_back(StackSlotInfo(XFI->getFPSpillSlot(),
+                                      Offset,
+                                      FramePtr));
+  }
+  std::sort(SpillList.begin(), SpillList.end(), CompareSSIOffset);
+}
+
+/// Creates an ordered list of EH info register 'spills'.
+/// These slots are only used by the unwinder and calls to llvm.eh.return().
+/// Registers are ordered according to their frame offset.
+/// As offsets are negative, the largest offsets will be first.
+static void GetEHSpillList(SmallVectorImpl<StackSlotInfo> &SpillList,
+                           MachineFrameInfo *MFI, XCoreFunctionInfo *XFI,
+                           const Constant *PersonalityFn,
+                           const TargetLowering *TL) {
+  assert(XFI->hasEHSpillSlot() && "There are no EH register spill slots");
+  const int *EHSlot = XFI->getEHSpillSlot();
+  SpillList.push_back(
+      StackSlotInfo(EHSlot[0], MFI->getObjectOffset(EHSlot[0]),
+                    TL->getExceptionPointerRegister(PersonalityFn)));
+  SpillList.push_back(
+      StackSlotInfo(EHSlot[0], MFI->getObjectOffset(EHSlot[1]),
+                    TL->getExceptionSelectorRegister(PersonalityFn)));
+  std::sort(SpillList.begin(), SpillList.end(), CompareSSIOffset);
+}
+
+static MachineMemOperand *
+getFrameIndexMMO(MachineBasicBlock &MBB, int FrameIndex, unsigned flags) {
+  MachineFunction *MF = MBB.getParent();
+  const MachineFrameInfo &MFI = *MF->getFrameInfo();
+  MachineMemOperand *MMO = MF->getMachineMemOperand(
+      MachinePointerInfo::getFixedStack(*MF, FrameIndex), flags,
+      MFI.getObjectSize(FrameIndex), MFI.getObjectAlignment(FrameIndex));
+  return MMO;
+}
+
+
+/// Restore clobbered registers with their spill slot value.
+/// The SP will be adjusted at the same time, thus the SpillList must be ordered
+/// with the largest (negative) offsets first.
+static void
+RestoreSpillList(MachineBasicBlock &MBB, MachineBasicBlock::iterator MBBI,
+                 DebugLoc dl, const TargetInstrInfo &TII, int &RemainingAdj,
+                 SmallVectorImpl<StackSlotInfo> &SpillList) {
+  for (unsigned i = 0, e = SpillList.size(); i != e; ++i) {
+    assert(SpillList[i].Offset % 4 == 0 && "Misaligned stack offset");
+    assert(SpillList[i].Offset <= 0 && "Unexpected positive stack offset");
+    int OffsetFromTop = - SpillList[i].Offset/4;
+    IfNeededLDAWSP(MBB, MBBI, dl, TII, OffsetFromTop, RemainingAdj);
+    int Offset = RemainingAdj - OffsetFromTop;
+    int Opcode = isImmU6(Offset) ? XCore::LDWSP_ru6 : XCore::LDWSP_lru6;
+    BuildMI(MBB, MBBI, dl, TII.get(Opcode), SpillList[i].Reg)
+      .addImm(Offset)
+      .addMemOperand(getFrameIndexMMO(MBB, SpillList[i].FI,
+                                      MachineMemOperand::MOLoad));
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// XCoreFrameLowering:
+//===----------------------------------------------------------------------===//
+
+XCoreFrameLowering::XCoreFrameLowering(const XCoreSubtarget &sti)
+  : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, 4, 0) {
+  // Do nothing
+}
+
+bool XCoreFrameLowering::hasFP(const MachineFunction &MF) const {
+  return MF.getTarget().Options.DisableFramePointerElim(MF) ||
+         MF.getFrameInfo()->hasVarSizedObjects();
+}
+
+void XCoreFrameLowering::emitPrologue(MachineFunction &MF,
+                                      MachineBasicBlock &MBB) const {
+  assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
+  MachineBasicBlock::iterator MBBI = MBB.begin();
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  MachineModuleInfo *MMI = &MF.getMMI();
+  const MCRegisterInfo *MRI = MMI->getContext().getRegisterInfo();
+  const XCoreInstrInfo &TII = *MF.getSubtarget<XCoreSubtarget>().getInstrInfo();
+  XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
+  // Debug location must be unknown since the first debug location is used
+  // to determine the end of the prologue.
