llvm/lib/Target/X86/X86ISelLowering.h

//===-- X86ISelLowering.h - X86 DAG Lowering Interface ----------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the interfaces that X86 uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_TARGET_X86_X86ISELLOWERING_H
#define LLVM_LIB_TARGET_X86_X86ISELLOWERING_H

#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetOptions.h"

namespace llvm {
  class X86Subtarget;
  class X86TargetMachine;

  namespace X86ISD {
    // X86 Specific DAG Nodes
    enum NodeType : unsigned {
      // Start the numbering where the builtin ops leave off.
      FIRST_NUMBER = ISD::BUILTIN_OP_END,

      /// Bit scan forward.
      BSF,
      /// Bit scan reverse.
      BSR,

      /// Double shift instructions. These correspond to
      /// X86::SHLDxx and X86::SHRDxx instructions.
      SHLD,
      SHRD,

      /// Bitwise logical AND of floating point values. This corresponds
      /// to X86::ANDPS or X86::ANDPD.
      FAND,

      /// Bitwise logical OR of floating point values. This corresponds
      /// to X86::ORPS or X86::ORPD.
      FOR,

      /// Bitwise logical XOR of floating point values. This corresponds
      /// to X86::XORPS or X86::XORPD.
      FXOR,

      ///  Bitwise logical ANDNOT of floating point values. This
      /// corresponds to X86::ANDNPS or X86::ANDNPD.
      FANDN,

      /// Bitwise logical right shift of floating point values. This
      /// corresponds to X86::PSRLDQ.
      FSRL,

      /// These operations represent an abstract X86 call
      /// instruction, which includes a bunch of information.  In particular the
      /// operands of these node are:
      ///
      ///     #0 - The incoming token chain
      ///     #1 - The callee
      ///     #2 - The number of arg bytes the caller pushes on the stack.
      ///     #3 - The number of arg bytes the callee pops off the stack.
      ///     #4 - The value to pass in AL/AX/EAX (optional)
      ///     #5 - The value to pass in DL/DX/EDX (optional)
      ///
      /// The result values of these nodes are:
      ///
      ///     #0 - The outgoing token chain
      ///     #1 - The first register result value (optional)
      ///     #2 - The second register result value (optional)
      ///
      CALL,

      /// This operation implements the lowering for readcyclecounter
      RDTSC_DAG,

      /// X86 Read Time-Stamp Counter and Processor ID.
      RDTSCP_DAG,

      /// X86 Read Performance Monitoring Counters.
      RDPMC_DAG,

      /// X86 compare and logical compare instructions.
      CMP, COMI, UCOMI,

      /// X86 bit-test instructions.
      BT,

      /// X86 SetCC. Operand 0 is condition code, and operand 1 is the EFLAGS
      /// operand, usually produced by a CMP instruction.
      SETCC,

      /// X86 Select
      SELECT,

      // Same as SETCC except it's materialized with a sbb and the value is all
      // one's or all zero's.
      SETCC_CARRY,  // R = carry_bit ? ~0 : 0

      /// X86 FP SETCC, implemented with CMP{cc}SS/CMP{cc}SD.
      /// Operands are two FP values to compare; result is a mask of
      /// 0s or 1s.  Generally DTRT for C/C++ with NaNs.
      FSETCC,

      /// X86 MOVMSK{pd|ps}, extracts sign bits of two or four FP values,
      /// result in an integer GPR.  Needs masking for scalar result.
      FGETSIGNx86,

      /// X86 conditional moves. Operand 0 and operand 1 are the two values
      /// to select from. Operand 2 is the condition code, and operand 3 is the
      /// flag operand produced by a CMP or TEST instruction. It also writes a
      /// flag result.
      CMOV,

      /// X86 conditional branches. Operand 0 is the chain operand, operand 1
      /// is the block to branch if condition is true, operand 2 is the
      /// condition code, and operand 3 is the flag operand produced by a CMP
      /// or TEST instruction.
      BRCOND,

      /// Return with a flag operand. Operand 0 is the chain operand, operand
      /// 1 is the number of bytes of stack to pop.
      RET_FLAG,

      /// Repeat fill, corresponds to X86::REP_STOSx.
      REP_STOS,

      /// Repeat move, corresponds to X86::REP_MOVSx.
      REP_MOVS,

      /// On Darwin, this node represents the result of the popl
      /// at function entry, used for PIC code.
      GlobalBaseReg,

      /// A wrapper node for TargetConstantPool,
      /// TargetExternalSymbol, and TargetGlobalAddress.
      Wrapper,

      /// Special wrapper used under X86-64 PIC mode for RIP
      /// relative displacements.
      WrapperRIP,

      /// Copies a 64-bit value from the low word of an XMM vector
      /// to an MMX vector.  If you think this is too close to the previous
      /// mnemonic, so do I; blame Intel.
      MOVDQ2Q,

      /// Copies a 32-bit value from the low word of a MMX
      /// vector to a GPR.
      MMX_MOVD2W,

      /// Copies a GPR into the low 32-bit word of a MMX vector
      /// and zero out the high word.
      MMX_MOVW2D,

