llvm/lib/Target/LoongArch/LoongArchFrameLowering.cpp

   1 //===-- LoongArchFrameLowering.cpp - LoongArch Frame Information -*- C++ -*-==//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains the LoongArch implementation of TargetFrameLowering class.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "LoongArchFrameLowering.h"
  14 #include "LoongArchMachineFunctionInfo.h"
  15 #include "LoongArchSubtarget.h"
  16 #include "MCTargetDesc/LoongArchBaseInfo.h"
  17 #include "MCTargetDesc/LoongArchMCTargetDesc.h"
  18 #include "llvm/CodeGen/MachineFrameInfo.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineInstrBuilder.h"
  21 #include "llvm/CodeGen/MachineRegisterInfo.h"
  22 #include "llvm/CodeGen/RegisterScavenging.h"
  23 #include "llvm/IR/DiagnosticInfo.h"
  24 #include "llvm/MC/MCDwarf.h"
  25
  26 using namespace llvm;
  27
  28 #define DEBUG_TYPE "loongarch-frame-lowering"
  29
  30 // Return true if the specified function should have a dedicated frame
  31 // pointer register.  This is true if frame pointer elimination is
  32 // disabled, if it needs dynamic stack realignment, if the function has
  33 // variable sized allocas, or if the frame address is taken.
  34 bool LoongArchFrameLowering::hasFP(const MachineFunction &MF) const {
  35   const TargetRegisterInfo *RegInfo = MF.getSubtarget().getRegisterInfo();
  36
  37   const MachineFrameInfo &MFI = MF.getFrameInfo();
  38   return MF.getTarget().Options.DisableFramePointerElim(MF) ||
  39          RegInfo->hasStackRealignment(MF) || MFI.hasVarSizedObjects() ||
  40          MFI.isFrameAddressTaken();
  41 }
  42
  43 bool LoongArchFrameLowering::hasBP(const MachineFunction &MF) const {
  44   const MachineFrameInfo &MFI = MF.getFrameInfo();
  45   const TargetRegisterInfo *TRI = STI.getRegisterInfo();
  46
  47   return MFI.hasVarSizedObjects() && TRI->hasStackRealignment(MF);
  48 }
  49
  50 void LoongArchFrameLowering::adjustReg(MachineBasicBlock &MBB,
  51                                        MachineBasicBlock::iterator MBBI,
  52                                        const DebugLoc &DL, Register DestReg,
  53                                        Register SrcReg, int64_t Val,
  54                                        MachineInstr::MIFlag Flag) const {
  55   const LoongArchInstrInfo *TII = STI.getInstrInfo();
  56   bool IsLA64 = STI.is64Bit();
  57   unsigned Addi = IsLA64 ? LoongArch::ADDI_D : LoongArch::ADDI_W;
  58
  59   if (DestReg == SrcReg && Val == 0)
  60     return;
  61
  62   if (isInt<12>(Val)) {
  63     // addi.w/d $DstReg, $SrcReg, Val
  64     BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
  65         .addReg(SrcReg)
  66         .addImm(Val)
  67         .setMIFlag(Flag);
  68     return;
  69   }
  70
  71   // Try to split the offset across two ADDIs. We need to keep the stack pointer
  72   // aligned after each ADDI. We need to determine the maximum value we can put
  73   // in each ADDI. In the negative direction, we can use -2048 which is always
  74   // sufficiently aligned. In the positive direction, we need to find the
  75   // largest 12-bit immediate that is aligned. Exclude -4096 since it can be
  76   // created with LU12I.W.
