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 //===- llvm/PassAnalysisSupport.h - Analysis Pass Support code --*- 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 stuff that is used to define and "use" Analysis Passes.
 // This file is automatically #included by Pass.h, so:
 //
 //           NO .CPP FILES SHOULD INCLUDE THIS FILE DIRECTLY
 //
 // Instead, #include Pass.h
 //
 //===----------------------------------------------------------------------===//
 
 #if !defined(LLVM_PASS_H) || defined(LLVM_PASSANALYSISSUPPORT_H)
 #error "Do not include <PassAnalysisSupport.h>; include <Pass.h> instead"
 #endif
 
 #ifndef LLVM_PASSANALYSISSUPPORT_H
 #define LLVM_PASSANALYSISSUPPORT_H
 
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include <cassert>
 #include <tuple>
 #include <utility>
 #include <vector>
 
 namespace llvm {
 
 class Function;
 class Pass;
 class PMDataManager;
 class StringRef;
 
 //===----------------------------------------------------------------------===//
 /// Represent the analysis usage information of a pass.  This tracks analyses
 /// that the pass REQUIRES (must be available when the pass runs), REQUIRES
 /// TRANSITIVE (must be available throughout the lifetime of the pass), and
 /// analyses that the pass PRESERVES (the pass does not invalidate the results
 /// of these analyses).  This information is provided by a pass to the Pass
 /// infrastructure through the getAnalysisUsage virtual function.
 ///
 class AnalysisUsage {
 public:
   using VectorType = SmallVectorImpl<AnalysisID>;
 
 private:
   /// Sets of analyses required and preserved by a pass
   // TODO: It's not clear that SmallVector is an appropriate data structure for
   // this usecase.  The sizes were picked to minimize wasted space, but are
   // otherwise fairly meaningless.
   SmallVector<AnalysisID, 8> Required;
   SmallVector<AnalysisID, 2> RequiredTransitive;
   SmallVector<AnalysisID, 2> Preserved;
   SmallVector<AnalysisID, 0> Used;
   bool PreservesAll = false;
 
   void pushUnique(VectorType &Set, AnalysisID ID) {
     if (!llvm::is_contained(Set, ID))
       Set.push_back(ID);
   }
 
 public:
   AnalysisUsage() = default;
 
   ///@{
   /// Add the specified ID to the required set of the usage info for a pass.
   AnalysisUsage &addRequiredID(const void *ID);
   AnalysisUsage &addRequiredID(char &ID);
   template<class PassClass>
   AnalysisUsage &addRequired() {
     return addRequiredID(PassClass::ID);
   }
 
   AnalysisUsage &addRequiredTransitiveID(char &ID);
   template<class PassClass>
   AnalysisUsage &addRequiredTransitive() {
     return addRequiredTransitiveID(PassClass::ID);
   }
   ///@}
 
   ///@{
   /// Add the specified ID to the set of analyses preserved by this pass.
   AnalysisUsage &addPreservedID(const void *ID) {
     pushUnique(Preserved, ID);
     return *this;
   }
   AnalysisUsage &addPreservedID(char &ID) {
     pushUnique(Preserved, &ID);
     return *this;
   }
   /// Add the specified Pass class to the set of analyses preserved by this pass.
   template<class PassClass>
   AnalysisUsage &addPreserved() {
     pushUnique(Preserved, &PassClass::ID);
     return *this;
   }
   ///@}
 
   ///@{
   /// Add the specified ID to the set of analyses used by this pass if they are
   /// available..
   AnalysisUsage &addUsedIfAvailableID(const void *ID) {
     pushUnique(Used, ID);
     return *this;
   }
   AnalysisUsage &addUsedIfAvailableID(char &ID) {
     pushUnique(Used, &ID);
     return *this;
   }
   /// Add the specified Pass class to the set of analyses used by this pass.
   template<class PassClass>
   AnalysisUsage &addUsedIfAvailable() {
     pushUnique(Used, &PassClass::ID);
     return *this;
   }
   ///@}
 
   /// Add the Pass with the specified argument string to the set of analyses
   /// preserved by this pass. If no such Pass exists, do nothing. This can be
   /// useful when a pass is trivially preserved, but may not be linked in. Be
   /// careful about spelling!
   AnalysisUsage &addPreserved(StringRef Arg);
 
   /// Set by analyses that do not transform their input at all
   void setPreservesAll() { PreservesAll = true; }
 
   /// Determine whether a pass said it does not transform its input at all
   bool getPreservesAll() const { return PreservesAll; }
 
   /// This function should be called by the pass, iff they do not:
   ///
   ///  1. Add or remove basic blocks from the function
   ///  2. Modify terminator instructions in any way.
   ///
   /// This function annotates the AnalysisUsage info object to say that analyses
   /// that only depend on the CFG are preserved by this pass.
   void setPreservesCFG();
 
   const VectorType &getRequiredSet() const { return Required; }
   const VectorType &getRequiredTransitiveSet() const {
     return RequiredTransitive;
   }
   const VectorType &getPreservedSet() const { return Preserved; }
   const VectorType &getUsedSet() const { return Used; }
 };
 
 //===----------------------------------------------------------------------===//
 /// AnalysisResolver - Simple interface used by Pass objects to pull all
 /// analysis information out of pass manager that is responsible to manage
 /// the pass.
 ///
 class AnalysisResolver {
 public:
   AnalysisResolver() = delete;
   explicit AnalysisResolver(PMDataManager &P) : PM(P) {}
 
