lib/Target/ARM/ARMInstructionSelector.cpp

   1 //===- ARMInstructionSelector.cpp ----------------------------*- 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 /// \file
   9 /// This file implements the targeting of the InstructionSelector class for ARM.
  10 /// \todo This should be generated by TableGen.
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "ARMRegisterBankInfo.h"
  14 #include "ARMSubtarget.h"
  15 #include "ARMTargetMachine.h"
  16 #include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
  17 #include "llvm/CodeGen/GlobalISel/InstructionSelectorImpl.h"
  18 #include "llvm/CodeGen/MachineConstantPool.h"
  19 #include "llvm/CodeGen/MachineRegisterInfo.h"
  20 #include "llvm/Support/Debug.h"
  21
  22 #define DEBUG_TYPE "arm-isel"
  23
  24 using namespace llvm;
  25
  26 namespace {
  27
  28 #define GET_GLOBALISEL_PREDICATE_BITSET
  29 #include "ARMGenGlobalISel.inc"
  30 #undef GET_GLOBALISEL_PREDICATE_BITSET
  31
  32 class ARMInstructionSelector : public InstructionSelector {
  33 public:
  34   ARMInstructionSelector(const ARMBaseTargetMachine &TM, const ARMSubtarget &STI,
  35                          const ARMRegisterBankInfo &RBI);
  36
  37   bool select(MachineInstr &I, CodeGenCoverage &CoverageInfo) const override;
  38   static const char *getName() { return DEBUG_TYPE; }
  39
  40 private:
  41   bool selectImpl(MachineInstr &I, CodeGenCoverage &CoverageInfo) const;
  42
  43   struct CmpConstants;
  44   struct InsertInfo;
  45
  46   bool selectCmp(CmpConstants Helper, MachineInstrBuilder &MIB,
  47                  MachineRegisterInfo &MRI) const;
  48
  49   // Helper for inserting a comparison sequence that sets \p ResReg to either 1
  50   // if \p LHSReg and \p RHSReg are in the relationship defined by \p Cond, or
  51   // \p PrevRes otherwise. In essence, it computes PrevRes OR (LHS Cond RHS).
  52   bool insertComparison(CmpConstants Helper, InsertInfo I, unsigned ResReg,
  53                         ARMCC::CondCodes Cond, unsigned LHSReg, unsigned RHSReg,
  54                         unsigned PrevRes) const;
  55
  56   // Set \p DestReg to \p Constant.
  57   void putConstant(InsertInfo I, unsigned DestReg, unsigned Constant) const;
  58
  59   bool selectGlobal(MachineInstrBuilder &MIB, MachineRegisterInfo &MRI) const;
  60   bool selectSelect(MachineInstrBuilder &MIB, MachineRegisterInfo &MRI) const;
  61   bool selectShift(unsigned ShiftOpc, MachineInstrBuilder &MIB) const;
  62
  63   // Check if the types match and both operands have the expected size and
  64   // register bank.
  65   bool validOpRegPair(MachineRegisterInfo &MRI, unsigned LHS, unsigned RHS,
  66                       unsigned ExpectedSize, unsigned ExpectedRegBankID) const;
  67
  68   // Check if the register has the expected size and register bank.
  69   bool validReg(MachineRegisterInfo &MRI, unsigned Reg, unsigned ExpectedSize,
  70                 unsigned ExpectedRegBankID) const;
  71
  72   const ARMBaseInstrInfo &TII;
  73   const ARMBaseRegisterInfo &TRI;
  74   const ARMBaseTargetMachine &TM;
  75   const ARMRegisterBankInfo &RBI;
  76   const ARMSubtarget &STI;
  77
  78   // FIXME: This is necessary because DAGISel uses "Subtarget->" and GlobalISel
  79   // uses "STI." in the code generated by TableGen. If we want to reuse some of
  80   // the custom C++ predicates written for DAGISel, we need to have both around.
  81   const ARMSubtarget *Subtarget = &STI;
  82
  83   // Store the opcodes that we might need, so we don't have to check what kind
  84   // of subtarget (ARM vs Thumb) we have all the time.
  85   struct OpcodeCache {
  86     unsigned ZEXT16;
  87     unsigned SEXT16;
  88
  89     unsigned ZEXT8;
  90     unsigned SEXT8;
  91
  92     // Used for implementing ZEXT/SEXT from i1
  93     unsigned AND;
  94     unsigned RSB;
  95
  96     unsigned STORE32;
  97     unsigned LOAD32;
  98
  99     unsigned STORE16;
 100     unsigned LOAD16;
 101
 102     unsigned STORE8;
 103     unsigned LOAD8;
 104
 105     unsigned ADDrr;
 106     unsigned ADDri;
 107
 108     // Used for G_ICMP
 109     unsigned CMPrr;
 110     unsigned MOVi;
 111     unsigned MOVCCi;
 112
 113     // Used for G_SELECT
 114     unsigned MOVCCr;
 115
 116     unsigned TSTri;
 117     unsigned Bcc;
 118
 119     // Used for G_GLOBAL_VALUE
 120     unsigned MOVi32imm;
 121     unsigned ConstPoolLoad;
 122     unsigned MOV_ga_pcrel;
 123     unsigned LDRLIT_ga_pcrel;
 124     unsigned LDRLIT_ga_abs;
 125
 126     OpcodeCache(const ARMSubtarget &STI);
 127   } const Opcodes;
 128
 129   // Select the opcode for simple extensions (that translate to a single SXT/UXT
 130   // instruction). Extension operations more complicated than that should not
 131   // invoke this. Returns the original opcode if it doesn't know how to select a
 132   // better one.
 133   unsigned selectSimpleExtOpc(unsigned Opc, unsigned Size) const;
 134
 135   // Select the opcode for simple loads and stores. Returns the original opcode
 136   // if it doesn't know how to select a better one.
 137   unsigned selectLoadStoreOpCode(unsigned Opc, unsigned RegBank,
 138                                  unsigned Size) const;
 139
 140   void renderVFPF32Imm(MachineInstrBuilder &New, const MachineInstr &Old) const;
 141   void renderVFPF64Imm(MachineInstrBuilder &New, const MachineInstr &Old) const;
 142
 143 #define GET_GLOBALISEL_PREDICATES_DECL
 144 #include "ARMGenGlobalISel.inc"
 145 #undef GET_GLOBALISEL_PREDICATES_DECL
 146
 147 // We declare the temporaries used by selectImpl() in the class to minimize the
 148 // cost of constructing placeholder values.
