RISCVISelLowering.h

Go to the documentation of this file.

//===-- RISCVISelLowering.h - RISCV DAG Lowering Interface ------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the interfaces that RISCV uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_LIB_TARGET_RISCV_RISCVISELLOWERING_H
#define LLVM_LIB_TARGET_RISCV_RISCVISELLOWERING_H
 
#include "RISCV.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/TargetLowering.h"
 
namespace llvm {
class RISCVSubtarget;
struct RISCVRegisterInfo;
namespace RISCVISD {
enum NodeType : unsigned {
  FIRST_NUMBER = ISD::BUILTIN_OP_END,
  RET_FLAG,
  URET_FLAG,
  SRET_FLAG,
  MRET_FLAG,
  CALL,
  /// Select with condition operator - This selects between a true value and
  /// a false value (ops #3 and #4) based on the boolean result of comparing
  /// the lhs and rhs (ops #0 and #1) of a conditional expression with the
  /// condition code in op #2, a XLenVT constant from the ISD::CondCode enum.
  /// The lhs and rhs are XLenVT integers. The true and false values can be
  /// integer or floating point.
  SELECT_CC,
  BuildPairF64,
  SplitF64,
  TAIL,
  // RV64I shifts, directly matching the semantics of the named RISC-V
  // instructions.
  SLLW,
  SRAW,
  SRLW,
  // 32-bit operations from RV64M that can't be simply matched with a pattern
  // at instruction selection time. These have undefined behavior for division
  // by 0 or overflow (divw) like their target independent counterparts.
  DIVW,
  DIVUW,
  REMUW,
  // RV64IB rotates, directly matching the semantics of the named RISC-V
  // instructions.
  ROLW,
  RORW,
  // RV64IB/RV32IB funnel shifts, with the semantics of the named RISC-V
  // instructions, but the same operand order as fshl/fshr intrinsics.
  FSR,
  FSL,
  // RV64IB funnel shifts, with the semantics of the named RISC-V instructions,
  // but the same operand order as fshl/fshr intrinsics.
  FSRW,
  FSLW,
  // FPR<->GPR transfer operations when the FPR is smaller than XLEN, needed as
  // XLEN is the only legal integer width.
  //
  // FMV_H_X matches the semantics of the FMV.H.X.
  // FMV_X_ANYEXTH is similar to FMV.X.H but has an any-extended result.
  // FMV_W_X_RV64 matches the semantics of the FMV.W.X.
  // FMV_X_ANYEXTW_RV64 is similar to FMV.X.W but has an any-extended result.
  //
  // This is a more convenient semantic for producing dagcombines that remove
  // unnecessary GPR->FPR->GPR moves.
  FMV_H_X,
  FMV_X_ANYEXTH,
  FMV_W_X_RV64,
  FMV_X_ANYEXTW_RV64,
  // READ_CYCLE_WIDE - A read of the 64-bit cycle CSR on a 32-bit target
  // (returns (Lo, Hi)). It takes a chain operand.
  READ_CYCLE_WIDE,
  // Generalized Reverse and Generalized Or-Combine - directly matching the
  // semantics of the named RISC-V instructions. Lowered as custom nodes as
  // TableGen chokes when faced with commutative permutations in deeply-nested
  // DAGs. Each node takes an input operand and a TargetConstant immediate
  // shift amount, and outputs a bit-manipulated version of input. All operands
  // are of type XLenVT.
  GREVI,
  GREVIW,
  GORCI,
  GORCIW,
  SHFLI,
  // Vector Extension
  // VMV_V_X_VL matches the semantics of vmv.v.x but includes an extra operand
  // for the VL value to be used for the operation.
  VMV_V_X_VL,
  // VFMV_V_F_VL matches the semantics of vfmv.v.f but includes an extra operand
  // for the VL value to be used for the operation.
  VFMV_V_F_VL,
  // VMV_X_S matches the semantics of vmv.x.s. The result is always XLenVT sign
  // extended from the vector element size.
  VMV_X_S,
  // VMV_S_XF_VL matches the semantics of vmv.s.x/vmv.s.f, depending on the
  // types of its operands. It carries a VL operand.
  VMV_S_XF_VL,
  // Splats an i64 scalar to a vector type (with element type i64) where the
  // scalar is a sign-extended i32.
  SPLAT_VECTOR_I64,
  // Read VLENB CSR
  READ_VLENB,
  // Truncates a RVV integer vector by one power-of-two. Carries both an extra
  // mask and VL operand.
  TRUNCATE_VECTOR_VL,
  // Unit-stride fault-only-first load
  VLEFF,
  VLEFF_MASK,
  // Matches the semantics of vslideup/vslidedown. The first operand is the
  // pass-thru operand, the second is the source vector, the third is the
  // XLenVT index (either constant or non-constant), the fourth is the mask
  // and the fifth the VL.
  VSLIDEUP_VL,
  VSLIDEDOWN_VL,
  // Matches the semantics of the vid.v instruction, with a mask and VL
  // operand.
  VID_VL,
  // Matches the semantics of the vfcnvt.rod function (Convert double-width
  // float to single-width float, rounding towards odd). Takes a double-width
  // float vector and produces a single-width float vector. Also has a mask and
  // VL operand.
  VFNCVT_ROD_VL,
  // These nodes match the semantics of the corresponding RVV vector reduction
  // instructions. They produce a vector result which is the reduction
  // performed over the first vector operand plus the first element of the
  // second vector operand. The first operand is an unconstrained vector type,
  // and the result and second operand's types are expected to be the
  // corresponding full-width LMUL=1 type for the first operand:
  //   nxv8i8 = vecreduce_add nxv32i8, nxv8i8
  //   nxv2i32 = vecreduce_add nxv8i32, nxv2i32
  // The different in types does introduce extra vsetvli instructions but
  // similarly it reduces the number of registers consumed per reduction.
  VECREDUCE_ADD,
  VECREDUCE_UMAX,
  VECREDUCE_SMAX,
  VECREDUCE_UMIN,
  VECREDUCE_SMIN,
  VECREDUCE_AND,
  VECREDUCE_OR,
  VECREDUCE_XOR,
  VECREDUCE_FADD,
  VECREDUCE_SEQ_FADD,
 
