lib/Target/SystemZ/SystemZFrameLowering.cpp - llvm - Git at Google

 //=====- SystemZFrameLowering.cpp - SystemZ Frame 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 SystemZ implementation of TargetFrameLowering class.
 //
 //===----------------------------------------------------------------------===//

 #include "SystemZFrameLowering.h"
 #include "SystemZInstrBuilder.h"
 #include "SystemZInstrInfo.h"
 #include "SystemZMachineFunctionInfo.h"
 #include "llvm/Function.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/Target/TargetData.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Support/CommandLine.h"

 using namespace llvm;

 SystemZFrameLowering::SystemZFrameLowering(const SystemZSubtarget &sti)
   : TargetFrameLowering(TargetFrameLowering::StackGrowsDown, 8, -160), STI(sti) {
   // Fill the spill offsets map
   static const unsigned SpillOffsTab[][2] = {
     { SystemZ::R2D,  0x10 },
     { SystemZ::R3D,  0x18 },
     { SystemZ::R4D,  0x20 },
     { SystemZ::R5D,  0x28 },
     { SystemZ::R6D,  0x30 },
     { SystemZ::R7D,  0x38 },
     { SystemZ::R8D,  0x40 },
     { SystemZ::R9D,  0x48 },
     { SystemZ::R10D, 0x50 },
     { SystemZ::R11D, 0x58 },
     { SystemZ::R12D, 0x60 },
     { SystemZ::R13D, 0x68 },
     { SystemZ::R14D, 0x70 },
     { SystemZ::R15D, 0x78 }
   };

   RegSpillOffsets.grow(SystemZ::NUM_TARGET_REGS);

   for (unsigned i = 0, e = array_lengthof(SpillOffsTab); i != e; ++i)
     RegSpillOffsets[SpillOffsTab[i][0]] = SpillOffsTab[i][1];
 }

 /// needsFP - 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 SystemZFrameLowering::hasFP(const MachineFunction &MF) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   return DisableFramePointerElim(MF) || MFI->hasVarSizedObjects();
 }

 /// emitSPUpdate - Emit a series of instructions to increment / decrement the
 /// stack pointer by a constant value.
 static
 void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
                   int64_t NumBytes, const TargetInstrInfo &TII) {
   unsigned Opc; uint64_t Chunk;
   bool isSub = NumBytes < 0;
   uint64_t Offset = isSub ? -NumBytes : NumBytes;

   if (Offset >= (1LL << 15) - 1) {
     Opc = SystemZ::ADD64ri32;
     Chunk = (1LL << 31) - 1;
   } else {
     Opc = SystemZ::ADD64ri16;
     Chunk = (1LL << 15) - 1;
   }

   DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

   while (Offset) {
     uint64_t ThisVal = (Offset > Chunk) ? Chunk : Offset;
     MachineInstr *MI =
       BuildMI(MBB, MBBI, DL, TII.get(Opc), SystemZ::R15D)
       .addReg(SystemZ::R15D).addImm(isSub ? -ThisVal : ThisVal);
     // The PSW implicit def is dead.
     MI->getOperand(3).setIsDead();
     Offset -= ThisVal;
   }
 }

 void SystemZFrameLowering::emitPrologue(MachineFunction &MF) const {
   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
   MachineFrameInfo *MFI = MF.getFrameInfo();
   const SystemZInstrInfo &TII =
     *static_cast<const SystemZInstrInfo*>(MF.getTarget().getInstrInfo());
   SystemZMachineFunctionInfo *SystemZMFI =
     MF.getInfo<SystemZMachineFunctionInfo>();
   MachineBasicBlock::iterator MBBI = MBB.begin();
   DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

   // Get the number of bytes to allocate from the FrameInfo.
   // Note that area for callee-saved stuff is already allocated, thus we need to
   // 'undo' the stack movement.
   uint64_t StackSize = MFI->getStackSize();
   StackSize -= SystemZMFI->getCalleeSavedFrameSize();

   uint64_t NumBytes = StackSize - getOffsetOfLocalArea();

   // Skip the callee-saved push instructions.
   while (MBBI != MBB.end() &&
          (MBBI->getOpcode() == SystemZ::MOV64mr ||
           MBBI->getOpcode() == SystemZ::MOV64mrm))
     ++MBBI;

   if (MBBI != MBB.end())
     DL = MBBI->getDebugLoc();

