AMDGPUISelLowering.h

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//===-- AMDGPUISelLowering.h - AMDGPU 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
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Interface definition of the TargetLowering class that is common
/// to all AMD GPUs.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_LIB_TARGET_AMDGPU_AMDGPUISELLOWERING_H
#define LLVM_LIB_TARGET_AMDGPU_AMDGPUISELLOWERING_H
 
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/TargetLowering.h"
 
namespace llvm {
 
class AMDGPUMachineFunctionInfo;
class AMDGPUSubtarget;
struct ArgDescriptor;
 
class AMDGPUTargetLowering : public TargetLowering {
private:
  const AMDGPUSubtarget *Subtarget;
 
  /// \returns AMDGPUISD::FFBH_U32 node if the incoming \p Op may have been
  /// legalized from a smaller type VT. Need to match pre-legalized type because
  /// the generic legalization inserts the add/sub between the select and
  /// compare.
  SDValue getFFBX_U32(SelectionDAG &DAG, SDValue Op, const SDLoc &DL, unsigned Opc) const;
 
public:
  /// \returns The minimum number of bits needed to store the value of \Op as an
  /// unsigned integer. Truncating to this size and then zero-extending to the
  /// original size will not change the value.
  static unsigned numBitsUnsigned(SDValue Op, SelectionDAG &DAG);
 
  /// \returns The minimum number of bits needed to store the value of \Op as a
  /// signed integer. Truncating to this size and then sign-extending to the
  /// original size will not change the value.
  static unsigned numBitsSigned(SDValue Op, SelectionDAG &DAG);
 
  /// \returns The known bits of a 24-bit multiply (MUL_U24/MUL_I24) with a
  /// \p BitWidth wide result, given the known bits of its operands. Only the
  /// low 24 bits of each operand are used, zero- or sign-extended depending on
  /// \p IsSigned.
  static KnownBits computeKnownBitsForMul24(const KnownBits &LHSKnown,
                                            const KnownBits &RHSKnown,
                                            unsigned BitWidth, bool IsSigned,
                                            bool SelfMultiply);
 
protected:
  SDValue LowerEXTRACT_SUBVECTOR(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerCONCAT_VECTORS(SDValue Op, SelectionDAG &DAG) const;
  /// Split a vector store into multiple scalar stores.
  /// \returns The resulting chain.
 
  SDValue LowerCTLS(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFCEIL(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFTRUNC(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFRINT(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFNEARBYINT(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerFROUNDEVEN(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFROUND(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFFLOOR(SDValue Op, SelectionDAG &DAG) const;
 
  static bool allowApproxFunc(const SelectionDAG &DAG, SDNodeFlags Flags);
  static bool needsDenormHandlingF32(const SelectionDAG &DAG, SDValue Src,
                                     SDNodeFlags Flags);
  SDValue getIsFinite(SelectionDAG &DAG, SDValue Op, SDNodeFlags Flags) const;
  std::pair<SDValue, SDValue> getScaledLogInput(SelectionDAG &DAG,
                                                const SDLoc SL, SDValue Op,
                                                SDNodeFlags Flags) const;
 
  SDValue LowerFLOG2(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFLOGCommon(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFLOGUnsafe(SDValue Op, const SDLoc &SL, SelectionDAG &DAG,
                          bool IsLog10, SDNodeFlags Flags) const;
  SDValue lowerFEXP2(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue lowerFEXPUnsafeImpl(SDValue Op, const SDLoc &SL, SelectionDAG &DAG,
                              SDNodeFlags Flags, bool IsExp10) const;
 