 149 #define GET_GLOBALISEL_TEMPORARIES_DECL
 150 #include "ARMGenGlobalISel.inc"
 151 #undef GET_GLOBALISEL_TEMPORARIES_DECL
 152 };
 153 } // end anonymous namespace
 154
 155 namespace llvm {
 156 InstructionSelector *
 157 createARMInstructionSelector(const ARMBaseTargetMachine &TM,
 158                              const ARMSubtarget &STI,
 159                              const ARMRegisterBankInfo &RBI) {
 160   return new ARMInstructionSelector(TM, STI, RBI);
 161 }
 162 }
 163
 164 const unsigned zero_reg = 0;
 165
 166 #define GET_GLOBALISEL_IMPL
 167 #include "ARMGenGlobalISel.inc"
 168 #undef GET_GLOBALISEL_IMPL
 169
 170 ARMInstructionSelector::ARMInstructionSelector(const ARMBaseTargetMachine &TM,
 171                                                const ARMSubtarget &STI,
 172                                                const ARMRegisterBankInfo &RBI)
 173     : InstructionSelector(), TII(*STI.getInstrInfo()),
 174       TRI(*STI.getRegisterInfo()), TM(TM), RBI(RBI), STI(STI), Opcodes(STI),
 175 #define GET_GLOBALISEL_PREDICATES_INIT
 176 #include "ARMGenGlobalISel.inc"
 177 #undef GET_GLOBALISEL_PREDICATES_INIT
 178 #define GET_GLOBALISEL_TEMPORARIES_INIT
 179 #include "ARMGenGlobalISel.inc"
 180 #undef GET_GLOBALISEL_TEMPORARIES_INIT
 181 {
 182 }
 183
 184 static const TargetRegisterClass *guessRegClass(unsigned Reg,
 185                                                 MachineRegisterInfo &MRI,
 186                                                 const TargetRegisterInfo &TRI,
 187                                                 const RegisterBankInfo &RBI) {
 188   const RegisterBank *RegBank = RBI.getRegBank(Reg, MRI, TRI);
 189   assert(RegBank && "Can't get reg bank for virtual register");
 190
 191   const unsigned Size = MRI.getType(Reg).getSizeInBits();
 192   assert((RegBank->getID() == ARM::GPRRegBankID ||
 193           RegBank->getID() == ARM::FPRRegBankID) &&
 194          "Unsupported reg bank");
 195
 196   if (RegBank->getID() == ARM::FPRRegBankID) {
 197     if (Size == 32)
 198       return &ARM::SPRRegClass;
 199     else if (Size == 64)
 200       return &ARM::DPRRegClass;
 201     else if (Size == 128)
 202       return &ARM::QPRRegClass;
 203     else
 204       llvm_unreachable("Unsupported destination size");
 205   }
 206
 207   return &ARM::GPRRegClass;
 208 }
 209
 210 static bool selectCopy(MachineInstr &I, const TargetInstrInfo &TII,
 211                        MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
 212                        const RegisterBankInfo &RBI) {
 213   unsigned DstReg = I.getOperand(0).getReg();
 214   if (TargetRegisterInfo::isPhysicalRegister(DstReg))
 215     return true;
 216
 217   const TargetRegisterClass *RC = guessRegClass(DstReg, MRI, TRI, RBI);
 218
 219   // No need to constrain SrcReg. It will get constrained when
 220   // we hit another of its uses or its defs.
 221   // Copies do not have constraints.
 222   if (!RBI.constrainGenericRegister(DstReg, *RC, MRI)) {
 223     LLVM_DEBUG(dbgs() << "Failed to constrain " << TII.getName(I.getOpcode())
 224                       << " operand\n");
 225     return false;
 226   }
 227   return true;
 228 }
 229
 230 static bool selectMergeValues(MachineInstrBuilder &MIB,
 231                               const ARMBaseInstrInfo &TII,
 232                               MachineRegisterInfo &MRI,
 233                               const TargetRegisterInfo &TRI,
 234                               const RegisterBankInfo &RBI) {
 235   assert(TII.getSubtarget().hasVFP2Base() && "Can't select merge without VFP");
 236
 237   // We only support G_MERGE_VALUES as a way to stick together two scalar GPRs
 238   // into one DPR.
 239   unsigned VReg0 = MIB->getOperand(0).getReg();
 240   (void)VReg0;
 241   assert(MRI.getType(VReg0).getSizeInBits() == 64 &&
 242          RBI.getRegBank(VReg0, MRI, TRI)->getID() == ARM::FPRRegBankID &&
 243          "Unsupported operand for G_MERGE_VALUES");
 244   unsigned VReg1 = MIB->getOperand(1).getReg();
 245   (void)VReg1;
 246   assert(MRI.getType(VReg1).getSizeInBits() == 32 &&
 247          RBI.getRegBank(VReg1, MRI, TRI)->getID() == ARM::GPRRegBankID &&
 248          "Unsupported operand for G_MERGE_VALUES");
 249   unsigned VReg2 = MIB->getOperand(2).getReg();
 250   (void)VReg2;
 251   assert(MRI.getType(VReg2).getSizeInBits() == 32 &&
 252          RBI.getRegBank(VReg2, MRI, TRI)->getID() == ARM::GPRRegBankID &&
 253          "Unsupported operand for G_MERGE_VALUES");
 254
 255   MIB->setDesc(TII.get(ARM::VMOVDRR));
 256   MIB.add(predOps(ARMCC::AL));
 257
 258   return true;
 259 }
 260
 261 static bool selectUnmergeValues(MachineInstrBuilder &MIB,
 262                                 const ARMBaseInstrInfo &TII,
 263                                 MachineRegisterInfo &MRI,
 264                                 const TargetRegisterInfo &TRI,
 265                                 const RegisterBankInfo &RBI) {
 266   assert(TII.getSubtarget().hasVFP2Base() &&
 267          "Can't select unmerge without VFP");
 268
 269   // We only support G_UNMERGE_VALUES as a way to break up one DPR into two
 270   // GPRs.
 271   unsigned VReg0 = MIB->getOperand(0).getReg();
 272   (void)VReg0;
 273   assert(MRI.getType(VReg0).getSizeInBits() == 32 &&
 274          RBI.getRegBank(VReg0, MRI, TRI)->getID() == ARM::GPRRegBankID &&
 275          "Unsupported operand for G_UNMERGE_VALUES");
 276   unsigned VReg1 = MIB->getOperand(1).getReg();
 277   (void)VReg1;
 278   assert(MRI.getType(VReg1).getSizeInBits() == 32 &&
 279          RBI.getRegBank(VReg1, MRI, TRI)->getID() == ARM::GPRRegBankID &&
 280          "Unsupported operand for G_UNMERGE_VALUES");
 281   unsigned VReg2 = MIB->getOperand(2).getReg();
 282   (void)VReg2;
 283   assert(MRI.getType(VReg2).getSizeInBits() == 64 &&
 284          RBI.getRegBank(VReg2, MRI, TRI)->getID() == ARM::FPRRegBankID &&
 285          "Unsupported operand for G_UNMERGE_VALUES");
 286
 287   MIB->setDesc(TII.get(ARM::VMOVRRD));
 288   MIB.add(predOps(ARMCC::AL));
 289
 290   return true;
 291 }
 292
 293 ARMInstructionSelector::OpcodeCache::OpcodeCache(const ARMSubtarget &STI) {
 294   bool isThumb = STI.isThumb();
 295
 296   using namespace TargetOpcode;
 297
 298 #define STORE_OPCODE(VAR, OPC) VAR = isThumb ? ARM::t2##OPC : ARM::OPC
 299   STORE_OPCODE(SEXT16, SXTH);
 300   STORE_OPCODE(ZEXT16, UXTH);
 301
 302   STORE_OPCODE(SEXT8, SXTB);
 303   STORE_OPCODE(ZEXT8, UXTB);
 304
 305   STORE_OPCODE(AND, ANDri);
 306   STORE_OPCODE(RSB, RSBri);
 307
 308   STORE_OPCODE(STORE32, STRi12);
 309   STORE_OPCODE(LOAD32, LDRi12);
 310
 311   // LDRH/STRH are special...