   // adjust stack pointer: R15 -= numbytes
   if (StackSize || MFI->hasCalls()) {
     assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
            "Invalid stack frame calculation!");
     emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, TII);
   }

   if (hasFP(MF)) {
     // Update R11 with the new base value...
     BuildMI(MBB, MBBI, DL, TII.get(SystemZ::MOV64rr), SystemZ::R11D)
       .addReg(SystemZ::R15D);

     // Mark the FramePtr as live-in in every block except the entry.
     for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
          I != E; ++I)
       I->addLiveIn(SystemZ::R11D);

   }
 }

 void SystemZFrameLowering::emitEpilogue(MachineFunction &MF,
                                     MachineBasicBlock &MBB) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
   const SystemZInstrInfo &TII =
     *static_cast<const SystemZInstrInfo*>(MF.getTarget().getInstrInfo());
   SystemZMachineFunctionInfo *SystemZMFI =
     MF.getInfo<SystemZMachineFunctionInfo>();
   unsigned RetOpcode = MBBI->getOpcode();

   switch (RetOpcode) {
   case SystemZ::RET: break;  // These are ok
   default:
     assert(0 && "Can only insert epilog into returning blocks");
   }

   // Get the number of bytes to allocate from the FrameInfo
   // Note that area for callee-saved stuff is already allocated, thus we need to
   // 'undo' the stack movement.
   uint64_t StackSize =
     MFI->getStackSize() - SystemZMFI->getCalleeSavedFrameSize();
   uint64_t NumBytes = StackSize - getOffsetOfLocalArea();

   // Skip the final terminator instruction.
   while (MBBI != MBB.begin()) {
     MachineBasicBlock::iterator PI = prior(MBBI);
     --MBBI;
     if (!PI->getDesc().isTerminator())
       break;
   }

   // During callee-saved restores emission stack frame was not yet finialized
   // (and thus - the stack size was unknown). Tune the offset having full stack
   // size in hands.
   if (StackSize || MFI->hasCalls()) {
     assert((MBBI->getOpcode() == SystemZ::MOV64rmm ||
             MBBI->getOpcode() == SystemZ::MOV64rm) &&
            "Expected to see callee-save register restore code");
     assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
            "Invalid stack frame calculation!");

     unsigned i = 0;
     MachineInstr &MI = *MBBI;
     while (!MI.getOperand(i).isImm()) {
       ++i;
       assert(i < MI.getNumOperands() && "Unexpected restore code!");
     }

     uint64_t Offset = NumBytes + MI.getOperand(i).getImm();
     // If Offset does not fit into 20-bit signed displacement field we need to
     // emit some additional code...
     if (Offset > 524287) {
       // Fold the displacement into load instruction as much as possible.
       NumBytes = Offset - 524287;
       Offset = 524287;
       emitSPUpdate(MBB, MBBI, NumBytes, TII);
     }

     MI.getOperand(i).ChangeToImmediate(Offset);
   }
 }

 int SystemZFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
                                           int FI) const {
   const MachineFrameInfo *MFI = MF.getFrameInfo();
   const SystemZMachineFunctionInfo *SystemZMFI =
     MF.getInfo<SystemZMachineFunctionInfo>();
   int Offset = MFI->getObjectOffset(FI) + MFI->getOffsetAdjustment();
   uint64_t StackSize = MFI->getStackSize();

   // Fixed objects are really located in the "previous" frame.
   if (FI < 0)
     StackSize -= SystemZMFI->getCalleeSavedFrameSize();

   Offset += StackSize - getOffsetOfLocalArea();

   // Skip the register save area if we generated the stack frame.
   if (StackSize || MFI->hasCalls())
     Offset -= getOffsetOfLocalArea();

   return Offset;
 }

 bool
 SystemZFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
                                             MachineBasicBlock::iterator MI,
                                         const std::vector<CalleeSavedInfo> &CSI,
                                           const TargetRegisterInfo *TRI) const {
   if (CSI.empty())
     return false;

   DebugLoc DL;
   if (MI != MBB.end()) DL = MI->getDebugLoc();