   PMDataManager &getPMDataManager() { return PM; }
 
   /// Find pass that is implementing PI.
   Pass *findImplPass(AnalysisID PI) {
     Pass *ResultPass = nullptr;
     for (const auto &AnalysisImpl : AnalysisImpls) {
       if (AnalysisImpl.first == PI) {
         ResultPass = AnalysisImpl.second;
         break;
       }
     }
     return ResultPass;
   }
 
   /// Find pass that is implementing PI. Initialize pass for Function F.
   std::tuple<Pass *, bool> findImplPass(Pass *P, AnalysisID PI, Function &F);
 
   void addAnalysisImplsPair(AnalysisID PI, Pass *P) {
     if (findImplPass(PI) == P)
       return;
     std::pair<AnalysisID, Pass*> pir = std::make_pair(PI,P);
     AnalysisImpls.push_back(pir);
   }
 
   /// Clear cache that is used to connect a pass to the analysis (PassInfo).
   void clearAnalysisImpls() {
     AnalysisImpls.clear();
   }
 
   /// Return analysis result or null if it doesn't exist.
   Pass *getAnalysisIfAvailable(AnalysisID ID) const;
 
 private:
   /// This keeps track of which passes implements the interfaces that are
   /// required by the current pass (to implement getAnalysis()).
   std::vector<std::pair<AnalysisID, Pass *>> AnalysisImpls;
 
   /// PassManager that is used to resolve analysis info
   PMDataManager &PM;
 };
 
 /// 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 *Pass::getAnalysisIfAvailable() const {
   assert(Resolver && "Pass not resident in a PassManager object!");
 
   const void *PI = &AnalysisType::ID;
 
   Pass *ResultPass = Resolver->getAnalysisIfAvailable(PI);
   if (!ResultPass) return nullptr;
 
   // Because the AnalysisType may not be a subclass of pass (for
   // AnalysisGroups), we use getAdjustedAnalysisPointer here to potentially
   // adjust the return pointer (because the class may multiply inherit, once
   // from pass, once from AnalysisType).
   return (AnalysisType*)ResultPass->getAdjustedAnalysisPointer(PI);
 }
 
 /// 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 &Pass::getAnalysis() const {
   assert(Resolver && "Pass has not been inserted into a PassManager object!");
   return getAnalysisID<AnalysisType>(&AnalysisType::ID);
 }
 
 template<typename AnalysisType>
 AnalysisType &Pass::getAnalysisID(AnalysisID PI) const {
   assert(PI && "getAnalysis for unregistered pass!");
   assert(Resolver&&"Pass has not been inserted into a PassManager object!");
   // PI *must* appear in AnalysisImpls.  Because the number of passes used
   // should be a small number, we just do a linear search over a (dense)
   // vector.
   Pass *ResultPass = Resolver->findImplPass(PI);
   assert(ResultPass &&
          "getAnalysis*() called on an analysis that was not "
          "'required' by pass!");
 
   // Because the AnalysisType may not be a subclass of pass (for
   // AnalysisGroups), we use getAdjustedAnalysisPointer here to potentially
   // adjust the return pointer (because the class may multiply inherit, once
   // from pass, once from AnalysisType).
   return *(AnalysisType*)ResultPass->getAdjustedAnalysisPointer(PI);
 }
 
 /// getAnalysis<AnalysisType>() - This function is used by subclasses to get
 /// to the analysis information that they claim to use by overriding the
 /// getAnalysisUsage function. If as part of the dependencies, an IR
 /// transformation is triggered (e.g. because the analysis requires
 /// BreakCriticalEdges), and Changed is non null, *Changed is updated.
 template <typename AnalysisType>
 AnalysisType &Pass::getAnalysis(Function &F, bool *Changed) {
   assert(Resolver &&"Pass has not been inserted into a PassManager object!");
 
   return getAnalysisID<AnalysisType>(&AnalysisType::ID, F, Changed);
 }
 
 template <typename AnalysisType>
 AnalysisType &Pass::getAnalysisID(AnalysisID PI, Function &F, bool *Changed) {
   assert(PI && "getAnalysis for unregistered pass!");
   assert(Resolver && "Pass has not been inserted into a PassManager object!");
   // PI *must* appear in AnalysisImpls.  Because the number of passes used
   // should be a small number, we just do a linear search over a (dense)
   // vector.
   Pass *ResultPass;
   bool LocalChanged;
   std::tie(ResultPass, LocalChanged) = Resolver->findImplPass(this, PI, F);
 
   assert(ResultPass && "Unable to find requested analysis info");
   if (Changed)
     *Changed |= LocalChanged;
   else
     assert(!LocalChanged &&
            "A pass trigged a code update but the update status is lost");
 
   // Because the AnalysisType may not be a subclass of pass (for
   // AnalysisGroups), we use getAdjustedAnalysisPointer here to potentially
   // adjust the return pointer (because the class may multiply inherit, once
   // from pass, once from AnalysisType).
   return *(AnalysisType*)ResultPass->getAdjustedAnalysisPointer(PI);
 }
 
 } // end namespace llvm
 
 #endif // LLVM_PASSANALYSISSUPPORT_H

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