 312   STORE16 = isThumb ? ARM::t2STRHi12 : ARM::STRH;
 313   LOAD16 = isThumb ? ARM::t2LDRHi12 : ARM::LDRH;
 314
 315   STORE_OPCODE(STORE8, STRBi12);
 316   STORE_OPCODE(LOAD8, LDRBi12);
 317
 318   STORE_OPCODE(ADDrr, ADDrr);
 319   STORE_OPCODE(ADDri, ADDri);
 320
 321   STORE_OPCODE(CMPrr, CMPrr);
 322   STORE_OPCODE(MOVi, MOVi);
 323   STORE_OPCODE(MOVCCi, MOVCCi);
 324
 325   STORE_OPCODE(MOVCCr, MOVCCr);
 326
 327   STORE_OPCODE(TSTri, TSTri);
 328   STORE_OPCODE(Bcc, Bcc);
 329
 330   STORE_OPCODE(MOVi32imm, MOVi32imm);
 331   ConstPoolLoad = isThumb ? ARM::t2LDRpci : ARM::LDRi12;
 332   STORE_OPCODE(MOV_ga_pcrel, MOV_ga_pcrel);
 333   LDRLIT_ga_pcrel = isThumb ? ARM::tLDRLIT_ga_pcrel : ARM::LDRLIT_ga_pcrel;
 334   LDRLIT_ga_abs = isThumb ? ARM::tLDRLIT_ga_abs : ARM::LDRLIT_ga_abs;
 335 #undef MAP_OPCODE
 336 }
 337
 338 unsigned ARMInstructionSelector::selectSimpleExtOpc(unsigned Opc,
 339                                                     unsigned Size) const {
 340   using namespace TargetOpcode;
 341
 342   if (Size != 8 && Size != 16)
 343     return Opc;
 344
 345   if (Opc == G_SEXT)
 346     return Size == 8 ? Opcodes.SEXT8 : Opcodes.SEXT16;
 347
 348   if (Opc == G_ZEXT)
 349     return Size == 8 ? Opcodes.ZEXT8 : Opcodes.ZEXT16;
 350
 351   return Opc;
 352 }
 353
 354 unsigned ARMInstructionSelector::selectLoadStoreOpCode(unsigned Opc,
 355                                                        unsigned RegBank,
 356                                                        unsigned Size) const {
 357   bool isStore = Opc == TargetOpcode::G_STORE;
 358
 359   if (RegBank == ARM::GPRRegBankID) {
 360     switch (Size) {
 361     case 1:
 362     case 8:
 363       return isStore ? Opcodes.STORE8 : Opcodes.LOAD8;
 364     case 16:
 365       return isStore ? Opcodes.STORE16 : Opcodes.LOAD16;
 366     case 32:
 367       return isStore ? Opcodes.STORE32 : Opcodes.LOAD32;
 368     default:
 369       return Opc;
 370     }
 371   }
 372
 373   if (RegBank == ARM::FPRRegBankID) {
 374     switch (Size) {
 375     case 32:
 376       return isStore ? ARM::VSTRS : ARM::VLDRS;
 377     case 64:
 378       return isStore ? ARM::VSTRD : ARM::VLDRD;
 379     default:
 380       return Opc;
 381     }
 382   }
 383
 384   return Opc;
 385 }
 386
 387 // When lowering comparisons, we sometimes need to perform two compares instead
 388 // of just one. Get the condition codes for both comparisons. If only one is
 389 // needed, the second member of the pair is ARMCC::AL.
 390 static std::pair<ARMCC::CondCodes, ARMCC::CondCodes>
 391 getComparePreds(CmpInst::Predicate Pred) {
 392   std::pair<ARMCC::CondCodes, ARMCC::CondCodes> Preds = {ARMCC::AL, ARMCC::AL};
 393   switch (Pred) {
 394   case CmpInst::FCMP_ONE:
 395     Preds = {ARMCC::GT, ARMCC::MI};
 396     break;
 397   case CmpInst::FCMP_UEQ:
 398     Preds = {ARMCC::EQ, ARMCC::VS};
 399     break;
 400   case CmpInst::ICMP_EQ:
 401   case CmpInst::FCMP_OEQ:
 402     Preds.first = ARMCC::EQ;
 403     break;
 404   case CmpInst::ICMP_SGT:
 405   case CmpInst::FCMP_OGT:
 406     Preds.first = ARMCC::GT;
 407     break;
 408   case CmpInst::ICMP_SGE:
 409   case CmpInst::FCMP_OGE:
 410     Preds.first = ARMCC::GE;
 411     break;
 412   case CmpInst::ICMP_UGT:
 413   case CmpInst::FCMP_UGT:
 414     Preds.first = ARMCC::HI;
 415     break;
 416   case CmpInst::FCMP_OLT:
 417     Preds.first = ARMCC::MI;
 418     break;
 419   case CmpInst::ICMP_ULE:
 420   case CmpInst::FCMP_OLE:
 421     Preds.first = ARMCC::LS;
 422     break;
 423   case CmpInst::FCMP_ORD:
 424     Preds.first = ARMCC::VC;
 425     break;
 426   case CmpInst::FCMP_UNO:
 427     Preds.first = ARMCC::VS;
 428     break;
 429   case CmpInst::FCMP_UGE:
 430     Preds.first = ARMCC::PL;
 431     break;
 432   case CmpInst::ICMP_SLT:
 433   case CmpInst::FCMP_ULT:
 434     Preds.first = ARMCC::LT;
 435     break;
 436   case CmpInst::ICMP_SLE:
 437   case CmpInst::FCMP_ULE:
 438     Preds.first = ARMCC::LE;
 439     break;
 440   case CmpInst::FCMP_UNE:
 441   case CmpInst::ICMP_NE:
 442     Preds.first = ARMCC::NE;
 443     break;
 444   case CmpInst::ICMP_UGE:
 445     Preds.first = ARMCC::HS;
 446     break;
 447   case CmpInst::ICMP_ULT:
 448     Preds.first = ARMCC::LO;
 449     break;
 450   default:
 451     break;
 452   }
 453   assert(Preds.first != ARMCC::AL && "No comparisons needed?");
 454   return Preds;
 455 }
 456
 457 struct ARMInstructionSelector::CmpConstants {
 458   CmpConstants(unsigned CmpOpcode, unsigned FlagsOpcode, unsigned SelectOpcode,
 459                unsigned OpRegBank, unsigned OpSize)
 460       : ComparisonOpcode(CmpOpcode), ReadFlagsOpcode(FlagsOpcode),
 461         SelectResultOpcode(SelectOpcode), OperandRegBankID(OpRegBank),
 462         OperandSize(OpSize) {}
 463
 464   // The opcode used for performing the comparison.