  SDValue lowerFEXPUnsafe(SDValue Op, const SDLoc &SL, SelectionDAG &DAG,
                          SDNodeFlags Flags) const;
  SDValue lowerFEXP10Unsafe(SDValue Op, const SDLoc &SL, SelectionDAG &DAG,
                            SDNodeFlags Flags) const;
  SDValue lowerFEXP(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFEXPF64(SDValue Op, SelectionDAG &DAG) const;
  SDValue lowerFPOW(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue lowerCTLZResults(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerCTLZ_CTTZ(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerINT_TO_FP16(SDValue Op, SelectionDAG &DAG, EVT FP16Ty) const;
  SDValue LowerINT_TO_FP32(SDValue Op, SelectionDAG &DAG, bool Signed) const;
  SDValue LowerINT_TO_FP64(SDValue Op, SelectionDAG &DAG, bool Signed) const;
  SDValue lowerINT_TO_FPImpl(SDValue Op, SelectionDAG &DAG, bool Signed) const;
  SDValue LowerUINT_TO_FP(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerSINT_TO_FP(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerFP_TO_INT64(SDValue Op, SelectionDAG &DAG, bool Signed) const;
  SDValue LowerFP_TO_FP16(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFP_TO_INT(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerFP_TO_INT_SAT(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerF64ToF16Safe(SDValue Src, const SDLoc &DL,
                            SelectionDAG &DAG) const;
 
  SDValue LowerSIGN_EXTEND_INREG(SDValue Op, SelectionDAG &DAG) const;
 
protected:
  /// Check whether value Val can be supported by v_mov_b64, for the current
  /// target.
  bool isInt64ImmLegal(SDNode *Val, SelectionDAG &DAG) const;
  SDValue performLoadCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performStoreCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performAssertSZExtCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performIntrinsicWOChainCombine(SDNode *N, DAGCombinerInfo &DCI) const;
 
  SDValue splitBinaryBitConstantOpImpl(DAGCombinerInfo &DCI, const SDLoc &SL,
                                       unsigned Opc, SDValue LHS,
                                       uint32_t ValLo, uint32_t ValHi) const;
  SDValue performShlCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performSraCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performSrlCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performTruncateCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performMulCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performMulLoHiCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performMulhsCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performMulhuCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performCtlz_CttzCombine(const SDLoc &SL, SDValue Cond, SDValue LHS,
                             SDValue RHS, DAGCombinerInfo &DCI) const;
 
  SDValue foldFreeOpFromSelect(TargetLowering::DAGCombinerInfo &DCI,
                               SDValue N) const;
  SDValue performSelectCombine(SDNode *N, DAGCombinerInfo &DCI) const;
 
  TargetLowering::NegatibleCost
  getConstantNegateCost(const ConstantFPSDNode *C) const;
 
  bool isConstantCostlierToNegate(SDValue N) const;
  SDValue performFNegCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performFAbsCombine(SDNode *N, DAGCombinerInfo &DCI) const;
  SDValue performRcpCombine(SDNode *N, DAGCombinerInfo &DCI) const;
 
  static EVT getEquivalentMemType(LLVMContext &Context, EVT VT);
 
  virtual SDValue LowerGlobalAddress(AMDGPUMachineFunctionInfo *MFI, SDValue Op,
                                     SelectionDAG &DAG) const;
 
  SDValue LowerBlockAddress(SDValue Op, SelectionDAG &DAG) const;
 
  /// Return 64-bit value Op as two 32-bit integers.
  std::pair<SDValue, SDValue> split64BitValue(SDValue Op,
                                              SelectionDAG &DAG) const;
  SDValue getHiHalf64(SDValue Op, SelectionDAG &DAG) const;
 
  /// Split a vector type into two parts. The first part is a power of two
  /// vector. The second part is whatever is left over, and is a scalar if it
  /// would otherwise be a 1-vector.
  std::pair<EVT, EVT> getSplitDestVTs(const EVT &VT, SelectionDAG &DAG) const;
 
  /// Split a vector value into two parts of types LoVT and HiVT. HiVT could be
  /// scalar.
  std::pair<SDValue, SDValue> splitVector(const SDValue &N, const SDLoc &DL,
                                          const EVT &LoVT, const EVT &HighVT,
                                          SelectionDAG &DAG) const;
 
  /// Split a vector load into 2 loads of half the vector.
  SDValue SplitVectorLoad(SDValue Op, SelectionDAG &DAG) const;
 