      /// Extract an 8-bit value from a vector and zero extend it to
      /// i32, corresponds to X86::PEXTRB.
      PEXTRB,

      /// Extract a 16-bit value from a vector and zero extend it to
      /// i32, corresponds to X86::PEXTRW.
      PEXTRW,

      /// Insert any element of a 4 x float vector into any element
      /// of a destination 4 x floatvector.
      INSERTPS,

      /// Insert the lower 8-bits of a 32-bit value to a vector,
      /// corresponds to X86::PINSRB.
      PINSRB,

      /// Insert the lower 16-bits of a 32-bit value to a vector,
      /// corresponds to X86::PINSRW.
      PINSRW, MMX_PINSRW,

      /// Shuffle 16 8-bit values within a vector.
      PSHUFB,

      /// Bitwise Logical AND NOT of Packed FP values.
      ANDNP,

      /// Copy integer sign.
      PSIGN,

      /// Blend where the selector is an immediate.
      BLENDI,

      /// Blend where the condition has been shrunk.
      /// This is used to emphasize that the condition mask is
      /// no more valid for generic VSELECT optimizations.
      SHRUNKBLEND,

      /// Combined add and sub on an FP vector.
      ADDSUB,
      //  FP vector ops with rounding mode.
      FADD_RND,
      FSUB_RND,
      FMUL_RND,
      FDIV_RND,
      
      // Integer add/sub with unsigned saturation.
      ADDUS,
      SUBUS,
      // Integer add/sub with signed saturation.
      ADDS,
      SUBS,

      /// Integer horizontal add.
      HADD,

      /// Integer horizontal sub.
      HSUB,

      /// Floating point horizontal add.
      FHADD,

      /// Floating point horizontal sub.
      FHSUB,

      /// Unsigned integer max and min.
      UMAX, UMIN,

      /// Signed integer max and min.
      SMAX, SMIN,

      /// Floating point max and min.
      FMAX, FMIN,

      /// Commutative FMIN and FMAX.
      FMAXC, FMINC,

      /// Floating point reciprocal-sqrt and reciprocal approximation.
      /// Note that these typically require refinement
      /// in order to obtain suitable precision.
      FRSQRT, FRCP,

      // Thread Local Storage.
      TLSADDR,

      // Thread Local Storage. A call to get the start address
      // of the TLS block for the current module.
      TLSBASEADDR,

      // Thread Local Storage.  When calling to an OS provided
      // thunk at the address from an earlier relocation.
      TLSCALL,

      // Exception Handling helpers.
      EH_RETURN,

      // SjLj exception handling setjmp.
      EH_SJLJ_SETJMP,

      // SjLj exception handling longjmp.
      EH_SJLJ_LONGJMP,

      /// Tail call return. See X86TargetLowering::LowerCall for
      /// the list of operands.
      TC_RETURN,

      // Vector move to low scalar and zero higher vector elements.
      VZEXT_MOVL,

      // Vector integer zero-extend.
      VZEXT,

      // Vector integer signed-extend.
      VSEXT,

      // Vector integer truncate.
      VTRUNC,

      // Vector integer truncate with mask.
      VTRUNCM,

      // Vector FP extend.
      VFPEXT,

      // Vector FP round.
      VFPROUND,

      // 128-bit vector logical left / right shift
      VSHLDQ, VSRLDQ,

      // Vector shift elements
      VSHL, VSRL, VSRA,

      // Vector shift elements by immediate
      VSHLI, VSRLI, VSRAI,

      // Vector packed double/float comparison.
      CMPP,

      // Vector integer comparisons.
      PCMPEQ, PCMPGT,
      // Vector integer comparisons, the result is in a mask vector.
      PCMPEQM, PCMPGTM,

      /// Vector comparison generating mask bits for fp and
      /// integer signed and unsigned data types.
      CMPM,
      CMPMU,
      // Vector comparison with rounding mode for FP values
      CMPM_RND,

      // Arithmetic operations with FLAGS results.
      ADD, SUB, ADC, SBB, SMUL,
      INC, DEC, OR, XOR, AND,

      BEXTR,  // Bit field extract

      UMUL, // LOW, HI, FLAGS = umul LHS, RHS

      // 8-bit SMUL/UMUL - AX, FLAGS = smul8/umul8 AL, RHS
      SMUL8, UMUL8,

      // 8-bit divrem that zero-extend the high result (AH).
      UDIVREM8_ZEXT_HREG,
      SDIVREM8_SEXT_HREG,

      // X86-specific multiply by immediate.
      MUL_IMM,

      // Vector bitwise comparisons.
      PTEST,

      // Vector packed fp sign bitwise comparisons.
      TESTP,

      // Vector "test" in AVX-512, the result is in a mask vector.
      TESTM,
      TESTNM,