+  DebugLoc dl;
+
+  if (MFI->getMaxAlignment() > getStackAlignment())
+    report_fatal_error("emitPrologue unsupported alignment: "
+                       + Twine(MFI->getMaxAlignment()));
+
+  const AttributeSet &PAL = MF.getFunction()->getAttributes();
+  if (PAL.hasAttrSomewhere(Attribute::Nest))
+    BuildMI(MBB, MBBI, dl, TII.get(XCore::LDWSP_ru6), XCore::R11).addImm(0);
+    // FIX: Needs addMemOperand() but can't use getFixedStack() or getStack().
+
+  // Work out frame sizes.
+  // We will adjust the SP in stages towards the final FrameSize.
+  assert(MFI->getStackSize()%4 == 0 && "Misaligned frame size");
+  const int FrameSize = MFI->getStackSize() / 4;
+  int Adjusted = 0;
+
+  bool saveLR = XFI->hasLRSpillSlot();
+  bool UseENTSP = saveLR && FrameSize
+                  && (MFI->getObjectOffset(XFI->getLRSpillSlot()) == 0);
+  if (UseENTSP)
+    saveLR = false;
+  bool FP = hasFP(MF);
+  bool emitFrameMoves = XCoreRegisterInfo::needsFrameMoves(MF);
+
+  if (UseENTSP) {
+    // Allocate space on the stack at the same time as saving LR.
+    Adjusted = (FrameSize > MaxImmU16) ? MaxImmU16 : FrameSize;
+    int Opcode = isImmU6(Adjusted) ? XCore::ENTSP_u6 : XCore::ENTSP_lu6;
+    MBB.addLiveIn(XCore::LR);
+    MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(Opcode));
+    MIB.addImm(Adjusted);
+    MIB->addRegisterKilled(XCore::LR, MF.getSubtarget().getRegisterInfo(),
+                           true);
+    if (emitFrameMoves) {
+      EmitDefCfaOffset(MBB, MBBI, dl, TII, MMI, Adjusted*4);
+      unsigned DRegNum = MRI->getDwarfRegNum(XCore::LR, true);
+      EmitCfiOffset(MBB, MBBI, dl, TII, MMI, DRegNum, 0);
+    }
+  }
+
+  // If necessary, save LR and FP to the stack, as we EXTSP.
+  SmallVector<StackSlotInfo,2> SpillList;
+  GetSpillList(SpillList, MFI, XFI, saveLR, FP);
+  // We want the nearest (negative) offsets first, so reverse list.
+  std::reverse(SpillList.begin(), SpillList.end());
+  for (unsigned i = 0, e = SpillList.size(); i != e; ++i) {
+    assert(SpillList[i].Offset % 4 == 0 && "Misaligned stack offset");
+    assert(SpillList[i].Offset <= 0 && "Unexpected positive stack offset");
+    int OffsetFromTop = - SpillList[i].Offset/4;
+    IfNeededExtSP(MBB, MBBI, dl, TII, MMI, OffsetFromTop, Adjusted, FrameSize,
+                  emitFrameMoves);
+    int Offset = Adjusted - OffsetFromTop;
+    int Opcode = isImmU6(Offset) ? XCore::STWSP_ru6 : XCore::STWSP_lru6;
+    MBB.addLiveIn(SpillList[i].Reg);
+    BuildMI(MBB, MBBI, dl, TII.get(Opcode))
+      .addReg(SpillList[i].Reg, RegState::Kill)
+      .addImm(Offset)
+      .addMemOperand(getFrameIndexMMO(MBB, SpillList[i].FI,
+                                      MachineMemOperand::MOStore));
+    if (emitFrameMoves) {
+      unsigned DRegNum = MRI->getDwarfRegNum(SpillList[i].Reg, true);
+      EmitCfiOffset(MBB, MBBI, dl, TII, MMI, DRegNum, SpillList[i].Offset);
+    }
+  }
+
+  // Complete any remaining Stack adjustment.
+  IfNeededExtSP(MBB, MBBI, dl, TII, MMI, FrameSize, Adjusted, FrameSize,
+                emitFrameMoves);
+  assert(Adjusted==FrameSize && "IfNeededExtSP has not completed adjustment");
+
+  if (FP) {
+    // Set the FP from the SP.