  /// Widen a suitably aligned v3 load. For all other cases, split the input
  /// vector load.
  SDValue WidenOrSplitVectorLoad(SDValue Op, SelectionDAG &DAG) const;
 
  /// Split a vector store into 2 stores of half the vector.
  SDValue SplitVectorStore(SDValue Op, SelectionDAG &DAG) const;
 
  SDValue LowerSDIVREM(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerUDIVREM(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerDIVREMToFloat(SDValue Op, SelectionDAG &DAG, bool sign) const;
  void LowerUDIVREM64(SDValue Op, SelectionDAG &DAG,
                                    SmallVectorImpl<SDValue> &Results) const;
 
  void analyzeFormalArgumentsCompute(
    CCState &State,
    const SmallVectorImpl<ISD::InputArg> &Ins) const;
 
public:
  AMDGPUTargetLowering(const TargetMachine &TM, const TargetSubtargetInfo &STI,
                       const AMDGPUSubtarget &AMDGPUSTI);
 
  static inline SDValue stripBitcast(SDValue Val) {
    return Val.getOpcode() == ISD::BITCAST ? Val.getOperand(0) : Val;
  }
 
  static bool shouldFoldFNegIntoSrc(SDNode *FNeg, SDValue FNegSrc);
  static bool allUsesHaveSourceMods(const SDNode *N,
                                    unsigned CostThreshold = 4);
  bool isFAbsFree(EVT VT) const override;
  bool isFNegFree(EVT VT) const override;
  bool isTruncateFree(EVT Src, EVT Dest) const override;
  bool isTruncateFree(Type *Src, Type *Dest) const override;
 
  bool isZExtFree(Type *Src, Type *Dest) const override;
  bool isZExtFree(EVT Src, EVT Dest) const override;
 
  SDValue getNegatedExpression(SDValue Op, SelectionDAG &DAG,
                               bool LegalOperations, bool ForCodeSize,
                               NegatibleCost &Cost,
                               unsigned Depth) const override;
 
  bool isNarrowingProfitable(SDNode *N, EVT SrcVT, EVT DestVT) const override;
 
  bool isDesirableToCommuteWithShift(const SDNode *N,
                                     CombineLevel Level) const override;
 
  EVT getTypeForExtReturn(LLVMContext &Context, EVT VT,
                          ISD::NodeType ExtendKind) const override;
 
  unsigned getVectorIdxWidth(const DataLayout &) const override;
  bool isSelectSupported(SelectSupportKind) const override;
 
  FPImmAction getFPImmAction(const APFloat &Imm, EVT VT,
                             bool ForCodeSize) const override;
  bool ShouldShrinkFPConstant(EVT VT) const override;
  bool shouldReduceLoadWidth(SDNode *Load, ISD::LoadExtType ExtType, EVT ExtVT,
                             std::optional<unsigned> ByteOffset) const override;
 
  bool isLoadBitCastBeneficial(EVT, EVT, const SelectionDAG &DAG,
                               const MachineMemOperand &MMO) const final;
  bool shouldCombineMemoryType(EVT VT) const;
 
  bool storeOfVectorConstantIsCheap(bool IsZero, EVT MemVT,
                                    unsigned NumElem,
                                    unsigned AS) const override;
  bool aggressivelyPreferBuildVectorSources(EVT VecVT) const override;
  bool isCheapToSpeculateCttz(Type *Ty) const override;
  bool isCheapToSpeculateCtlz(Type *Ty) const override;
 
  bool isSDNodeAlwaysUniform(const SDNode *N) const override;
 
  // FIXME: This hook should not exist
  AtomicExpansionKind shouldCastAtomicLoadInIR(LoadInst *LI) const override {
    return AtomicExpansionKind::None;
  }
 
  AtomicExpansionKind shouldCastAtomicStoreInIR(StoreInst *SI) const override {
    return AtomicExpansionKind::None;
  }
 
