lib/Target/AArch64/AArch64RegisterInfo.cpp

   1 //===- AArch64RegisterInfo.cpp - AArch64 Register Information -------------===//
   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 AArch64 implementation of the TargetRegisterInfo
  10 // class.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "AArch64RegisterInfo.h"
  15 #include "AArch64FrameLowering.h"
  16 #include "AArch64InstrInfo.h"
  17 #include "AArch64MachineFunctionInfo.h"
  18 #include "AArch64Subtarget.h"
  19 #include "MCTargetDesc/AArch64AddressingModes.h"
  20 #include "llvm/ADT/BitVector.h"
  21 #include "llvm/ADT/Triple.h"
  22 #include "llvm/CodeGen/MachineFrameInfo.h"
  23 #include "llvm/CodeGen/MachineInstrBuilder.h"
  24 #include "llvm/CodeGen/MachineRegisterInfo.h"
  25 #include "llvm/CodeGen/RegisterScavenging.h"
  26 #include "llvm/IR/Function.h"
  27 #include "llvm/IR/DiagnosticInfo.h"
  28 #include "llvm/Support/raw_ostream.h"
  29 #include "llvm/CodeGen/TargetFrameLowering.h"
  30 #include "llvm/Target/TargetOptions.h"
  31
  32 using namespace llvm;
  33
  34 #define GET_REGINFO_TARGET_DESC
  35 #include "AArch64GenRegisterInfo.inc"
  36
  37 AArch64RegisterInfo::AArch64RegisterInfo(const Triple &TT)
  38     : AArch64GenRegisterInfo(AArch64::LR), TT(TT) {
  39   AArch64_MC::initLLVMToCVRegMapping(this);
  40 }
  41
  42 const MCPhysReg *
  43 AArch64RegisterInfo::getCalleeSavedRegs(const MachineFunction *MF) const {
  44   assert(MF && "Invalid MachineFunction pointer.");
  45   if (MF->getSubtarget<AArch64Subtarget>().isTargetWindows())
  46     return CSR_Win_AArch64_AAPCS_SaveList;
  47   if (MF->getFunction().getCallingConv() == CallingConv::GHC)
  48     // GHC set of callee saved regs is empty as all those regs are
  49     // used for passing STG regs around
  50     return CSR_AArch64_NoRegs_SaveList;
  51   if (MF->getFunction().getCallingConv() == CallingConv::AnyReg)
  52     return CSR_AArch64_AllRegs_SaveList;
  53   if (MF->getFunction().getCallingConv() == CallingConv::AArch64_VectorCall)
  54     return CSR_AArch64_AAVPCS_SaveList;
  55   if (MF->getFunction().getCallingConv() == CallingConv::CXX_FAST_TLS)
  56     return MF->getInfo<AArch64FunctionInfo>()->isSplitCSR() ?
  57            CSR_AArch64_CXX_TLS_Darwin_PE_SaveList :
  58            CSR_AArch64_CXX_TLS_Darwin_SaveList;
  59   if (MF->getSubtarget<AArch64Subtarget>().getTargetLowering()
  60           ->supportSwiftError() &&
  61       MF->getFunction().getAttributes().hasAttrSomewhere(
  62           Attribute::SwiftError))
  63     return CSR_AArch64_AAPCS_SwiftError_SaveList;
  64   if (MF->getFunction().getCallingConv() == CallingConv::PreserveMost)
  65     return CSR_AArch64_RT_MostRegs_SaveList;
  66   else
  67     return CSR_AArch64_AAPCS_SaveList;
  68 }
  69
  70 const MCPhysReg *AArch64RegisterInfo::getCalleeSavedRegsViaCopy(
  71     const MachineFunction *MF) const {
  72   assert(MF && "Invalid MachineFunction pointer.");
  73   if (MF->getFunction().getCallingConv() == CallingConv::CXX_FAST_TLS &&
  74       MF->getInfo<AArch64FunctionInfo>()->isSplitCSR())
  75     return CSR_AArch64_CXX_TLS_Darwin_ViaCopy_SaveList;
  76   return nullptr;
  77 }
  78
  79 void AArch64RegisterInfo::UpdateCustomCalleeSavedRegs(
  80     MachineFunction &MF) const {
  81   const MCPhysReg *CSRs = getCalleeSavedRegs(&MF);
  82   SmallVector<MCPhysReg, 32> UpdatedCSRs;
  83   for (const MCPhysReg *I = CSRs; *I; ++I)
  84     UpdatedCSRs.push_back(*I);
  85
  86   for (size_t i = 0; i < AArch64::GPR64commonRegClass.getNumRegs(); ++i) {
  87     if (MF.getSubtarget<AArch64Subtarget>().isXRegCustomCalleeSaved(i)) {
  88       UpdatedCSRs.push_back(AArch64::GPR64commonRegClass.getRegister(i));
  89     }
  90   }
  91   // Register lists are zero-terminated.
