llvm/lib/Target/LoongArch/LoongArchFrameLowering.cpp - llvm-project - Git at Google

 //===-- LoongArchFrameLowering.cpp - LoongArch Frame Information -*- C++ -*-==//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains the LoongArch implementation of TargetFrameLowering class.
 //
 //===----------------------------------------------------------------------===//

 #include "LoongArchFrameLowering.h"
 #include "LoongArchMachineFunctionInfo.h"
 #include "LoongArchSubtarget.h"
 #include "MCTargetDesc/LoongArchBaseInfo.h"
 #include "MCTargetDesc/LoongArchMCTargetDesc.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/MC/MCDwarf.h"

 using namespace llvm;

 #define DEBUG_TYPE "loongarch-frame-lowering"

 // Return true if the specified function should have a dedicated frame
 // pointer register.  This is true if frame pointer elimination is
 // disabled, if it needs dynamic stack realignment, if the function has
 // variable sized allocas, or if the frame address is taken.
 bool LoongArchFrameLowering::hasFPImpl(const MachineFunction &MF) const {
   const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();

   const MachineFrameInfo &MFI = MF.getFrameInfo();
   return MF.getTarget().Options.DisableFramePointerElim(MF) ||
          RegInfo->hasStackRealignment(MF) || MFI.hasVarSizedObjects() ||
          MFI.isFrameAddressTaken();
 }

 bool LoongArchFrameLowering::hasBP(const MachineFunction &MF) const {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
   const TargetRegisterInfo *TRI = STI.getRegisterInfo();

   return MFI.hasVarSizedObjects() && TRI->hasStackRealignment(MF);
 }

 void LoongArchFrameLowering::adjustReg(MachineBasicBlock &MBB,
                                        MachineBasicBlock::iterator MBBI,
                                        const DebugLoc &DL, Register DestReg,
                                        Register SrcReg, int64_t Val,
                                        MachineInstr::MIFlag Flag) const {
   const LoongArchInstrInfo *TII = STI.getInstrInfo();
   bool IsLA64 = STI.is64Bit();
   unsigned Addi = IsLA64 ? LoongArch::ADDI_D : LoongArch::ADDI_W;

   if (DestReg == SrcReg && Val == 0)
     return;

   if (isInt<12>(Val)) {
     // addi.w/d $DstReg, $SrcReg, Val
     BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
         .addReg(SrcReg)
         .addImm(Val)
         .setMIFlag(Flag);
     return;
   }

   // Try to split the offset across two ADDIs. We need to keep the stack pointer
   // aligned after each ADDI. We need to determine the maximum value we can put
   // in each ADDI. In the negative direction, we can use -2048 which is always
   // sufficiently aligned. In the positive direction, we need to find the
   // largest 12-bit immediate that is aligned. Exclude -4096 since it can be
   // created with LU12I.W.
   assert(getStackAlign().value() < 2048 && "Stack alignment too large");
   int64_t MaxPosAdjStep = 2048 - getStackAlign().value();
   if (Val > -4096 && Val <= (2 * MaxPosAdjStep)) {
     int64_t FirstAdj = Val < 0 ? -2048 : MaxPosAdjStep;
     Val -= FirstAdj;
     BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
         .addReg(SrcReg)
         .addImm(FirstAdj)
         .setMIFlag(Flag);
     BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
         .addReg(DestReg, RegState::Kill)
         .addImm(Val)
         .setMIFlag(Flag);
     return;
   }

   unsigned Opc = IsLA64 ? LoongArch::ADD_D : LoongArch::ADD_W;
   if (Val < 0) {
     Val = -Val;
     Opc = IsLA64 ? LoongArch::SUB_D : LoongArch::SUB_W;
   }

   MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
   Register ScratchReg = MRI.createVirtualRegister(&LoongArch::GPRRegClass);
   TII->movImm(MBB, MBBI, DL, ScratchReg, Val, Flag);
   BuildMI(MBB, MBBI, DL, TII->get(Opc), DestReg)
       .addReg(SrcReg)
       .addReg(ScratchReg, RegState::Kill)
       .setMIFlag(Flag);
 }

 // Determine the size of the frame and maximum call frame size.
 void LoongArchFrameLowering::determineFrameLayout(MachineFunction &MF) const {
   MachineFrameInfo &MFI = MF.getFrameInfo();

   // Get the number of bytes to allocate from the FrameInfo.
   uint64_t FrameSize = MFI.getStackSize();

   // Make sure the frame is aligned.
   FrameSize = alignTo(FrameSize, getStackAlign());