  77   assert(getStackAlign().value() < 2048 && "Stack alignment too large");
  78   int64_t MaxPosAdjStep = 2048 - getStackAlign().value();
  79   if (Val > -4096 && Val <= (2 * MaxPosAdjStep)) {
  80     int64_t FirstAdj = Val < 0 ? -2048 : MaxPosAdjStep;
  81     Val -= FirstAdj;
  82     BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
  83         .addReg(SrcReg)
  84         .addImm(FirstAdj)
  85         .setMIFlag(Flag);
  86     BuildMI(MBB, MBBI, DL, TII->get(Addi), DestReg)
  87         .addReg(DestReg, RegState::Kill)
  88         .addImm(Val)
  89         .setMIFlag(Flag);
  90     return;
  91   }
  92
  93   unsigned Opc = IsLA64 ? LoongArch::ADD_D : LoongArch::ADD_W;
  94   if (Val < 0) {
  95     Val = -Val;
  96     Opc = IsLA64 ? LoongArch::SUB_D : LoongArch::SUB_W;
  97   }
  98
  99   MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
 100   Register ScratchReg = MRI.createVirtualRegister(&LoongArch::GPRRegClass);
 101   TII->movImm(MBB, MBBI, DL, ScratchReg, Val, Flag);
 102   BuildMI(MBB, MBBI, DL, TII->get(Opc), DestReg)
 103       .addReg(SrcReg)
 104       .addReg(ScratchReg, RegState::Kill)
 105       .setMIFlag(Flag);
 106 }
 107
 108 // Determine the size of the frame and maximum call frame size.
 109 void LoongArchFrameLowering::determineFrameLayout(MachineFunction &MF) const {
 110   MachineFrameInfo &MFI = MF.getFrameInfo();
 111
 112   // Get the number of bytes to allocate from the FrameInfo.
 113   uint64_t FrameSize = MFI.getStackSize();
 114
 115   // Make sure the frame is aligned.
 116   FrameSize = alignTo(FrameSize, getStackAlign());
 117
 118   // Update frame info.
 119   MFI.setStackSize(FrameSize);
 120 }
 121
 122 static uint64_t estimateFunctionSizeInBytes(const LoongArchInstrInfo *TII,
 123                                             const MachineFunction &MF) {
 124   uint64_t FuncSize = 0;
 125   for (auto &MBB : MF)
 126     for (auto &MI : MBB)
 127       FuncSize += TII->getInstSizeInBytes(MI);
 128   return FuncSize;
 129 }
 130
 131 static bool needScavSlotForCFR(MachineFunction &MF) {
 132   if (!MF.getSubtarget<LoongArchSubtarget>().hasBasicF())
 133     return false;
 134   for (auto &MBB : MF)
 135     for (auto &MI : MBB)
 136       if (MI.getOpcode() == LoongArch::PseudoST_CFR)
 137         return true;
 138   return false;
 139 }
 140
 141 void LoongArchFrameLowering::processFunctionBeforeFrameFinalized(
 142     MachineFunction &MF, RegScavenger *RS) const {
 143   const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
 144   const TargetRegisterClass &RC = LoongArch::GPRRegClass;
 145   const LoongArchInstrInfo *TII = STI.getInstrInfo();
 146   LoongArchMachineFunctionInfo *LAFI =
 147       MF.getInfo<LoongArchMachineFunctionInfo>();
 148   MachineFrameInfo &MFI = MF.getFrameInfo();
 149
 150   unsigned ScavSlotsNum = 0;
 151
 152   // Far branches beyond 27-bit offset require a spill slot for scratch
 153   // register.
 154   bool IsLargeFunction = !isInt<27>(estimateFunctionSizeInBytes(TII, MF));
 155   if (IsLargeFunction)
 156     ScavSlotsNum = 1;
 157
 158   // estimateStackSize has been observed to under-estimate the final stack
 159   // size, so give ourselves wiggle-room by checking for stack size
 160   // representable an 11-bit signed field rather than 12-bits.
 161   if (!isInt<11>(MFI.estimateStackSize(MF)))
 162     ScavSlotsNum = std::max(ScavSlotsNum, 1u);
 163
 164   // For CFR spill.
 165   if (needScavSlotForCFR(MF))
 166     ++ScavSlotsNum;
 167
 168   // Create emergency spill slots.
