SelectionDAGISel.h

Go to the documentation of this file.

//===-- llvm/CodeGen/SelectionDAGISel.h - Common Base Class------*- 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 implements the SelectionDAGISel class, which is used as the common
// base class for SelectionDAG-based instruction selectors.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CODEGEN_SELECTIONDAGISEL_H
#define LLVM_CODEGEN_SELECTIONDAGISEL_H
 
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/SelectionDAG.h"
#include "llvm/IR/BasicBlock.h"
#include <memory>
 
namespace llvm {
class AAResults;
class AssumptionCache;
class TargetInstrInfo;
class TargetMachine;
class SelectionDAGBuilder;
class SDValue;
class MachineRegisterInfo;
class MachineFunction;
class OptimizationRemarkEmitter;
class TargetLowering;
class TargetLibraryInfo;
class FunctionLoweringInfo;
class SwiftErrorValueTracking;
class GCFunctionInfo;
class ScheduleDAGSDNodes;
 
/// SelectionDAGISel - This is the common base class used for SelectionDAG-based
/// pattern-matching instruction selectors.
class SelectionDAGISel : public MachineFunctionPass {
public:
  TargetMachine &TM;
  const TargetLibraryInfo *LibInfo;
  std::unique_ptr<FunctionLoweringInfo> FuncInfo;
  SwiftErrorValueTracking *SwiftError;
  MachineFunction *MF;
  MachineRegisterInfo *RegInfo;
  SelectionDAG *CurDAG;
  std::unique_ptr<SelectionDAGBuilder> SDB;
  AAResults *AA = nullptr;
  AssumptionCache *AC = nullptr;
  GCFunctionInfo *GFI = nullptr;
  CodeGenOpt::Level OptLevel;
  const TargetInstrInfo *TII;
  const TargetLowering *TLI;
  bool FastISelFailed;
  SmallPtrSet<const Instruction *, 4> ElidedArgCopyInstrs;
 
  /// Current optimization remark emitter.
  /// Used to report things like combines and FastISel failures.
  std::unique_ptr<OptimizationRemarkEmitter> ORE;
 
  explicit SelectionDAGISel(char &ID, TargetMachine &tm,
                            CodeGenOpt::Level OL = CodeGenOpt::Default);
  ~SelectionDAGISel() override;
 
  const TargetLowering *getTargetLowering() const { return TLI; }
 
  void getAnalysisUsage(AnalysisUsage &AU) const override;
 
  bool runOnMachineFunction(MachineFunction &MF) override;
 
  virtual void emitFunctionEntryCode() {}
 
  /// PreprocessISelDAG - This hook allows targets to hack on the graph before
  /// instruction selection starts.
  virtual void PreprocessISelDAG() {}
 
  /// PostprocessISelDAG() - This hook allows the target to hack on the graph
  /// right after selection.
  virtual void PostprocessISelDAG() {}
 
  /// Main hook for targets to transform nodes into machine nodes.
  virtual void Select(SDNode *N) = 0;
 
  /// SelectInlineAsmMemoryOperand - Select the specified address as a target
  /// addressing mode, according to the specified constraint.  If this does
  /// not match or is not implemented, return true.  The resultant operands
  /// (which will appear in the machine instruction) should be added to the
  /// OutOps vector.
  virtual bool SelectInlineAsmMemoryOperand(const SDValue &Op,
                                            unsigned ConstraintID,
                                            std::vector<SDValue> &OutOps) {
    return true;
  }
 
  /// IsProfitableToFold - Returns true if it's profitable to fold the specific
  /// operand node N of U during instruction selection that starts at Root.
  virtual bool IsProfitableToFold(SDValue N, SDNode *U, SDNode *Root) const;
 
  /// IsLegalToFold - Returns true if the specific operand node N of
  /// U can be folded during instruction selection that starts at Root.
  /// FIXME: This is a static member function because the MSP430/X86
  /// targets, which uses it during isel.  This could become a proper member.
  static bool IsLegalToFold(SDValue N, SDNode *U, SDNode *Root,
                            CodeGenOpt::Level OptLevel,
                            bool IgnoreChains = false);
 
  static void InvalidateNodeId(SDNode *N);
  static int getUninvalidatedNodeId(SDNode *N);
 
  static void EnforceNodeIdInvariant(SDNode *N);
 
