LLVM 源码分析 （一） pass 类

Pass interface - Implemented by all 'passes'. Subclass this if you are an interprocedural optimization or you do not fit into any of the more constrained passes described below. 

 

摘取自pass.h  更清晰显示pass类

#include "llvm/Support/Compiler.h"
#include <string>

namespace llvm {

class BasicBlock;
class Function;
class Module;
class AnalysisUsage;
class PassInfo;
class ImmutablePass;
class PMStack;
class AnalysisResolver;
class PMDataManager;
class raw_ostream;
class StringRef;

// AnalysisID - Use the PassInfo to identify a pass...
typedef const void* AnalysisID;

/// Different types of internal pass managers. External pass managers
/// (PassManager and FunctionPassManager) are not represented here.
/// Ordering of pass manager types is important here.
enum PassManagerType {
  PMT_Unknown = 0,
  PMT_ModulePassManager = 1, ///< MPPassManager
  PMT_CallGraphPassManager,  ///< CGPassManager
  PMT_FunctionPassManager,   ///< FPPassManager
  PMT_LoopPassManager,       ///< LPPassManager
  PMT_RegionPassManager,     ///< RGPassManager
  PMT_BasicBlockPassManager, ///< BBPassManager
  PMT_Last
};

// Different types of passes.
enum PassKind {
  PT_BasicBlock,
  PT_Region,
  PT_Loop,
  PT_Function,
  PT_CallGraphSCC,
  PT_Module,
  PT_PassManager
};

//===----------------------------------------------------------------------===//
/// Pass interface - Implemented by all 'passes'.  Subclass this if you are an
/// interprocedural optimization or you do not fit into any of the more
/// constrained passes described below.
///
class Pass {
  AnalysisResolver *Resolver;  // Used to resolve analysis
  const void *PassID;
  PassKind Kind;
  void operator=(const Pass&) LLVM_DELETED_FUNCTION;
  Pass(const Pass &) LLVM_DELETED_FUNCTION;

public:
  explicit Pass(PassKind K, char &pid) : Resolver(0), PassID(&pid), Kind(K) { }
  virtual ~Pass();


  PassKind getPassKind() const { return Kind; }

  /// getPassName - Return a nice clean name for a pass.  This usually
  /// implemented in terms of the name that is registered by one of the
  /// Registration templates, but can be overloaded directly.
  ///
  virtual const char *getPassName() const;

  /// getPassID - Return the PassID number that corresponds to this pass.
  AnalysisID getPassID() const {
    return PassID;
  }

  /// print - Print out the internal state of the pass.  This is called by
  /// Analyze to print out the contents of an analysis.  Otherwise it is not
  /// necessary to implement this method.  Beware that the module pointer MAY be
  /// null.  This automatically forwards to a virtual function that does not
  /// provide the Module* in case the analysis doesn't need it it can just be
  /// ignored.
  ///
  virtual void print(raw_ostream &O, const Module *M) const;
  void dump() const; // dump - Print to stderr.

  /// createPrinterPass - Get a Pass appropriate to print the IR this
  /// pass operates on (Module, Function or MachineFunction).
  virtual Pass *createPrinterPass(raw_ostream &O,
                                  const std::string &Banner) const = 0;

  /// Each pass is responsible for assigning a pass manager to itself.
  /// PMS is the stack of available pass manager.
  virtual void assignPassManager(PMStack &,
                                 PassManagerType) {}
  /// Check if available pass managers are suitable for this pass or not.
  virtual void preparePassManager(PMStack &);

  ///  Return what kind of Pass Manager can manage this pass.
  virtual PassManagerType getPotentialPassManagerType() const;

  // Access AnalysisResolver
  void setResolver(AnalysisResolver *AR);
  AnalysisResolver *getResolver() const { return Resolver; }

  /// getAnalysisUsage - This function should be overriden by passes that need
  /// analysis information to do their job.  If a pass specifies that it uses a
  /// particular analysis result to this function, it can then use the
  /// getAnalysis<AnalysisType>() function, below.
  ///
  virtual void getAnalysisUsage(AnalysisUsage &) const;

  /// releaseMemory() - This member can be implemented by a pass if it wants to
  /// be able to release its memory when it is no longer needed.  The default
  /// behavior of passes is to hold onto memory for the entire duration of their
  /// lifetime (which is the entire compile time).  For pipelined passes, this
  /// is not a big deal because that memory gets recycled every time the pass is
  /// invoked on another program unit.  For IP passes, it is more important to
  /// free memory when it is unused.
  ///
  /// Optionally implement this function to release pass memory when it is no
  /// longer used.
  ///
  virtual void releaseMemory();

  /// getAdjustedAnalysisPointer - This method is used when a pass implements
  /// an analysis interface through multiple inheritance.  If needed, it should
  /// override this to adjust the this pointer as needed for the specified pass
  /// info.
  virtual void *getAdjustedAnalysisPointer(AnalysisID ID);
  virtual ImmutablePass *getAsImmutablePass();
  virtual PMDataManager *getAsPMDataManager();