  AtomicExpansionKind shouldCastAtomicRMWIInIR(AtomicRMWInst *) const override {
    return AtomicExpansionKind::None;
  }
 
  bool shouldIssueAtomicLoadForAtomicEmulationLoop() const override {
    return false;
  }
 
  static CCAssignFn *CCAssignFnForCall(CallingConv::ID CC, bool IsVarArg);
  static CCAssignFn *CCAssignFnForReturn(CallingConv::ID CC, bool IsVarArg);
 
  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 addTokenForArgument(SDValue Chain,
                              SelectionDAG &DAG,
                              MachineFrameInfo &MFI,
                              int ClobberedFI) const;
 
  SDValue lowerUnhandledCall(CallLoweringInfo &CLI,
                             SmallVectorImpl<SDValue> &InVals,
                             StringRef Reason) const;
  SDValue LowerCall(CallLoweringInfo &CLI,
                    SmallVectorImpl<SDValue> &InVals) const override;
 
  SDValue LowerDYNAMIC_STACKALLOC(SDValue Op, SelectionDAG &DAG) const;
  SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const override;
  SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
  bool SimplifyDemandedBitsForTargetNode(SDValue Op,
                                         const APInt &OriginalDemandedBits,
                                         const APInt &OriginalDemandedElts,
                                         KnownBits &Known,
                                         TargetLoweringOpt &TLO,
                                         unsigned Depth) const override;
 
  void ReplaceNodeResults(SDNode * N,
                          SmallVectorImpl<SDValue> &Results,
                          SelectionDAG &DAG) const override;
 
  SDValue combineFMinMaxLegacyImpl(const SDLoc &DL, EVT VT, SDValue LHS,
                                   SDValue RHS, SDValue True, SDValue False,
                                   SDValue CC, SDNodeFlags Flags,
                                   DAGCombinerInfo &DCI) const;
 
  /// \p Flags must be the select flags, not the compare (SELECT_CC
  /// flags come from the fcmp and say nothing about the selected value).
  SDValue combineFMinMaxLegacy(const SDLoc &DL, EVT VT, SDValue LHS,
                               SDValue RHS, SDValue True, SDValue False,
                               SDValue CC, SDNodeFlags Flags,
                               DAGCombinerInfo &DCI) const;
 
  // FIXME: Turn off MergeConsecutiveStores() before Instruction Selection for
  // AMDGPU.  Commit r319036,
  // (https://github.com/llvm/llvm-project/commit/db77e57ea86d941a4262ef60261692f4cb6893e6)
  // turned on MergeConsecutiveStores() before Instruction Selection for all
  // targets.  Enough AMDGPU compiles go into an infinite loop (
  // MergeConsecutiveStores() merges two stores; LegalizeStoreOps() un-merges;
  // MergeConsecutiveStores() re-merges, etc. ) to warrant turning it off for
  // now.
  bool mergeStoresAfterLegalization(EVT) const override { return false; }
 
  bool isFsqrtCheap(SDValue Operand, SelectionDAG &DAG) const override {
    return true;
  }
  SDValue getSqrtEstimate(SDValue Operand, SelectionDAG &DAG, int Enabled,
                           int &RefinementSteps, bool &UseOneConstNR,
                           bool Reciprocal) const override;
  SDValue getRecipEstimate(SDValue Operand, SelectionDAG &DAG, int Enabled,
                           int &RefinementSteps) const override;
 
  virtual SDNode *PostISelFolding(MachineSDNode *N,
                                  SelectionDAG &DAG) const = 0;
 
  /// Determine which of the bits specified in \p Mask are known to be
  /// either zero or one and return them in the \p KnownZero and \p KnownOne
  /// bitsets.
  void computeKnownBitsForTargetNode(const SDValue Op,
                                     KnownBits &Known,
                                     const APInt &DemandedElts,
                                     const SelectionDAG &DAG,
                                     unsigned Depth = 0) const override;
 
  unsigned ComputeNumSignBitsForTargetNode(SDValue Op, const APInt &DemandedElts,
                                           const SelectionDAG &DAG,
                                           unsigned Depth = 0) const override;
 
