Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release:

MFC r309142 (by emaste):

Add WITH_LLD_AS_LD build knob

If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation

MFC r310840:

Reapply 310775, now it also builds correctly if lldb is disabled:

Move llvm-objdump from CLANG_EXTRAS to installed by default

We currently install three tools from binutils 2.17.50: as, ld, and
objdump. Work is underway to migrate to a permissively-licensed
tool-chain, with one goal being the retirement of binutils 2.17.50.

LLVM's llvm-objdump is intended to be compatible with GNU objdump
although it is currently missing some options and may have formatting
differences. Enable it by default for testing and further investigation.
It may later be changed to install as /usr/bin/objdump, it becomes a
fully viable replacement.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D8879

MFC r312855 (by emaste):

Rename LLD_AS_LD to LLD_IS_LD, for consistency with CLANG_IS_CC

Reported by:	Dan McGregor <dan.mcgregor usask.ca>

MFC r313559 | glebius | 2017-02-10 18:34:48 +0100 (Fri, 10 Feb 2017) | 5 lines

Don't check struct rtentry on FreeBSD, it is an internal kernel structure.
On other systems it may be API structure for SIOCADDRT/SIOCDELRT.

Reviewed by:	emaste, dim

MFC r314152 (by jkim):

Remove an assembler flag, which is redundant since r309124.  The upstream
took care of it by introducing a macro NO_EXEC_STACK_DIRECTIVE.

http://llvm.org/viewvc/llvm-project?rev=273500&view=rev

Reviewed by:	dim

MFC r314564:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
4.0.0 (branches/release_40 296509).  The release will follow soon.

Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
support to build; see UPDATING for more information.

Also note that as of 4.0.0, lld should be able to link the base system
on amd64 and aarch64.  See the WITH_LLD_IS_LLD setting in src.conf(5).
Though please be aware that this is work in progress.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/4.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Jan Beich, Antoine Brodin and Eric Fiselier for
their help.

Relnotes:	yes
Exp-run:	antoine
PR:		215969, 216008

MFC r314708:

For now, revert r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

This commit is the cause of excessive compile times on skein_block.c
(and possibly other files) during kernel builds on amd64.

We never saw the problematic behavior described in this upstream commit,
so for now it is better to revert it.  An upstream bug has been filed
here: https://bugs.llvm.org/show_bug.cgi?id=32142

Reported by:	mjg

MFC r314795:

Reapply r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

Pull in r296992 from upstream llvm trunk (by Sanjoy Das):

  [SCEV] Decrease the recursion threshold for CompareValueComplexity

  Fixes PR32142.

  r287232 accidentally increased the recursion threshold for
  CompareValueComplexity from 2 to 32.  This change reverses that
  change by introducing a separate flag for CompareValueComplexity's
  threshold.

The latter revision fixes the excessive compile times for skein_block.c.

MFC r314907 | mmel | 2017-03-08 12:40:27 +0100 (Wed, 08 Mar 2017) | 7 lines

Unbreak ARMv6 world.

The new compiler_rt library imported with clang 4.0.0 have several fatal
issues (non-functional __udivsi3 for example) with ARM specific instrict
functions. As temporary workaround, until upstream solve these problems,
disable all thumb[1][2] related feature.

MFC r315016:

Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release.
We were already very close to the last release candidate, so this is a
pretty minor update.

Relnotes:	yes

MFC r316005:

Revert r314907, and pull in r298713 from upstream compiler-rt trunk (by
Weiming Zhao):

  builtins: Select correct code fragments when compiling for Thumb1/Thum2/ARM ISA.

  Summary:
  Value of __ARM_ARCH_ISA_THUMB isn't based on the actual compilation
  mode (-mthumb, -marm), it reflect's capability of given CPU.

  Due to this:
   - use  __tbumb__ and __thumb2__ insteand of __ARM_ARCH_ISA_THUMB
   - use '.thumb' directive consistently  in all affected files
   - decorate all thumb functions using
     DEFINE_COMPILERRT_THUMB_FUNCTION()

  ---------
  Note: This patch doesn't fix broken Thumb1 variant of __udivsi3 !