  92   UpdatedCSRs.push_back(0);
  93   MF.getRegInfo().setCalleeSavedRegs(UpdatedCSRs);
  94 }
  95
  96 const TargetRegisterClass *
  97 AArch64RegisterInfo::getSubClassWithSubReg(const TargetRegisterClass *RC,
  98                                        unsigned Idx) const {
  99   // edge case for GPR/FPR register classes
 100   if (RC == &AArch64::GPR32allRegClass && Idx == AArch64::hsub)
 101     return &AArch64::FPR32RegClass;
 102   else if (RC == &AArch64::GPR64allRegClass && Idx == AArch64::hsub)
 103     return &AArch64::FPR64RegClass;
 104
 105   // Forward to TableGen's default version.
 106   return AArch64GenRegisterInfo::getSubClassWithSubReg(RC, Idx);
 107 }
 108
 109 const uint32_t *
 110 AArch64RegisterInfo::getCallPreservedMask(const MachineFunction &MF,
 111                                           CallingConv::ID CC) const {
 112   bool SCS = MF.getFunction().hasFnAttribute(Attribute::ShadowCallStack);
 113   if (CC == CallingConv::GHC)
 114     // This is academic because all GHC calls are (supposed to be) tail calls
 115     return SCS ? CSR_AArch64_NoRegs_SCS_RegMask : CSR_AArch64_NoRegs_RegMask;
 116   if (CC == CallingConv::AnyReg)
 117     return SCS ? CSR_AArch64_AllRegs_SCS_RegMask : CSR_AArch64_AllRegs_RegMask;
 118   if (CC == CallingConv::CXX_FAST_TLS)
 119     return SCS ? CSR_AArch64_CXX_TLS_Darwin_SCS_RegMask
 120                : CSR_AArch64_CXX_TLS_Darwin_RegMask;
 121   if (CC == CallingConv::AArch64_VectorCall)
 122     return SCS ? CSR_AArch64_AAVPCS_SCS_RegMask : CSR_AArch64_AAVPCS_RegMask;
 123   if (MF.getSubtarget<AArch64Subtarget>().getTargetLowering()
 124           ->supportSwiftError() &&
 125       MF.getFunction().getAttributes().hasAttrSomewhere(Attribute::SwiftError))
 126     return SCS ? CSR_AArch64_AAPCS_SwiftError_SCS_RegMask
 127                : CSR_AArch64_AAPCS_SwiftError_RegMask;
 128   if (CC == CallingConv::PreserveMost)
 129     return SCS ? CSR_AArch64_RT_MostRegs_SCS_RegMask
 130                : CSR_AArch64_RT_MostRegs_RegMask;
 131   else
 132     return SCS ? CSR_AArch64_AAPCS_SCS_RegMask : CSR_AArch64_AAPCS_RegMask;
 133 }
 134
 135 const uint32_t *AArch64RegisterInfo::getTLSCallPreservedMask() const {
 136   if (TT.isOSDarwin())
 137     return CSR_AArch64_TLS_Darwin_RegMask;
 138
 139   assert(TT.isOSBinFormatELF() && "Invalid target");
 140   return CSR_AArch64_TLS_ELF_RegMask;
 141 }
 142
 143 void AArch64RegisterInfo::UpdateCustomCallPreservedMask(MachineFunction &MF,
 144                                                  const uint32_t **Mask) const {
 145   uint32_t *UpdatedMask = MF.allocateRegMask();
 146   unsigned RegMaskSize = MachineOperand::getRegMaskSize(getNumRegs());
 147   memcpy(UpdatedMask, *Mask, sizeof(UpdatedMask[0]) * RegMaskSize);
 148
 149   for (size_t i = 0; i < AArch64::GPR64commonRegClass.getNumRegs(); ++i) {
 150     if (MF.getSubtarget<AArch64Subtarget>().isXRegCustomCalleeSaved(i)) {
 151       for (MCSubRegIterator SubReg(AArch64::GPR64commonRegClass.getRegister(i),
 152                                    this, true);
 153            SubReg.isValid(); ++SubReg) {
 154         // See TargetRegisterInfo::getCallPreservedMask for how to interpret the
 155         // register mask.
