NVPTXISelLowering.h

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//===-- NVPTXISelLowering.h - NVPTX 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 NVPTX uses to lower LLVM code into a
// selection DAG.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_LIB_TARGET_NVPTX_NVPTXISELLOWERING_H
#define LLVM_LIB_TARGET_NVPTX_NVPTXISELLOWERING_H
 
#include "NVPTX.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/Support/AtomicOrdering.h"
 
namespace llvm {
 
class NVPTXSubtarget;
 
//===--------------------------------------------------------------------===//
// TargetLowering Implementation
//===--------------------------------------------------------------------===//
class NVPTXTargetLowering : public TargetLowering {
public:
  explicit NVPTXTargetLowering(const NVPTXTargetMachine &TM,
                               const NVPTXSubtarget &STI);
  SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
 
  bool getTgtMemIntrinsic(IntrinsicInfo &Info, const CallInst &I,
                          MachineFunction &MF,
                          unsigned Intrinsic) const override;
 
  Align getFunctionArgumentAlignment(const Function *F, Type *Ty, unsigned Idx,
                                     const DataLayout &DL) const;
 
  /// getFunctionParamOptimizedAlign - since function arguments are passed via
  /// .param space, we may want to increase their alignment in a way that
  /// ensures that we can effectively vectorize their loads & stores. We can
  /// increase alignment only if the function has internal or has private
  /// linkage as for other linkage types callers may already rely on default
  /// alignment. To allow using 128-bit vectorized loads/stores, this function
  /// ensures that alignment is 16 or greater.
  Align getFunctionParamOptimizedAlign(const Function *F, Type *ArgTy,
                                       const DataLayout &DL) const;
 
  /// Helper for computing alignment of a device function byval parameter.
  Align getFunctionByValParamAlign(const Function *F, Type *ArgTy,
                                   Align InitialAlign,
                                   const DataLayout &DL) const;
 
  // Helper for getting a function parameter name. Name is composed from
  // its index and the function name. Negative index corresponds to special
  // parameter (unsized array) used for passing variable arguments.
  std::string getParamName(const Function *F, int Idx) const;
 
  /// isLegalAddressingMode - Return true if the addressing mode represented
  /// by AM is legal for this target, for a load/store of the specified type
  /// Used to guide target specific optimizations, like loop strength
  /// reduction (LoopStrengthReduce.cpp) and memory optimization for
  /// address mode (CodeGenPrepare.cpp)
  bool isLegalAddressingMode(const DataLayout &DL, const AddrMode &AM, Type *Ty,
                             unsigned AS,
                             Instruction *I = nullptr) const override;
 
  bool isTruncateFree(Type *SrcTy, Type *DstTy) const override {
    // Truncating 64-bit to 32-bit is free in SASS.
    if (!SrcTy->isIntegerTy() || !DstTy->isIntegerTy())
      return false;
    return SrcTy->getPrimitiveSizeInBits() == 64 &&
           DstTy->getPrimitiveSizeInBits() == 32;
  }
 
  EVT getSetCCResultType(const DataLayout &DL, LLVMContext &Ctx,
                         EVT VT) const override {
    if (VT.isVector())
      return EVT::getVectorVT(Ctx, MVT::i1, VT.getVectorNumElements());
    return MVT::i1;
  }
 
  ConstraintType getConstraintType(StringRef Constraint) const override;
  std::pair<unsigned, const TargetRegisterClass *>
  getRegForInlineAsmConstraint(const TargetRegisterInfo *TRI,
                               StringRef Constraint, MVT VT) const override;
 
  SDValue LowerFormalArguments(SDValue Chain, CallingConv::ID CallConv,
                               bool isVarArg,
                               const SmallVectorImpl<ISD::InputArg> &Ins,
                               const SDLoc &dl, SelectionDAG &DAG,
                               SmallVectorImpl<SDValue> &InVals) const override;
 
  SDValue LowerCall(CallLoweringInfo &CLI,
                    SmallVectorImpl<SDValue> &InVals) const override;
 
  SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerSTACKSAVE(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerSTACKRESTORE(SDValue Op, SelectionDAG &DAG) const;
 
  std::string getPrototype(const DataLayout &DL, Type *, const ArgListTy &,
                           const SmallVectorImpl<ISD::OutputArg> &,
                           std::optional<unsigned> FirstVAArg,
                           const CallBase &CB, unsigned UniqueCallSite) const;
 
  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;
 
  void LowerAsmOperandForConstraint(SDValue Op, StringRef Constraint,
                                    std::vector<SDValue> &Ops,
                                    SelectionDAG &DAG) const override;
 
  const NVPTXTargetMachine *nvTM;
 
  // PTX always uses 32-bit shift amounts
  MVT getScalarShiftAmountTy(const DataLayout &, EVT) const override {
    return MVT::i32;
  }
 
  TargetLoweringBase::LegalizeTypeAction
  getPreferredVectorAction(MVT VT) const override;
 