   // Update frame info.
   MFI.setStackSize(FrameSize);
 }

 static uint64_t estimateFunctionSizeInBytes(const LoongArchInstrInfo *TII,
                                             const MachineFunction &MF) {
   uint64_t FuncSize = 0;
   for (auto &MBB : MF)
     for (auto &MI : MBB)
       FuncSize += TII->getInstSizeInBytes(MI);
   return FuncSize;
 }

 static bool needScavSlotForCFR(MachineFunction &MF) {
   if (!MF.getSubtarget<LoongArchSubtarget>().hasBasicF())
     return false;
   for (auto &MBB : MF)
     for (auto &MI : MBB)
       if (MI.getOpcode() == LoongArch::PseudoST_CFR)
         return true;
   return false;
 }

 void LoongArchFrameLowering::processFunctionBeforeFrameFinalized(
     MachineFunction &MF, RegScavenger *RS) const {
   const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
   const TargetRegisterClass &RC = LoongArch::GPRRegClass;
   const LoongArchInstrInfo *TII = STI.getInstrInfo();
   LoongArchMachineFunctionInfo *LAFI =
       MF.getInfo<LoongArchMachineFunctionInfo>();
   MachineFrameInfo &MFI = MF.getFrameInfo();

   unsigned ScavSlotsNum = 0;

   // Far branches beyond 27-bit offset require a spill slot for scratch
   // register.
   bool IsLargeFunction = !isInt<27>(estimateFunctionSizeInBytes(TII, MF));
   if (IsLargeFunction)
     ScavSlotsNum = 1;

   // estimateStackSize has been observed to under-estimate the final stack
   // size, so give ourselves wiggle-room by checking for stack size
   // representable an 11-bit signed field rather than 12-bits.
   if (!isInt<11>(MFI.estimateStackSize(MF)))
     ScavSlotsNum = std::max(ScavSlotsNum, 1u);

   // For CFR spill.
   if (needScavSlotForCFR(MF))
     ++ScavSlotsNum;

   // Create emergency spill slots.
   for (unsigned i = 0; i < ScavSlotsNum; ++i) {
     int FI =
         MFI.CreateSpillStackObject(RI->getSpillSize(RC), RI->getSpillAlign(RC));
     RS->addScavengingFrameIndex(FI);
     if (IsLargeFunction && LAFI->getBranchRelaxationSpillFrameIndex() == -1)
       LAFI->setBranchRelaxationSpillFrameIndex(FI);
     LLVM_DEBUG(dbgs() << "Allocated FI(" << FI
                       << ") as the emergency spill slot.\n");
   }
 }

 void LoongArchFrameLowering::emitPrologue(MachineFunction &MF,
                                           MachineBasicBlock &MBB) const {
   MachineFrameInfo &MFI = MF.getFrameInfo();
   auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
   const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
   const LoongArchInstrInfo *TII = STI.getInstrInfo();
   MachineBasicBlock::iterator MBBI = MBB.begin();
   bool IsLA64 = STI.is64Bit();

   Register SPReg = LoongArch::R3;
   Register FPReg = LoongArch::R22;

   // Debug location must be unknown since the first debug location is used
   // to determine the end of the prologue.
   DebugLoc DL;
   // All calls are tail calls in GHC calling conv, and functions have no
   // prologue/epilogue.
   if (MF.getFunction().getCallingConv() == CallingConv::GHC)
     return;
   // Determine the correct frame layout
   determineFrameLayout(MF);

   // First, compute final stack size.
   uint64_t StackSize = MFI.getStackSize();
   uint64_t RealStackSize = StackSize;

   // Early exit if there is no need to allocate space in the stack.
   if (StackSize == 0 && !MFI.adjustsStack())
     return;

   uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
   // Split the SP adjustment to reduce the offsets of callee saved spill.
   if (FirstSPAdjustAmount)
     StackSize = FirstSPAdjustAmount;

   // Adjust stack.
   adjustReg(MBB, MBBI, DL, SPReg, SPReg, -StackSize, MachineInstr::FrameSetup);
   // Emit ".cfi_def_cfa_offset StackSize".
   unsigned CFIIndex =
       MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, StackSize));
   BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
       .addCFIIndex(CFIIndex)
       .setMIFlag(MachineInstr::FrameSetup);

   const auto &CSI = MFI.getCalleeSavedInfo();

   // The frame pointer is callee-saved, and code has been generated for us to
   // save it to the stack. We need to skip over the storing of callee-saved
   // registers as the frame pointer must be modified after it has been saved
   // to the stack, not before.
   std::advance(MBBI, CSI.size());

   // Iterate over list of callee-saved registers and emit .cfi_offset
   // directives.
   for (const auto &Entry : CSI) {
     int64_t Offset = MFI.getObjectOffset(Entry.getFrameIdx());
     unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
         nullptr, RI->getDwarfRegNum(Entry.getReg(), true), Offset));
     BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
         .addCFIIndex(CFIIndex)
         .setMIFlag(MachineInstr::FrameSetup);
   }

   // Generate new FP.
   if (hasFP(MF)) {
     adjustReg(MBB, MBBI, DL, FPReg, SPReg,
               StackSize - LoongArchFI->getVarArgsSaveSize(),
               MachineInstr::FrameSetup);

     // Emit ".cfi_def_cfa $fp, LoongArchFI->getVarArgsSaveSize()"
     unsigned CFIIndex = MF.addFrameInst(
         MCCFIInstruction::cfiDefCfa(nullptr, RI->getDwarfRegNum(FPReg, true),
                                     LoongArchFI->getVarArgsSaveSize()));
     BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
         .addCFIIndex(CFIIndex)
         .setMIFlag(MachineInstr::FrameSetup);
   }