 465   const unsigned ComparisonOpcode;
 466
 467   // The opcode used for reading the flags set by the comparison. May be
 468   // ARM::INSTRUCTION_LIST_END if we don't need to read the flags.
 469   const unsigned ReadFlagsOpcode;
 470
 471   // The opcode used for materializing the result of the comparison.
 472   const unsigned SelectResultOpcode;
 473
 474   // The assumed register bank ID for the operands.
 475   const unsigned OperandRegBankID;
 476
 477   // The assumed size in bits for the operands.
 478   const unsigned OperandSize;
 479 };
 480
 481 struct ARMInstructionSelector::InsertInfo {
 482   InsertInfo(MachineInstrBuilder &MIB)
 483       : MBB(*MIB->getParent()), InsertBefore(std::next(MIB->getIterator())),
 484         DbgLoc(MIB->getDebugLoc()) {}
 485
 486   MachineBasicBlock &MBB;
 487   const MachineBasicBlock::instr_iterator InsertBefore;
 488   const DebugLoc &DbgLoc;
 489 };
 490
 491 void ARMInstructionSelector::putConstant(InsertInfo I, unsigned DestReg,
 492                                          unsigned Constant) const {
 493   (void)BuildMI(I.MBB, I.InsertBefore, I.DbgLoc, TII.get(Opcodes.MOVi))
 494       .addDef(DestReg)
 495       .addImm(Constant)
 496       .add(predOps(ARMCC::AL))
 497       .add(condCodeOp());
 498 }
 499
 500 bool ARMInstructionSelector::validOpRegPair(MachineRegisterInfo &MRI,
 501                                             unsigned LHSReg, unsigned RHSReg,
 502                                             unsigned ExpectedSize,
 503                                             unsigned ExpectedRegBankID) const {
 504   return MRI.getType(LHSReg) == MRI.getType(RHSReg) &&
 505          validReg(MRI, LHSReg, ExpectedSize, ExpectedRegBankID) &&
 506          validReg(MRI, RHSReg, ExpectedSize, ExpectedRegBankID);
 507 }
 508
 509 bool ARMInstructionSelector::validReg(MachineRegisterInfo &MRI, unsigned Reg,
 510                                       unsigned ExpectedSize,
 511                                       unsigned ExpectedRegBankID) const {
 512   if (MRI.getType(Reg).getSizeInBits() != ExpectedSize) {
 513     LLVM_DEBUG(dbgs() << "Unexpected size for register");
 514     return false;
 515   }
 516
 517   if (RBI.getRegBank(Reg, MRI, TRI)->getID() != ExpectedRegBankID) {
 518     LLVM_DEBUG(dbgs() << "Unexpected register bank for register");
 519     return false;
 520   }
 521
 522   return true;
 523 }
 524
 525 bool ARMInstructionSelector::selectCmp(CmpConstants Helper,
 526                                        MachineInstrBuilder &MIB,
 527                                        MachineRegisterInfo &MRI) const {
 528   const InsertInfo I(MIB);
 529
 530   auto ResReg = MIB->getOperand(0).getReg();
 531   if (!validReg(MRI, ResReg, 1, ARM::GPRRegBankID))
 532     return false;
 533
 534   auto Cond =
 535       static_cast<CmpInst::Predicate>(MIB->getOperand(1).getPredicate());
 536   if (Cond == CmpInst::FCMP_TRUE || Cond == CmpInst::FCMP_FALSE) {
 537     putConstant(I, ResReg, Cond == CmpInst::FCMP_TRUE ? 1 : 0);
 538     MIB->eraseFromParent();
 539     return true;
 540   }
 541
 542   auto LHSReg = MIB->getOperand(2).getReg();
 543   auto RHSReg = MIB->getOperand(3).getReg();
 544   if (!validOpRegPair(MRI, LHSReg, RHSReg, Helper.OperandSize,
 545                       Helper.OperandRegBankID))
 546     return false;
 547
 548   auto ARMConds = getComparePreds(Cond);
 549   auto ZeroReg = MRI.createVirtualRegister(&ARM::GPRRegClass);
 550   putConstant(I, ZeroReg, 0);
 551
 552   if (ARMConds.second == ARMCC::AL) {
 553     // Simple case, we only need one comparison and we're done.
 554     if (!insertComparison(Helper, I, ResReg, ARMConds.first, LHSReg, RHSReg,
 555                           ZeroReg))
 556       return false;
 557   } else {
 558     // Not so simple, we need two successive comparisons.
 559     auto IntermediateRes = MRI.createVirtualRegister(&ARM::GPRRegClass);
 560     if (!insertComparison(Helper, I, IntermediateRes, ARMConds.first, LHSReg,
 561                           RHSReg, ZeroReg))
 562       return false;
 563     if (!insertComparison(Helper, I, ResReg, ARMConds.second, LHSReg, RHSReg,
 564                           IntermediateRes))
 565       return false;
 566   }
 567
 568   MIB->eraseFromParent();
 569   return true;
 570 }
 571
 572 bool ARMInstructionSelector::insertComparison(CmpConstants Helper, InsertInfo I,
 573                                               unsigned ResReg,
 574                                               ARMCC::CondCodes Cond,
 575                                               unsigned LHSReg, unsigned RHSReg,
 576                                               unsigned PrevRes) const {
 577   // Perform the comparison.
 578   auto CmpI =
 579       BuildMI(I.MBB, I.InsertBefore, I.DbgLoc, TII.get(Helper.ComparisonOpcode))
 580           .addUse(LHSReg)
 581           .addUse(RHSReg)
 582           .add(predOps(ARMCC::AL));
 583   if (!constrainSelectedInstRegOperands(*CmpI, TII, TRI, RBI))
 584     return false;
 585
 586   // Read the comparison flags (if necessary).
 587   if (Helper.ReadFlagsOpcode != ARM::INSTRUCTION_LIST_END) {
 588     auto ReadI = BuildMI(I.MBB, I.InsertBefore, I.DbgLoc,
 589                          TII.get(Helper.ReadFlagsOpcode))
 590                      .add(predOps(ARMCC::AL));
 591     if (!constrainSelectedInstRegOperands(*ReadI, TII, TRI, RBI))
 592       return false;
 593   }
 594
 595   // Select either 1 or the previous result based on the value of the flags.
