SelectionDAGTargetInfo.h

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//==- llvm/CodeGen/SelectionDAGTargetInfo.h - SelectionDAG Info --*- C++ -*-==//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file declares the SelectionDAGTargetInfo class, which targets can
// subclass to parameterize the SelectionDAG lowering and instruction
// selection process.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_SELECTIONDAGTARGETINFO_H
#define LLVM_CODEGEN_SELECTIONDAGTARGETINFO_H

#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/SelectionDAGNodes.h"
#include "llvm/Support/CodeGen.h"
#include <utility>

namespace llvm {

class SelectionDAG;

//===----------------------------------------------------------------------===//
/// Targets can subclass this to parameterize the
/// SelectionDAG lowering and instruction selection process.
///
class SelectionDAGTargetInfo {
public:
  explicit SelectionDAGTargetInfo() = default;
  SelectionDAGTargetInfo(const SelectionDAGTargetInfo &) = delete;
  SelectionDAGTargetInfo &operator=(const SelectionDAGTargetInfo &) = delete;
  virtual ~SelectionDAGTargetInfo();

  /// Emit target-specific code that performs a memcpy.
  /// This can be used by targets to provide code sequences for cases
  /// that don't fit the target's parameters for simple loads/stores and can be
  /// more efficient than using a library call. This function can return a null
  /// SDValue if the target declines to use custom code and a different
  /// lowering strategy should be used.
  ///
  /// If AlwaysInline is true, the size is constant and the target should not
  /// emit any calls and is strongly encouraged to attempt to emit inline code
  /// even if it is beyond the usual threshold because this intrinsic is being
  /// expanded in a place where calls are not feasible (e.g. within the prologue
  /// for another call). If the target chooses to decline an AlwaysInline
  /// request here, legalize will resort to using simple loads and stores.
  virtual SDValue EmitTargetCodeForMemcpy(SelectionDAG &DAG, const SDLoc &dl,
                                          SDValue Chain, SDValue Op1,
                                          SDValue Op2, SDValue Op3,
                                          unsigned Align, bool isVolatile,
                                          bool AlwaysInline,
                                          MachinePointerInfo DstPtrInfo,
                                          MachinePointerInfo SrcPtrInfo) const {
    return SDValue();
  }

  /// Emit target-specific code that performs a memmove.
  /// This can be used by targets to provide code sequences for cases
  /// that don't fit the target's parameters for simple loads/stores and can be
  /// more efficient than using a library call. This function can return a null
  /// SDValue if the target declines to use custom code and a different
  /// lowering strategy should be used.
  virtual SDValue EmitTargetCodeForMemmove(
      SelectionDAG &DAG, const SDLoc &dl, SDValue Chain, SDValue Op1,
      SDValue Op2, SDValue Op3, unsigned Align, bool isVolatile,
      MachinePointerInfo DstPtrInfo, MachinePointerInfo SrcPtrInfo) const {
    return SDValue();
  }

  /// Emit target-specific code that performs a memset.
  /// This can be used by targets to provide code sequences for cases
  /// that don't fit the target's parameters for simple stores and can be more
  /// efficient than using a library call. This function can return a null
  /// SDValue if the target declines to use custom code and a different
  /// lowering strategy should be used.
  virtual SDValue EmitTargetCodeForMemset(SelectionDAG &DAG, const SDLoc &dl,
                                          SDValue Chain, SDValue Op1,
                                          SDValue Op2, SDValue Op3,
                                          unsigned Align, bool isVolatile,
                                          MachinePointerInfo DstPtrInfo) const {
    return SDValue();
  }

  /// Emit target-specific code that performs a memcmp, in cases where that is
  /// faster than a libcall. The first returned SDValue is the result of the
  /// memcmp and the second is the chain. Both SDValues can be null if a normal
  /// libcall should be used.
  virtual std::pair<SDValue, SDValue>
  EmitTargetCodeForMemcmp(SelectionDAG &DAG, const SDLoc &dl, SDValue Chain,
                          SDValue Op1, SDValue Op2, SDValue Op3,
                          MachinePointerInfo Op1PtrInfo,
                          MachinePointerInfo Op2PtrInfo) const {
    return std::make_pair(SDValue(), SDValue());
  }

  /// Emit target-specific code that performs a memchr, in cases where that is
  /// faster than a libcall. The first returned SDValue is the result of the
  /// memchr and the second is the chain. Both SDValues can be null if a normal
  /// libcall should be used.
  virtual std::pair<SDValue, SDValue>
  EmitTargetCodeForMemchr(SelectionDAG &DAG, const SDLoc &dl, SDValue Chain,
                          SDValue Src, SDValue Char, SDValue Length,
                          MachinePointerInfo SrcPtrInfo) const {
    return std::make_pair(SDValue(), SDValue());
  }

  /// Emit target-specific code that performs a strcpy or stpcpy, in cases
  /// where that is faster than a libcall.
  /// The first returned SDValue is the result of the copy (the start
  /// of the destination string for strcpy, a pointer to the null terminator
  /// for stpcpy) and the second is the chain.  Both SDValues can be null
  /// if a normal libcall should be used.
  virtual std::pair<SDValue, SDValue>
  EmitTargetCodeForStrcpy(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain,
                          SDValue Dest, SDValue Src,
                          MachinePointerInfo DestPtrInfo,
                          MachinePointerInfo SrcPtrInfo, bool isStpcpy) const {
    return std::make_pair(SDValue(), SDValue());
  }

  /// Emit target-specific code that performs a strcmp, in cases where that is
  /// faster than a libcall.
  /// The first returned SDValue is the result of the strcmp and the second is
  /// the chain. Both SDValues can be null if a normal libcall should be used.
  virtual std::pair<SDValue, SDValue>
  EmitTargetCodeForStrcmp(SelectionDAG &DAG, const SDLoc &dl, SDValue Chain,
                          SDValue Op1, SDValue Op2,
                          MachinePointerInfo Op1PtrInfo,
                          MachinePointerInfo Op2PtrInfo) const {
    return std::make_pair(SDValue(), SDValue());
  }

  virtual std::pair<SDValue, SDValue>
  EmitTargetCodeForStrlen(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain,
                          SDValue Src, MachinePointerInfo SrcPtrInfo) const {
    return std::make_pair(SDValue(), SDValue());
  }

  virtual std::pair<SDValue, SDValue>
  EmitTargetCodeForStrnlen(SelectionDAG &DAG, const SDLoc &DL, SDValue Chain,
                           SDValue Src, SDValue MaxLength,
                           MachinePointerInfo SrcPtrInfo) const {
    return std::make_pair(SDValue(), SDValue());
  }

  // Return true when the decision to generate FMA's (or FMS, FMLA etc) rather
  // than FMUL and ADD is delegated to the machine combiner.
  virtual bool generateFMAsInMachineCombiner(CodeGenOpt::Level OptLevel) const {
    return false;
  }
};

} // end namespace llvm

#endif // LLVM_CODEGEN_SELECTIONDAGTARGETINFO_H