  /// verifyAnalysis() - This member can be implemented by a analysis pass to
  /// check state of analysis information.
  virtual void verifyAnalysis() const;

  // dumpPassStructure - Implement the -debug-passes=PassStructure option
  virtual void dumpPassStructure(unsigned Offset = 0);

  // lookupPassInfo - Return the pass info object for the specified pass class,
  // or null if it is not known.
  static const PassInfo *lookupPassInfo(const void *TI);

  // lookupPassInfo - Return the pass info object for the pass with the given
  // argument string, or null if it is not known.
  static const PassInfo *lookupPassInfo(StringRef Arg);

  // createPass - Create a object for the specified pass class,
  // or null if it is not known.
  static Pass *createPass(AnalysisID ID);

  /// getAnalysisIfAvailable<AnalysisType>() - Subclasses use this function to
  /// get analysis information that might be around, for example to update it.
  /// This is different than getAnalysis in that it can fail (if the analysis
  /// results haven't been computed), so should only be used if you can handle
  /// the case when the analysis is not available.  This method is often used by
  /// transformation APIs to update analysis results for a pass automatically as
  /// the transform is performed.
  ///
  template<typename AnalysisType> AnalysisType *
    getAnalysisIfAvailable() const; // Defined in PassAnalysisSupport.h

  /// mustPreserveAnalysisID - This method serves the same function as
  /// getAnalysisIfAvailable, but works if you just have an AnalysisID.  This
  /// obviously cannot give you a properly typed instance of the class if you
  /// don't have the class name available (use getAnalysisIfAvailable if you
  /// do), but it can tell you if you need to preserve the pass at least.
  ///
  bool mustPreserveAnalysisID(char &AID) const;

  /// getAnalysis<AnalysisType>() - This function is used by subclasses to get
  /// to the analysis information that they claim to use by overriding the
  /// getAnalysisUsage function.
  ///
  template<typename AnalysisType>
  AnalysisType &getAnalysis() const; // Defined in PassAnalysisSupport.h

  template<typename AnalysisType>
  AnalysisType &getAnalysis(Function &F); // Defined in PassAnalysisSupport.h

  template<typename AnalysisType>
  AnalysisType &getAnalysisID(AnalysisID PI) const;

  template<typename AnalysisType>
  AnalysisType &getAnalysisID(AnalysisID PI, Function &F);
};

来自vs2008

来自doxygen

1.assignPassManager

  /// Each pass is responsible for assigning a pass manager to itself.
  /// PMS is the stack of available pass manager.
  virtual void assignPassManager(PMStack &,
                                 PassManagerType) {}

 Reimplemented in llvm::BasicBlockPass, llvm::FunctionPass, llvm::ModulePass, llvm::RegionPass, llvm::CallGraphSCCPass, and llvm::LoopPass.

eg.

  // Add the requested pass to the best available pass manager.
  P->assignPassManager(activeStack, getTopLevelPassManagerType());

2.preparePassManager

 

  /// Check if available pass managers are suitable for this pass or not.
  virtual void preparePassManager(PMStack &);

eg.

  // Give pass a chance to prepare the stage.
  P->preparePassManager(activeStack);

3.getPotentialPassManagerType

  ///  Return what kind of Pass Manager can manage this pass.
  virtual PassManagerType getPotentialPassManagerType() const;

4.getPassManagerType

  virtual PassManagerType getPassManagerType() const { 
    return PMT_CallGraphPassManager; 
  }
  

 

enum PassManagerType {
  PMT_Unknown = 0,
  PMT_ModulePassManager = 1, ///< MPPassManager
  PMT_CallGraphPassManager,  ///< CGPassManager
  PMT_FunctionPassManager,   ///< FPPassManager
  PMT_LoopPassManager,       ///< LPPassManager
  PMT_RegionPassManager,     ///< RGPassManager
  PMT_BasicBlockPassManager, ///< BBPassManager
  PMT_Last
};

 

5.createPass

  // createPass - Create a object for the specified pass class,
  // or null if it is not known.
  static Pass *createPass(AnalysisID ID);

 eg.

  AnalysisID FinalID = overridePass(PassID, TargetID);
  if (FinalID == 0)
    return FinalID;

  Pass *P = Pass::createPass(FinalID);

6.createPrinterPass

  /// createPrinterPass - Get a Pass appropriate to print the IR this
  /// pass operates on (Module, Function or MachineFunction).
  virtual Pass *createPrinterPass(raw_ostream &O,
                                  const std::string &Banner) const = 0;

 Implemented in llvm::PassManagerImpl, llvm::BasicBlockPass, llvm::MPPassManager, llvm::FunctionPass, llvm::ModulePass, llvm::FunctionPassManagerImpl, llvm::RegionPass, llvm::CallGraphSCCPass, and llvm::LoopPass.

eg.