  Reviewers: weimingz, rengolin, compnerd

  Subscribers: aemerson, dim

  Differential Revision: https://reviews.llvm.org/D30938

Discussed with:	mmel

1 files changed, 538 insertions, 0 deletions

diff --git a/contrib/llvm/lib/Target/AVR/AVRFrameLowering.cpp b/contrib/llvm/lib/Target/AVR/AVRFrameLowering.cpp
new file mode 100644
index 0000000..b8cb221
--- /dev/null
+++ b/contrib/llvm/lib/Target/AVR/AVRFrameLowering.cpp
@@ -0,0 +1,538 @@
+//===-- AVRFrameLowering.cpp - AVR 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 AVR implementation of TargetFrameLowering class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "AVRFrameLowering.h"
+
+#include "AVR.h"
+#include "AVRInstrInfo.h"
+#include "AVRMachineFunctionInfo.h"
+#include "AVRTargetMachine.h"
+#include "MCTargetDesc/AVRMCTargetDesc.h"
+
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/IR/Function.h"
+
+#include <vector>
+
+namespace llvm {
+
+AVRFrameLowering::AVRFrameLowering()
+    : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, 1, -2) {}
+
+bool AVRFrameLowering::canSimplifyCallFramePseudos(
+    const MachineFunction &MF) const {
+  // Always simplify call frame pseudo instructions, even when
+  // hasReservedCallFrame is false.
+  return true;
+}
+
+bool AVRFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
+  // Reserve call frame memory in function prologue under the following
+  // conditions:
+  // - Y pointer is reserved to be the frame pointer.
+  // - The function does not contain variable sized objects.
+
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  return hasFP(MF) && !MFI.hasVarSizedObjects();
+}
+
+void AVRFrameLowering::emitPrologue(MachineFunction &MF,
+                                    MachineBasicBlock &MBB) const {
+  MachineBasicBlock::iterator MBBI = MBB.begin();
+  CallingConv::ID CallConv = MF.getFunction()->getCallingConv();
+  DebugLoc DL = (MBBI != MBB.end()) ? MBBI->getDebugLoc() : DebugLoc();
+  const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
+  const AVRInstrInfo &TII = *STI.getInstrInfo();
+
+  // Interrupt handlers re-enable interrupts in function entry.
+  if (CallConv == CallingConv::AVR_INTR) {
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::BSETs))
+        .addImm(0x07)
+        .setMIFlag(MachineInstr::FrameSetup);
+  }
+
+  // Emit special prologue code to save R1, R0 and SREG in interrupt/signal
+  // handlers before saving any other registers.
+  if (CallConv == CallingConv::AVR_INTR ||
+      CallConv == CallingConv::AVR_SIGNAL) {
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::PUSHWRr))
+        .addReg(AVR::R1R0, RegState::Kill)
+        .setMIFlag(MachineInstr::FrameSetup);
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::INRdA), AVR::R0)
+        .addImm(0x3f)
+        .setMIFlag(MachineInstr::FrameSetup);
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::PUSHRr))
+        .addReg(AVR::R0, RegState::Kill)
+        .setMIFlag(MachineInstr::FrameSetup);
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::EORRdRr))
+        .addReg(AVR::R0, RegState::Define)
+        .addReg(AVR::R0, RegState::Kill)
+        .addReg(AVR::R0, RegState::Kill)
+        .setMIFlag(MachineInstr::FrameSetup);
+  }
+
+  // Early exit if the frame pointer is not needed in this function.
+  if (!hasFP(MF)) {
+    return;
+  }
+
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  const AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();
+  unsigned FrameSize = MFI.getStackSize() - AFI->getCalleeSavedFrameSize();
+
+  // Skip the callee-saved push instructions.
+  while (
+      (MBBI != MBB.end()) && MBBI->getFlag(MachineInstr::FrameSetup) &&
+      (MBBI->getOpcode() == AVR::PUSHRr || MBBI->getOpcode() == AVR::PUSHWRr)) {
+    ++MBBI;
+  }
+
+  // Update Y with the new base value.
+  BuildMI(MBB, MBBI, DL, TII.get(AVR::SPREAD), AVR::R29R28)