   MachineFunction &MF = *MBB.getParent();
   const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
   SystemZMachineFunctionInfo *MFI = MF.getInfo<SystemZMachineFunctionInfo>();
   unsigned CalleeFrameSize = 0;

   // Scan the callee-saved and find the bounds of register spill area.
   unsigned LowReg = 0, HighReg = 0, StartOffset = -1U, EndOffset = 0;
   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
     unsigned Reg = CSI[i].getReg();
     if (!SystemZ::FP64RegClass.contains(Reg)) {
       unsigned Offset = RegSpillOffsets[Reg];
       CalleeFrameSize += 8;
       if (StartOffset > Offset) {
         LowReg = Reg; StartOffset = Offset;
       }
       if (EndOffset < Offset) {
         HighReg = Reg; EndOffset = RegSpillOffsets[Reg];
       }
     }
   }

   // Save information for epilogue inserter.
   MFI->setCalleeSavedFrameSize(CalleeFrameSize);
   MFI->setLowReg(LowReg); MFI->setHighReg(HighReg);

   // Save GPRs
   if (StartOffset) {
     // Build a store instruction. Use STORE MULTIPLE instruction if there are many
     // registers to store, otherwise - just STORE.
     MachineInstrBuilder MIB =
       BuildMI(MBB, MI, DL, TII.get((LowReg == HighReg ?
                                     SystemZ::MOV64mr : SystemZ::MOV64mrm)));

     // Add store operands.
     MIB.addReg(SystemZ::R15D).addImm(StartOffset);
     if (LowReg == HighReg)
       MIB.addReg(0);
     MIB.addReg(LowReg, RegState::Kill);
     if (LowReg != HighReg)
       MIB.addReg(HighReg, RegState::Kill);

     // Do a second scan adding regs as being killed by instruction
     for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
       unsigned Reg = CSI[i].getReg();
       // Add the callee-saved register as live-in. It's killed at the spill.
       MBB.addLiveIn(Reg);
       if (Reg != LowReg && Reg != HighReg)
         MIB.addReg(Reg, RegState::ImplicitKill);
     }
   }

   // Save FPRs
   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
     unsigned Reg = CSI[i].getReg();
     if (SystemZ::FP64RegClass.contains(Reg)) {
       MBB.addLiveIn(Reg);
       TII.storeRegToStackSlot(MBB, MI, Reg, true, CSI[i].getFrameIdx(),
                               &SystemZ::FP64RegClass, TRI);
     }
   }

   return true;
 }

 bool
 SystemZFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
                                               MachineBasicBlock::iterator MI,
                                         const std::vector<CalleeSavedInfo> &CSI,
                                           const TargetRegisterInfo *TRI) const {
   if (CSI.empty())
     return false;

   DebugLoc DL;
   if (MI != MBB.end()) DL = MI->getDebugLoc();

   MachineFunction &MF = *MBB.getParent();
   const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
   SystemZMachineFunctionInfo *MFI = MF.getInfo<SystemZMachineFunctionInfo>();

   // Restore FP registers
   for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
     unsigned Reg = CSI[i].getReg();
     if (SystemZ::FP64RegClass.contains(Reg))
       TII.loadRegFromStackSlot(MBB, MI, Reg, CSI[i].getFrameIdx(),
                                &SystemZ::FP64RegClass, TRI);
   }

   // Restore GP registers
   unsigned LowReg = MFI->getLowReg(), HighReg = MFI->getHighReg();
   unsigned StartOffset = RegSpillOffsets[LowReg];

   if (StartOffset) {
     // Build a load instruction. Use LOAD MULTIPLE instruction if there are many
     // registers to load, otherwise - just LOAD.
     MachineInstrBuilder MIB =
       BuildMI(MBB, MI, DL, TII.get((LowReg == HighReg ?
                                     SystemZ::MOV64rm : SystemZ::MOV64rmm)));
     // Add store operands.
     MIB.addReg(LowReg, RegState::Define);
     if (LowReg != HighReg)
       MIB.addReg(HighReg, RegState::Define);

     MIB.addReg(hasFP(MF) ? SystemZ::R11D : SystemZ::R15D);
     MIB.addImm(StartOffset);
     if (LowReg == HighReg)
       MIB.addReg(0);