  // Opcodes used by the DAG state machine:
  enum BuiltinOpcodes {
    OPC_Scope,
    OPC_RecordNode,
    OPC_RecordChild0, OPC_RecordChild1, OPC_RecordChild2, OPC_RecordChild3,
    OPC_RecordChild4, OPC_RecordChild5, OPC_RecordChild6, OPC_RecordChild7,
    OPC_RecordMemRef,
    OPC_CaptureGlueInput,
    OPC_MoveChild,
    OPC_MoveChild0, OPC_MoveChild1, OPC_MoveChild2, OPC_MoveChild3,
    OPC_MoveChild4, OPC_MoveChild5, OPC_MoveChild6, OPC_MoveChild7,
    OPC_MoveParent,
    OPC_CheckSame,
    OPC_CheckChild0Same, OPC_CheckChild1Same,
    OPC_CheckChild2Same, OPC_CheckChild3Same,
    OPC_CheckPatternPredicate,
    OPC_CheckPredicate,
    OPC_CheckPredicateWithOperands,
    OPC_CheckOpcode,
    OPC_SwitchOpcode,
    OPC_CheckType,
    OPC_CheckTypeRes,
    OPC_SwitchType,
    OPC_CheckChild0Type, OPC_CheckChild1Type, OPC_CheckChild2Type,
    OPC_CheckChild3Type, OPC_CheckChild4Type, OPC_CheckChild5Type,
    OPC_CheckChild6Type, OPC_CheckChild7Type,
    OPC_CheckInteger,
    OPC_CheckChild0Integer, OPC_CheckChild1Integer, OPC_CheckChild2Integer,
    OPC_CheckChild3Integer, OPC_CheckChild4Integer,
    OPC_CheckCondCode, OPC_CheckChild2CondCode,
    OPC_CheckValueType,
    OPC_CheckComplexPat,
    OPC_CheckAndImm, OPC_CheckOrImm,
    OPC_CheckImmAllOnesV,
    OPC_CheckImmAllZerosV,
    OPC_CheckFoldableChainNode,
 
    OPC_EmitInteger,
    OPC_EmitStringInteger,
    OPC_EmitRegister,
    OPC_EmitRegister2,
    OPC_EmitConvertToTarget,
    OPC_EmitMergeInputChains,
    OPC_EmitMergeInputChains1_0,
    OPC_EmitMergeInputChains1_1,
    OPC_EmitMergeInputChains1_2,
    OPC_EmitCopyToReg,
    OPC_EmitCopyToReg2,
    OPC_EmitNodeXForm,
    OPC_EmitNode,
    // Space-optimized forms that implicitly encode number of result VTs.
    OPC_EmitNode0, OPC_EmitNode1, OPC_EmitNode2,
    OPC_MorphNodeTo,
    // Space-optimized forms that implicitly encode number of result VTs.
    OPC_MorphNodeTo0, OPC_MorphNodeTo1, OPC_MorphNodeTo2,
    OPC_CompleteMatch,
    // Contains offset in table for pattern being selected
    OPC_Coverage
  };
 
  enum {
    OPFL_None       = 0,  // Node has no chain or glue input and isn't variadic.
    OPFL_Chain      = 1,     // Node has a chain input.
    OPFL_GlueInput  = 2,     // Node has a glue input.
    OPFL_GlueOutput = 4,     // Node has a glue output.
    OPFL_MemRefs    = 8,     // Node gets accumulated MemRefs.
    OPFL_Variadic0  = 1<<4,  // Node is variadic, root has 0 fixed inputs.
    OPFL_Variadic1  = 2<<4,  // Node is variadic, root has 1 fixed inputs.
    OPFL_Variadic2  = 3<<4,  // Node is variadic, root has 2 fixed inputs.
    OPFL_Variadic3  = 4<<4,  // Node is variadic, root has 3 fixed inputs.
    OPFL_Variadic4  = 5<<4,  // Node is variadic, root has 4 fixed inputs.
    OPFL_Variadic5  = 6<<4,  // Node is variadic, root has 5 fixed inputs.
    OPFL_Variadic6  = 7<<4,  // Node is variadic, root has 6 fixed inputs.
 