  // Vector binary and unary ops with a mask as a third operand, and VL as a
  // fourth operand.
  // FIXME: Can we replace these with ISD::VP_*?
  ADD_VL,
  AND_VL,
  MUL_VL,
  OR_VL,
  SDIV_VL,
  SHL_VL,
  SREM_VL,
  SRA_VL,
  SRL_VL,
  SUB_VL,
  UDIV_VL,
  UREM_VL,
  XOR_VL,
  FADD_VL,
  FSUB_VL,
  FMUL_VL,
  FDIV_VL,
  FNEG_VL,
  FABS_VL,
  FSQRT_VL,
  FMA_VL,
  SMIN_VL,
  SMAX_VL,
  UMIN_VL,
  UMAX_VL,
  MULHS_VL,
  MULHU_VL,
  FP_TO_SINT_VL,
  FP_TO_UINT_VL,
  SINT_TO_FP_VL,
  UINT_TO_FP_VL,
  FP_ROUND_VL,
  FP_EXTEND_VL,
 
  // Vector compare producing a mask. Fourth operand is input mask. Fifth
  // operand is VL.
  SETCC_VL,
 
  // Vector select with an additional VL operand. This operation is unmasked.
  VSELECT_VL,
 
  // Mask binary operators.
  VMAND_VL,
  VMOR_VL,
  VMXOR_VL,
 
  // Set mask vector to all zeros or ones.
  VMCLR_VL,
  VMSET_VL,
 
  // Matches the semantics of vrgather.vx with an extra operand for VL.
  VRGATHER_VX_VL,
 
  // Vector sign/zero extend with additional mask & VL operands.
  VSEXT_VL,
  VZEXT_VL,
 
  // Memory opcodes start here.
  VLE_VL = ISD::FIRST_TARGET_MEMORY_OPCODE,
  VSE_VL,
 