     // Do a second scan adding regs as being defined by instruction
     for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
       unsigned Reg = CSI[i].getReg();
       if (Reg != LowReg && Reg != HighReg)
         MIB.addReg(Reg, RegState::ImplicitDefine);
     }
   }

   return true;
 }

 void
 SystemZFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
                                                        RegScavenger *RS) const {
   // Determine whether R15/R14 will ever be clobbered inside the function. And
   // if yes - mark it as 'callee' saved.
   MachineFrameInfo *FFI = MF.getFrameInfo();
   MachineRegisterInfo &MRI = MF.getRegInfo();

   // Check whether high FPRs are ever used, if yes - we need to save R15 as
   // well.
   static const unsigned HighFPRs[] = {
     SystemZ::F8L,  SystemZ::F9L,  SystemZ::F10L, SystemZ::F11L,
     SystemZ::F12L, SystemZ::F13L, SystemZ::F14L, SystemZ::F15L,
     SystemZ::F8S,  SystemZ::F9S,  SystemZ::F10S, SystemZ::F11S,
     SystemZ::F12S, SystemZ::F13S, SystemZ::F14S, SystemZ::F15S,
   };

   bool HighFPRsUsed = false;
   for (unsigned i = 0, e = array_lengthof(HighFPRs); i != e; ++i)
     HighFPRsUsed |= MRI.isPhysRegUsed(HighFPRs[i]);

   if (FFI->hasCalls())
     /* FIXME: function is varargs */
     /* FIXME: function grabs RA */
     /* FIXME: function calls eh_return */
     MRI.setPhysRegUsed(SystemZ::R14D);

   if (HighFPRsUsed ||
       FFI->hasCalls() ||
       FFI->getObjectIndexEnd() != 0 || // Contains automatic variables
       FFI->hasVarSizedObjects() // Function calls dynamic alloca's
       /* FIXME: function is varargs */)
     MRI.setPhysRegUsed(SystemZ::R15D);
 }
	//=====- SystemZFrameLowering.cpp - SystemZ Frame 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 SystemZ implementation of TargetFrameLowering class.
	//
	//===----------------------------------------------------------------------===//

	#include "SystemZFrameLowering.h"
	#include "SystemZInstrBuilder.h"
	#include "SystemZInstrInfo.h"
	#include "SystemZMachineFunctionInfo.h"
	#include "llvm/Function.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/Target/TargetData.h"
	#include "llvm/Target/TargetOptions.h"
	#include "llvm/Support/CommandLine.h"

	using namespace llvm;

	SystemZFrameLowering::SystemZFrameLowering(const SystemZSubtarget &sti)
	: TargetFrameLowering(TargetFrameLowering::StackGrowsDown, 8, -160), STI(sti) {
	// Fill the spill offsets map
	static const unsigned SpillOffsTab[][2] = {
	{ SystemZ::R2D, 0x10 },
	{ SystemZ::R3D, 0x18 },
	{ SystemZ::R4D, 0x20 },
	{ SystemZ::R5D, 0x28 },
	{ SystemZ::R6D, 0x30 },
	{ SystemZ::R7D, 0x38 },
	{ SystemZ::R8D, 0x40 },
	{ SystemZ::R9D, 0x48 },
	{ SystemZ::R10D, 0x50 },
	{ SystemZ::R11D, 0x58 },
	{ SystemZ::R12D, 0x60 },
	{ SystemZ::R13D, 0x68 },
	{ SystemZ::R14D, 0x70 },
	{ SystemZ::R15D, 0x78 }
	};

	RegSpillOffsets.grow(SystemZ::NUM_TARGET_REGS);

	for (unsigned i = 0, e = array_lengthof(SpillOffsTab); i != e; ++i)
	RegSpillOffsets[SpillOffsTab[i][0]] = SpillOffsTab[i][1];
	}

	/// needsFP - 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 SystemZFrameLowering::hasFP(const MachineFunction &MF) const {
	const MachineFrameInfo *MFI = MF.getFrameInfo();
	return DisableFramePointerElim(MF) \|\| MFI->hasVarSizedObjects();
	}