      // OR/AND test for masks
      KORTEST,

      // Several flavors of instructions with vector shuffle behaviors.
      PACKSS,
      PACKUS,
      // Intra-lane alignr
      PALIGNR,
      // AVX512 inter-lane alignr
      VALIGN,
      PSHUFD,
      PSHUFHW,
      PSHUFLW,
      SHUFP,
      MOVDDUP,
      MOVSHDUP,
      MOVSLDUP,
      MOVLHPS,
      MOVLHPD,
      MOVHLPS,
      MOVLPS,
      MOVLPD,
      MOVSD,
      MOVSS,
      UNPCKL,
      UNPCKH,
      VPERMILPV,
      VPERMILPI,
      VPERMV,
      VPERMV3,
      VPERMIV3,
      VPERMI,
      VPERM2X128,
      VBROADCAST,
      // Insert/Extract vector element
      VINSERT,
      VEXTRACT,

      // Vector multiply packed unsigned doubleword integers
      PMULUDQ,
      // Vector multiply packed signed doubleword integers
      PMULDQ,

      // FMA nodes
      FMADD,
      FNMADD,
      FMSUB,
      FNMSUB,
      FMADDSUB,
      FMSUBADD,
      // FMA with rounding mode
      FMADD_RND,
      FNMADD_RND,
      FMSUB_RND,
      FNMSUB_RND,
      FMADDSUB_RND,
      FMSUBADD_RND,
      RNDSCALE,

      // Compress and expand
      COMPRESS,
      EXPAND,

      // Save xmm argument registers to the stack, according to %al. An operator
      // is needed so that this can be expanded with control flow.
      VASTART_SAVE_XMM_REGS,

      // Windows's _chkstk call to do stack probing.
      WIN_ALLOCA,

      // For allocating variable amounts of stack space when using
      // segmented stacks. Check if the current stacklet has enough space, and
      // falls back to heap allocation if not.
      SEG_ALLOCA,

      // Windows's _ftol2 runtime routine to do fptoui.
      WIN_FTOL,

      // Memory barrier
      MEMBARRIER,
      MFENCE,
      SFENCE,
      LFENCE,

      // Store FP status word into i16 register.
      FNSTSW16r,

      // Store contents of %ah into %eflags.
      SAHF,

      // Get a random integer and indicate whether it is valid in CF.
      RDRAND,

      // Get a NIST SP800-90B & C compliant random integer and
      // indicate whether it is valid in CF.
      RDSEED,

      PCMPISTRI,
      PCMPESTRI,

      // Test if in transactional execution.
      XTEST,

      // ERI instructions
      RSQRT28, RCP28, EXP2,

      // Compare and swap.
      LCMPXCHG_DAG = ISD::FIRST_TARGET_MEMORY_OPCODE,
      LCMPXCHG8_DAG,
      LCMPXCHG16_DAG,

      // Load, scalar_to_vector, and zero extend.
      VZEXT_LOAD,

      // Store FP control world into i16 memory.
      FNSTCW16m,

      /// This instruction implements FP_TO_SINT with the
      /// integer destination in memory and a FP reg source.  This corresponds
      /// to the X86::FIST*m instructions and the rounding mode change stuff. It
      /// has two inputs (token chain and address) and two outputs (int value
      /// and token chain).
      FP_TO_INT16_IN_MEM,
      FP_TO_INT32_IN_MEM,
      FP_TO_INT64_IN_MEM,

      /// This instruction implements SINT_TO_FP with the
      /// integer source in memory and FP reg result.  This corresponds to the
      /// X86::FILD*m instructions. It has three inputs (token chain, address,
      /// and source type) and two outputs (FP value and token chain). FILD_FLAG
      /// also produces a flag).
      FILD,
      FILD_FLAG,

      /// This instruction implements an extending load to FP stack slots.
      /// This corresponds to the X86::FLD32m / X86::FLD64m. It takes a chain
      /// operand, ptr to load from, and a ValueType node indicating the type
      /// to load to.
      FLD,

      /// This instruction implements a truncating store to FP stack
      /// slots. This corresponds to the X86::FST32m / X86::FST64m. It takes a
      /// chain operand, value to store, address, and a ValueType to store it
      /// as.
      FST,

      /// This instruction grabs the address of the next argument
      /// from a va_list. (reads and modifies the va_list in memory)
      VAARG_64

      // WARNING: Do not add anything in the end unless you want the node to
      // have memop! In fact, starting from ATOMADD64_DAG all opcodes will be
      // thought as target memory ops!
    };
  }

  /// Define some predicates that are used for node matching.
  namespace X86 {
    /// Return true if the specified
    /// EXTRACT_SUBVECTOR operand specifies a vector extract that is
    /// suitable for input to VEXTRACTF128, VEXTRACTI128 instructions.
    bool isVEXTRACT128Index(SDNode *N);

    /// Return true if the specified
    /// INSERT_SUBVECTOR operand specifies a subvector insert that is
    /// suitable for input to VINSERTF128, VINSERTI128 instructions.
    bool isVINSERT128Index(SDNode *N);

    /// Return true if the specified
    /// EXTRACT_SUBVECTOR operand specifies a vector extract that is
    /// suitable for input to VEXTRACTF64X4, VEXTRACTI64X4 instructions.
    bool isVEXTRACT256Index(SDNode *N);