+      .addReg(AVR::SP)
+      .setMIFlag(MachineInstr::FrameSetup);
+
+  // Mark the FramePtr as live-in in every block except the entry.
+  for (MachineFunction::iterator I = std::next(MF.begin()), E = MF.end();
+       I != E; ++I) {
+    I->addLiveIn(AVR::R29R28);
+  }
+
+  if (!FrameSize) {
+    return;
+  }
+
+  // Reserve the necessary frame memory by doing FP -= <size>.
+  unsigned Opcode = (isUInt<6>(FrameSize)) ? AVR::SBIWRdK : AVR::SUBIWRdK;
+
+  MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(Opcode), AVR::R29R28)
+                         .addReg(AVR::R29R28, RegState::Kill)
+                         .addImm(FrameSize)
+                         .setMIFlag(MachineInstr::FrameSetup);
+  // The SREG implicit def is dead.
+  MI->getOperand(3).setIsDead();
+
+  // Write back R29R28 to SP and temporarily disable interrupts.
+  BuildMI(MBB, MBBI, DL, TII.get(AVR::SPWRITE), AVR::SP)
+      .addReg(AVR::R29R28)
+      .setMIFlag(MachineInstr::FrameSetup);
+}
+
+void AVRFrameLowering::emitEpilogue(MachineFunction &MF,
+                                    MachineBasicBlock &MBB) const {
+  CallingConv::ID CallConv = MF.getFunction()->getCallingConv();
+  bool isHandler = (CallConv == CallingConv::AVR_INTR ||
+                    CallConv == CallingConv::AVR_SIGNAL);
+
+  // Early exit if the frame pointer is not needed in this function except for
+  // signal/interrupt handlers where special code generation is required.
+  if (!hasFP(MF) && !isHandler) {
+    return;
+  }
+
+  MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
+  assert(MBBI->getDesc().isReturn() &&
+         "Can only insert epilog into returning blocks");
+
+  DebugLoc DL = MBBI->getDebugLoc();
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  const AVRMachineFunctionInfo *AFI = MF.getInfo<AVRMachineFunctionInfo>();
+  unsigned FrameSize = MFI.getStackSize() - AFI->getCalleeSavedFrameSize();
+  const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
+  const AVRInstrInfo &TII = *STI.getInstrInfo();
+
+  // Emit special epilogue code to restore R1, R0 and SREG in interrupt/signal
+  // handlers at the very end of the function, just before reti.
+  if (isHandler) {
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::POPRd), AVR::R0);
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::OUTARr))
+        .addImm(0x3f)
+        .addReg(AVR::R0, RegState::Kill);
+    BuildMI(MBB, MBBI, DL, TII.get(AVR::POPWRd), AVR::R1R0);
+  }
+
+  // Early exit if there is no need to restore the frame pointer.
+  if (!FrameSize) {
+    return;
+  }
+
+  // Skip the callee-saved pop instructions.
+  while (MBBI != MBB.begin()) {
+    MachineBasicBlock::iterator PI = std::prev(MBBI);
+    int Opc = PI->getOpcode();
+
+    if (Opc != AVR::POPRd && Opc != AVR::POPWRd && !PI->isTerminator()) {
+      break;
+    }
+
+    --MBBI;
+  }
+
+  unsigned Opcode;
+
+  // Select the optimal opcode depending on how big it is.
+  if (isUInt<6>(FrameSize)) {
+    Opcode = AVR::ADIWRdK;
+  } else {
+    Opcode = AVR::SUBIWRdK;
+    FrameSize = -FrameSize;
+  }
+
+  // Restore the frame pointer by doing FP += <size>.
+  MachineInstr *MI = BuildMI(MBB, MBBI, DL, TII.get(Opcode), AVR::R29R28)
+                         .addReg(AVR::R29R28, RegState::Kill)
+                         .addImm(FrameSize);
+  // The SREG implicit def is dead.
+  MI->getOperand(3).setIsDead();
+
+  // Write back R29R28 to SP and temporarily disable interrupts.
+  BuildMI(MBB, MBBI, DL, TII.get(AVR::SPWRITE), AVR::SP)
+      .addReg(AVR::R29R28, RegState::Kill);
+}
+
+// Return true if the specified function should have a dedicated frame
+// pointer register. This is true if the function meets any of the following
+// conditions:
+//  - a register has been spilled
+//  - has allocas
+//  - input arguments are passed using the stack
+//