+    BuildMI(MBB, MBBI, dl, TII.get(XCore::LDAWSP_ru6), FramePtr).addImm(0);
+    if (emitFrameMoves)
+      EmitDefCfaRegister(MBB, MBBI, dl, TII, MMI,
+                         MRI->getDwarfRegNum(FramePtr, true));
+  }
+
+  if (emitFrameMoves) {
+    // Frame moves for callee saved.
+    for (const auto &SpillLabel : XFI->getSpillLabels()) {
+      MachineBasicBlock::iterator Pos = SpillLabel.first;
+      ++Pos;
+      const CalleeSavedInfo &CSI = SpillLabel.second;
+      int Offset = MFI->getObjectOffset(CSI.getFrameIdx());
+      unsigned DRegNum = MRI->getDwarfRegNum(CSI.getReg(), true);
+      EmitCfiOffset(MBB, Pos, dl, TII, MMI, DRegNum, Offset);
+    }
+    if (XFI->hasEHSpillSlot()) {
+      // The unwinder requires stack slot & CFI offsets for the exception info.
+      // We do not save/spill these registers.
+      const Function *Fn = MF.getFunction();
+      const Constant *PersonalityFn =
+          Fn->hasPersonalityFn() ? Fn->getPersonalityFn() : nullptr;
+      SmallVector<StackSlotInfo, 2> SpillList;
+      GetEHSpillList(SpillList, MFI, XFI, PersonalityFn,
+                     MF.getSubtarget().getTargetLowering());
+      assert(SpillList.size()==2 && "Unexpected SpillList size");
+      EmitCfiOffset(MBB, MBBI, dl, TII, MMI,
+                    MRI->getDwarfRegNum(SpillList[0].Reg, true),
+                    SpillList[0].Offset);
+      EmitCfiOffset(MBB, MBBI, dl, TII, MMI,
+                    MRI->getDwarfRegNum(SpillList[1].Reg, true),
+                    SpillList[1].Offset);
+    }
+  }
+}
+
+void XCoreFrameLowering::emitEpilogue(MachineFunction &MF,
+                                     MachineBasicBlock &MBB) const {
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
+  const XCoreInstrInfo &TII = *MF.getSubtarget<XCoreSubtarget>().getInstrInfo();
+  XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
+  DebugLoc dl = MBBI->getDebugLoc();
+  unsigned RetOpcode = MBBI->getOpcode();
+
+  // Work out frame sizes.
+  // We will adjust the SP in stages towards the final FrameSize.
+  int RemainingAdj = MFI->getStackSize();
+  assert(RemainingAdj%4 == 0 && "Misaligned frame size");
+  RemainingAdj /= 4;
+
+  if (RetOpcode == XCore::EH_RETURN) {
+    // 'Restore' the exception info the unwinder has placed into the stack
+    // slots.
+    const Function *Fn = MF.getFunction();
+    const Constant *PersonalityFn =
+        Fn->hasPersonalityFn() ? Fn->getPersonalityFn() : nullptr;
+    SmallVector<StackSlotInfo, 2> SpillList;
+    GetEHSpillList(SpillList, MFI, XFI, PersonalityFn,
+                   MF.getSubtarget().getTargetLowering());
+    RestoreSpillList(MBB, MBBI, dl, TII, RemainingAdj, SpillList);
+
+    // Return to the landing pad.
+    unsigned EhStackReg = MBBI->getOperand(0).getReg();
+    unsigned EhHandlerReg = MBBI->getOperand(1).getReg();
+    BuildMI(MBB, MBBI, dl, TII.get(XCore::SETSP_1r)).addReg(EhStackReg);
+    BuildMI(MBB, MBBI, dl, TII.get(XCore::BAU_1r)).addReg(EhHandlerReg);
+    MBB.erase(MBBI);  // Erase the previous return instruction.
+    return;
+  }
+
+  bool restoreLR = XFI->hasLRSpillSlot();
+  bool UseRETSP = restoreLR && RemainingAdj
+                  && (MFI->getObjectOffset(XFI->getLRSpillSlot()) == 0);
+  if (UseRETSP)
+    restoreLR = false;
+  bool FP = hasFP(MF);
+
+  if (FP) // Restore the stack pointer.
+    BuildMI(MBB, MBBI, dl, TII.get(XCore::SETSP_1r)).addReg(FramePtr);
+
+  // If necessary, restore LR and FP from the stack, as we EXTSP.
+  SmallVector<StackSlotInfo,2> SpillList;
+  GetSpillList(SpillList, MFI, XFI, restoreLR, FP);
+  RestoreSpillList(MBB, MBBI, dl, TII, RemainingAdj, SpillList);
+
+  if (RemainingAdj) {
+    // Complete all but one of the remaining Stack adjustments.