  // WARNING: Do not add anything in the end unless you want the node to
  // have memop! In fact, starting from FIRST_TARGET_MEMORY_OPCODE all
  // opcodes will be thought as target memory ops!
};
} // namespace RISCVISD
 
class RISCVTargetLowering : public TargetLowering {
  const RISCVSubtarget &Subtarget;
 
public:
  explicit RISCVTargetLowering(const TargetMachine &TM,
                               const RISCVSubtarget &STI);
 
  const RISCVSubtarget &getSubtarget() const { return Subtarget; }
 
  bool getTgtMemIntrinsic(IntrinsicInfo &Info, const CallInst &I,
                          MachineFunction &MF,
                          unsigned Intrinsic) const override;
  bool isLegalAddressingMode(const DataLayout &DL, const AddrMode &AM, Type *Ty,
                             unsigned AS,
                             Instruction *I = nullptr) const override;
  bool isLegalICmpImmediate(int64_t Imm) const override;
  bool isLegalAddImmediate(int64_t Imm) const override;
  bool isTruncateFree(Type *SrcTy, Type *DstTy) const override;
  bool isTruncateFree(EVT SrcVT, EVT DstVT) const override;
  bool isZExtFree(SDValue Val, EVT VT2) const override;
  bool isSExtCheaperThanZExt(EVT SrcVT, EVT DstVT) const override;
  bool isCheapToSpeculateCttz() const override;
  bool isCheapToSpeculateCtlz() const override;
  bool isFPImmLegal(const APFloat &Imm, EVT VT,
                    bool ForCodeSize) const override;
 
  bool hasBitPreservingFPLogic(EVT VT) const override;
  bool
  shouldExpandBuildVectorWithShuffles(EVT VT,
                                      unsigned DefinedValues) const override;
 
  // Provide custom lowering hooks for some operations.
  SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
  void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue> &Results,
                          SelectionDAG &DAG) const override;
 
  SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
  bool targetShrinkDemandedConstant(SDValue Op, const APInt &DemandedBits,
                                    const APInt &DemandedElts,
                                    TargetLoweringOpt &TLO) const override;
 
  void computeKnownBitsForTargetNode(const SDValue Op,
                                     KnownBits &Known,
                                     const APInt &DemandedElts,
                                     const SelectionDAG &DAG,
                                     unsigned Depth) const override;
  unsigned ComputeNumSignBitsForTargetNode(SDValue Op,
                                           const APInt &DemandedElts,
                                           const SelectionDAG &DAG,
                                           unsigned Depth) const override;
 
  // This method returns the name of a target specific DAG node.
  const char *getTargetNodeName(unsigned Opcode) const override;
 
  ConstraintType getConstraintType(StringRef Constraint) const override;
 
  unsigned getInlineAsmMemConstraint(StringRef ConstraintCode) const override;
 
  std::pair<unsigned, const TargetRegisterClass *>
  getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                               StringRef Constraint, MVT VT) const override;
 
  void LowerAsmOperandForConstraint(SDValue Op, std::string &Constraint,
                                    std::vector<SDValue> &Ops,
                                    SelectionDAG &DAG) const override;
 
  MachineBasicBlock *
  EmitInstrWithCustomInserter(MachineInstr &MI,
                              MachineBasicBlock *BB) const override;
 
  EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Context,
                         EVT VT) const override;
 
  bool convertSetCCLogicToBitwiseLogic(EVT VT) const override {
    return VT.isScalarInteger();
  }
  bool convertSelectOfConstantsToMath(EVT VT) const override { return true; }
 
  bool shouldInsertFencesForAtomic(const Instruction *I) const override {
    return isa<LoadInst>(I) || isa<StoreInst>(I);
  }
  Instruction *emitLeadingFence(IRBuilder<> &Builder, Instruction *Inst,
                                AtomicOrdering Ord) const override;
  Instruction *emitTrailingFence(IRBuilder<> &Builder, Instruction *Inst,
                                 AtomicOrdering Ord) const override;
 
  bool isFMAFasterThanFMulAndFAdd(const MachineFunction &MF,
                                  EVT VT) const override;
 
  ISD::NodeType getExtendForAtomicOps() const override {
    return ISD::SIGN_EXTEND;
  }
 