 596   auto Mov1I = BuildMI(I.MBB, I.InsertBefore, I.DbgLoc,
 597                        TII.get(Helper.SelectResultOpcode))
 598                    .addDef(ResReg)
 599                    .addUse(PrevRes)
 600                    .addImm(1)
 601                    .add(predOps(Cond, ARM::CPSR));
 602   if (!constrainSelectedInstRegOperands(*Mov1I, TII, TRI, RBI))
 603     return false;
 604
 605   return true;
 606 }
 607
 608 bool ARMInstructionSelector::selectGlobal(MachineInstrBuilder &MIB,
 609                                           MachineRegisterInfo &MRI) const {
 610   if ((STI.isROPI() || STI.isRWPI()) && !STI.isTargetELF()) {
 611     LLVM_DEBUG(dbgs() << "ROPI and RWPI only supported for ELF\n");
 612     return false;
 613   }
 614
 615   auto GV = MIB->getOperand(1).getGlobal();
 616   if (GV->isThreadLocal()) {
 617     LLVM_DEBUG(dbgs() << "TLS variables not supported yet\n");
 618     return false;
 619   }
 620
 621   auto &MBB = *MIB->getParent();
 622   auto &MF = *MBB.getParent();
 623
 624   bool UseMovt = STI.useMovt();
 625
 626   unsigned Size = TM.getPointerSize(0);
 627   unsigned Alignment = 4;
 628
 629   auto addOpsForConstantPoolLoad = [&MF, Alignment,
 630                                     Size](MachineInstrBuilder &MIB,
 631                                           const GlobalValue *GV, bool IsSBREL) {
 632     assert((MIB->getOpcode() == ARM::LDRi12 ||
 633             MIB->getOpcode() == ARM::t2LDRpci) &&
 634            "Unsupported instruction");
 635     auto ConstPool = MF.getConstantPool();
 636     auto CPIndex =
 637         // For SB relative entries we need a target-specific constant pool.
 638         // Otherwise, just use a regular constant pool entry.
 639         IsSBREL
 640             ? ConstPool->getConstantPoolIndex(
 641                   ARMConstantPoolConstant::Create(GV, ARMCP::SBREL), Alignment)
 642             : ConstPool->getConstantPoolIndex(GV, Alignment);
 643     MIB.addConstantPoolIndex(CPIndex, /*Offset*/ 0, /*TargetFlags*/ 0)
 644         .addMemOperand(MF.getMachineMemOperand(
 645             MachinePointerInfo::getConstantPool(MF), MachineMemOperand::MOLoad,
 646             Size, Alignment));
 647     if (MIB->getOpcode() == ARM::LDRi12)
 648       MIB.addImm(0);
 649     MIB.add(predOps(ARMCC::AL));
 650   };
 651
 652   auto addGOTMemOperand = [this, &MF, Alignment](MachineInstrBuilder &MIB) {
 653     MIB.addMemOperand(MF.getMachineMemOperand(
 654         MachinePointerInfo::getGOT(MF), MachineMemOperand::MOLoad,
 655         TM.getProgramPointerSize(), Alignment));
 656   };
 657
 658   if (TM.isPositionIndependent()) {
 659     bool Indirect = STI.isGVIndirectSymbol(GV);
 660
 661     // For ARM mode, we have different pseudoinstructions for direct accesses
 662     // and indirect accesses, and the ones for indirect accesses include the
 663     // load from GOT. For Thumb mode, we use the same pseudoinstruction for both
 664     // direct and indirect accesses, and we need to manually generate the load
 665     // from GOT.
 666     bool UseOpcodeThatLoads = Indirect && !STI.isThumb();
 667
 668     // FIXME: Taking advantage of MOVT for ELF is pretty involved, so we don't
 669     // support it yet. See PR28229.
 670     unsigned Opc =
 671         UseMovt && !STI.isTargetELF()
 672             ? (UseOpcodeThatLoads ? (unsigned)ARM::MOV_ga_pcrel_ldr
 673                                   : Opcodes.MOV_ga_pcrel)
 674             : (UseOpcodeThatLoads ? (unsigned)ARM::LDRLIT_ga_pcrel_ldr
 675                                   : Opcodes.LDRLIT_ga_pcrel);
 676     MIB->setDesc(TII.get(Opc));
 677
 678     int TargetFlags = ARMII::MO_NO_FLAG;
 679     if (STI.isTargetDarwin())
 680       TargetFlags |= ARMII::MO_NONLAZY;
 681     if (STI.isGVInGOT(GV))
 682       TargetFlags |= ARMII::MO_GOT;
 683     MIB->getOperand(1).setTargetFlags(TargetFlags);
 684
 685     if (Indirect) {
 686       if (!UseOpcodeThatLoads) {
 687         auto ResultReg = MIB->getOperand(0).getReg();
 688         auto AddressReg = MRI.createVirtualRegister(&ARM::GPRRegClass);
 689
 690         MIB->getOperand(0).setReg(AddressReg);
 691
 692         auto InsertBefore = std::next(MIB->getIterator());
 693         auto MIBLoad = BuildMI(MBB, InsertBefore, MIB->getDebugLoc(),
 694                                TII.get(Opcodes.LOAD32))
 695                            .addDef(ResultReg)
 696                            .addReg(AddressReg)
 697                            .addImm(0)
 698                            .add(predOps(ARMCC::AL));
 699         addGOTMemOperand(MIBLoad);
 700
 701         if (!constrainSelectedInstRegOperands(*MIBLoad, TII, TRI, RBI))
 702           return false;
 703       } else {
 704         addGOTMemOperand(MIB);
 705       }
 706     }
 707
 708     return constrainSelectedInstRegOperands(*MIB, TII, TRI, RBI);
 709   }
 710
 711   bool isReadOnly = STI.getTargetLowering()->isReadOnly(GV);
 712   if (STI.isROPI() && isReadOnly) {
 713     unsigned Opc = UseMovt ? Opcodes.MOV_ga_pcrel : Opcodes.LDRLIT_ga_pcrel;
 714     MIB->setDesc(TII.get(Opc));
 715     return constrainSelectedInstRegOperands(*MIB, TII, TRI, RBI);
 716   }
 717   if (STI.isRWPI() && !isReadOnly) {
 718     auto Offset = MRI.createVirtualRegister(&ARM::GPRRegClass);
 719     MachineInstrBuilder OffsetMIB;
 720     if (UseMovt) {
 721       OffsetMIB = BuildMI(MBB, *MIB, MIB->getDebugLoc(),
 722                           TII.get(Opcodes.MOVi32imm), Offset);
 723       OffsetMIB.addGlobalAddress(GV, /*Offset*/ 0, ARMII::MO_SBREL);
 724     } else {
 725       // Load the offset from the constant pool.
 726       OffsetMIB = BuildMI(MBB, *MIB, MIB->getDebugLoc(),
 727                           TII.get(Opcodes.ConstPoolLoad), Offset);
 728       addOpsForConstantPoolLoad(OffsetMIB, GV, /*IsSBREL*/ true);
 729     }
 730     if (!constrainSelectedInstRegOperands(*OffsetMIB, TII, TRI, RBI))
 731       return false;
 732
 733     // Add the offset to the SB register.