   // Emit the second SP adjustment after saving callee saved registers.
   if (FirstSPAdjustAmount) {
     uint64_t SecondSPAdjustAmount = RealStackSize - FirstSPAdjustAmount;
     assert(SecondSPAdjustAmount > 0 &&
            "SecondSPAdjustAmount should be greater than zero");
     adjustReg(MBB, MBBI, DL, SPReg, SPReg, -SecondSPAdjustAmount,
               MachineInstr::FrameSetup);

     if (!hasFP(MF)) {
       // If we are using a frame-pointer, and thus emitted ".cfi_def_cfa fp, 0",
       // don't emit an sp-based .cfi_def_cfa_offset
       // Emit ".cfi_def_cfa_offset RealStackSize"
       unsigned CFIIndex = MF.addFrameInst(
           MCCFIInstruction::cfiDefCfaOffset(nullptr, RealStackSize));
       BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
           .addCFIIndex(CFIIndex)
           .setMIFlag(MachineInstr::FrameSetup);
     }
   }

   if (hasFP(MF)) {
     // Realign stack.
     if (RI->hasStackRealignment(MF)) {
       unsigned Align = Log2(MFI.getMaxAlign());
       assert(Align > 0 && "The stack realignment size is invalid!");
       BuildMI(MBB, MBBI, DL,
               TII->get(IsLA64 ? LoongArch::BSTRINS_D : LoongArch::BSTRINS_W),
               SPReg)
           .addReg(SPReg)
           .addReg(LoongArch::R0)
           .addImm(Align - 1)
           .addImm(0)
           .setMIFlag(MachineInstr::FrameSetup);
       // FP will be used to restore the frame in the epilogue, so we need
       // another base register BP to record SP after re-alignment. SP will
       // track the current stack after allocating variable sized objects.
       if (hasBP(MF)) {
         // move BP, $sp
         BuildMI(MBB, MBBI, DL, TII->get(LoongArch::OR),
                 LoongArchABI::getBPReg())
             .addReg(SPReg)
             .addReg(LoongArch::R0)
             .setMIFlag(MachineInstr::FrameSetup);
       }
     }
   }
 }

 void LoongArchFrameLowering::emitEpilogue(MachineFunction &MF,
                                           MachineBasicBlock &MBB) const {
   const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
   MachineFrameInfo &MFI = MF.getFrameInfo();
   auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
   Register SPReg = LoongArch::R3;
   // All calls are tail calls in GHC calling conv, and functions have no
   // prologue/epilogue.
   if (MF.getFunction().getCallingConv() == CallingConv::GHC)
     return;
   MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
   DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

   const auto &CSI = MFI.getCalleeSavedInfo();
   // Skip to before the restores of callee-saved registers.
   auto LastFrameDestroy = MBBI;
   if (!CSI.empty())
     LastFrameDestroy = std::prev(MBBI, CSI.size());

   // Get the number of bytes from FrameInfo.
   uint64_t StackSize = MFI.getStackSize();

   // Restore the stack pointer.
   if (RI->hasStackRealignment(MF) || MFI.hasVarSizedObjects()) {
     assert(hasFP(MF) && "frame pointer should not have been eliminated");
     adjustReg(MBB, LastFrameDestroy, DL, SPReg, LoongArch::R22,
               -StackSize + LoongArchFI->getVarArgsSaveSize(),
               MachineInstr::FrameDestroy);
   }

   uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
   if (FirstSPAdjustAmount) {
     uint64_t SecondSPAdjustAmount = StackSize - FirstSPAdjustAmount;
     assert(SecondSPAdjustAmount > 0 &&
            "SecondSPAdjustAmount should be greater than zero");

     adjustReg(MBB, LastFrameDestroy, DL, SPReg, SPReg, SecondSPAdjustAmount,
               MachineInstr::FrameDestroy);
     StackSize = FirstSPAdjustAmount;
   }

   // Deallocate stack
   adjustReg(MBB, MBBI, DL, SPReg, SPReg, StackSize, MachineInstr::FrameDestroy);
 }

 // We would like to split the SP adjustment to reduce prologue/epilogue
 // as following instructions. In this way, the offset of the callee saved
 // register could fit in a single store.
 // e.g.
 //   addi.d  $sp, $sp, -2032
 //   st.d    $ra, $sp,  2024
 //   st.d    $fp, $sp,  2016
 //   addi.d  $sp, $sp,   -16
 uint64_t LoongArchFrameLowering::getFirstSPAdjustAmount(
     const MachineFunction &MF) const {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
   const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();

   // Return the FirstSPAdjustAmount if the StackSize can not fit in a signed
   // 12-bit and there exists a callee-saved register needing to be pushed.
   if (!isInt<12>(MFI.getStackSize()) && (CSI.size() > 0)) {
     // FirstSPAdjustAmount is chosen as (2048 - StackAlign) because 2048 will
     // cause sp = sp + 2048 in the epilogue to be split into multiple
     // instructions. Offsets smaller than 2048 can fit in a single load/store
     // instruction, and we have to stick with the stack alignment.
     // So (2048 - StackAlign) will satisfy the stack alignment.
     return 2048 - getStackAlign().value();
   }
   return 0;
 }

 void LoongArchFrameLowering::determineCalleeSaves(MachineFunction &MF,
                                                   BitVector &SavedRegs,
                                                   RegScavenger *RS) const {
   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
   // Unconditionally spill RA and FP only if the function uses a frame
   // pointer.
   if (hasFP(MF)) {
     SavedRegs.set(LoongArch::R1);
     SavedRegs.set(LoongArch::R22);
   }
   // Mark BP as used if function has dedicated base pointer.
   if (hasBP(MF))
     SavedRegs.set(LoongArchABI::getBPReg());
 }