 169   for (unsigned i = 0; i < ScavSlotsNum; ++i) {
 170     int FI = MFI.CreateStackObject(RI->getSpillSize(RC), RI->getSpillAlign(RC),
 171                                    false);
 172     RS->addScavengingFrameIndex(FI);
 173     if (IsLargeFunction && LAFI->getBranchRelaxationSpillFrameIndex() == -1)
 174       LAFI->setBranchRelaxationSpillFrameIndex(FI);
 175     LLVM_DEBUG(dbgs() << "Allocated FI(" << FI
 176                       << ") as the emergency spill slot.\n");
 177   }
 178 }
 179
 180 void LoongArchFrameLowering::emitPrologue(MachineFunction &MF,
 181                                           MachineBasicBlock &MBB) const {
 182   MachineFrameInfo &MFI = MF.getFrameInfo();
 183   auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
 184   const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
 185   const LoongArchInstrInfo *TII = STI.getInstrInfo();
 186   MachineBasicBlock::iterator MBBI = MBB.begin();
 187   bool IsLA64 = STI.is64Bit();
 188
 189   Register SPReg = LoongArch::R3;
 190   Register FPReg = LoongArch::R22;
 191
 192   // Debug location must be unknown since the first debug location is used
 193   // to determine the end of the prologue.
 194   DebugLoc DL;
 195   // All calls are tail calls in GHC calling conv, and functions have no
 196   // prologue/epilogue.
 197   if (MF.getFunction().getCallingConv() == CallingConv::GHC)
 198     return;
 199   // Determine the correct frame layout
 200   determineFrameLayout(MF);
 201
 202   // First, compute final stack size.
 203   uint64_t StackSize = MFI.getStackSize();
 204   uint64_t RealStackSize = StackSize;
 205
 206   // Early exit if there is no need to allocate space in the stack.
 207   if (StackSize == 0 && !MFI.adjustsStack())
 208     return;
 209
 210   uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
 211   // Split the SP adjustment to reduce the offsets of callee saved spill.
 212   if (FirstSPAdjustAmount)
 213     StackSize = FirstSPAdjustAmount;
 214
 215   // Adjust stack.
 216   adjustReg(MBB, MBBI, DL, SPReg, SPReg, -StackSize, MachineInstr::FrameSetup);
 217   // Emit ".cfi_def_cfa_offset StackSize".
 218   unsigned CFIIndex =
 219       MF.addFrameInst(MCCFIInstruction::cfiDefCfaOffset(nullptr, StackSize));
 220   BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
 221       .addCFIIndex(CFIIndex)
 222       .setMIFlag(MachineInstr::FrameSetup);
 223
 224   const auto &CSI = MFI.getCalleeSavedInfo();
 225
 226   // The frame pointer is callee-saved, and code has been generated for us to
 227   // save it to the stack. We need to skip over the storing of callee-saved
 228   // registers as the frame pointer must be modified after it has been saved
 229   // to the stack, not before.
 230   std::advance(MBBI, CSI.size());
 231
 232   // Iterate over list of callee-saved registers and emit .cfi_offset
 233   // directives.
 234   for (const auto &Entry : CSI) {
 235     int64_t Offset = MFI.getObjectOffset(Entry.getFrameIdx());
 236     unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createOffset(
 237         nullptr, RI->getDwarfRegNum(Entry.getReg(), true), Offset));
 238     BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
 239         .addCFIIndex(CFIIndex)
 240         .setMIFlag(MachineInstr::FrameSetup);
 241   }
 242
 243   // Generate new FP.
 244   if (hasFP(MF)) {
 245     adjustReg(MBB, MBBI, DL, FPReg, SPReg,
 246               StackSize - LoongArchFI->getVarArgsSaveSize(),
 247               MachineInstr::FrameSetup);
 248
 249     // Emit ".cfi_def_cfa $fp, LoongArchFI->getVarArgsSaveSize()"
 250     unsigned CFIIndex = MF.addFrameInst(
 251         MCCFIInstruction::cfiDefCfa(nullptr, RI->getDwarfRegNum(FPReg, true),
 252                                     LoongArchFI->getVarArgsSaveSize()));
 253     BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
 254         .addCFIIndex(CFIIndex)
 255         .setMIFlag(MachineInstr::FrameSetup);
 256   }
 257
 258   // Emit the second SP adjustment after saving callee saved registers.