    Pass *PP = P->createPrinterPass(
      dbgs(), std::string("*** IR Dump Before ") + P->getPassName() + " ***");

7.print

 /// print - Print out the internal state of the pass.  This is called by
  /// Analyze to print out the contents of an analysis.  Otherwise it is not
  /// necessary to implement this method.  Beware that the module pointer MAY be
  /// null.  This automatically forwards to a virtual function that does not
  /// provide the Module* in case the analysis doesn't need it it can just be
  /// ignored.
  ///
  virtual void print(raw_ostream &O, const Module *M) const;

8.dump

    /// dump - print descriptor to dbgs() with a newline.
    void dump() const;

9 getPassName

/// getPassName - Return a nice clean name for a pass.  This usually
/// implemented in terms of the name that is registered by one of the
/// Registration templates, but can be overloaded directly.
///
const char *Pass::getPassName() const {
  AnalysisID AID =  getPassID();
  const PassInfo *PI = PassRegistry::getPassRegistry()->getPassInfo(AID);
  if (PI)
    return PI->getPassName();
  return "Unnamed pass: implement Pass::getPassName()";
}

 

10.getPassID

  /// getPassID - Return the PassID number that corresponds to this pass.
  AnalysisID getPassID() const {
    return PassID;
  }

11. getPassKind

PassKind getPassKind() const { return Kind; }

12.setResolver

void Pass::setResolver(AnalysisResolver *AR) {
  assert(!Resolver && "Resolver is already set");
  Resolver = AR;
}

13.getResolver

 AnalysisResolver *getResolver() const { return Resolver; }

 

14.

  /// getAnalysisUsage - This function should be overriden by passes that need
  /// analysis information to do their job.  If a pass specifies that it uses a
  /// particular analysis result to this function, it can then use the
  /// getAnalysis<AnalysisType>() function, below.
  ///
  virtual void getAnalysisUsage(AnalysisUsage &) const;

eg

 virtual void getAnalysisUsage(AnalysisUsage &AU) const;

15.getAnalysis

 /// getAnalysis<AnalysisType>() - This function is used by subclasses to get
  /// to the analysis information that they claim to use by overriding the
  /// getAnalysisUsage function.
  ///
  template<typename AnalysisType>
  AnalysisType &getAnalysis() const; // Defined in PassAnalysisSupport.h

  template<typename AnalysisType>
  AnalysisType &getAnalysis(Function &F); // Defined in PassAnalysisSupport.h

16 mustPreserveAnalysisID

 /// mustPreserveAnalysisID - This method serves the same function as
  /// getAnalysisIfAvailable, but works if you just have an AnalysisID.  This
  /// obviously cannot give you a properly typed instance of the class if you
  /// don't have the class name available (use getAnalysisIfAvailable if you
  /// do), but it can tell you if you need to preserve the pass at least.
        bool Pass::mustPreserveAnalysisID(char &AID) const {
  return Resolver->getAnalysisIfAvailable(&AID, true) != 0;
}

 

17.getAnalysisIfAvailable<AnalysisType>()

  /// getAnalysisIfAvailable<AnalysisType>() - Subclasses use this function to
  /// get analysis information that might be around, for example to update it.
  /// This is different than getAnalysis in that it can fail (if the analysis
  /// results haven't been computed), so should only be used if you can handle
  /// the case when the analysis is not available.  This method is often used by
  /// transformation APIs to update analysis results for a pass automatically as
  /// the transform is performed.
  ///
  template<typename AnalysisType> AnalysisType *
    getAnalysisIfAvailable() const; // Defined in PassAnalysisSupport.h

eg

MachineDominatorTree *MDT =  P->getAnalysisIfAvailable<MachineDominatorTree>()

18.  lookupPassInfo 用处很小 整个源码都没有用到

// lookupPassInfo - Return the pass info object for the pass with the given
  // argument string, or null if it is not known.
  static const PassInfo *lookupPassInfo(StringRef Arg);

19,getAdjustedAnalysisPointer
 

  /// getAdjustedAnalysisPointer - This method is used when a pass implements
  /// an analysis interface through multiple inheritance.  If needed, it should
  /// override this to adjust the this pointer as needed for the specified pass
  /// info.
  virtual void *getAdjustedAnalysisPointer(AnalysisID ID);

20.releaseMemory

  /// releaseMemory() - This member can be implemented by a pass if it wants to
  /// be able to release its memory when it is no longer needed.  The default
  /// behavior of passes is to hold onto memory for the entire duration of their
  /// lifetime (which is the entire compile time).  For pipelined passes, this
  /// is not a big deal because that memory gets recycled every time the pass is
  /// invoked on another program unit.  For IP passes, it is more important to
  /// free memory when it is unused.
  ///
  /// Optionally implement this function to release pass memory when it is no
  /// longer used.
  ///
  virtual void releaseMemory();