 // Do not preserve stack space within prologue for outgoing variables if the
 // function contains variable size objects.
 // Let eliminateCallFramePseudoInstr preserve stack space for it.
 bool LoongArchFrameLowering::hasReservedCallFrame(
     const MachineFunction &MF) const {
   return !MF.getFrameInfo().hasVarSizedObjects();
 }

 // Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions.
 MachineBasicBlock::iterator
 LoongArchFrameLowering::eliminateCallFramePseudoInstr(
     MachineFunction &MF, MachineBasicBlock &MBB,
     MachineBasicBlock::iterator MI) const {
   Register SPReg = LoongArch::R3;
   DebugLoc DL = MI->getDebugLoc();

   if (!hasReservedCallFrame(MF)) {
     // If space has not been reserved for a call frame, ADJCALLSTACKDOWN and
     // ADJCALLSTACKUP must be converted to instructions manipulating the stack
     // pointer. This is necessary when there is a variable length stack
     // allocation (e.g. alloca), which means it's not possible to allocate
     // space for outgoing arguments from within the function prologue.
     int64_t Amount = MI->getOperand(0).getImm();

     if (Amount != 0) {
       // Ensure the stack remains aligned after adjustment.
       Amount = alignSPAdjust(Amount);

       if (MI->getOpcode() == LoongArch::ADJCALLSTACKDOWN)
         Amount = -Amount;

       adjustReg(MBB, MI, DL, SPReg, SPReg, Amount, MachineInstr::NoFlags);
     }
   }

   return MBB.erase(MI);
 }

 bool LoongArchFrameLowering::spillCalleeSavedRegisters(
     MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
     ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
   if (CSI.empty())
     return true;

   MachineFunction *MF = MBB.getParent();
   const TargetInstrInfo &TII = *MF->getSubtarget().getInstrInfo();

   // Insert the spill to the stack frame.
   for (auto &CS : CSI) {
     MCRegister Reg = CS.getReg();
     // If the register is RA and the return address is taken by method
     // LoongArchTargetLowering::lowerRETURNADDR, don't set kill flag.
     bool IsKill =
         !(Reg == LoongArch::R1 && MF->getFrameInfo().isReturnAddressTaken());
     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
     TII.storeRegToStackSlot(MBB, MI, Reg, IsKill, CS.getFrameIdx(), RC, TRI,
                             Register());
   }

   return true;
 }

 StackOffset LoongArchFrameLowering::getFrameIndexReference(
     const MachineFunction &MF, int FI, Register &FrameReg) const {
   const MachineFrameInfo &MFI = MF.getFrameInfo();
   const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();
   auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
   uint64_t StackSize = MFI.getStackSize();
   uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);

   // Callee-saved registers should be referenced relative to the stack
   // pointer (positive offset), otherwise use the frame pointer (negative
   // offset).
   const auto &CSI = MFI.getCalleeSavedInfo();
   int MinCSFI = 0;
   int MaxCSFI = -1;
   StackOffset Offset =
       StackOffset::getFixed(MFI.getObjectOffset(FI) - getOffsetOfLocalArea() +
                             MFI.getOffsetAdjustment());

   if (CSI.size()) {
     MinCSFI = CSI[0].getFrameIdx();
     MaxCSFI = CSI[CSI.size() - 1].getFrameIdx();
   }

   if (FI >= MinCSFI && FI <= MaxCSFI) {
     FrameReg = LoongArch::R3;
     if (FirstSPAdjustAmount)
       Offset += StackOffset::getFixed(FirstSPAdjustAmount);
     else
       Offset += StackOffset::getFixed(StackSize);
   } else if (RI->hasStackRealignment(MF) && !MFI.isFixedObjectIndex(FI)) {
     // If the stack was realigned, the frame pointer is set in order to allow
     // SP to be restored, so we need another base register to record the stack
     // after realignment.
     FrameReg = hasBP(MF) ? LoongArchABI::getBPReg() : LoongArch::R3;
     Offset += StackOffset::getFixed(StackSize);
   } else {
     FrameReg = RI->getFrameRegister(MF);
     if (hasFP(MF))
       Offset += StackOffset::getFixed(LoongArchFI->getVarArgsSaveSize());
     else
       Offset += StackOffset::getFixed(StackSize);
   }

   return Offset;
 }

 bool LoongArchFrameLowering::enableShrinkWrapping(
     const MachineFunction &MF) const {
   // Keep the conventional code flow when not optimizing.
   if (MF.getFunction().hasOptNone())
     return false;

   return true;
 }
	//===-- LoongArchFrameLowering.cpp - LoongArch Frame Information -- C++ --==//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	//
	// This file contains the LoongArch implementation of TargetFrameLowering class.
	//
	//===----------------------------------------------------------------------===//