 259   if (FirstSPAdjustAmount) {
 260     uint64_t SecondSPAdjustAmount = RealStackSize - FirstSPAdjustAmount;
 261     assert(SecondSPAdjustAmount > 0 &&
 262            "SecondSPAdjustAmount should be greater than zero");
 263     adjustReg(MBB, MBBI, DL, SPReg, SPReg, -SecondSPAdjustAmount,
 264               MachineInstr::FrameSetup);
 265
 266     if (!hasFP(MF)) {
 267       // If we are using a frame-pointer, and thus emitted ".cfi_def_cfa fp, 0",
 268       // don't emit an sp-based .cfi_def_cfa_offset
 269       // Emit ".cfi_def_cfa_offset RealStackSize"
 270       unsigned CFIIndex = MF.addFrameInst(
 271           MCCFIInstruction::cfiDefCfaOffset(nullptr, RealStackSize));
 272       BuildMI(MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION))
 273           .addCFIIndex(CFIIndex)
 274           .setMIFlag(MachineInstr::FrameSetup);
 275     }
 276   }
 277
 278   if (hasFP(MF)) {
 279     // Realign stack.
 280     if (RI->hasStackRealignment(MF)) {
 281       unsigned Align = Log2(MFI.getMaxAlign());
 282       assert(Align > 0 && "The stack realignment size is invalid!");
 283       BuildMI(MBB, MBBI, DL,
 284               TII->get(IsLA64 ? LoongArch::BSTRINS_D : LoongArch::BSTRINS_W),
 285               SPReg)
 286           .addReg(SPReg)
 287           .addReg(LoongArch::R0)
 288           .addImm(Align - 1)
 289           .addImm(0)
 290           .setMIFlag(MachineInstr::FrameSetup);
 291       // FP will be used to restore the frame in the epilogue, so we need
 292       // another base register BP to record SP after re-alignment. SP will
 293       // track the current stack after allocating variable sized objects.
 294       if (hasBP(MF)) {
 295         // move BP, $sp
 296         BuildMI(MBB, MBBI, DL, TII->get(LoongArch::OR),
 297                 LoongArchABI::getBPReg())
 298             .addReg(SPReg)
 299             .addReg(LoongArch::R0)
 300             .setMIFlag(MachineInstr::FrameSetup);
 301       }
 302     }
 303   }
 304 }
 305
 306 void LoongArchFrameLowering::emitEpilogue(MachineFunction &MF,
 307                                           MachineBasicBlock &MBB) const {
 308   const LoongArchRegisterInfo *RI = STI.getRegisterInfo();
 309   MachineFrameInfo &MFI = MF.getFrameInfo();
 310   auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
 311   Register SPReg = LoongArch::R3;
 312   // All calls are tail calls in GHC calling conv, and functions have no
 313   // prologue/epilogue.
 314   if (MF.getFunction().getCallingConv() == CallingConv::GHC)
 315     return;
 316   MachineBasicBlock::iterator MBBI = MBB.getFirstTerminator();
 317   DebugLoc DL = MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc();
 318
 319   const auto &CSI = MFI.getCalleeSavedInfo();
 320   // Skip to before the restores of callee-saved registers.
 321   auto LastFrameDestroy = MBBI;
 322   if (!CSI.empty())
 323     LastFrameDestroy = std::prev(MBBI, CSI.size());
 324
 325   // Get the number of bytes from FrameInfo.
 326   uint64_t StackSize = MFI.getStackSize();
 327
 328   // Restore the stack pointer.