  // Get the degree of precision we want from 32-bit floating point division
  // operations.
  NVPTX::DivPrecisionLevel getDivF32Level(const MachineFunction &MF,
                                          const SDNode &N) const;
 
  // Get whether we should use a precise or approximate 32-bit floating point
  // sqrt instruction.
  bool usePrecSqrtF32(const SDNode *N = nullptr) const;
 
  // Get whether we should use instructions that flush floating-point denormals
  // to sign-preserving zero.
  bool useF32FTZ(const MachineFunction &MF) const;
 
  SDValue getSqrtEstimate(SDValue Operand, SelectionDAG &DAG, int Enabled,
                          int &ExtraSteps, bool &UseOneConst,
                          bool Reciprocal) const override;
 
  unsigned combineRepeatedFPDivisors() const override { return 2; }
 
  bool allowFMA(MachineFunction &MF, CodeGenOptLevel OptLevel) const;
 
  bool isFMAFasterThanFMulAndFAdd(const MachineFunction &MF,
                                  EVT) const override {
    return true;
  }
 
  // The default is the same as pointer type, but brx.idx only accepts i32
  MVT getJumpTableRegTy(const DataLayout &) const override { return MVT::i32; }
 
  unsigned getJumpTableEncoding() const override;
 
  bool enableAggressiveFMAFusion(EVT VT) const override { return true; }
 
  // The default is to transform llvm.ctlz(x, false) (where false indicates that
  // x == 0 is not undefined behavior) into a branch that checks whether x is 0
  // and avoids calling ctlz in that case.  We have a dedicated ctlz
  // instruction, so we say that ctlz is cheap to speculate.
  bool isCheapToSpeculateCtlz(Type *Ty) const override { return true; }
 
  AtomicExpansionKind shouldCastAtomicLoadInIR(LoadInst *LI) const override {
    return AtomicExpansionKind::None;
  }
 
  AtomicExpansionKind shouldCastAtomicStoreInIR(StoreInst *SI) const override {
    return AtomicExpansionKind::None;
  }
 
  AtomicExpansionKind
  shouldExpandAtomicRMWInIR(AtomicRMWInst *AI) const override;
 
  bool aggressivelyPreferBuildVectorSources(EVT VecVT) const override {
    // There's rarely any point of packing something into a vector type if we
    // already have the source data.
    return true;
  }
 
  bool shouldInsertFencesForAtomic(const Instruction *) const override;
 
  AtomicOrdering
  atomicOperationOrderAfterFenceSplit(const Instruction *I) const override;
 
  Instruction *emitLeadingFence(IRBuilderBase &Builder, Instruction *Inst,
                                AtomicOrdering Ord) const override;
  Instruction *emitTrailingFence(IRBuilderBase &Builder, Instruction *Inst,
                                 AtomicOrdering Ord) const override;
 
  unsigned getPreferredFPToIntOpcode(unsigned Op, EVT FromVT,
                                     EVT ToVT) const override;
 
  void computeKnownBitsForTargetNode(const SDValue Op, KnownBits &Known,
                                     const APInt &DemandedElts,
                                     const SelectionDAG &DAG,
                                     unsigned Depth = 0) const override;
  bool SimplifyDemandedBitsForTargetNode(SDValue Op, const APInt &DemandedBits,
                                         const APInt &DemandedElts,
                                         KnownBits &Known,
                                         TargetLoweringOpt &TLO,
                                         unsigned Depth = 0) const override;
 
private:
  const NVPTXSubtarget &STI; // cache the subtarget here
  mutable unsigned GlobalUniqueCallSite;
 
  SDValue getParamSymbol(SelectionDAG &DAG, int I, EVT T) const;
  SDValue getCallParamSymbol(SelectionDAG &DAG, int I, EVT T) const;
  SDValue LowerADDRSPACECAST(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerBITCAST(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerCONCAT_VECTORS(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerVECREDUCE(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerEXTRACT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerINSERT_VECTOR_ELT(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerFCOPYSIGN(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerFROUND(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFROUND32(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFROUND64(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue PromoteBinOpIfF32FTZ(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerINT_TO_FP(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFP_TO_INT(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerFP_ROUND(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFP_EXTEND(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerLOAD(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerMLOAD(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerSTORE(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerSTOREi1(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerShiftRightParts(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerShiftLeftParts(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerBR_JT(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerVAARG(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerVASTART(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerCopyToReg_128(SDValue Op, SelectionDAG &DAG) const;
  unsigned getNumRegisters(LLVMContext &Context, EVT VT,
                           std::optional<MVT> RegisterVT) const override;
  bool
  splitValueIntoRegisterParts(SelectionDAG &DAG, const SDLoc &DL, SDValue Val,
                              SDValue *Parts, unsigned NumParts, MVT PartVT,
                              std::optional<CallingConv::ID> CC) const override;
 
  void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue> &Results,
                          SelectionDAG &DAG) const override;
  SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
  Align getArgumentAlignment(const CallBase *CB, Type *Ty, unsigned Idx,
                             const DataLayout &DL) const;
};
 
} // namespace llvm
 
#endif