+    IfNeededLDAWSP(MBB, MBBI, dl, TII, 0, RemainingAdj);
+    if (UseRETSP) {
+      // Fold prologue into return instruction
+      assert(RetOpcode == XCore::RETSP_u6
+             || RetOpcode == XCore::RETSP_lu6);
+      int Opcode = isImmU6(RemainingAdj) ? XCore::RETSP_u6 : XCore::RETSP_lu6;
+      MachineInstrBuilder MIB = BuildMI(MBB, MBBI, dl, TII.get(Opcode))
+                                  .addImm(RemainingAdj);
+      for (unsigned i = 3, e = MBBI->getNumOperands(); i < e; ++i)
+        MIB->addOperand(MBBI->getOperand(i)); // copy any variadic operands
+      MBB.erase(MBBI);  // Erase the previous return instruction.
+    } else {
+      int Opcode = isImmU6(RemainingAdj) ? XCore::LDAWSP_ru6 :
+                                           XCore::LDAWSP_lru6;
+      BuildMI(MBB, MBBI, dl, TII.get(Opcode), XCore::SP).addImm(RemainingAdj);
+      // Don't erase the return instruction.
+    }
+  } // else Don't erase the return instruction.
+}
+
+bool XCoreFrameLowering::
+spillCalleeSavedRegisters(MachineBasicBlock &MBB,
+                          MachineBasicBlock::iterator MI,
+                          const std::vector<CalleeSavedInfo> &CSI,
+                          const TargetRegisterInfo *TRI) const {
+  if (CSI.empty())
+    return true;
+
+  MachineFunction *MF = MBB.getParent();
+  const TargetInstrInfo &TII = *MF->getSubtarget().getInstrInfo();
+  XCoreFunctionInfo *XFI = MF->getInfo<XCoreFunctionInfo>();
+  bool emitFrameMoves = XCoreRegisterInfo::needsFrameMoves(*MF);
+
+  DebugLoc DL;
+  if (MI != MBB.end() && !MI->isDebugValue())
+    DL = MI->getDebugLoc();
+
+  for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
+                                                    it != CSI.end(); ++it) {
+    unsigned Reg = it->getReg();
+    assert(Reg != XCore::LR && !(Reg == XCore::R10 && hasFP(*MF)) &&
+           "LR & FP are always handled in emitPrologue");
+
+    // Add the callee-saved register as live-in. It's killed at the spill.
+    MBB.addLiveIn(Reg);
+    const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
+    TII.storeRegToStackSlot(MBB, MI, Reg, true, it->getFrameIdx(), RC, TRI);
+    if (emitFrameMoves) {
+      auto Store = MI;
+      --Store;
+      XFI->getSpillLabels().push_back(std::make_pair(Store, *it));
+    }
+  }
+  return true;
+}
+
+bool XCoreFrameLowering::
+restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
+                            MachineBasicBlock::iterator MI,
+                            const std::vector<CalleeSavedInfo> &CSI,
+                            const TargetRegisterInfo *TRI) const{
+  MachineFunction *MF = MBB.getParent();
+  const TargetInstrInfo &TII = *MF->getSubtarget().getInstrInfo();
+  bool AtStart = MI == MBB.begin();
+  MachineBasicBlock::iterator BeforeI = MI;
+  if (!AtStart)
+    --BeforeI;
+  for (std::vector<CalleeSavedInfo>::const_iterator it = CSI.begin();
+                                                    it != CSI.end(); ++it) {
+    unsigned Reg = it->getReg();
+    assert(Reg != XCore::LR && !(Reg == XCore::R10 && hasFP(*MF)) &&
+           "LR & FP are always handled in emitEpilogue");
+
+    const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
+    TII.loadRegFromStackSlot(MBB, MI, Reg, it->getFrameIdx(), RC, TRI);
+    assert(MI != MBB.begin() &&
+           "loadRegFromStackSlot didn't insert any code!");
+    // Insert in reverse order.  loadRegFromStackSlot can insert multiple
+    // instructions.