    /// Return true if the specified
    /// INSERT_SUBVECTOR operand specifies a subvector insert that is
    /// suitable for input to VINSERTF64X4, VINSERTI64X4 instructions.
    bool isVINSERT256Index(SDNode *N);

    /// Return the appropriate
    /// immediate to extract the specified EXTRACT_SUBVECTOR index
    /// with VEXTRACTF128, VEXTRACTI128 instructions.
    unsigned getExtractVEXTRACT128Immediate(SDNode *N);

    /// Return the appropriate
    /// immediate to insert at the specified INSERT_SUBVECTOR index
    /// with VINSERTF128, VINSERT128 instructions.
    unsigned getInsertVINSERT128Immediate(SDNode *N);

    /// Return the appropriate
    /// immediate to extract the specified EXTRACT_SUBVECTOR index
    /// with VEXTRACTF64X4, VEXTRACTI64x4 instructions.
    unsigned getExtractVEXTRACT256Immediate(SDNode *N);

    /// Return the appropriate
    /// immediate to insert at the specified INSERT_SUBVECTOR index
    /// with VINSERTF64x4, VINSERTI64x4 instructions.
    unsigned getInsertVINSERT256Immediate(SDNode *N);

    /// Returns true if Elt is a constant zero or floating point constant +0.0.
    bool isZeroNode(SDValue Elt);

    /// Returns true of the given offset can be
    /// fit into displacement field of the instruction.
    bool isOffsetSuitableForCodeModel(int64_t Offset, CodeModel::Model M,
                                      bool hasSymbolicDisplacement = true);


    /// Determines whether the callee is required to pop its
    /// own arguments. Callee pop is necessary to support tail calls.
    bool isCalleePop(CallingConv::ID CallingConv,
                     bool is64Bit, bool IsVarArg, bool TailCallOpt);

    /// AVX512 static rounding constants.  These need to match the values in
    /// avx512fintrin.h.
    enum STATIC_ROUNDING {
      TO_NEAREST_INT = 0,
      TO_NEG_INF = 1,
      TO_POS_INF = 2,
      TO_ZERO = 3,
      CUR_DIRECTION = 4
    };
  }

  //===--------------------------------------------------------------------===//
  //  X86 Implementation of the TargetLowering interface
  class X86TargetLowering final : public TargetLowering {
  public:
    explicit X86TargetLowering(const X86TargetMachine &TM,
                               const X86Subtarget &STI);

    unsigned getJumpTableEncoding() const override;

    MVT getScalarShiftAmountTy(EVT LHSTy) const override { return MVT::i8; }

    const MCExpr *
    LowerCustomJumpTableEntry(const MachineJumpTableInfo *MJTI,
                              const MachineBasicBlock *MBB, unsigned uid,
                              MCContext &Ctx) const override;

    /// Returns relocation base for the given PIC jumptable.
    SDValue getPICJumpTableRelocBase(SDValue Table,
                                     SelectionDAG &DAG) const override;
    const MCExpr *
    getPICJumpTableRelocBaseExpr(const MachineFunction *MF,
                                 unsigned JTI, MCContext &Ctx) const override;

    /// Return the desired alignment for ByVal aggregate
    /// function arguments in the caller parameter area. For X86, aggregates
    /// that contains are placed at 16-byte boundaries while the rest are at
    /// 4-byte boundaries.
    unsigned getByValTypeAlignment(Type *Ty) const override;

    /// Returns the target specific optimal type for load
    /// and store operations as a result of memset, memcpy, and memmove
    /// lowering. If DstAlign is zero that means it's safe to destination
    /// alignment can satisfy any constraint. Similarly if SrcAlign is zero it
    /// means there isn't a need to check it against alignment requirement,
    /// probably because the source does not need to be loaded. If 'IsMemset' is
    /// true, that means it's expanding a memset. If 'ZeroMemset' is true, that
    /// means it's a memset of zero. 'MemcpyStrSrc' indicates whether the memcpy
    /// source is constant so it does not need to be loaded.
    /// It returns EVT::Other if the type should be determined using generic
    /// target-independent logic.
    EVT getOptimalMemOpType(uint64_t Size, unsigned DstAlign, unsigned SrcAlign,
                            bool IsMemset, bool ZeroMemset, bool MemcpyStrSrc,
                            MachineFunction &MF) const override;

    /// Returns true if it's safe to use load / store of the
    /// specified type to expand memcpy / memset inline. This is mostly true
    /// for all types except for some special cases. For example, on X86
    /// targets without SSE2 f64 load / store are done with fldl / fstpl which
    /// also does type conversion. Note the specified type doesn't have to be
    /// legal as the hook is used before type legalization.
    bool isSafeMemOpType(MVT VT) const override;

    /// Returns true if the target allows
    /// unaligned memory accesses. of the specified type. Returns whether it
    /// is "fast" by reference in the second argument.
    bool allowsMisalignedMemoryAccesses(EVT VT, unsigned AS, unsigned Align,
                                       bool *Fast) const override;

    /// Provide custom lowering hooks for some operations.
    ///
    SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;

    /// Replace the results of node with an illegal result
    /// type with new values built out of custom code.
    ///
    void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue>&Results,
                            SelectionDAG &DAG) const override;


    SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;

    /// Return true if the target has native support for
    /// the specified value type and it is 'desirable' to use the type for the
    /// given node type. e.g. On x86 i16 is legal, but undesirable since i16
    /// instruction encodings are longer and some i16 instructions are slow.
    bool isTypeDesirableForOp(unsigned Opc, EVT VT) const override;

    /// Return true if the target has native support for the
    /// specified value type and it is 'desirable' to use the type. e.g. On x86
    /// i16 is legal, but undesirable since i16 instruction encodings are longer
    /// and some i16 instructions are slow.
    bool IsDesirableToPromoteOp(SDValue Op, EVT &PVT) const override;

    MachineBasicBlock *
      EmitInstrWithCustomInserter(MachineInstr *MI,
                                  MachineBasicBlock *MBB) const override;


    /// This method returns the name of a target specific DAG node.
    const char *getTargetNodeName(unsigned Opcode) const override;

    bool isCheapToSpeculateCttz() const override;

    bool isCheapToSpeculateCtlz() const override;

    /// Return the value type to use for ISD::SETCC.
    EVT getSetCCResultType(LLVMContext &Context, EVT VT) const override;

    /// Determine which of the bits specified in Mask are known to be either
    /// zero or one and return them in the KnownZero/KnownOne bitsets.
    void computeKnownBitsForTargetNode(const SDValue Op,
                                       APInt &KnownZero,
                                       APInt &KnownOne,
                                       const SelectionDAG &DAG,
                                       unsigned Depth = 0) const override;

    /// Determine the number of bits in the operation that are sign bits.
    unsigned ComputeNumSignBitsForTargetNode(SDValue Op,
                                             const SelectionDAG &DAG,
                                             unsigned Depth) const override;

    bool isGAPlusOffset(SDNode *N, const GlobalValue* &GA,
                        int64_t &Offset) const override;

    SDValue getReturnAddressFrameIndex(SelectionDAG &DAG) const;

    bool ExpandInlineAsm(CallInst *CI) const override;

    ConstraintType
      getConstraintType(const std::string &Constraint) const override;

    /// Examine constraint string and operand type and determine a weight value.
    /// The operand object must already have been set up with the operand type.
    ConstraintWeight
      getSingleConstraintMatchWeight(AsmOperandInfo &info,
                                     const char *constraint) const override;

    const char *LowerXConstraint(EVT ConstraintVT) const override;

    /// Lower the specified operand into the Ops vector. If it is invalid, don't
    /// add anything to Ops. If hasMemory is true it means one of the asm
    /// constraint of the inline asm instruction being processed is 'm'.
    void LowerAsmOperandForConstraint(SDValue Op,
                                      std::string &Constraint,
                                      std::vector<SDValue> &Ops,
                                      SelectionDAG &DAG) const override;

    unsigned getInlineAsmMemConstraint(
        const std::string &ConstraintCode) const override {
      // FIXME: Map different constraints differently.
      return InlineAsm::Constraint_m;
    }

    /// Given a physical register constraint
    /// (e.g. {edx}), return the register number and the register class for the
    /// register.  This should only be used for C_Register constraints.  On
    /// error, this returns a register number of 0.
    std::pair<unsigned, const TargetRegisterClass *>
    getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                                 const std::string &Constraint,
                                 MVT VT) const override;

    /// Return true if the addressing mode represented
    /// by AM is legal for this target, for a load/store of the specified type.
    bool isLegalAddressingMode(const AddrMode &AM, Type *Ty) const override;

    /// Return true if the specified immediate is legal
    /// icmp immediate, that is the target has icmp instructions which can
    /// compare a register against the immediate without having to materialize
    /// the immediate into a register.
    bool isLegalICmpImmediate(int64_t Imm) const override;

    /// Return true if the specified immediate is legal
    /// add immediate, that is the target has add instructions which can
    /// add a register and the immediate without having to materialize
    /// the immediate into a register.
    bool isLegalAddImmediate(int64_t Imm) const override;

    /// \brief Return the cost of the scaling factor used in the addressing
    /// mode represented by AM for this target, for a load/store
    /// of the specified type.
    /// If the AM is supported, the return value must be >= 0.
    /// If the AM is not supported, it returns a negative value.
    int getScalingFactorCost(const AddrMode &AM, Type *Ty) const override;

    bool isVectorShiftByScalarCheap(Type *Ty) const override;

    /// Return true if it's free to truncate a value of
    /// type Ty1 to type Ty2. e.g. On x86 it's free to truncate a i32 value in
    /// register EAX to i16 by referencing its sub-register AX.
    bool isTruncateFree(Type *Ty1, Type *Ty2) const override;
    bool isTruncateFree(EVT VT1, EVT VT2) const override;

    bool allowTruncateForTailCall(Type *Ty1, Type *Ty2) const override;