 156         UpdatedMask[*SubReg / 32] |= 1u << (*SubReg % 32);
 157       }
 158     }
 159   }
 160   *Mask = UpdatedMask;
 161 }
 162
 163 const uint32_t *AArch64RegisterInfo::getNoPreservedMask() const {
 164   return CSR_AArch64_NoRegs_RegMask;
 165 }
 166
 167 const uint32_t *
 168 AArch64RegisterInfo::getThisReturnPreservedMask(const MachineFunction &MF,
 169                                                 CallingConv::ID CC) const {
 170   // This should return a register mask that is the same as that returned by
 171   // getCallPreservedMask but that additionally preserves the register used for
 172   // the first i64 argument (which must also be the register used to return a
 173   // single i64 return value)
 174   //
 175   // In case that the calling convention does not use the same register for
 176   // both, the function should return NULL (does not currently apply)
 177   assert(CC != CallingConv::GHC && "should not be GHC calling convention.");
 178   return CSR_AArch64_AAPCS_ThisReturn_RegMask;
 179 }
 180
 181 const uint32_t *AArch64RegisterInfo::getWindowsStackProbePreservedMask() const {
 182   return CSR_AArch64_StackProbe_Windows_RegMask;
 183 }
 184
 185 BitVector
 186 AArch64RegisterInfo::getReservedRegs(const MachineFunction &MF) const {
 187   const AArch64FrameLowering *TFI = getFrameLowering(MF);
 188
 189   // FIXME: avoid re-calculating this every time.
 190   BitVector Reserved(getNumRegs());
 191   markSuperRegs(Reserved, AArch64::WSP);
 192   markSuperRegs(Reserved, AArch64::WZR);
 193
 194   if (TFI->hasFP(MF) || TT.isOSDarwin())
 195     markSuperRegs(Reserved, AArch64::W29);
 196
 197   for (size_t i = 0; i < AArch64::GPR32commonRegClass.getNumRegs(); ++i) {
 198     if (MF.getSubtarget<AArch64Subtarget>().isXRegisterReserved(i))
 199       markSuperRegs(Reserved, AArch64::GPR32commonRegClass.getRegister(i));
 200   }
 201
 202   if (hasBasePointer(MF))
 203     markSuperRegs(Reserved, AArch64::W19);
 204
 205   // SLH uses register W16/X16 as the taint register.