+    if (AtStart)
+      MI = MBB.begin();
+    else {
+      MI = BeforeI;
+      ++MI;
+    }
+  }
+  return true;
+}
+
+// This function eliminates ADJCALLSTACKDOWN,
+// ADJCALLSTACKUP pseudo instructions
+void XCoreFrameLowering::
+eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
+                              MachineBasicBlock::iterator I) const {
+  const XCoreInstrInfo &TII = *MF.getSubtarget<XCoreSubtarget>().getInstrInfo();
+  if (!hasReservedCallFrame(MF)) {
+    // Turn the adjcallstackdown instruction into 'extsp <amt>' and the
+    // adjcallstackup instruction into 'ldaw sp, sp[<amt>]'
+    MachineInstr *Old = I;
+    uint64_t 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 = getStackAlignment();
+      Amount = (Amount+Align-1)/Align*Align;
+
+      assert(Amount%4 == 0);
+      Amount /= 4;
+
+      bool isU6 = isImmU6(Amount);
+      if (!isU6 && !isImmU16(Amount)) {
+        // FIX could emit multiple instructions in this case.
+#ifndef NDEBUG
+        errs() << "eliminateCallFramePseudoInstr size too big: "
+               << Amount << "\n";
+#endif
+        llvm_unreachable(nullptr);
+      }
+
+      MachineInstr *New;
+      if (Old->getOpcode() == XCore::ADJCALLSTACKDOWN) {
+        int Opcode = isU6 ? XCore::EXTSP_u6 : XCore::EXTSP_lu6;
+        New=BuildMI(MF, Old->getDebugLoc(), TII.get(Opcode))
+          .addImm(Amount);
+      } else {
+        assert(Old->getOpcode() == XCore::ADJCALLSTACKUP);
+        int Opcode = isU6 ? XCore::LDAWSP_ru6 : XCore::LDAWSP_lru6;
+        New=BuildMI(MF, Old->getDebugLoc(), TII.get(Opcode), XCore::SP)
+          .addImm(Amount);
+      }
+
+      // Replace the pseudo instruction with a new instruction...
+      MBB.insert(I, New);
+    }
+  }
+
+  MBB.erase(I);
+}
+
+void XCoreFrameLowering::determineCalleeSaves(MachineFunction &MF,
+                                              BitVector &SavedRegs,
+                                              RegScavenger *RS) const {
+  TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
+
+  XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
+
+  const MachineRegisterInfo &MRI = MF.getRegInfo();
+  bool LRUsed = MRI.isPhysRegModified(XCore::LR);
+
+  if (!LRUsed && !MF.getFunction()->isVarArg() &&
+      MF.getFrameInfo()->estimateStackSize(MF))
+    // If we need to extend the stack it is more efficient to use entsp / retsp.
+    // We force the LR to be saved so these instructions are used.
+    LRUsed = true;
+
+  if (MF.getMMI().callsUnwindInit() || MF.getMMI().callsEHReturn()) {
+    // The unwinder expects to find spill slots for the exception info regs R0
+    // & R1. These are used during llvm.eh.return() to 'restore' the exception
+    // info. N.B. we do not spill or restore R0, R1 during normal operation.
+    XFI->createEHSpillSlot(MF);
+    // As we will  have a stack, we force the LR to be saved.
+    LRUsed = true;
+  }
+
+  if (LRUsed) {
+    // We will handle the LR in the prologue/epilogue
+    // and allocate space on the stack ourselves.
+    SavedRegs.reset(XCore::LR);
+    XFI->createLRSpillSlot(MF);
+  }
+
+  if (hasFP(MF))
+    // A callee save register is used to hold the FP.
+    // This needs saving / restoring in the epilogue / prologue.
+    XFI->createFPSpillSlot(MF);
+}
+
+void XCoreFrameLowering::
+processFunctionBeforeFrameFinalized(MachineFunction &MF,
+                                    RegScavenger *RS) const {
+  assert(RS && "requiresRegisterScavenging failed");
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  const TargetRegisterClass *RC = &XCore::GRRegsRegClass;
+  XCoreFunctionInfo *XFI = MF.getInfo<XCoreFunctionInfo>();
+  // Reserve slots close to SP or frame pointer for Scavenging spills.
+  // When using SP for small frames, we don't need any scratch registers.
+  // When using SP for large frames, we may need 2 scratch registers.
+  // When using FP, for large or small frames, we may need 1 scratch register.
+  if (XFI->isLargeFrame(MF) || hasFP(MF))
+    RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+                                                       RC->getAlignment(),
+                                                       false));
+  if (XFI->isLargeFrame(MF) && !hasFP(MF))
+    RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+                                                       RC->getAlignment(),
+                                                       false));
+}