  ISD::NodeType getExtendForAtomicCmpSwapArg() const override {
    return ISD::SIGN_EXTEND;
  }
 
  bool shouldExpandShift(SelectionDAG &DAG, SDNode *N) const override {
    if (DAG.getMachineFunction().getFunction().hasMinSize())
      return false;
    return true;
  }
  bool isDesirableToCommuteWithShift(const SDNode *N,
                                     CombineLevel Level) const override;
 
  /// If a physical register, this returns the register that receives the
  /// exception address on entry to an EH pad.
  Register
  getExceptionPointerRegister(const Constant *PersonalityFn) const override;
 
  /// If a physical register, this returns the register that receives the
  /// exception typeid on entry to a landing pad.
  Register
  getExceptionSelectorRegister(const Constant *PersonalityFn) const override;
 
  bool shouldExtendTypeInLibCall(EVT Type) const override;
  bool shouldSignExtendTypeInLibCall(EVT Type, bool IsSigned) const override;
 
  /// Returns the register with the specified architectural or ABI name. This
  /// method is necessary to lower the llvm.read_register.* and
  /// llvm.write_register.* intrinsics. Allocatable registers must be reserved
  /// with the clang -ffixed-xX flag for access to be allowed.
  Register getRegisterByName(const char *RegName, LLT VT,
                             const MachineFunction &MF) const override;
 
  // Lower incoming arguments, copy physregs into vregs
  SDValue LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv,
                               bool IsVarArg,
                               const SmallVectorImpl<ISD::InputArg> &Ins,
                               const SDLoc &DL, SelectionDAG &DAG,
                               SmallVectorImpl<SDValue> &InVals) const override;
  bool CanLowerReturn(CallingConv::ID CallConv, MachineFunction &MF,
                      bool IsVarArg,
                      const SmallVectorImpl<ISD::OutputArg> &Outs,
                      LLVMContext &Context) const override;
  SDValue LowerReturn(SDValue Chain, CallingConv::ID CallConv, bool IsVarArg,
                      const SmallVectorImpl<ISD::OutputArg> &Outs,
                      const SmallVectorImpl<SDValue> &OutVals, const SDLoc &DL,
                      SelectionDAG &DAG) const override;
  SDValue LowerCall(TargetLowering::CallLoweringInfo &CLI,
                    SmallVectorImpl<SDValue> &InVals) const override;
 
  bool shouldConvertConstantLoadToIntImm(const APInt &Imm,
                                         Type *Ty) const override {
    return true;
  }
  bool mayBeEmittedAsTailCall(const CallInst *CI) const override;
  bool shouldConsiderGEPOffsetSplit() const override { return true; }
 
  bool decomposeMulByConstant(LLVMContext &Context, EVT VT,
                              SDValue C) const override;
 
  TargetLowering::AtomicExpansionKind
  shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const override;
  Value *emitMaskedAtomicRMWIntrinsic(IRBuilder<> &Builder, AtomicRMWInst *AI,
                                      Value *AlignedAddr, Value *Incr,
                                      Value *Mask, Value *ShiftAmt,
                                      AtomicOrdering Ord) const override;
  TargetLowering::AtomicExpansionKind
  shouldExpandAtomicCmpXchgInIR(AtomicCmpXchgInst *CI) const override;
  Value *emitMaskedAtomicCmpXchgIntrinsic(IRBuilder<> &Builder,
                                          AtomicCmpXchgInst *CI,
                                          Value *AlignedAddr, Value *CmpVal,
                                          Value *NewVal, Value *Mask,
                                          AtomicOrdering Ord) const override;
 