 206   if (MF.getFunction().hasFnAttribute(Attribute::SpeculativeLoadHardening))
 207     markSuperRegs(Reserved, AArch64::W16);
 208
 209   assert(checkAllSuperRegsMarked(Reserved));
 210   return Reserved;
 211 }
 212
 213 bool AArch64RegisterInfo::isReservedReg(const MachineFunction &MF,
 214                                       unsigned Reg) const {
 215   return getReservedRegs(MF)[Reg];
 216 }
 217
 218 bool AArch64RegisterInfo::isAnyArgRegReserved(const MachineFunction &MF) const {
 219   return std::any_of(std::begin(*AArch64::GPR64argRegClass.MC),
 220                      std::end(*AArch64::GPR64argRegClass.MC),
 221                      [this, &MF](MCPhysReg r){return isReservedReg(MF, r);});
 222 }
 223
 224 void AArch64RegisterInfo::emitReservedArgRegCallError(
 225     const MachineFunction &MF) const {
 226   const Function &F = MF.getFunction();
 227   F.getContext().diagnose(DiagnosticInfoUnsupported{F, "AArch64 doesn't support"
 228     " function calls if any of the argument registers is reserved."});
 229 }
 230
 231 bool AArch64RegisterInfo::isAsmClobberable(const MachineFunction &MF,
 232                                           unsigned PhysReg) const {
 233   return !isReservedReg(MF, PhysReg);
 234 }
 235
 236 bool AArch64RegisterInfo::isConstantPhysReg(unsigned PhysReg) const {
 237   return PhysReg == AArch64::WZR || PhysReg == AArch64::XZR;
 238 }
 239
 240 const TargetRegisterClass *
 241 AArch64RegisterInfo::getPointerRegClass(const MachineFunction &MF,
 242                                       unsigned Kind) const {
 243   return &AArch64::GPR64spRegClass;
 244 }
 245
 246 const TargetRegisterClass *
 247 AArch64RegisterInfo::getCrossCopyRegClass(const TargetRegisterClass *RC) const {
 248   if (RC == &AArch64::CCRRegClass)
 249     return &AArch64::GPR64RegClass; // Only MSR & MRS copy NZCV.
 250   return RC;
 251 }
 252
 253 unsigned AArch64RegisterInfo::getBaseRegister() const { return AArch64::X19; }
 254
 255 bool AArch64RegisterInfo::hasBasePointer(const MachineFunction &MF) const {
 256   const MachineFrameInfo &MFI = MF.getFrameInfo();
 257
 258   // In the presence of variable sized objects or funclets, if the fixed stack
 259   // size is large enough that referencing from the FP won't result in things
 260   // being in range relatively often, we can use a base pointer to allow access
 261   // from the other direction like the SP normally works.
 262   //
 263   // Furthermore, if both variable sized objects are present, and the
 264   // stack needs to be dynamically re-aligned, the base pointer is the only
 265   // reliable way to reference the locals.
 266   if (MFI.hasVarSizedObjects() || MF.hasEHFunclets()) {
 267     if (needsStackRealignment(MF))
 268       return true;
 269     // Conservatively estimate whether the negative offset from the frame
 270     // pointer will be sufficient to reach. If a function has a smallish
 271     // frame, it's less likely to have lots of spills and callee saved
 272     // space, so it's all more likely to be within range of the frame pointer.
 273     // If it's wrong, we'll materialize the constant and still get to the
 274     // object; it's just suboptimal. Negative offsets use the unscaled
 275     // load/store instructions, which have a 9-bit signed immediate.
 276     return MFI.getLocalFrameSize() >= 256;
 277   }
 278
 279   return false;
 280 }
 281
 282 Register
 283 AArch64RegisterInfo::getFrameRegister(const MachineFunction &MF) const {
 284   const AArch64FrameLowering *TFI = getFrameLowering(MF);
 285   return TFI->hasFP(MF) ? AArch64::FP : AArch64::SP;
 286 }
 287
 288 bool AArch64RegisterInfo::requiresRegisterScavenging(
 289     const MachineFunction &MF) const {
 290   return true;
 291 }
 292
 293 bool AArch64RegisterInfo::requiresVirtualBaseRegisters(
 294     const MachineFunction &MF) const {
 295   return true;
 296 }
 297
 298 bool
 299 AArch64RegisterInfo::useFPForScavengingIndex(const MachineFunction &MF) const {
 300   // This function indicates whether the emergency spillslot should be placed
 301   // close to the beginning of the stackframe (closer to FP) or the end
 302   // (closer to SP).
 303   //
 304   // The beginning works most reliably if we have a frame pointer.