 329   if (RI->hasStackRealignment(MF) || MFI.hasVarSizedObjects()) {
 330     assert(hasFP(MF) && "frame pointer should not have been eliminated");
 331     adjustReg(MBB, LastFrameDestroy, DL, SPReg, LoongArch::R22,
 332               -StackSize + LoongArchFI->getVarArgsSaveSize(),
 333               MachineInstr::FrameDestroy);
 334   }
 335
 336   uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
 337   if (FirstSPAdjustAmount) {
 338     uint64_t SecondSPAdjustAmount = StackSize - FirstSPAdjustAmount;
 339     assert(SecondSPAdjustAmount > 0 &&
 340            "SecondSPAdjustAmount should be greater than zero");
 341
 342     adjustReg(MBB, LastFrameDestroy, DL, SPReg, SPReg, SecondSPAdjustAmount,
 343               MachineInstr::FrameDestroy);
 344     StackSize = FirstSPAdjustAmount;
 345   }
 346
 347   // Deallocate stack
 348   adjustReg(MBB, MBBI, DL, SPReg, SPReg, StackSize, MachineInstr::FrameDestroy);
 349 }
 350
 351 // We would like to split the SP adjustment to reduce prologue/epilogue
 352 // as following instructions. In this way, the offset of the callee saved
 353 // register could fit in a single store.
 354 // e.g.
 355 //   addi.d  $sp, $sp, -2032
 356 //   st.d    $ra, $sp,  2024
 357 //   st.d    $fp, $sp,  2016
 358 //   addi.d  $sp, $sp,   -16
 359 uint64_t LoongArchFrameLowering::getFirstSPAdjustAmount(
 360     const MachineFunction &MF) const {
 361   const MachineFrameInfo &MFI = MF.getFrameInfo();
 362   const std::vector<CalleeSavedInfo> &CSI = MFI.getCalleeSavedInfo();
 363
 364   // Return the FirstSPAdjustAmount if the StackSize can not fit in a signed
 365   // 12-bit and there exists a callee-saved register needing to be pushed.
 366   if (!isInt<12>(MFI.getStackSize()) && (CSI.size() > 0)) {
 367     // FirstSPAdjustAmount is chosen as (2048 - StackAlign) because 2048 will
 368     // cause sp = sp + 2048 in the epilogue to be split into multiple
 369     // instructions. Offsets smaller than 2048 can fit in a single load/store
 370     // instruction, and we have to stick with the stack alignment.
 371     // So (2048 - StackAlign) will satisfy the stack alignment.
 372     return 2048 - getStackAlign().value();
 373   }
 374   return 0;
 375 }
 376
 377 void LoongArchFrameLowering::determineCalleeSaves(MachineFunction &MF,
 378                                                   BitVector &SavedRegs,
 379                                                   RegScavenger *RS) const {
 380   TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
 381   // Unconditionally spill RA and FP only if the function uses a frame
 382   // pointer.
 383   if (hasFP(MF)) {
 384     SavedRegs.set(LoongArch::R1);
 385     SavedRegs.set(LoongArch::R22);
 386   }
 387   // Mark BP as used if function has dedicated base pointer.
 388   if (hasBP(MF))
 389     SavedRegs.set(LoongArchABI::getBPReg());
 390 }
 391
 392 // Do not preserve stack space within prologue for outgoing variables if the
 393 // function contains variable size objects.
 394 // Let eliminateCallFramePseudoInstr preserve stack space for it.
 395 bool LoongArchFrameLowering::hasReservedCallFrame(
 396     const MachineFunction &MF) const {
 397   return !MF.getFrameInfo().hasVarSizedObjects();
 398 }
 399
 400 // Eliminate ADJCALLSTACKDOWN, ADJCALLSTACKUP pseudo instructions.
 401 MachineBasicBlock::iterator
 402 LoongArchFrameLowering::eliminateCallFramePseudoInstr(
 403     MachineFunction &MF, MachineBasicBlock &MBB,
 404     MachineBasicBlock::iterator MI) const {
 405   Register SPReg = LoongArch::R3;
 406   DebugLoc DL = MI->getDebugLoc();
 407
 408   if (!hasReservedCallFrame(MF)) {
 409     // If space has not been reserved for a call frame, ADJCALLSTACKDOWN and
 410     // ADJCALLSTACKUP must be converted to instructions manipulating the stack
 411     // pointer. This is necessary when there is a variable length stack
 412     // allocation (e.g. alloca), which means it's not possible to allocate
 413     // space for outgoing arguments from within the function prologue.
 414     int64_t Amount = MI->getOperand(0).getImm();
 415
 416     if (Amount != 0) {
 417       // Ensure the stack remains aligned after adjustment.