  /// Returns true if the target allows unaligned memory accesses of the
  /// specified type.
  bool allowsMisalignedMemoryAccesses(
      EVT VT, unsigned AddrSpace = 0, Align Alignment = Align(1),
      MachineMemOperand::Flags Flags = MachineMemOperand::MONone,
      bool *Fast = nullptr) const override;
 
  static RISCVVLMUL getLMUL(MVT VT);
  static unsigned getRegClassIDForLMUL(RISCVVLMUL LMul);
  static unsigned getSubregIndexByMVT(MVT VT, unsigned Index);
  static unsigned getRegClassIDForVecVT(MVT VT);
  static std::pair<unsigned, unsigned>
  decomposeSubvectorInsertExtractToSubRegs(MVT VecVT, MVT SubVecVT,
                                           unsigned InsertExtractIdx,
                                           const RISCVRegisterInfo *TRI);
  static MVT getContainerForFixedLengthVector(SelectionDAG &DAG, MVT VT,
                                              const RISCVSubtarget &Subtarget);
 
private:
  void analyzeInputArgs(MachineFunction &MF, CCState &CCInfo,
                        const SmallVectorImpl<ISD::InputArg> &Ins,
                        bool IsRet) const;
  void analyzeOutputArgs(MachineFunction &MF, CCState &CCInfo,
                         const SmallVectorImpl<ISD::OutputArg> &Outs,
                         bool IsRet, CallLoweringInfo *CLI) const;
 
  template <class NodeTy>
  SDValue getAddr(NodeTy *N, SelectionDAG &DAG, bool IsLocal = true) const;
 
  SDValue getStaticTLSAddr(GlobalAddressSDNode *N, SelectionDAG &DAG,
                           bool UseGOT) const;
  SDValue getDynamicTLSAddr(GlobalAddressSDNode *N, SelectionDAG &DAG) const;
 
  SDValue lowerGlobalAddress(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerBlockAddress(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerConstantPool(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerJumpTable(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerGlobalTLSAddress(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerSELECT(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerVASTART(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerRETURNADDR(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerShiftLeftParts(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerShiftRightParts(SDValue Op, SelectionDAG &DAG, bool IsSRA) const;
  SDValue lowerSPLATVECTOR(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerVectorMaskExt(SDValue Op, SelectionDAG &DAG,
                             int64_t ExtTrueVal) const;
  SDValue lowerVectorMaskTrunc(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerINSERT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerEXTRACT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerINTRINSIC_WO_CHAIN(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerINTRINSIC_W_CHAIN(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerVECREDUCE(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFPVECREDUCE(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerINSERT_SUBVECTOR(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerEXTRACT_SUBVECTOR(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFixedLengthVectorLoadToRVV(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFixedLengthVectorStoreToRVV(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFixedLengthVectorSetccToRVV(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFixedLengthVectorLogicOpToRVV(SDValue Op, SelectionDAG &DAG,
                                             unsigned MaskOpc,
                                             unsigned VecOpc) const;
  SDValue lowerFixedLengthVectorSelectToRVV(SDValue Op,
                                            SelectionDAG &DAG) const;
  SDValue lowerToScalableOp(SDValue Op, SelectionDAG &DAG, unsigned NewOpc,
                            bool HasMask = true) const;
  SDValue lowerFixedLengthVectorExtendToRVV(SDValue Op, SelectionDAG &DAG,
                                            unsigned ExtendOpc) const;
 
  bool isEligibleForTailCallOptimization(
      CCState &CCInfo, CallLoweringInfo &CLI, MachineFunction &MF,
      const SmallVector<CCValAssign, 16> &ArgLocs) const;
 
  /// Generate error diagnostics if any register used by CC has been marked
  /// reserved.
  void validateCCReservedRegs(
      const SmallVectorImpl<std::pair<llvm::Register, llvm::SDValue>> &Regs,
      MachineFunction &MF) const;
 
  bool useRVVForFixedLengthVectorVT(MVT VT) const;
};
 
namespace RISCV {
// We use 64 bits as the known part in the scalable vector types.
static constexpr unsigned RVVBitsPerBlock = 64;
} // namespace RISCV
 
namespace RISCVVIntrinsicsTable {
 
struct RISCVVIntrinsicInfo {
  unsigned IntrinsicID;
  uint8_t ExtendedOperand;
};
 
using namespace RISCV;
 
#define GET_RISCVVIntrinsicsTable_DECL
#include "RISCVGenSearchableTables.inc"
 
} // end namespace RISCVVIntrinsicsTable
 
} // end namespace llvm
 
#endif