 305   const AArch64FrameLowering &TFI = *getFrameLowering(MF);
 306   return TFI.hasFP(MF);
 307 }
 308
 309 bool AArch64RegisterInfo::requiresFrameIndexScavenging(
 310     const MachineFunction &MF) const {
 311   return true;
 312 }
 313
 314 bool
 315 AArch64RegisterInfo::cannotEliminateFrame(const MachineFunction &MF) const {
 316   const MachineFrameInfo &MFI = MF.getFrameInfo();
 317   if (MF.getTarget().Options.DisableFramePointerElim(MF) && MFI.adjustsStack())
 318     return true;
 319   return MFI.hasVarSizedObjects() || MFI.isFrameAddressTaken();
 320 }
 321
 322 /// needsFrameBaseReg - Returns true if the instruction's frame index
 323 /// reference would be better served by a base register other than FP
 324 /// or SP. Used by LocalStackFrameAllocation to determine which frame index
 325 /// references it should create new base registers for.
 326 bool AArch64RegisterInfo::needsFrameBaseReg(MachineInstr *MI,
 327                                             int64_t Offset) const {
 328   for (unsigned i = 0; !MI->getOperand(i).isFI(); ++i)
 329     assert(i < MI->getNumOperands() &&
 330            "Instr doesn't have FrameIndex operand!");
 331
 332   // It's the load/store FI references that cause issues, as it can be difficult
 333   // to materialize the offset if it won't fit in the literal field. Estimate
 334   // based on the size of the local frame and some conservative assumptions
 335   // about the rest of the stack frame (note, this is pre-regalloc, so
 336   // we don't know everything for certain yet) whether this offset is likely
 337   // to be out of range of the immediate. Return true if so.
 338
 339   // We only generate virtual base registers for loads and stores, so
 340   // return false for everything else.
 341   if (!MI->mayLoad() && !MI->mayStore())
 342     return false;
 343
 344   // Without a virtual base register, if the function has variable sized
 345   // objects, all fixed-size local references will be via the frame pointer,
 346   // Approximate the offset and see if it's legal for the instruction.
 347   // Note that the incoming offset is based on the SP value at function entry,
 348   // so it'll be negative.
 349   MachineFunction &MF = *MI->getParent()->getParent();
 350   const AArch64FrameLowering *TFI = getFrameLowering(MF);
 351   MachineFrameInfo &MFI = MF.getFrameInfo();
 352
 353   // Estimate an offset from the frame pointer.
 354   // Conservatively assume all GPR callee-saved registers get pushed.
 355   // FP, LR, X19-X28, D8-D15. 64-bits each.
 356   int64_t FPOffset = Offset - 16 * 20;
 357   // Estimate an offset from the stack pointer.
 358   // The incoming offset is relating to the SP at the start of the function,
 359   // but when we access the local it'll be relative to the SP after local
 360   // allocation, so adjust our SP-relative offset by that allocation size.
 361   Offset += MFI.getLocalFrameSize();
 362   // Assume that we'll have at least some spill slots allocated.
 363   // FIXME: This is a total SWAG number. We should run some statistics
 364   //        and pick a real one.
 365   Offset += 128; // 128 bytes of spill slots
 366
 367   // If there is a frame pointer, try using it.
 368   // The FP is only available if there is no dynamic realignment. We
 369   // don't know for sure yet whether we'll need that, so we guess based
 370   // on whether there are any local variables that would trigger it.
 371   if (TFI->hasFP(MF) && isFrameOffsetLegal(MI, AArch64::FP, FPOffset))
 372     return false;
 373
 374   // If we can reference via the stack pointer or base pointer, try that.
 375   // FIXME: This (and the code that resolves the references) can be improved
 376   //        to only disallow SP relative references in the live range of
 377   //        the VLA(s). In practice, it's unclear how much difference that
 378   //        would make, but it may be worth doing.
 379   if (isFrameOffsetLegal(MI, AArch64::SP, Offset))
 380     return false;
 381
 382   // The offset likely isn't legal; we want to allocate a virtual base register.