 734     MIB->setDesc(TII.get(Opcodes.ADDrr));
 735     MIB->RemoveOperand(1);
 736     MIB.addReg(ARM::R9) // FIXME: don't hardcode R9
 737         .addReg(Offset)
 738         .add(predOps(ARMCC::AL))
 739         .add(condCodeOp());
 740
 741     return constrainSelectedInstRegOperands(*MIB, TII, TRI, RBI);
 742   }
 743
 744   if (STI.isTargetELF()) {
 745     if (UseMovt) {
 746       MIB->setDesc(TII.get(Opcodes.MOVi32imm));
 747     } else {
 748       // Load the global's address from the constant pool.
 749       MIB->setDesc(TII.get(Opcodes.ConstPoolLoad));
 750       MIB->RemoveOperand(1);
 751       addOpsForConstantPoolLoad(MIB, GV, /*IsSBREL*/ false);
 752     }
 753   } else if (STI.isTargetMachO()) {
 754     if (UseMovt)
 755       MIB->setDesc(TII.get(Opcodes.MOVi32imm));
 756     else
 757       MIB->setDesc(TII.get(Opcodes.LDRLIT_ga_abs));
 758   } else {
 759     LLVM_DEBUG(dbgs() << "Object format not supported yet\n");
 760     return false;
 761   }
 762
 763   return constrainSelectedInstRegOperands(*MIB, TII, TRI, RBI);
 764 }
 765
 766 bool ARMInstructionSelector::selectSelect(MachineInstrBuilder &MIB,
 767                                           MachineRegisterInfo &MRI) const {
 768   auto &MBB = *MIB->getParent();
 769   auto InsertBefore = std::next(MIB->getIterator());
 770   auto &DbgLoc = MIB->getDebugLoc();
 771
 772   // Compare the condition to 1.
 773   auto CondReg = MIB->getOperand(1).getReg();
 774   assert(validReg(MRI, CondReg, 1, ARM::GPRRegBankID) &&
 775          "Unsupported types for select operation");
 776   auto CmpI = BuildMI(MBB, InsertBefore, DbgLoc, TII.get(Opcodes.TSTri))
 777                   .addUse(CondReg)
 778                   .addImm(1)
 779                   .add(predOps(ARMCC::AL));
 780   if (!constrainSelectedInstRegOperands(*CmpI, TII, TRI, RBI))
 781     return false;
 782
 783   // Move a value into the result register based on the result of the
 784   // comparison.
 785   auto ResReg = MIB->getOperand(0).getReg();
 786   auto TrueReg = MIB->getOperand(2).getReg();
 787   auto FalseReg = MIB->getOperand(3).getReg();
 788   assert(validOpRegPair(MRI, ResReg, TrueReg, 32, ARM::GPRRegBankID) &&
 789          validOpRegPair(MRI, TrueReg, FalseReg, 32, ARM::GPRRegBankID) &&
 790          "Unsupported types for select operation");
 791   auto Mov1I = BuildMI(MBB, InsertBefore, DbgLoc, TII.get(Opcodes.MOVCCr))
 792                    .addDef(ResReg)
 793                    .addUse(TrueReg)
 794                    .addUse(FalseReg)
 795                    .add(predOps(ARMCC::EQ, ARM::CPSR));
 796   if (!constrainSelectedInstRegOperands(*Mov1I, TII, TRI, RBI))
 797     return false;
 798
 799   MIB->eraseFromParent();
 800   return true;
 801 }
 802
 803 bool ARMInstructionSelector::selectShift(unsigned ShiftOpc,
 804                                          MachineInstrBuilder &MIB) const {
 805   assert(!STI.isThumb() && "Unsupported subtarget");
 806   MIB->setDesc(TII.get(ARM::MOVsr));
 807   MIB.addImm(ShiftOpc);
 808   MIB.add(predOps(ARMCC::AL)).add(condCodeOp());
 809   return constrainSelectedInstRegOperands(*MIB, TII, TRI, RBI);
 810 }
 811
 812 void ARMInstructionSelector::renderVFPF32Imm(
 813     MachineInstrBuilder &NewInstBuilder, const MachineInstr &OldInst) const {
 814   assert(OldInst.getOpcode() == TargetOpcode::G_FCONSTANT &&
 815          "Expected G_FCONSTANT");
 816
 817   APFloat FPImmValue = OldInst.getOperand(1).getFPImm()->getValueAPF();
 818   int FPImmEncoding = ARM_AM::getFP32Imm(FPImmValue);
 819   assert(FPImmEncoding != -1 && "Invalid immediate value");
 820
 821   NewInstBuilder.addImm(FPImmEncoding);
 822 }
 823
 824 void ARMInstructionSelector::renderVFPF64Imm(
 825     MachineInstrBuilder &NewInstBuilder, const MachineInstr &OldInst) const {
 826   assert(OldInst.getOpcode() == TargetOpcode::G_FCONSTANT &&
 827          "Expected G_FCONSTANT");
 828
 829   APFloat FPImmValue = OldInst.getOperand(1).getFPImm()->getValueAPF();
 830   int FPImmEncoding = ARM_AM::getFP64Imm(FPImmValue);
 831   assert(FPImmEncoding != -1 && "Invalid immediate value");
 832
 833   NewInstBuilder.addImm(FPImmEncoding);
 834 }
 835
 836 bool ARMInstructionSelector::select(MachineInstr &I,
 837                                     CodeGenCoverage &CoverageInfo) const {
 838   assert(I.getParent() && "Instruction should be in a basic block!");
 839   assert(I.getParent()->getParent() && "Instruction should be in a function!");
 840
 841   auto &MBB = *I.getParent();
 842   auto &MF = *MBB.getParent();
 843   auto &MRI = MF.getRegInfo();
 844
 845   if (!isPreISelGenericOpcode(I.getOpcode())) {
 846     if (I.isCopy())
 847       return selectCopy(I, TII, MRI, TRI, RBI);
 848
 849     return true;
 850   }
 851
 852   using namespace TargetOpcode;
 853
 854   if (selectImpl(I, CoverageInfo))
 855     return true;
 856
 857   MachineInstrBuilder MIB{MF, I};
 858   bool isSExt = false;
 859
 860   switch (I.getOpcode()) {
 861   case G_SEXT:
 862     isSExt = true;
 863     LLVM_FALLTHROUGH;
 864   case G_ZEXT: {
 865     assert(MRI.getType(I.getOperand(0).getReg()).getSizeInBits() <= 32 &&
 866            "Unsupported destination size for extension");
 867
 868     LLT SrcTy = MRI.getType(I.getOperand(1).getReg());
 869     unsigned SrcSize = SrcTy.getSizeInBits();
 870     switch (SrcSize) {
 871     case 1: {
 872       // ZExt boils down to & 0x1; for SExt we also subtract that from 0
 873       I.setDesc(TII.get(Opcodes.AND));
 874       MIB.addImm(1).add(predOps(ARMCC::AL)).add(condCodeOp());
 875
 876       if (isSExt) {
 877         unsigned SExtResult = I.getOperand(0).getReg();
 878
 879         // Use a new virtual register for the result of the AND
 880         unsigned AndResult = MRI.createVirtualRegister(&ARM::GPRRegClass);
 881         I.getOperand(0).setReg(AndResult);
 882
 883         auto InsertBefore = std::next(I.getIterator());
 884         auto SubI =
 885             BuildMI(MBB, InsertBefore, I.getDebugLoc(), TII.get(Opcodes.RSB))
 886                 .addDef(SExtResult)
 887                 .addUse(AndResult)
 888                 .addImm(0)
 889                 .add(predOps(ARMCC::AL))
 890                 .add(condCodeOp());
 891         if (!constrainSelectedInstRegOperands(*SubI, TII, TRI, RBI))
 892           return false;
 893       }
 894       break;
 895     }
 896     case 8:
 897     case 16: {
 898       unsigned NewOpc = selectSimpleExtOpc(I.getOpcode(), SrcSize);
 899       if (NewOpc == I.getOpcode())
 900         return false;
 901       I.setDesc(TII.get(NewOpc));
 902       MIB.addImm(0).add(predOps(ARMCC::AL));
 903       break;
 904     }
 905     default:
 906       LLVM_DEBUG(dbgs() << "Unsupported source size for extension");
 907       return false;
 908     }
 909     break;
 910   }
 911   case G_ANYEXT:
 912   case G_TRUNC: {
 913     // The high bits are undefined, so there's nothing special to do, just
 914     // treat it as a copy.