+// Notice that strictly this is not a frame pointer because it contains SP after
+// frame allocation instead of having the original SP in function entry.
+bool AVRFrameLowering::hasFP(const MachineFunction &MF) const {
+  const AVRMachineFunctionInfo *FuncInfo = MF.getInfo<AVRMachineFunctionInfo>();
+
+  return (FuncInfo->getHasSpills() || FuncInfo->getHasAllocas() ||
+          FuncInfo->getHasStackArgs());
+}
+
+bool AVRFrameLowering::spillCalleeSavedRegisters(
+    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+    const std::vector<CalleeSavedInfo> &CSI,
+    const TargetRegisterInfo *TRI) const {
+  if (CSI.empty()) {
+    return false;
+  }
+
+  unsigned CalleeFrameSize = 0;
+  DebugLoc DL = MBB.findDebugLoc(MI);
+  MachineFunction &MF = *MBB.getParent();
+  const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
+  const TargetInstrInfo &TII = *STI.getInstrInfo();
+  AVRMachineFunctionInfo *AVRFI = MF.getInfo<AVRMachineFunctionInfo>();
+
+  for (unsigned i = CSI.size(); i != 0; --i) {
+    unsigned Reg = CSI[i - 1].getReg();
+    bool IsNotLiveIn = !MBB.isLiveIn(Reg);
+
+    assert(TRI->getMinimalPhysRegClass(Reg)->getSize() == 1 &&
+           "Invalid register size");
+
+    // Add the callee-saved register as live-in only if it is not already a
+    // live-in register, this usually happens with arguments that are passed
+    // through callee-saved registers.
+    if (IsNotLiveIn) {
+      MBB.addLiveIn(Reg);
+    }
+
+    // Do not kill the register when it is an input argument.
+    BuildMI(MBB, MI, DL, TII.get(AVR::PUSHRr))
+        .addReg(Reg, getKillRegState(IsNotLiveIn))
+        .setMIFlag(MachineInstr::FrameSetup);
+    ++CalleeFrameSize;
+  }
+
+  AVRFI->setCalleeSavedFrameSize(CalleeFrameSize);
+
+  return true;
+}
+
+bool AVRFrameLowering::restoreCalleeSavedRegisters(
+    MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+    const std::vector<CalleeSavedInfo> &CSI,
+    const TargetRegisterInfo *TRI) const {
+  if (CSI.empty()) {
+    return false;
+  }
+
+  DebugLoc DL = MBB.findDebugLoc(MI);
+  const MachineFunction &MF = *MBB.getParent();
+  const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
+  const TargetInstrInfo &TII = *STI.getInstrInfo();
+
+  for (const CalleeSavedInfo &CCSI : CSI) {
+    unsigned Reg = CCSI.getReg();
+
+    assert(TRI->getMinimalPhysRegClass(Reg)->getSize() == 1 &&
+           "Invalid register size");
+
+    BuildMI(MBB, MI, DL, TII.get(AVR::POPRd), Reg);
+  }
+
+  return true;
+}
+
+/// Replace pseudo store instructions that pass arguments through the stack with
+/// real instructions. If insertPushes is true then all instructions are
+/// replaced with push instructions, otherwise regular std instructions are
+/// inserted.
+static void fixStackStores(MachineBasicBlock &MBB,
+                           MachineBasicBlock::iterator MI,
+                           const TargetInstrInfo &TII, bool insertPushes) {
+  const AVRSubtarget &STI = MBB.getParent()->getSubtarget<AVRSubtarget>();
+  const TargetRegisterInfo &TRI = *STI.getRegisterInfo();
+
+  // Iterate through the BB until we hit a call instruction or we reach the end.
+  for (auto I = MI, E = MBB.end(); I != E && !I->isCall();) {
+    MachineBasicBlock::iterator NextMI = std::next(I);
+    MachineInstr &MI = *I;
+    unsigned Opcode = I->getOpcode();
+
+    // Only care of pseudo store instructions where SP is the base pointer.
+    if (Opcode != AVR::STDSPQRr && Opcode != AVR::STDWSPQRr) {
+      I = NextMI;
+      continue;
+    }
+
+    assert(MI.getOperand(0).getReg() == AVR::SP &&
+           "Invalid register, should be SP!");
+    if (insertPushes) {
+      // Replace this instruction with a push.
+      unsigned SrcReg = MI.getOperand(2).getReg();
+      bool SrcIsKill = MI.getOperand(2).isKill();
+
+      // We can't use PUSHWRr here because when expanded the order of the new