    OPFL_VariadicInfo = OPFL_Variadic6
  };
 
  /// getNumFixedFromVariadicInfo - Transform an EmitNode flags word into the
  /// number of fixed arity values that should be skipped when copying from the
  /// root.
  static inline int getNumFixedFromVariadicInfo(unsigned Flags) {
    return ((Flags&OPFL_VariadicInfo) >> 4)-1;
  }
 
 
protected:
  /// DAGSize - Size of DAG being instruction selected.
  ///
  unsigned DAGSize = 0;
 
  /// ReplaceUses - replace all uses of the old node F with the use
  /// of the new node T.
  void ReplaceUses(SDValue F, SDValue T) {
    CurDAG->ReplaceAllUsesOfValueWith(F, T);
    EnforceNodeIdInvariant(T.getNode());
  }
 
  /// ReplaceUses - replace all uses of the old nodes F with the use
  /// of the new nodes T.
  void ReplaceUses(const SDValue *F, const SDValue *T, unsigned Num) {
    CurDAG->ReplaceAllUsesOfValuesWith(F, T, Num);
    for (unsigned i = 0; i < Num; ++i)
      EnforceNodeIdInvariant(T[i].getNode());
  }
 
  /// ReplaceUses - replace all uses of the old node F with the use
  /// of the new node T.
  void ReplaceUses(SDNode *F, SDNode *T) {
    CurDAG->ReplaceAllUsesWith(F, T);
    EnforceNodeIdInvariant(T);
  }
 
  /// Replace all uses of \c F with \c T, then remove \c F from the DAG.
  void ReplaceNode(SDNode *F, SDNode *T) {
    CurDAG->ReplaceAllUsesWith(F, T);
    EnforceNodeIdInvariant(T);
    CurDAG->RemoveDeadNode(F);
  }
 
  /// SelectInlineAsmMemoryOperands - Calls to this are automatically generated
  /// by tblgen.  Others should not call it.
  void SelectInlineAsmMemoryOperands(std::vector<SDValue> &Ops,
                                     const SDLoc &DL);
 
  /// getPatternForIndex - Patterns selected by tablegen during ISEL
  virtual StringRef getPatternForIndex(unsigned index) {
    llvm_unreachable("Tblgen should generate the implementation of this!");
  }
 
  /// getIncludePathForIndex - get the td source location of pattern instantiation
  virtual StringRef getIncludePathForIndex(unsigned index) {
    llvm_unreachable("Tblgen should generate the implementation of this!");
  }
 
  bool shouldOptForSize(const MachineFunction *MF) const {
    return CurDAG->shouldOptForSize();
  }
 
public:
  // Calls to these predicates are generated by tblgen.
  bool CheckAndMask(SDValue LHS, ConstantSDNode *RHS,
                    int64_t DesiredMaskS) const;
  bool CheckOrMask(SDValue LHS, ConstantSDNode *RHS,
                    int64_t DesiredMaskS) const;
 
 
  /// CheckPatternPredicate - This function is generated by tblgen in the
  /// target.  It runs the specified pattern predicate and returns true if it
  /// succeeds or false if it fails.  The number is a private implementation
  /// detail to the code tblgen produces.
  virtual bool CheckPatternPredicate(unsigned PredNo) const {
    llvm_unreachable("Tblgen should generate the implementation of this!");
  }
 
  /// CheckNodePredicate - This function is generated by tblgen in the target.
  /// It runs node predicate number PredNo and returns true if it succeeds or
  /// false if it fails.  The number is a private implementation
  /// detail to the code tblgen produces.
  virtual bool CheckNodePredicate(SDNode *N, unsigned PredNo) const {
    llvm_unreachable("Tblgen should generate the implementation of this!");
  }
 