 383   return true;
 384 }
 385
 386 bool AArch64RegisterInfo::isFrameOffsetLegal(const MachineInstr *MI,
 387                                              unsigned BaseReg,
 388                                              int64_t Offset) const {
 389   assert(Offset <= INT_MAX && "Offset too big to fit in int.");
 390   assert(MI && "Unable to get the legal offset for nil instruction.");
 391   int SaveOffset = Offset;
 392   return isAArch64FrameOffsetLegal(*MI, SaveOffset) & AArch64FrameOffsetIsLegal;
 393 }
 394
 395 /// Insert defining instruction(s) for BaseReg to be a pointer to FrameIdx
 396 /// at the beginning of the basic block.
 397 void AArch64RegisterInfo::materializeFrameBaseRegister(MachineBasicBlock *MBB,
 398                                                        unsigned BaseReg,
 399                                                        int FrameIdx,
 400                                                        int64_t Offset) const {
 401   MachineBasicBlock::iterator Ins = MBB->begin();
 402   DebugLoc DL; // Defaults to "unknown"
 403   if (Ins != MBB->end())
 404     DL = Ins->getDebugLoc();
 405   const MachineFunction &MF = *MBB->getParent();
 406   const AArch64InstrInfo *TII =
 407       MF.getSubtarget<AArch64Subtarget>().getInstrInfo();
 408   const MCInstrDesc &MCID = TII->get(AArch64::ADDXri);
 409   MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
 410   MRI.constrainRegClass(BaseReg, TII->getRegClass(MCID, 0, this, MF));
 411   unsigned Shifter = AArch64_AM::getShifterImm(AArch64_AM::LSL, 0);
 412
 413   BuildMI(*MBB, Ins, DL, MCID, BaseReg)
 414       .addFrameIndex(FrameIdx)
 415       .addImm(Offset)
 416       .addImm(Shifter);
 417 }
 418
 419 void AArch64RegisterInfo::resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
 420                                             int64_t Offset) const {
 421   int Off = Offset; // ARM doesn't need the general 64-bit offsets
 422   unsigned i = 0;
 423
 424   while (!MI.getOperand(i).isFI()) {
 425     ++i;
 426     assert(i < MI.getNumOperands() && "Instr doesn't have FrameIndex operand!");
 427   }
 428   const MachineFunction *MF = MI.getParent()->getParent();
 429   const AArch64InstrInfo *TII =
 430       MF->getSubtarget<AArch64Subtarget>().getInstrInfo();
 431   bool Done = rewriteAArch64FrameIndex(MI, i, BaseReg, Off, TII);
 432   assert(Done && "Unable to resolve frame index!");
 433   (void)Done;
 434 }
 435
 436 void AArch64RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
 437                                               int SPAdj, unsigned FIOperandNum,
 438                                               RegScavenger *RS) const {
 439   assert(SPAdj == 0 && "Unexpected");
 440
 441   MachineInstr &MI = *II;
 442   MachineBasicBlock &MBB = *MI.getParent();
 443   MachineFunction &MF = *MBB.getParent();
 444   const AArch64InstrInfo *TII =
 445       MF.getSubtarget<AArch64Subtarget>().getInstrInfo();
 446   const AArch64FrameLowering *TFI = getFrameLowering(MF);
 447
 448   int FrameIndex = MI.getOperand(FIOperandNum).getIndex();
 449   unsigned FrameReg;
 450   int Offset;
 451
 452   // Special handling of dbg_value, stackmap and patchpoint instructions.
 453   if (MI.isDebugValue() || MI.getOpcode() == TargetOpcode::STACKMAP ||
 454       MI.getOpcode() == TargetOpcode::PATCHPOINT) {
 455     Offset = TFI->resolveFrameIndexReference(MF, FrameIndex, FrameReg,
 456                                              /*PreferFP=*/true,
 457                                              /*ForSimm=*/false);
 458     Offset += MI.getOperand(FIOperandNum + 1).getImm();
 459     MI.getOperand(FIOperandNum).ChangeToRegister(FrameReg, false /*isDef*/);
 460     MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset);
 461     return;
 462   }
 463
 464   if (MI.getOpcode() == TargetOpcode::LOCAL_ESCAPE) {
 465     MachineOperand &FI = MI.getOperand(FIOperandNum);
 466     Offset = TFI->getNonLocalFrameIndexReference(MF, FrameIndex);
 467     FI.ChangeToImmediate(Offset);
 468     return;
 469   }
 470
 471   if (MI.getOpcode() == AArch64::TAGPstack) {
 472     // TAGPstack must use the virtual frame register in its 3rd operand.