+      // instructions are reversed from what we need. Perform the expansion now.
+      if (Opcode == AVR::STDWSPQRr) {
+        BuildMI(MBB, I, MI.getDebugLoc(), TII.get(AVR::PUSHRr))
+            .addReg(TRI.getSubReg(SrcReg, AVR::sub_hi),
+                    getKillRegState(SrcIsKill));
+        BuildMI(MBB, I, MI.getDebugLoc(), TII.get(AVR::PUSHRr))
+            .addReg(TRI.getSubReg(SrcReg, AVR::sub_lo),
+                    getKillRegState(SrcIsKill));
+      } else {
+        BuildMI(MBB, I, MI.getDebugLoc(), TII.get(AVR::PUSHRr))
+            .addReg(SrcReg, getKillRegState(SrcIsKill));
+      }
+
+      MI.eraseFromParent();
+      I = NextMI;
+      continue;
+    }
+
+    // Replace this instruction with a regular store. Use Y as the base
+    // pointer since it is guaranteed to contain a copy of SP.
+    unsigned STOpc =
+        (Opcode == AVR::STDWSPQRr) ? AVR::STDWPtrQRr : AVR::STDPtrQRr;
+
+    MI.setDesc(TII.get(STOpc));
+    MI.getOperand(0).setReg(AVR::R29R28);
+
+    I = NextMI;
+  }
+}
+
+MachineBasicBlock::iterator AVRFrameLowering::eliminateCallFramePseudoInstr(
+    MachineFunction &MF, MachineBasicBlock &MBB,
+    MachineBasicBlock::iterator MI) const {
+  const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
+  const TargetFrameLowering &TFI = *STI.getFrameLowering();
+  const AVRInstrInfo &TII = *STI.getInstrInfo();
+
+  // There is nothing to insert when the call frame memory is allocated during
+  // function entry. Delete the call frame pseudo and replace all pseudo stores
+  // with real store instructions.
+  if (TFI.hasReservedCallFrame(MF)) {
+    fixStackStores(MBB, MI, TII, false);
+    return MBB.erase(MI);
+  }
+
+  DebugLoc DL = MI->getDebugLoc();
+  unsigned int Opcode = MI->getOpcode();
+  int Amount = MI->getOperand(0).getImm();
+
+  // Adjcallstackup does not need to allocate stack space for the call, instead
+  // we insert push instructions that will allocate the necessary stack.
+  // For adjcallstackdown we convert it into an 'adiw reg, <amt>' handling
+  // the read and write of SP in I/O space.
+  if (Amount != 0) {
+    assert(TFI.getStackAlignment() == 1 && "Unsupported stack alignment");
+
+    if (Opcode == TII.getCallFrameSetupOpcode()) {
+      fixStackStores(MBB, MI, TII, true);
+    } else {
+      assert(Opcode == TII.getCallFrameDestroyOpcode());
+
+      // Select the best opcode to adjust SP based on the offset size.
+      unsigned addOpcode;
+      if (isUInt<6>(Amount)) {
+        addOpcode = AVR::ADIWRdK;
+      } else {
+        addOpcode = AVR::SUBIWRdK;
+        Amount = -Amount;
+      }
+
+      // Build the instruction sequence.
+      BuildMI(MBB, MI, DL, TII.get(AVR::SPREAD), AVR::R31R30).addReg(AVR::SP);
+
+      MachineInstr *New = BuildMI(MBB, MI, DL, TII.get(addOpcode), AVR::R31R30)
+                              .addReg(AVR::R31R30, RegState::Kill)
+                              .addImm(Amount);
+      New->getOperand(3).setIsDead();
+
+      BuildMI(MBB, MI, DL, TII.get(AVR::SPWRITE), AVR::SP)
+          .addReg(AVR::R31R30, RegState::Kill);
+    }
+  }
+
+  return MBB.erase(MI);
+}
+
+void AVRFrameLowering::determineCalleeSaves(MachineFunction &MF,
+                                            BitVector &SavedRegs,
+                                            RegScavenger *RS) const {
+  TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
+
+  // Spill register Y when it is used as the frame pointer.
+  if (hasFP(MF)) {
+    SavedRegs.set(AVR::R29R28);
+    SavedRegs.set(AVR::R29);
+    SavedRegs.set(AVR::R28);
+  }
+}
+/// The frame analyzer pass.
+///
+/// Scans the function for allocas and used arguments
+/// that are passed through the stack.
+struct AVRFrameAnalyzer : public MachineFunctionPass {
+  static char ID;
+  AVRFrameAnalyzer() : MachineFunctionPass(ID) {}
+
+  bool runOnMachineFunction(MachineFunction &MF) {