	/// emitSPUpdate - Emit a series of instructions to increment / decrement the
	/// stack pointer by a constant value.
	static
	void emitSPUpdate(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
	int64_t NumBytes, const TargetInstrInfo &TII) {
	unsigned Opc; uint64_t Chunk;
	bool isSub = NumBytes < 0;
	uint64_t Offset = isSub ? -NumBytes : NumBytes;

	if (Offset >= (1LL << 15) - 1) {
	Opc = SystemZ::ADD64ri32;
	Chunk = (1LL << 31) - 1;
	} else {
	Opc = SystemZ::ADD64ri16;
	Chunk = (1LL << 15) - 1;
	}

	DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

	while (Offset) {
	uint64_t ThisVal = (Offset > Chunk) ? Chunk : Offset;
	MachineInstr *MI =
	BuildMI(MBB, MBBI, DL, TII.get(Opc), SystemZ::R15D)
	.addReg(SystemZ::R15D).addImm(isSub ? -ThisVal : ThisVal);
	// The PSW implicit def is dead.
	MI->getOperand(3).setIsDead();
	Offset -= ThisVal;
	}
	}

	void SystemZFrameLowering::emitPrologue(MachineFunction &MF) const {
	MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB
	MachineFrameInfo *MFI = MF.getFrameInfo();
	const SystemZInstrInfo &TII =
	static_cast<const SystemZInstrInfo>(MF.getTarget().getInstrInfo());
	SystemZMachineFunctionInfo *SystemZMFI =
	MF.getInfo<SystemZMachineFunctionInfo>();
	MachineBasicBlock::iterator MBBI = MBB.begin();
	DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

	// Get the number of bytes to allocate from the FrameInfo.
	// Note that area for callee-saved stuff is already allocated, thus we need to
	// 'undo' the stack movement.
	uint64_t StackSize = MFI->getStackSize();
	StackSize -= SystemZMFI->getCalleeSavedFrameSize();

	uint64_t NumBytes = StackSize - getOffsetOfLocalArea();

	// Skip the callee-saved push instructions.
	while (MBBI != MBB.end() &&
	(MBBI->getOpcode() == SystemZ::MOV64mr \|\|
	MBBI->getOpcode() == SystemZ::MOV64mrm))
	++MBBI;

	if (MBBI != MBB.end())
	DL = MBBI->getDebugLoc();

	// adjust stack pointer: R15 -= numbytes
	if (StackSize \|\| MFI->hasCalls()) {
	assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
	"Invalid stack frame calculation!");
	emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, TII);
	}

	if (hasFP(MF)) {
	// Update R11 with the new base value...
	BuildMI(MBB, MBBI, DL, TII.get(SystemZ::MOV64rr), SystemZ::R11D)
	.addReg(SystemZ::R15D);

	// Mark the FramePtr as live-in in every block except the entry.
	for (MachineFunction::iterator I = llvm::next(MF.begin()), E = MF.end();
	I != E; ++I)
	I->addLiveIn(SystemZ::R11D);

	}
	}

	void SystemZFrameLowering::emitEpilogue(MachineFunction &MF,
	MachineBasicBlock &MBB) const {
	const MachineFrameInfo *MFI = MF.getFrameInfo();
	MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
	const SystemZInstrInfo &TII =
	static_cast<const SystemZInstrInfo>(MF.getTarget().getInstrInfo());
	SystemZMachineFunctionInfo *SystemZMFI =
	MF.getInfo<SystemZMachineFunctionInfo>();
	unsigned RetOpcode = MBBI->getOpcode();

	switch (RetOpcode) {
	case SystemZ::RET: break; // These are ok
	default:
	assert(0 && "Can only insert epilog into returning blocks");
	}

	// Get the number of bytes to allocate from the FrameInfo
	// Note that area for callee-saved stuff is already allocated, thus we need to
	// 'undo' the stack movement.
	uint64_t StackSize =
	MFI->getStackSize() - SystemZMFI->getCalleeSavedFrameSize();
	uint64_t NumBytes = StackSize - getOffsetOfLocalArea();

	// Skip the final terminator instruction.
	while (MBBI != MBB.begin()) {
	MachineBasicBlock::iterator PI = prior(MBBI);
	--MBBI;
	if (!PI->getDesc().isTerminator())
	break;
	}