 915     auto SrcReg = I.getOperand(1).getReg();
 916     auto DstReg = I.getOperand(0).getReg();
 917
 918     const auto &SrcRegBank = *RBI.getRegBank(SrcReg, MRI, TRI);
 919     const auto &DstRegBank = *RBI.getRegBank(DstReg, MRI, TRI);
 920
 921     if (SrcRegBank.getID() == ARM::FPRRegBankID) {
 922       // This should only happen in the obscure case where we have put a 64-bit
 923       // integer into a D register. Get it out of there and keep only the
 924       // interesting part.
 925       assert(I.getOpcode() == G_TRUNC && "Unsupported operand for G_ANYEXT");
 926       assert(DstRegBank.getID() == ARM::GPRRegBankID &&
 927              "Unsupported combination of register banks");
 928       assert(MRI.getType(SrcReg).getSizeInBits() == 64 && "Unsupported size");
 929       assert(MRI.getType(DstReg).getSizeInBits() <= 32 && "Unsupported size");
 930
 931       unsigned IgnoredBits = MRI.createVirtualRegister(&ARM::GPRRegClass);
 932       auto InsertBefore = std::next(I.getIterator());
 933       auto MovI =
 934           BuildMI(MBB, InsertBefore, I.getDebugLoc(), TII.get(ARM::VMOVRRD))
 935               .addDef(DstReg)
 936               .addDef(IgnoredBits)
 937               .addUse(SrcReg)
 938               .add(predOps(ARMCC::AL));
 939       if (!constrainSelectedInstRegOperands(*MovI, TII, TRI, RBI))
 940         return false;
 941
 942       MIB->eraseFromParent();
 943       return true;
 944     }
 945
 946     if (SrcRegBank.getID() != DstRegBank.getID()) {
 947       LLVM_DEBUG(
 948           dbgs() << "G_TRUNC/G_ANYEXT operands on different register banks\n");
 949       return false;
 950     }
 951
 952     if (SrcRegBank.getID() != ARM::GPRRegBankID) {
 953       LLVM_DEBUG(dbgs() << "G_TRUNC/G_ANYEXT on non-GPR not supported yet\n");
 954       return false;
 955     }
 956
 957     I.setDesc(TII.get(COPY));
 958     return selectCopy(I, TII, MRI, TRI, RBI);
 959   }
 960   case G_CONSTANT: {
 961     if (!MRI.getType(I.getOperand(0).getReg()).isPointer()) {
 962       // Non-pointer constants should be handled by TableGen.
 963       LLVM_DEBUG(dbgs() << "Unsupported constant type\n");
 964       return false;
 965     }
 966
 967     auto &Val = I.getOperand(1);
 968     if (Val.isCImm()) {
 969       if (!Val.getCImm()->isZero()) {
 970         LLVM_DEBUG(dbgs() << "Unsupported pointer constant value\n");
 971         return false;
 972       }
 973       Val.ChangeToImmediate(0);
 974     } else {
 975       assert(Val.isImm() && "Unexpected operand for G_CONSTANT");
 976       if (Val.getImm() != 0) {
 977         LLVM_DEBUG(dbgs() << "Unsupported pointer constant value\n");
 978         return false;
 979       }
 980     }
 981
 982     assert(!STI.isThumb() && "Unsupported subtarget");
 983     I.setDesc(TII.get(ARM::MOVi));
 984     MIB.add(predOps(ARMCC::AL)).add(condCodeOp());
 985     break;
 986   }
 987   case G_FCONSTANT: {
 988     // Load from constant pool
 989     unsigned Size = MRI.getType(I.getOperand(0).getReg()).getSizeInBits() / 8;
 990     unsigned Alignment = Size;
 991
 992     assert((Size == 4 || Size == 8) && "Unsupported FP constant type");
 993     auto LoadOpcode = Size == 4 ? ARM::VLDRS : ARM::VLDRD;
 994
 995     auto ConstPool = MF.getConstantPool();
 996     auto CPIndex =
 997         ConstPool->getConstantPoolIndex(I.getOperand(1).getFPImm(), Alignment);
 998     MIB->setDesc(TII.get(LoadOpcode));
 999     MIB->RemoveOperand(1);
1000     MIB.addConstantPoolIndex(CPIndex, /*Offset*/ 0, /*TargetFlags*/ 0)
1001         .addMemOperand(
1002             MF.getMachineMemOperand(MachinePointerInfo::getConstantPool(MF),
1003                                     MachineMemOperand::MOLoad, Size, Alignment))
1004         .addImm(0)
1005         .add(predOps(ARMCC::AL));
1006     break;
1007   }
1008   case G_INTTOPTR:
1009   case G_PTRTOINT: {
1010     auto SrcReg = I.getOperand(1).getReg();
1011     auto DstReg = I.getOperand(0).getReg();
1012
1013     const auto &SrcRegBank = *RBI.getRegBank(SrcReg, MRI, TRI);
1014     const auto &DstRegBank = *RBI.getRegBank(DstReg, MRI, TRI);
1015
1016     if (SrcRegBank.getID() != DstRegBank.getID()) {
1017       LLVM_DEBUG(
1018           dbgs()
1019           << "G_INTTOPTR/G_PTRTOINT operands on different register banks\n");
1020       return false;
1021     }
1022
1023     if (SrcRegBank.getID() != ARM::GPRRegBankID) {
1024       LLVM_DEBUG(
1025           dbgs() << "G_INTTOPTR/G_PTRTOINT on non-GPR not supported yet\n");
1026       return false;
1027     }
1028
1029     I.setDesc(TII.get(COPY));
1030     return selectCopy(I, TII, MRI, TRI, RBI);
1031   }
1032   case G_SELECT:
1033     return selectSelect(MIB, MRI);
1034   case G_ICMP: {
1035     CmpConstants Helper(Opcodes.CMPrr, ARM::INSTRUCTION_LIST_END,
1036                         Opcodes.MOVCCi, ARM::GPRRegBankID, 32);
1037     return selectCmp(Helper, MIB, MRI);
1038   }
1039   case G_FCMP: {