+    const MachineFrameInfo &MFI = MF.getFrameInfo();
+    AVRMachineFunctionInfo *FuncInfo = MF.getInfo<AVRMachineFunctionInfo>();
+
+    // If there are no fixed frame indexes during this stage it means there
+    // are allocas present in the function.
+    if (MFI.getNumObjects() != MFI.getNumFixedObjects()) {
+      // Check for the type of allocas present in the function. We only care
+      // about fixed size allocas so do not give false positives if only
+      // variable sized allocas are present.
+      for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
+        // Variable sized objects have size 0.
+        if (MFI.getObjectSize(i)) {
+          FuncInfo->setHasAllocas(true);
+          break;
+        }
+      }
+    }
+
+    // If there are fixed frame indexes present, scan the function to see if
+    // they are really being used.
+    if (MFI.getNumFixedObjects() == 0) {
+      return false;
+    }
+
+    // Ok fixed frame indexes present, now scan the function to see if they
+    // are really being used, otherwise we can ignore them.
+    for (const MachineBasicBlock &BB : MF) {
+      for (const MachineInstr &MI : BB) {
+        int Opcode = MI.getOpcode();
+
+        if ((Opcode != AVR::LDDRdPtrQ) && (Opcode != AVR::LDDWRdPtrQ) &&
+            (Opcode != AVR::STDPtrQRr) && (Opcode != AVR::STDWPtrQRr)) {
+          continue;
+        }
+
+        for (const MachineOperand &MO : MI.operands()) {
+          if (!MO.isFI()) {
+            continue;
+          }
+
+          if (MFI.isFixedObjectIndex(MO.getIndex())) {
+            FuncInfo->setHasStackArgs(true);
+            return false;
+          }
+        }
+      }
+    }
+
+    return false;
+  }
+
+  StringRef getPassName() const { return "AVR Frame Analyzer"; }
+};
+
+char AVRFrameAnalyzer::ID = 0;
+
+/// Creates instance of the frame analyzer pass.
+FunctionPass *createAVRFrameAnalyzerPass() { return new AVRFrameAnalyzer(); }
+
+/// Create the Dynalloca Stack Pointer Save/Restore pass.
+/// Insert a copy of SP before allocating the dynamic stack memory and restore
+/// it in function exit to restore the original SP state. This avoids the need
+/// of reserving a register pair for a frame pointer.
+struct AVRDynAllocaSR : public MachineFunctionPass {
+  static char ID;
+  AVRDynAllocaSR() : MachineFunctionPass(ID) {}
+
+  bool runOnMachineFunction(MachineFunction &MF) {
+    // Early exit when there are no variable sized objects in the function.
+    if (!MF.getFrameInfo().hasVarSizedObjects()) {
+      return false;
+    }
+
+    const AVRSubtarget &STI = MF.getSubtarget<AVRSubtarget>();
+    const TargetInstrInfo &TII = *STI.getInstrInfo();
+    MachineBasicBlock &EntryMBB = MF.front();
+    MachineBasicBlock::iterator MBBI = EntryMBB.begin();
+    DebugLoc DL = EntryMBB.findDebugLoc(MBBI);
+
+    unsigned SPCopy =
+        MF.getRegInfo().createVirtualRegister(&AVR::DREGSRegClass);
+
+    // Create a copy of SP in function entry before any dynallocas are
+    // inserted.
+    BuildMI(EntryMBB, MBBI, DL, TII.get(AVR::COPY), SPCopy).addReg(AVR::SP);
+
+    // Restore SP in all exit basic blocks.
+    for (MachineBasicBlock &MBB : MF) {
+      // If last instruction is a return instruction, add a restore copy.
+      if (!MBB.empty() && MBB.back().isReturn()) {
+        MBBI = MBB.getLastNonDebugInstr();
+        DL = MBBI->getDebugLoc();
+        BuildMI(MBB, MBBI, DL, TII.get(AVR::COPY), AVR::SP)
+            .addReg(SPCopy, RegState::Kill);
+      }
+    }
+
+    return true;
+  }
+
+  StringRef getPassName() const {
+    return "AVR dynalloca stack pointer save/restore";
+  }
+};
+
+char AVRDynAllocaSR::ID = 0;
+
+/// createAVRDynAllocaSRPass - returns an instance of the dynalloca stack
+/// pointer save/restore pass.
+FunctionPass *createAVRDynAllocaSRPass() { return new AVRDynAllocaSR(); }
+
+} // end of namespace llvm
+