	// During callee-saved restores emission stack frame was not yet finialized
	// (and thus - the stack size was unknown). Tune the offset having full stack
	// size in hands.
	if (StackSize \|\| MFI->hasCalls()) {
	assert((MBBI->getOpcode() == SystemZ::MOV64rmm \|\|
	MBBI->getOpcode() == SystemZ::MOV64rm) &&
	"Expected to see callee-save register restore code");
	assert(MF.getRegInfo().isPhysRegUsed(SystemZ::R15D) &&
	"Invalid stack frame calculation!");

	unsigned i = 0;
	MachineInstr &MI = *MBBI;
	while (!MI.getOperand(i).isImm()) {
	++i;
	assert(i < MI.getNumOperands() && "Unexpected restore code!");
	}

	uint64_t Offset = NumBytes + MI.getOperand(i).getImm();
	// If Offset does not fit into 20-bit signed displacement field we need to
	// emit some additional code...
	if (Offset > 524287) {
	// Fold the displacement into load instruction as much as possible.
	NumBytes = Offset - 524287;
	Offset = 524287;
	emitSPUpdate(MBB, MBBI, NumBytes, TII);
	}

	MI.getOperand(i).ChangeToImmediate(Offset);
	}
	}

	int SystemZFrameLowering::getFrameIndexOffset(const MachineFunction &MF,
	int FI) const {
	const MachineFrameInfo *MFI = MF.getFrameInfo();
	const SystemZMachineFunctionInfo *SystemZMFI =
	MF.getInfo<SystemZMachineFunctionInfo>();
	int Offset = MFI->getObjectOffset(FI) + MFI->getOffsetAdjustment();
	uint64_t StackSize = MFI->getStackSize();

	// Fixed objects are really located in the "previous" frame.
	if (FI < 0)
	StackSize -= SystemZMFI->getCalleeSavedFrameSize();

	Offset += StackSize - getOffsetOfLocalArea();

	// Skip the register save area if we generated the stack frame.
	if (StackSize \|\| MFI->hasCalls())
	Offset -= getOffsetOfLocalArea();

	return Offset;
	}

	bool
	SystemZFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MI,
	const std::vector<CalleeSavedInfo> &CSI,
	const TargetRegisterInfo *TRI) const {
	if (CSI.empty())
	return false;

	DebugLoc DL;
	if (MI != MBB.end()) DL = MI->getDebugLoc();

	MachineFunction &MF = *MBB.getParent();
	const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
	SystemZMachineFunctionInfo *MFI = MF.getInfo<SystemZMachineFunctionInfo>();
	unsigned CalleeFrameSize = 0;

	// Scan the callee-saved and find the bounds of register spill area.
	unsigned LowReg = 0, HighReg = 0, StartOffset = -1U, EndOffset = 0;
	for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
	unsigned Reg = CSI[i].getReg();
	if (!SystemZ::FP64RegClass.contains(Reg)) {
	unsigned Offset = RegSpillOffsets[Reg];
	CalleeFrameSize += 8;
	if (StartOffset > Offset) {
	LowReg = Reg; StartOffset = Offset;
	}
	if (EndOffset < Offset) {
	HighReg = Reg; EndOffset = RegSpillOffsets[Reg];
	}
	}
	}

	// Save information for epilogue inserter.
	MFI->setCalleeSavedFrameSize(CalleeFrameSize);
	MFI->setLowReg(LowReg); MFI->setHighReg(HighReg);

	// Save GPRs
	if (StartOffset) {
	// Build a store instruction. Use STORE MULTIPLE instruction if there are many
	// registers to store, otherwise - just STORE.
	MachineInstrBuilder MIB =
	BuildMI(MBB, MI, DL, TII.get((LowReg == HighReg ?
	SystemZ::MOV64mr : SystemZ::MOV64mrm)));

	// Add store operands.
	MIB.addReg(SystemZ::R15D).addImm(StartOffset);
	if (LowReg == HighReg)
	MIB.addReg(0);
	MIB.addReg(LowReg, RegState::Kill);
	if (LowReg != HighReg)
	MIB.addReg(HighReg, RegState::Kill);