	#include "LoongArchFrameLowering.h"
	#include "LoongArchMachineFunctionInfo.h"
	#include "LoongArchSubtarget.h"
	#include "MCTargetDesc/LoongArchBaseInfo.h"
	#include "MCTargetDesc/LoongArchMCTargetDesc.h"
	#include "llvm/CodeGen/MachineFrameInfo.h"
	#include "llvm/CodeGen/MachineFunction.h"
	#include "llvm/CodeGen/MachineInstrBuilder.h"
	#include "llvm/CodeGen/MachineRegisterInfo.h"
	#include "llvm/CodeGen/RegisterScavenging.h"
	#include "llvm/IR/DiagnosticInfo.h"
	#include "llvm/MC/MCDwarf.h"

	using namespace llvm;

	#define DEBUG_TYPE "loongarch-frame-lowering"

	// Return true if the specified function should have a dedicated frame
	// pointer register. This is true if frame pointer elimination is
	// disabled, if it needs dynamic stack realignment, if the function has
	// variable sized allocas, or if the frame address is taken.
	bool LoongArchFrameLowering::hasFPImpl(const MachineFunction &MF) const {
	const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();

	const MachineFrameInfo &MFI = MF.getFrameInfo();
	return MF.getTarget().Options.DisableFramePointerElim(MF) \|\|
	RegInfo->hasStackRealignment(MF) \|\| MFI.hasVarSizedObjects() \|\|
	MFI.isFrameAddressTaken();
	}

	bool LoongArchFrameLowering::hasBP(const MachineFunction &MF) const {
	const MachineFrameInfo &MFI = MF.getFrameInfo();
	const TargetRegisterInfo *TRI = STI.getRegisterInfo();

	return MFI.hasVarSizedObjects() && TRI->hasStackRealignment(MF);
	}

	void LoongArchFrameLowering::adjustReg(MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MBBI,
	const DebugLoc &DL, Register DestReg,
	Register SrcReg, int64_t Val,
	MachineInstr::MIFlag Flag) const {
	const LoongArchInstrInfo *TII = STI.getInstrInfo();
	bool IsLA64 = STI.is64Bit();
	unsigned Addi = IsLA64 ? LoongArch::ADDI_D : LoongArch::ADDI_W;

	if (DestReg == SrcReg && Val == 0)
	return;

	if (isInt<12>(Val)) {
	// addi.w/d $DstReg, $SrcReg, Val
	BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
	.addReg(SrcReg)
	.addImm(Val)
	.setMIFlag(Flag);
	return;
	}

	// Try to split the offset across two ADDIs. We need to keep the stack pointer
	// aligned after each ADDI. We need to determine the maximum value we can put
	// in each ADDI. In the negative direction, we can use -2048 which is always
	// sufficiently aligned. In the positive direction, we need to find the
	// largest 12-bit immediate that is aligned. Exclude -4096 since it can be
	// created with LU12I.W.
	assert(getStackAlign().value() < 2048 && "Stack alignment too large");
	int64_t MaxPosAdjStep = 2048 - getStackAlign().value();
	if (Val > -4096 && Val <= (2 * MaxPosAdjStep)) {
	int64_t FirstAdj = Val < 0 ? -2048 : MaxPosAdjStep;
	Val -= FirstAdj;
	BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
	.addReg(SrcReg)
	.addImm(FirstAdj)
	.setMIFlag(Flag);
	BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
	.addReg(DestReg, RegState::Kill)
	.addImm(Val)
	.setMIFlag(Flag);
	return;
	}

	unsigned Opc = IsLA64 ? LoongArch::ADD_D : LoongArch::ADD_W;
	if (Val < 0) {
	Val = -Val;
	Opc = IsLA64 ? LoongArch::SUB_D : LoongArch::SUB_W;
	}

	MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
	Register ScratchReg = MRI.createVirtualRegister(&LoongArch::GPRRegClass);
	TII->movImm(MBB, MBBI, DL, ScratchReg, Val, Flag);
	BuildMI(MBB, MBBI, DL, TII->get(Opc), DestReg)
	.addReg(SrcReg)
	.addReg(ScratchReg, RegState::Kill)
	.setMIFlag(Flag);
	}

	// Determine the size of the frame and maximum call frame size.
	void LoongArchFrameLowering::determineFrameLayout(MachineFunction &MF) const {
	MachineFrameInfo &MFI = MF.getFrameInfo();

	// Get the number of bytes to allocate from the FrameInfo.
	uint64_t FrameSize = MFI.getStackSize();

	// Make sure the frame is aligned.
	FrameSize = alignTo(FrameSize, getStackAlign());