 473     const MachineFrameInfo &MFI = MF.getFrameInfo();
 474     const AArch64FunctionInfo *AFI = MF.getInfo<AArch64FunctionInfo>();
 475     FrameReg = MI.getOperand(3).getReg();
 476     Offset =
 477         MFI.getObjectOffset(FrameIndex) + AFI->getTaggedBasePointerOffset();
 478   } else {
 479     Offset = TFI->resolveFrameIndexReference(
 480         MF, FrameIndex, FrameReg, /*PreferFP=*/false, /*ForSimm=*/true);
 481   }
 482
 483   // Modify MI as necessary to handle as much of 'Offset' as possible
 484   if (rewriteAArch64FrameIndex(MI, FIOperandNum, FrameReg, Offset, TII))
 485     return;
 486
 487   assert((!RS || !RS->isScavengingFrameIndex(FrameIndex)) &&
 488          "Emergency spill slot is out of reach");
 489
 490   // If we get here, the immediate doesn't fit into the instruction.  We folded
 491   // as much as possible above.  Handle the rest, providing a register that is
 492   // SP+LargeImm.
 493   unsigned ScratchReg =
 494       MF.getRegInfo().createVirtualRegister(&AArch64::GPR64RegClass);
 495   emitFrameOffset(MBB, II, MI.getDebugLoc(), ScratchReg, FrameReg, Offset, TII);
 496   MI.getOperand(FIOperandNum).ChangeToRegister(ScratchReg, false, false, true);
 497 }
 498
 499 unsigned AArch64RegisterInfo::getRegPressureLimit(const TargetRegisterClass *RC,
 500                                                   MachineFunction &MF) const {
 501   const AArch64FrameLowering *TFI = getFrameLowering(MF);
 502
 503   switch (RC->getID()) {
 504   default:
 505     return 0;
 506   case AArch64::GPR32RegClassID:
 507   case AArch64::GPR32spRegClassID:
 508   case AArch64::GPR32allRegClassID:
 509   case AArch64::GPR64spRegClassID:
 510   case AArch64::GPR64allRegClassID:
 511   case AArch64::GPR64RegClassID:
 512   case AArch64::GPR32commonRegClassID:
 513   case AArch64::GPR64commonRegClassID:
 514     return 32 - 1                                   // XZR/SP
 515               - (TFI->hasFP(MF) || TT.isOSDarwin()) // FP
 516               - MF.getSubtarget<AArch64Subtarget>().getNumXRegisterReserved()
 517               - hasBasePointer(MF);  // X19
 518   case AArch64::FPR8RegClassID:
 519   case AArch64::FPR16RegClassID:
 520   case AArch64::FPR32RegClassID:
 521   case AArch64::FPR64RegClassID:
 522   case AArch64::FPR128RegClassID:
 523     return 32;
 524
 525   case AArch64::DDRegClassID:
 526   case AArch64::DDDRegClassID:
 527   case AArch64::DDDDRegClassID:
 528   case AArch64::QQRegClassID:
 529   case AArch64::QQQRegClassID:
 530   case AArch64::QQQQRegClassID:
 531     return 32;
 532
 533   case AArch64::FPR128_loRegClassID:
 534     return 16;
 535   }
 536 }
 537
 538 unsigned AArch64RegisterInfo::getLocalAddressRegister(
 539   const MachineFunction &MF) const {
 540   const auto &MFI = MF.getFrameInfo();
 541   if (!MF.hasEHFunclets() && !MFI.hasVarSizedObjects())
 542     return AArch64::SP;
 543   else if (needsStackRealignment(MF))
 544     return getBaseRegister();
 545   return getFrameRegister(MF);
 546 }