1040     assert(STI.hasVFP2Base() && "Can't select fcmp without VFP");
1041
1042     unsigned OpReg = I.getOperand(2).getReg();
1043     unsigned Size = MRI.getType(OpReg).getSizeInBits();
1044
1045     if (Size == 64 && !STI.hasFP64()) {
1046       LLVM_DEBUG(dbgs() << "Subtarget only supports single precision");
1047       return false;
1048     }
1049     if (Size != 32 && Size != 64) {
1050       LLVM_DEBUG(dbgs() << "Unsupported size for G_FCMP operand");
1051       return false;
1052     }
1053
1054     CmpConstants Helper(Size == 32 ? ARM::VCMPS : ARM::VCMPD, ARM::FMSTAT,
1055                         Opcodes.MOVCCi, ARM::FPRRegBankID, Size);
1056     return selectCmp(Helper, MIB, MRI);
1057   }
1058   case G_LSHR:
1059     return selectShift(ARM_AM::ShiftOpc::lsr, MIB);
1060   case G_ASHR:
1061     return selectShift(ARM_AM::ShiftOpc::asr, MIB);
1062   case G_SHL: {
1063     return selectShift(ARM_AM::ShiftOpc::lsl, MIB);
1064   }
1065   case G_GEP:
1066     I.setDesc(TII.get(Opcodes.ADDrr));
1067     MIB.add(predOps(ARMCC::AL)).add(condCodeOp());
1068     break;
1069   case G_FRAME_INDEX:
1070     // Add 0 to the given frame index and hope it will eventually be folded into
1071     // the user(s).
1072     I.setDesc(TII.get(Opcodes.ADDri));
1073     MIB.addImm(0).add(predOps(ARMCC::AL)).add(condCodeOp());
1074     break;
1075   case G_GLOBAL_VALUE:
1076     return selectGlobal(MIB, MRI);
1077   case G_STORE:
1078   case G_LOAD: {
1079     const auto &MemOp = **I.memoperands_begin();
1080     if (MemOp.getOrdering() != AtomicOrdering::NotAtomic) {
1081       LLVM_DEBUG(dbgs() << "Atomic load/store not supported yet\n");
1082       return false;
1083     }
1084
1085     unsigned Reg = I.getOperand(0).getReg();
1086     unsigned RegBank = RBI.getRegBank(Reg, MRI, TRI)->getID();
1087
1088     LLT ValTy = MRI.getType(Reg);
1089     const auto ValSize = ValTy.getSizeInBits();
1090
1091     assert((ValSize != 64 || STI.hasVFP2Base()) &&
1092            "Don't know how to load/store 64-bit value without VFP");
1093
1094     const auto NewOpc = selectLoadStoreOpCode(I.getOpcode(), RegBank, ValSize);
1095     if (NewOpc == G_LOAD || NewOpc == G_STORE)
1096       return false;
1097
1098     if (ValSize == 1 && NewOpc == Opcodes.STORE8) {
1099       // Before storing a 1-bit value, make sure to clear out any unneeded bits.
1100       unsigned OriginalValue = I.getOperand(0).getReg();
1101
1102       unsigned ValueToStore = MRI.createVirtualRegister(&ARM::GPRRegClass);
1103       I.getOperand(0).setReg(ValueToStore);
1104
1105       auto InsertBefore = I.getIterator();
1106       auto AndI = BuildMI(MBB, InsertBefore, I.getDebugLoc(), TII.get(Opcodes.AND))
1107         .addDef(ValueToStore)
1108         .addUse(OriginalValue)
1109         .addImm(1)
1110         .add(predOps(ARMCC::AL))
1111         .add(condCodeOp());
1112       if (!constrainSelectedInstRegOperands(*AndI, TII, TRI, RBI))
1113         return false;
1114     }
1115
1116     I.setDesc(TII.get(NewOpc));
1117
1118     if (NewOpc == ARM::LDRH || NewOpc == ARM::STRH)
1119       // LDRH has a funny addressing mode (there's already a FIXME for it).
1120       MIB.addReg(0);
1121     MIB.addImm(0).add(predOps(ARMCC::AL));
1122     break;
1123   }
1124   case G_MERGE_VALUES: {
1125     if (!selectMergeValues(MIB, TII, MRI, TRI, RBI))
1126       return false;
1127     break;
1128   }
1129   case G_UNMERGE_VALUES: {
1130     if (!selectUnmergeValues(MIB, TII, MRI, TRI, RBI))
1131       return false;
1132     break;
1133   }
1134   case G_BRCOND: {
1135     if (!validReg(MRI, I.getOperand(0).getReg(), 1, ARM::GPRRegBankID)) {
1136       LLVM_DEBUG(dbgs() << "Unsupported condition register for G_BRCOND");
1137       return false;
1138     }
1139
1140     // Set the flags.
1141     auto Test =
1142         BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(Opcodes.TSTri))
1143             .addReg(I.getOperand(0).getReg())
1144             .addImm(1)
1145             .add(predOps(ARMCC::AL));
1146     if (!constrainSelectedInstRegOperands(*Test, TII, TRI, RBI))
1147       return false;
1148
1149     // Branch conditionally.
1150     auto Branch =
1151         BuildMI(*I.getParent(), I, I.getDebugLoc(), TII.get(Opcodes.Bcc))
1152             .add(I.getOperand(1))
1153             .add(predOps(ARMCC::NE, ARM::CPSR));
1154     if (!constrainSelectedInstRegOperands(*Branch, TII, TRI, RBI))
1155       return false;
1156     I.eraseFromParent();
1157     return true;
1158   }
1159   case G_PHI: {
1160     I.setDesc(TII.get(PHI));
1161
1162     unsigned DstReg = I.getOperand(0).getReg();
1163     const TargetRegisterClass *RC = guessRegClass(DstReg, MRI, TRI, RBI);
1164     if (!RBI.constrainGenericRegister(DstReg, *RC, MRI)) {
1165       break;
1166     }
1167
1168     return true;
1169   }
1170   default:
1171     return false;
1172   }
1173
1174   return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
1175 }