	// Update frame info.
	MFI.setStackSize(FrameSize);
	}

	static uint64_t estimateFunctionSizeInBytes(const LoongArchInstrInfo *TII,
	const MachineFunction &MF) {
	uint64_t FuncSize = 0;
	for (auto &MBB : MF)
	for (auto &MI : MBB)
	FuncSize += TII->getInstSizeInBytes(MI);
	return FuncSize;
	}

	static bool needScavSlotForCFR(MachineFunction &MF) {
	if (!MF.getSubtarget<LoongArchSubtarget>().hasBasicF())
	return false;
	for (auto &MBB : MF)
	for (auto &MI : MBB)
	if (MI.getOpcode() == LoongArch::PseudoST_CFR)
	return true;
	return false;
	}

	void LoongArchFrameLowering::processFunctionBeforeFrameFinalized(
	MachineFunction &MF, RegScavenger *RS) const {
	const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
	const TargetRegisterClass &RC = LoongArch::GPRRegClass;
	const LoongArchInstrInfo *TII = STI.getInstrInfo();
	LoongArchMachineFunctionInfo *LAFI =
	MF.getInfo<LoongArchMachineFunctionInfo>();
	MachineFrameInfo &MFI = MF.getFrameInfo();

	unsigned ScavSlotsNum = 0;

	// Far branches beyond 27-bit offset require a spill slot for scratch
	// register.
	bool IsLargeFunction = !isInt<27>(estimateFunctionSizeInBytes(TII, MF));
	if (IsLargeFunction)
	ScavSlotsNum = 1;

	// estimateStackSize has been observed to under-estimate the final stack
	// size, so give ourselves wiggle-room by checking for stack size
	// representable an 11-bit signed field rather than 12-bits.
	if (!isInt<11>(MFI.estimateStackSize(MF)))
	ScavSlotsNum = std::max(ScavSlotsNum, 1u);

	// For CFR spill.
	if (needScavSlotForCFR(MF))
	++ScavSlotsNum;

	// Create emergency spill slots.
	for (unsigned i = 0; i < ScavSlotsNum; ++i) {
	int FI =
	MFI.CreateSpillStackObject(RI->getSpillSize(RC), RI->getSpillAlign(RC));
	RS->addScavengingFrameIndex(FI);
	if (IsLargeFunction && LAFI->getBranchRelaxationSpillFrameIndex() == -1)
	LAFI->setBranchRelaxationSpillFrameIndex(FI);
	LLVM_DEBUG(dbgs() << "Allocated FI(" << FI
	<< ") as the emergency spill slot.\n");
	}
	}

	void LoongArchFrameLowering::emitPrologue(MachineFunction &MF,
	MachineBasicBlock &MBB) const {
	MachineFrameInfo &MFI = MF.getFrameInfo();
	auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
	const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
	const LoongArchInstrInfo *TII = STI.getInstrInfo();
	MachineBasicBlock::iterator MBBI = MBB.begin();
	bool IsLA64 = STI.is64Bit();

	Register SPReg = LoongArch::R3;
	Register FPReg = LoongArch::R22;

	// Debug location must be unknown since the first debug location is used
	// to determine the end of the prologue.
	DebugLoc DL;
	// All calls are tail calls in GHC calling conv, and functions have no
	// prologue/epilogue.
	if (MF.getFunction().getCallingConv() == CallingConv::GHC)
	return;
	// Determine the correct frame layout
	determineFrameLayout(MF);

	// First, compute final stack size.
	uint64_t StackSize = MFI.getStackSize();
	uint64_t RealStackSize = StackSize;

	// Early exit if there is no need to allocate space in the stack.
	if (StackSize == 0 && !MFI.adjustsStack())
	return;

	uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
	// Split the SP adjustment to reduce the offsets of callee saved spill.
	if (FirstSPAdjustAmount)
	StackSize = FirstSPAdjustAmount;

	// Adjust stack.
	adjustReg(MBB, MBBI, DL, SPReg, SPReg, -StackSize, MachineInstr::FrameSetup);
	// Emit ".cfi_def_cfa_offset StackSize".
	unsigned CFIIndex =
	MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, StackSize));
	BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
	.addCFIIndex(CFIIndex)
	.setMIFlag(MachineInstr::FrameSetup);

	const auto &CSI = MFI.getCalleeSavedInfo();

	// The frame pointer is callee-saved, and code has been generated for us to
	// save it to the stack. We need to skip over the storing of callee-saved
	// registers as the frame pointer must be modified after it has been saved
	// to the stack, not before.
	std::advance(MBBI, CSI.size());

	// Iterate over list of callee-saved registers and emit .cfi_offset
	// directives.
	for (const auto &Entry : CSI) {
	int64_t Offset = MFI.getObjectOffset(Entry.getFrameIdx());
	unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
	nullptr, RI->getDwarfRegNum(Entry.getReg(), true), Offset));
	BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
	.addCFIIndex(CFIIndex)
	.setMIFlag(MachineInstr::FrameSetup);
	}

	// Generate new FP.
	if (hasFP(MF)) {
	adjustReg(MBB, MBBI, DL, FPReg, SPReg,
	StackSize - LoongArchFI->getVarArgsSaveSize(),
	MachineInstr::FrameSetup);

	// Emit ".cfi_def_cfa $fp, LoongArchFI->getVarArgsSaveSize()"
	unsigned CFIIndex = MF.addFrameInst(
	MCCFIInstruction::cfiDefCfa(nullptr, RI->getDwarfRegNum(FPReg, true),
	LoongArchFI->getVarArgsSaveSize()));
	BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
	.addCFIIndex(CFIIndex)
	.setMIFlag(MachineInstr::FrameSetup);
	}