    /// Return true if any actual instruction that defines a
    /// value of type Ty1 implicit zero-extends the value to Ty2 in the result
    /// register. This does not necessarily include registers defined in
    /// unknown ways, such as incoming arguments, or copies from unknown
    /// virtual registers. Also, if isTruncateFree(Ty2, Ty1) is true, this
    /// does not necessarily apply to truncate instructions. e.g. on x86-64,
    /// all instructions that define 32-bit values implicit zero-extend the
    /// result out to 64 bits.
    bool isZExtFree(Type *Ty1, Type *Ty2) const override;
    bool isZExtFree(EVT VT1, EVT VT2) const override;
    bool isZExtFree(SDValue Val, EVT VT2) const override;

    /// Return true if folding a vector load into ExtVal (a sign, zero, or any
    /// extend node) is profitable.
    bool isVectorLoadExtDesirable(SDValue) const override;

    /// Return true if an FMA operation is faster than a pair of fmul and fadd
    /// instructions. fmuladd intrinsics will be expanded to FMAs when this
    /// method returns true, otherwise fmuladd is expanded to fmul + fadd.
    bool isFMAFasterThanFMulAndFAdd(EVT VT) const override;

    /// Return true if it's profitable to narrow
    /// operations of type VT1 to VT2. e.g. on x86, it's profitable to narrow
    /// from i32 to i8 but not from i32 to i16.
    bool isNarrowingProfitable(EVT VT1, EVT VT2) const override;

    /// Returns true if the target can instruction select the
    /// specified FP immediate natively. If false, the legalizer will
    /// materialize the FP immediate as a load from a constant pool.
    bool isFPImmLegal(const APFloat &Imm, EVT VT) const override;

    /// Targets can use this to indicate that they only support *some*
    /// VECTOR_SHUFFLE operations, those with specific masks. By default, if a
    /// target supports the VECTOR_SHUFFLE node, all mask values are assumed to
    /// be legal.
    bool isShuffleMaskLegal(const SmallVectorImpl<int> &Mask,
                            EVT VT) const override;

    /// Similar to isShuffleMaskLegal. This is used by Targets can use this to
    /// indicate if there is a suitable VECTOR_SHUFFLE that can be used to
    /// replace a VAND with a constant pool entry.
    bool isVectorClearMaskLegal(const SmallVectorImpl<int> &Mask,
                                EVT VT) const override;

    /// If true, then instruction selection should
    /// seek to shrink the FP constant of the specified type to a smaller type
    /// in order to save space and / or reduce runtime.
    bool ShouldShrinkFPConstant(EVT VT) const override {
      // Don't shrink FP constpool if SSE2 is available since cvtss2sd is more
      // expensive than a straight movsd. On the other hand, it's important to
      // shrink long double fp constant since fldt is very slow.
      return !X86ScalarSSEf64 || VT == MVT::f80;
    }

    /// Return true if we believe it is correct and profitable to reduce the
    /// load node to a smaller type.
    bool shouldReduceLoadWidth(SDNode *Load, ISD::LoadExtType ExtTy,
                               EVT NewVT) const override;

    /// Return true if the specified scalar FP type is computed in an SSE
    /// register, not on the X87 floating point stack.
    bool isScalarFPTypeInSSEReg(EVT VT) const {
      return (VT == MVT::f64 && X86ScalarSSEf64) || // f64 is when SSE2
      (VT == MVT::f32 && X86ScalarSSEf32);   // f32 is when SSE1
    }

    /// Return true if the target uses the MSVC _ftol2 routine for fptoui.
    bool isTargetFTOL() const;

    /// Return true if the MSVC _ftol2 routine should be used for fptoui to the
    /// given type.
    bool isIntegerTypeFTOL(EVT VT) const {
      return isTargetFTOL() && VT == MVT::i64;
    }

    /// \brief Returns true if it is beneficial to convert a load of a constant
    /// to just the constant itself.
    bool shouldConvertConstantLoadToIntImm(const APInt &Imm,
                                           Type *Ty) const override;

    /// Return true if EXTRACT_SUBVECTOR is cheap for this result type
    /// with this index.
    bool isExtractSubvectorCheap(EVT ResVT, unsigned Index) const override;

    /// Intel processors have a unified instruction and data cache
    const char * getClearCacheBuiltinName() const override {
      return nullptr; // nothing to do, move along.
    }

    unsigned getRegisterByName(const char* RegName, EVT VT) const override;

    /// This method returns a target specific FastISel object,
    /// or null if the target does not support "fast" ISel.
    FastISel *createFastISel(FunctionLoweringInfo &funcInfo,
                             const TargetLibraryInfo *libInfo) const override;

    /// Return true if the target stores stack protector cookies at a fixed
    /// offset in some non-standard address space, and populates the address
    /// space and offset as appropriate.
    bool getStackCookieLocation(unsigned &AddressSpace,
                                unsigned &Offset) const override;

    SDValue BuildFILD(SDValue Op, EVT SrcVT, SDValue Chain, SDValue StackSlot,
                      SelectionDAG &DAG) const;

    bool isNoopAddrSpaceCast(unsigned SrcAS, unsigned DestAS) const override;

    bool useLoadStackGuardNode() const override;
    /// \brief Customize the preferred legalization strategy for certain types.
    LegalizeTypeAction getPreferredVectorAction(EVT VT) const override;

  protected:
    std::pair<const TargetRegisterClass *, uint8_t>
    findRepresentativeClass(const TargetRegisterInfo *TRI,
                            MVT VT) const override;

  private:
    /// Keep a pointer to the X86Subtarget around so that we can
    /// make the right decision when generating code for different targets.
    const X86Subtarget *Subtarget;
    const DataLayout *TD;