  /// CheckNodePredicateWithOperands - This function is generated by tblgen in
  /// the target.
  /// It runs node predicate number PredNo and returns true if it succeeds or
  /// false if it fails.  The number is a private implementation detail to the
  /// code tblgen produces.
  virtual bool CheckNodePredicateWithOperands(
      SDNode *N, unsigned PredNo,
      const SmallVectorImpl<SDValue> &Operands) const {
    llvm_unreachable("Tblgen should generate the implementation of this!");
  }
 
  virtual bool CheckComplexPattern(SDNode *Root, SDNode *Parent, SDValue N,
                                   unsigned PatternNo,
                        SmallVectorImpl<std::pair<SDValue, SDNode*> > &Result) {
    llvm_unreachable("Tblgen should generate the implementation of this!");
  }
 
  virtual SDValue RunSDNodeXForm(SDValue V, unsigned XFormNo) {
    llvm_unreachable("Tblgen should generate this!");
  }
 
  void SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
                        unsigned TableSize);
 
  /// Return true if complex patterns for this target can mutate the
  /// DAG.
  virtual bool ComplexPatternFuncMutatesDAG() const {
    return false;
  }
 
  /// Return whether the node may raise an FP exception.
  bool mayRaiseFPException(SDNode *Node) const;
 
  bool isOrEquivalentToAdd(const SDNode *N) const;
 
private:
 
  // Calls to these functions are generated by tblgen.
  void Select_INLINEASM(SDNode *N);
  void Select_READ_REGISTER(SDNode *Op);
  void Select_WRITE_REGISTER(SDNode *Op);
  void Select_UNDEF(SDNode *N);
  void CannotYetSelect(SDNode *N);
 
  void Select_FREEZE(SDNode *N);
  void Select_ARITH_FENCE(SDNode *N);
  void Select_MEMBARRIER(SDNode *N);
 
  void pushStackMapLiveVariable(SmallVectorImpl<SDValue> &Ops, SDValue Operand,
                                SDLoc DL);
  void Select_STACKMAP(SDNode *N);
  void Select_PATCHPOINT(SDNode *N);
 
private:
  void DoInstructionSelection();
  SDNode *MorphNode(SDNode *Node, unsigned TargetOpc, SDVTList VTList,
                    ArrayRef<SDValue> Ops, unsigned EmitNodeInfo);
 
  /// Prepares the landing pad to take incoming values or do other EH
  /// personality specific tasks. Returns true if the block should be
  /// instruction selected, false if no code should be emitted for it.
  bool PrepareEHLandingPad();
 
  // Mark and Report IPToState for each Block under AsynchEH
  void reportIPToStateForBlocks(MachineFunction *Fn);
 
  /// Perform instruction selection on all basic blocks in the function.
  void SelectAllBasicBlocks(const Function &Fn);
 
  /// Perform instruction selection on a single basic block, for
  /// instructions between \p Begin and \p End.  \p HadTailCall will be set
  /// to true if a call in the block was translated as a tail call.
  void SelectBasicBlock(BasicBlock::const_iterator Begin,
                        BasicBlock::const_iterator End,
                        bool &HadTailCall);
  void FinishBasicBlock();
 
  void CodeGenAndEmitDAG();
 
  /// Generate instructions for lowering the incoming arguments of the
  /// given function.
  void LowerArguments(const Function &F);
 
  void ComputeLiveOutVRegInfo();
 
  /// Create the scheduler. If a specific scheduler was specified
  /// via the SchedulerRegistry, use it, otherwise select the
  /// one preferred by the target.
  ///
  ScheduleDAGSDNodes *CreateScheduler();
 
  /// OpcodeOffset - This is a cache used to dispatch efficiently into isel
  /// state machines that start with a OPC_SwitchOpcode node.
  std::vector<unsigned> OpcodeOffset;
 
  void UpdateChains(SDNode *NodeToMatch, SDValue InputChain,
                    SmallVectorImpl<SDNode *> &ChainNodesMatched,
                    bool isMorphNodeTo);
};
 
}
 
#endif /* LLVM_CODEGEN_SELECTIONDAGISEL_H */