	// Emit the second SP adjustment after saving callee saved registers.
	if (FirstSPAdjustAmount) {
	uint64_t SecondSPAdjustAmount = RealStackSize - FirstSPAdjustAmount;
	assert(SecondSPAdjustAmount > 0 &&
	"SecondSPAdjustAmount should be greater than zero");
	adjustReg(MBB, MBBI, DL, SPReg, SPReg, -SecondSPAdjustAmount,
	MachineInstr::FrameSetup);

	if (!hasFP(MF)) {
	// If we are using a frame-pointer, and thus emitted ".cfi_def_cfa fp, 0",
	// don't emit an sp-based .cfi_def_cfa_offset
	// Emit ".cfi_def_cfa_offset RealStackSize"
	unsigned CFIIndex = MF.addFrameInst(
	MCCFIInstruction::cfiDefCfaOffset(nullptr, RealStackSize));
	BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
	.addCFIIndex(CFIIndex)
	.setMIFlag(MachineInstr::FrameSetup);
	}
	}

	if (hasFP(MF)) {
	// Realign stack.
	if (RI->hasStackRealignment(MF)) {
	unsigned Align = Log2(MFI.getMaxAlign());
	assert(Align > 0 && "The stack realignment size is invalid!");
	BuildMI(MBB, MBBI, DL,
	TII->get(IsLA64 ? LoongArch::BSTRINS_D : LoongArch::BSTRINS_W),
	SPReg)
	.addReg(SPReg)
	.addReg(LoongArch::R0)
	.addImm(Align - 1)
	.addImm(0)
	.setMIFlag(MachineInstr::FrameSetup);
	// FP will be used to restore the frame in the epilogue, so we need
	// another base register BP to record SP after re-alignment. SP will
	// track the current stack after allocating variable sized objects.
	if (hasBP(MF)) {
	// move BP, $sp
	BuildMI(MBB, MBBI, DL, TII->get(LoongArch::OR),
	LoongArchABI::getBPReg())
	.addReg(SPReg)
	.addReg(LoongArch::R0)
	.setMIFlag(MachineInstr::FrameSetup);
	}
	}
	}
	}

	void LoongArchFrameLowering::emitEpilogue(MachineFunction &MF,
	MachineBasicBlock &MBB) const {
	const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
	MachineFrameInfo &MFI = MF.getFrameInfo();
	auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
	Register SPReg = LoongArch::R3;
	// All calls are tail calls in GHC calling conv, and functions have no
	// prologue/epilogue.
	if (MF.getFunction().getCallingConv() == CallingConv::GHC)
	return;
	MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
	DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();

	const auto &CSI = MFI.getCalleeSavedInfo();
	// Skip to before the restores of callee-saved registers.
	auto LastFrameDestroy = MBBI;
	if (!CSI.empty())
	LastFrameDestroy = std::prev(MBBI, CSI.size());

	// Get the number of bytes from FrameInfo.
	uint64_t StackSize = MFI.getStackSize();

	// Restore the stack pointer.
	if (RI->hasStackRealignment(MF) \|\| MFI.hasVarSizedObjects()) {
	assert(hasFP(MF) && "frame pointer should not have been eliminated");
	adjustReg(MBB, LastFrameDestroy, DL, SPReg, LoongArch::R22,
	-StackSize + LoongArchFI->getVarArgsSaveSize(),
	MachineInstr::FrameDestroy);
	}

	uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
	if (FirstSPAdjustAmount) {
	uint64_t SecondSPAdjustAmount = StackSize - FirstSPAdjustAmount;
	assert(SecondSPAdjustAmount > 0 &&
	"SecondSPAdjustAmount should be greater than zero");

	adjustReg(MBB, LastFrameDestroy, DL, SPReg, SPReg, SecondSPAdjustAmount,
	MachineInstr::FrameDestroy);
	StackSize = FirstSPAdjustAmount;
	}

	// Deallocate stack
	adjustReg(MBB, MBBI, DL, SPReg, SPReg, StackSize, MachineInstr::FrameDestroy);
	}

	// We would like to split the SP adjustment to reduce prologue/epilogue
	// as following instructions. In this way, the offset of the callee saved
	// register could fit in a single store.
	// e.g.
	// addi.d $sp, $sp, -2032
	// st.d $ra, $sp, 2024
	// st.d $fp, $sp, 2016
	// addi.d $sp, $sp, -16
	uint64_t LoongArchFrameLowering::getFirstSPAdjustAmount(
	const MachineFunction &MF) const {
	const MachineFrameInfo &MFI = MF.getFrameInfo();
	const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();