    /// Select between SSE or x87 floating point ops.
    /// When SSE is available, use it for f32 operations.
    /// When SSE2 is available, use it for f64 operations.
    bool X86ScalarSSEf32;
    bool X86ScalarSSEf64;

    /// A list of legal FP immediates.
    std::vector<APFloat> LegalFPImmediates;

    /// Indicate that this x86 target can instruction
    /// select the specified FP immediate natively.
    void addLegalFPImmediate(const APFloat& Imm) {
      LegalFPImmediates.push_back(Imm);
    }

    SDValue LowerCallResult(SDValue Chain, SDValue InFlag,
                            CallingConv::ID CallConv, bool isVarArg,
                            const SmallVectorImpl<ISD::InputArg> &Ins,
                            SDLoc dl, SelectionDAG &DAG,
                            SmallVectorImpl<SDValue> &InVals) const;
    SDValue LowerMemArgument(SDValue Chain,
                             CallingConv::ID CallConv,
                             const SmallVectorImpl<ISD::InputArg> &ArgInfo,
                             SDLoc dl, SelectionDAG &DAG,
                             const CCValAssign &VA,  MachineFrameInfo *MFI,
                              unsigned i) const;
    SDValue LowerMemOpCallTo(SDValue Chain, SDValue StackPtr, SDValue Arg,
                             SDLoc dl, SelectionDAG &DAG,
                             const CCValAssign &VA,
                             ISD::ArgFlagsTy Flags) const;

    // Call lowering helpers.

    /// Check whether the call is eligible for tail call optimization. Targets
    /// that want to do tail call optimization should implement this function.
    bool IsEligibleForTailCallOptimization(SDValue Callee,
                                           CallingConv::ID CalleeCC,
                                           bool isVarArg,
                                           bool isCalleeStructRet,
                                           bool isCallerStructRet,
                                           Type *RetTy,
                                    const SmallVectorImpl<ISD::OutputArg> &Outs,
                                    const SmallVectorImpl<SDValue> &OutVals,
                                    const SmallVectorImpl<ISD::InputArg> &Ins,
                                           SelectionDAG& DAG) const;
    bool IsCalleePop(bool isVarArg, CallingConv::ID CallConv) const;
    SDValue EmitTailCallLoadRetAddr(SelectionDAG &DAG, SDValue &OutRetAddr,
                                SDValue Chain, bool IsTailCall, bool Is64Bit,
                                int FPDiff, SDLoc dl) const;

    unsigned GetAlignedArgumentStackSize(unsigned StackSize,
                                         SelectionDAG &DAG) const;

    std::pair<SDValue,SDValue> FP_TO_INTHelper(SDValue Op, SelectionDAG &DAG,
                                               bool isSigned,
                                               bool isReplace) const;

    SDValue LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerBUILD_VECTORvXi1(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerVSELECT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerEXTRACT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
    SDValue ExtractBitFromMaskVector(SDValue Op, SelectionDAG &DAG) const;
    SDValue InsertBitToMaskVector(SDValue Op, SelectionDAG &DAG) const;

    SDValue LowerINSERT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerConstantPool(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerBlockAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalAddress(const GlobalValue *GV, SDLoc dl,
                               int64_t Offset, SelectionDAG &DAG) const;
    SDValue LowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerExternalSymbol(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerSINT_TO_FP(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerUINT_TO_FP(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerUINT_TO_FP_i64(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerUINT_TO_FP_i32(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerUINT_TO_FP_vec(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerTRUNCATE(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFP_TO_SINT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFP_TO_UINT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerToBT(SDValue And, ISD::CondCode CC,
                      SDLoc dl, SelectionDAG &DAG) const;
    SDValue LowerSETCC(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerSELECT(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerBRCOND(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerMEMSET(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerJumpTable(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerVASTART(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerVAARG(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerRETURNADDR(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFRAME_TO_ARGS_OFFSET(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerEH_RETURN(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerEH_SJLJ_SETJMP(SDValue Op, SelectionDAG &DAG) const;
    SDValue lowerEH_SJLJ_LONGJMP(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerINIT_TRAMPOLINE(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerFLT_ROUNDS_(SDValue Op, SelectionDAG &DAG) const;
    SDValue LowerWin64_i128OP(SDValue Op, SelectionDAG &DAG) const;

    SDValue
      LowerFormalArguments(SDValue Chain,
                           CallingConv::ID CallConv, bool isVarArg,
                           const SmallVectorImpl<ISD::InputArg> &Ins,
                           SDLoc dl, SelectionDAG &DAG,
                           SmallVectorImpl<SDValue> &InVals) const override;
    SDValue LowerCall(CallLoweringInfo &CLI,
                      SmallVectorImpl<SDValue> &InVals) const override;