	// Do a second scan adding regs as being killed by instruction
	for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
	unsigned Reg = CSI[i].getReg();
	// Add the callee-saved register as live-in. It's killed at the spill.
	MBB.addLiveIn(Reg);
	if (Reg != LowReg && Reg != HighReg)
	MIB.addReg(Reg, RegState::ImplicitKill);
	}
	}

	// Save FPRs
	for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
	unsigned Reg = CSI[i].getReg();
	if (SystemZ::FP64RegClass.contains(Reg)) {
	MBB.addLiveIn(Reg);
	TII.storeRegToStackSlot(MBB, MI, Reg, true, CSI[i].getFrameIdx(),
	&SystemZ::FP64RegClass, TRI);
	}
	}

	return true;
	}

	bool
	SystemZFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MI,
	const std::vector<CalleeSavedInfo> &CSI,
	const TargetRegisterInfo *TRI) const {
	if (CSI.empty())
	return false;

	DebugLoc DL;
	if (MI != MBB.end()) DL = MI->getDebugLoc();

	MachineFunction &MF = *MBB.getParent();
	const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
	SystemZMachineFunctionInfo *MFI = MF.getInfo<SystemZMachineFunctionInfo>();

	// Restore FP registers
	for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
	unsigned Reg = CSI[i].getReg();
	if (SystemZ::FP64RegClass.contains(Reg))
	TII.loadRegFromStackSlot(MBB, MI, Reg, CSI[i].getFrameIdx(),
	&SystemZ::FP64RegClass, TRI);
	}

	// Restore GP registers
	unsigned LowReg = MFI->getLowReg(), HighReg = MFI->getHighReg();
	unsigned StartOffset = RegSpillOffsets[LowReg];

	if (StartOffset) {
	// Build a load instruction. Use LOAD MULTIPLE instruction if there are many
	// registers to load, otherwise - just LOAD.
	MachineInstrBuilder MIB =
	BuildMI(MBB, MI, DL, TII.get((LowReg == HighReg ?
	SystemZ::MOV64rm : SystemZ::MOV64rmm)));
	// Add store operands.
	MIB.addReg(LowReg, RegState::Define);
	if (LowReg != HighReg)
	MIB.addReg(HighReg, RegState::Define);

	MIB.addReg(hasFP(MF) ? SystemZ::R11D : SystemZ::R15D);
	MIB.addImm(StartOffset);
	if (LowReg == HighReg)
	MIB.addReg(0);

	// Do a second scan adding regs as being defined by instruction
	for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
	unsigned Reg = CSI[i].getReg();
	if (Reg != LowReg && Reg != HighReg)
	MIB.addReg(Reg, RegState::ImplicitDefine);
	}
	}

	return true;
	}

	void
	SystemZFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
	RegScavenger *RS) const {
	// Determine whether R15/R14 will ever be clobbered inside the function. And
	// if yes - mark it as 'callee' saved.
	MachineFrameInfo *FFI = MF.getFrameInfo();
	MachineRegisterInfo &MRI = MF.getRegInfo();

	// Check whether high FPRs are ever used, if yes - we need to save R15 as
	// well.
	static const unsigned HighFPRs[] = {
	SystemZ::F8L, SystemZ::F9L, SystemZ::F10L, SystemZ::F11L,
	SystemZ::F12L, SystemZ::F13L, SystemZ::F14L, SystemZ::F15L,
	SystemZ::F8S, SystemZ::F9S, SystemZ::F10S, SystemZ::F11S,
	SystemZ::F12S, SystemZ::F13S, SystemZ::F14S, SystemZ::F15S,
	};

	bool HighFPRsUsed = false;
	for (unsigned i = 0, e = array_lengthof(HighFPRs); i != e; ++i)
	HighFPRsUsed \|= MRI.isPhysRegUsed(HighFPRs[i]);

	if (FFI->hasCalls())
	/* FIXME: function is varargs */
	/* FIXME: function grabs RA */
	/* FIXME: function calls eh_return */
	MRI.setPhysRegUsed(SystemZ::R14D);

	if (HighFPRsUsed \|\|
	FFI->hasCalls() \|\|
	FFI->getObjectIndexEnd() != 0 \|\| // Contains automatic variables
	FFI->hasVarSizedObjects() // Function calls dynamic alloca's
	/* FIXME: function is varargs */)
	MRI.setPhysRegUsed(SystemZ::R15D);
	}