	// Return the FirstSPAdjustAmount if the StackSize can not fit in a signed
	// 12-bit and there exists a callee-saved register needing to be pushed.
	if (!isInt<12>(MFI.getStackSize()) && (CSI.size() > 0)) {
	// FirstSPAdjustAmount is chosen as (2048 - StackAlign) because 2048 will
	// cause sp = sp + 2048 in the epilogue to be split into multiple
	// instructions. Offsets smaller than 2048 can fit in a single load/store
	// instruction, and we have to stick with the stack alignment.
	// So (2048 - StackAlign) will satisfy the stack alignment.
	return 2048 - getStackAlign().value();
	}
	return 0;
	}

	void LoongArchFrameLowering::determineCalleeSaves(MachineFunction &MF,
	BitVector &SavedRegs,
	RegScavenger *RS) const {
	TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
	// Unconditionally spill RA and FP only if the function uses a frame
	// pointer.
	if (hasFP(MF)) {
	SavedRegs.set(LoongArch::R1);
	SavedRegs.set(LoongArch::R22);
	}
	// Mark BP as used if function has dedicated base pointer.
	if (hasBP(MF))
	SavedRegs.set(LoongArchABI::getBPReg());
	}

	// Do not preserve stack space within prologue for outgoing variables if the
	// function contains variable size objects.
	// Let eliminateCallFramePseudoInstr preserve stack space for it.
	bool LoongArchFrameLowering::hasReservedCallFrame(
	const MachineFunction &MF) const {
	return !MF.getFrameInfo().hasVarSizedObjects();
	}

	// Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions.
	MachineBasicBlock::iterator
	LoongArchFrameLowering::eliminateCallFramePseudoInstr(
	MachineFunction &MF, MachineBasicBlock &MBB,
	MachineBasicBlock::iterator MI) const {
	Register SPReg = LoongArch::R3;
	DebugLoc DL = MI->getDebugLoc();

	if (!hasReservedCallFrame(MF)) {
	// If space has not been reserved for a call frame, ADJCALLSTACKDOWN and
	// ADJCALLSTACKUP must be converted to instructions manipulating the stack
	// pointer. This is necessary when there is a variable length stack
	// allocation (e.g. alloca), which means it's not possible to allocate
	// space for outgoing arguments from within the function prologue.
	int64_t Amount = MI->getOperand(0).getImm();

	if (Amount != 0) {
	// Ensure the stack remains aligned after adjustment.
	Amount = alignSPAdjust(Amount);

	if (MI->getOpcode() == LoongArch::ADJCALLSTACKDOWN)
	Amount = -Amount;

	adjustReg(MBB, MI, DL, SPReg, SPReg, Amount, MachineInstr::NoFlags);
	}
	}

	return MBB.erase(MI);
	}

	bool LoongArchFrameLowering::spillCalleeSavedRegisters(
	MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
	ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
	if (CSI.empty())
	return true;

	MachineFunction *MF = MBB.getParent();
	const TargetInstrInfo &TII = *MF->getSubtarget().getInstrInfo();

	// Insert the spill to the stack frame.
	for (auto &CS : CSI) {
	MCRegister Reg = CS.getReg();
	// If the register is RA and the return address is taken by method
	// LoongArchTargetLowering::lowerRETURNADDR, don't set kill flag.
	bool IsKill =
	!(Reg == LoongArch::R1 && MF->getFrameInfo().isReturnAddressTaken());
	const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
	TII.storeRegToStackSlot(MBB, MI, Reg, IsKill, CS.getFrameIdx(), RC, TRI,
	Register());
	}

	return true;
	}

	StackOffset LoongArchFrameLowering::getFrameIndexReference(
	const MachineFunction &MF, int FI, Register &FrameReg) const {
	const MachineFrameInfo &MFI = MF.getFrameInfo();
	const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();
	auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
	uint64_t StackSize = MFI.getStackSize();
	uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);

	// Callee-saved registers should be referenced relative to the stack
	// pointer (positive offset), otherwise use the frame pointer (negative
	// offset).
	const auto &CSI = MFI.getCalleeSavedInfo();
	int MinCSFI = 0;
	int MaxCSFI = -1;
	StackOffset Offset =
	StackOffset::getFixed(MFI.getObjectOffset(FI) - getOffsetOfLocalArea() +
	MFI.getOffsetAdjustment());

	if (CSI.size()) {
	MinCSFI = CSI[0].getFrameIdx();
	MaxCSFI = CSI[CSI.size() - 1].getFrameIdx();
	}

	if (FI >= MinCSFI && FI <= MaxCSFI) {
	FrameReg = LoongArch::R3;
	if (FirstSPAdjustAmount)
	Offset += StackOffset::getFixed(FirstSPAdjustAmount);
	else
	Offset += StackOffset::getFixed(StackSize);
	} else if (RI->hasStackRealignment(MF) && !MFI.isFixedObjectIndex(FI)) {
	// If the stack was realigned, the frame pointer is set in order to allow
	// SP to be restored, so we need another base register to record the stack
	// after realignment.
	FrameReg = hasBP(MF) ? LoongArchABI::getBPReg() : LoongArch::R3;
	Offset += StackOffset::getFixed(StackSize);
	} else {
	FrameReg = RI->getFrameRegister(MF);
	if (hasFP(MF))
	Offset += StackOffset::getFixed(LoongArchFI->getVarArgsSaveSize());
	else
	Offset += StackOffset::getFixed(StackSize);
	}

	return Offset;
	}

	bool LoongArchFrameLowering::enableShrinkWrapping(
	const MachineFunction &MF) const {
	// Keep the conventional code flow when not optimizing.
	if (MF.getFunction().hasOptNone())
	return false;

	return true;
	}