 418       Amount = alignSPAdjust(Amount);
 419
 420       if (MI->getOpcode() == LoongArch::ADJCALLSTACKDOWN)
 421         Amount = -Amount;
 422
 423       adjustReg(MBB, MI, DL, SPReg, SPReg, Amount, MachineInstr::NoFlags);
 424     }
 425   }
 426
 427   return MBB.erase(MI);
 428 }
 429
 430 bool LoongArchFrameLowering::spillCalleeSavedRegisters(
 431     MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
 432     ArrayRef<CalleeSavedInfo> CSI, const TargetRegisterInfo *TRI) const {
 433   if (CSI.empty())
 434     return true;
 435
 436   MachineFunction *MF = MBB.getParent();
 437   const TargetInstrInfo &TII = *MF->getSubtarget().getInstrInfo();
 438
 439   // Insert the spill to the stack frame.
 440   for (auto &CS : CSI) {
 441     Register Reg = CS.getReg();
 442     // If the register is RA and the return address is taken by method
 443     // LoongArchTargetLowering::lowerRETURNADDR, don't set kill flag.
 444     bool IsKill =
 445         !(Reg == LoongArch::R1 && MF->getFrameInfo().isReturnAddressTaken());
 446     const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
 447     TII.storeRegToStackSlot(MBB, MI, Reg, IsKill, CS.getFrameIdx(), RC, TRI,
 448                             Register());
 449   }
 450
 451   return true;
 452 }
 453
 454 StackOffset LoongArchFrameLowering::getFrameIndexReference(
 455     const MachineFunction &MF, int FI, Register &FrameReg) const {
 456   const MachineFrameInfo &MFI = MF.getFrameInfo();
 457   const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();
 458   auto *LoongArchFI = MF.getInfo<LoongArchMachineFunctionInfo>();
 459   uint64_t StackSize = MFI.getStackSize();
 460   uint64_t FirstSPAdjustAmount = getFirstSPAdjustAmount(MF);
 461
 462   // Callee-saved registers should be referenced relative to the stack
 463   // pointer (positive offset), otherwise use the frame pointer (negative
 464   // offset).
 465   const auto &CSI = MFI.getCalleeSavedInfo();
 466   int MinCSFI = 0;
 467   int MaxCSFI = -1;
 468   StackOffset Offset =
 469       StackOffset::getFixed(MFI.getObjectOffset(FI) - getOffsetOfLocalArea() +
 470                             MFI.getOffsetAdjustment());
 471
 472   if (CSI.size()) {
 473     MinCSFI = CSI[0].getFrameIdx();
 474     MaxCSFI = CSI[CSI.size() - 1].getFrameIdx();
 475   }
 476
 477   if (FI >= MinCSFI && FI <= MaxCSFI) {
 478     FrameReg = LoongArch::R3;
 479     if (FirstSPAdjustAmount)
 480       Offset += StackOffset::getFixed(FirstSPAdjustAmount);
 481     else
 482       Offset += StackOffset::getFixed(StackSize);
 483   } else if (RI->hasStackRealignment(MF) && !MFI.isFixedObjectIndex(FI)) {
 484     // If the stack was realigned, the frame pointer is set in order to allow
 485     // SP to be restored, so we need another base register to record the stack
 486     // after realignment.
 487     FrameReg = hasBP(MF) ? LoongArchABI::getBPReg() : LoongArch::R3;
 488     Offset += StackOffset::getFixed(StackSize);
 489   } else {
 490     FrameReg = RI->getFrameRegister(MF);
 491     if (hasFP(MF))
 492       Offset += StackOffset::getFixed(LoongArchFI->getVarArgsSaveSize());
 493     else
 494       Offset += StackOffset::getFixed(StackSize);
 495   }
 496
 497   return Offset;
 498 }
 499
 500 bool LoongArchFrameLowering::enableShrinkWrapping(
 501     const MachineFunction &MF) const {
 502   // Keep the conventional code flow when not optimizing.
 503   if (MF.getFunction().hasOptNone())
 504     return false;
 505
 506   return true;
 507 }