  unsigned computeNumSignBitsForTargetInstr(GISelValueTracking &Analysis,
                                            Register R,
                                            const APInt &DemandedElts,
                                            const MachineRegisterInfo &MRI,
                                            unsigned Depth = 0) const override;
 
  bool canCreateUndefOrPoisonForTargetNode(
      SDValue Op, const APInt &DemandedElts, const SelectionDAG &DAG,
      UndefPoisonKind Kind, bool ConsiderFlags, unsigned Depth) const override;
 
  bool isKnownNeverNaNForTargetNode(SDValue Op, const APInt &DemandedElts,
                                    const SelectionDAG &DAG, bool SNaN = false,
                                    unsigned Depth = 0) const override;
 
  bool isReassocProfitable(MachineRegisterInfo &MRI, Register N0,
                           Register N1) const override;
 
  /// Helper function that adds Reg to the LiveIn list of the DAG's
  /// MachineFunction.
  ///
  /// \returns a RegisterSDNode representing Reg if \p RawReg is true, otherwise
  /// a copy from the register.
  SDValue CreateLiveInRegister(SelectionDAG &DAG,
                               const TargetRegisterClass *RC,
                               Register Reg, EVT VT,
                               const SDLoc &SL,
                               bool RawReg = false) const;
  SDValue CreateLiveInRegister(SelectionDAG &DAG,
                               const TargetRegisterClass *RC,
                               Register Reg, EVT VT) const {
    return CreateLiveInRegister(DAG, RC, Reg, VT, SDLoc(DAG.getEntryNode()));
  }
 
  // Returns the raw live in register rather than a copy from it.
  SDValue CreateLiveInRegisterRaw(SelectionDAG &DAG,
                                  const TargetRegisterClass *RC,
                                  Register Reg, EVT VT) const {
    return CreateLiveInRegister(DAG, RC, Reg, VT, SDLoc(DAG.getEntryNode()), true);
  }
 
  /// Similar to CreateLiveInRegister, except value maybe loaded from a stack
  /// slot rather than passed in a register.
  SDValue loadStackInputValue(SelectionDAG &DAG,
                              EVT VT,
                              const SDLoc &SL,
                              int64_t Offset) const;
 
  SDValue storeStackInputValue(SelectionDAG &DAG,
                               const SDLoc &SL,
                               SDValue Chain,
                               SDValue ArgVal,
                               int64_t Offset) const;
 
  SDValue loadInputValue(SelectionDAG &DAG,
                         const TargetRegisterClass *RC,
                         EVT VT, const SDLoc &SL,
                         const ArgDescriptor &Arg) const;
 
  enum ImplicitParameter {
    FIRST_IMPLICIT,
    PRIVATE_BASE,
    SHARED_BASE,
    QUEUE_PTR,
  };
 
  /// Helper function that returns the byte offset of the given
  /// type of implicit parameter.
  uint32_t getImplicitParameterOffset(const MachineFunction &MF,
                                      const ImplicitParameter Param) const;
  uint32_t getImplicitParameterOffset(const uint64_t ExplicitKernArgSize,
                                      const ImplicitParameter Param) const;
 
  MVT getFenceOperandTy(const DataLayout &DL) const override {
    return MVT::i32;
  }
 
  bool hasMultipleConditionRegisters(EVT VT) const override {
    // FIXME: This is only partially true. If we have to do vector compares, any
    // SGPR pair can be a condition register. If we have a uniform condition, we
    // are better off doing SALU operations, where there is only one SCC. For
    // now, we don't have a way of knowing during instruction selection if a
    // condition will be uniform and we always use vector compares. Assume we
    // are using vector compares until that is fixed.
    return true;
  }
};
 
/// Strip fabs/fneg/fcopysign from a value to get the underlying source.
/// Useful for comparing values where sign doesn't matter (e.g., frexp).
inline SDValue peekFPSignOps(SDValue Val) {
  while (Val.getOpcode() == ISD::FNEG || Val.getOpcode() == ISD::FABS ||
         Val.getOpcode() == ISD::FCOPYSIGN)
    Val = Val.getOperand(0);
  return Val;
}
 
} // End namespace llvm
 
#endif