    SDValue LowerReturn(SDValue Chain,
                        CallingConv::ID CallConv, bool isVarArg,
                        const SmallVectorImpl<ISD::OutputArg> &Outs,
                        const SmallVectorImpl<SDValue> &OutVals,
                        SDLoc dl, SelectionDAG &DAG) const override;

    bool isUsedByReturnOnly(SDNode *N, SDValue &Chain) const override;

    bool mayBeEmittedAsTailCall(CallInst *CI) const override;

    EVT getTypeForExtArgOrReturn(LLVMContext &Context, EVT VT,
                                 ISD::NodeType ExtendKind) const override;

    bool CanLowerReturn(CallingConv::ID CallConv, MachineFunction &MF,
                        bool isVarArg,
                        const SmallVectorImpl<ISD::OutputArg> &Outs,
                        LLVMContext &Context) const override;

    const MCPhysReg *getScratchRegisters(CallingConv::ID CC) const override;

    bool shouldExpandAtomicLoadInIR(LoadInst *SI) const override;
    bool shouldExpandAtomicStoreInIR(StoreInst *SI) const override;
    TargetLoweringBase::AtomicRMWExpansionKind
    shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const override;

    LoadInst *
    lowerIdempotentRMWIntoFencedLoad(AtomicRMWInst *AI) const override;

    bool needsCmpXchgNb(const Type *MemType) const;

    /// Utility function to emit atomic-load-arith operations (and, or, xor,
    /// nand, max, min, umax, umin). It takes the corresponding instruction to
    /// expand, the associated machine basic block, and the associated X86
    /// opcodes for reg/reg.
    MachineBasicBlock *EmitAtomicLoadArith(MachineInstr *MI,
                                           MachineBasicBlock *MBB) const;

    /// Utility function to emit atomic-load-arith operations (and, or, xor,
    /// nand, add, sub, swap) for 64-bit operands on 32-bit target.
    MachineBasicBlock *EmitAtomicLoadArith6432(MachineInstr *MI,
                                               MachineBasicBlock *MBB) const;

    // Utility function to emit the low-level va_arg code for X86-64.
    MachineBasicBlock *EmitVAARG64WithCustomInserter(
                       MachineInstr *MI,
                       MachineBasicBlock *MBB) const;

    /// Utility function to emit the xmm reg save portion of va_start.
    MachineBasicBlock *EmitVAStartSaveXMMRegsWithCustomInserter(
                                                   MachineInstr *BInstr,
                                                   MachineBasicBlock *BB) const;

    MachineBasicBlock *EmitLoweredSelect(MachineInstr *I,
                                         MachineBasicBlock *BB) const;

    MachineBasicBlock *EmitLoweredWinAlloca(MachineInstr *MI,
                                              MachineBasicBlock *BB) const;

    MachineBasicBlock *EmitLoweredSegAlloca(MachineInstr *MI,
                                            MachineBasicBlock *BB) const;

    MachineBasicBlock *EmitLoweredTLSCall(MachineInstr *MI,
                                          MachineBasicBlock *BB) const;

    MachineBasicBlock *emitLoweredTLSAddr(MachineInstr *MI,
                                          MachineBasicBlock *BB) const;

    MachineBasicBlock *emitEHSjLjSetJmp(MachineInstr *MI,
                                        MachineBasicBlock *MBB) const;

    MachineBasicBlock *emitEHSjLjLongJmp(MachineInstr *MI,
                                         MachineBasicBlock *MBB) const;

    MachineBasicBlock *emitFMA3Instr(MachineInstr *MI,
                                     MachineBasicBlock *MBB) const;

    /// Emit nodes that will be selected as "test Op0,Op0", or something
    /// equivalent, for use with the given x86 condition code.
    SDValue EmitTest(SDValue Op0, unsigned X86CC, SDLoc dl,
                     SelectionDAG &DAG) const;

    /// Emit nodes that will be selected as "cmp Op0,Op1", or something
    /// equivalent, for use with the given x86 condition code.
    SDValue EmitCmp(SDValue Op0, SDValue Op1, unsigned X86CC, SDLoc dl,
                    SelectionDAG &DAG) const;

    /// Convert a comparison if required by the subtarget.
    SDValue ConvertCmpIfNecessary(SDValue Cmp, SelectionDAG &DAG) const;

    /// Use rsqrt* to speed up sqrt calculations.
    SDValue getRsqrtEstimate(SDValue Operand, DAGCombinerInfo &DCI,
                             unsigned &RefinementSteps,
                             bool &UseOneConstNR) const override;

    /// Use rcp* to speed up fdiv calculations.
    SDValue getRecipEstimate(SDValue Operand, DAGCombinerInfo &DCI,
                             unsigned &RefinementSteps) const override;

    /// Reassociate floating point divisions into multiply by reciprocal.
    bool combineRepeatedFPDivisors(unsigned NumUsers) const override;
  };

  namespace X86 {
    FastISel *createFastISel(FunctionLoweringInfo &funcInfo,
                             const TargetLibraryInfo *libInfo);
  }
}

#endif    // X86ISELLOWERING_H