include/llvm/PassAnalysisSupport.h

   1 //===- llvm/PassAnalysisSupport.h - Analysis Pass Support code --*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file defines stuff that is used to define and "use" Analysis Passes.
  10 // This file is automatically #included by Pass.h, so:
  11 //
  12 //           NO .CPP FILES SHOULD INCLUDE THIS FILE DIRECTLY
  13 //
  14 // Instead, #include Pass.h
  15 //
  16 //===----------------------------------------------------------------------===//
  17
  18 #ifndef LLVM_PASSANALYSISSUPPORT_H
  19 #define LLVM_PASSANALYSISSUPPORT_H
  20
  21 #include "Pass.h"
  22 #include "llvm/ADT/SmallVector.h"
  23 #include "llvm/ADT/StringRef.h"
  24 #include <cassert>
  25 #include <utility>
  26 #include <vector>
  27
  28 namespace llvm {
  29
  30 class Function;
  31 class Pass;
  32 class PMDataManager;
  33
  34 //===----------------------------------------------------------------------===//
  35 /// Represent the analysis usage information of a pass.  This tracks analyses
  36 /// that the pass REQUIRES (must be available when the pass runs), REQUIRES
  37 /// TRANSITIVE (must be available throughout the lifetime of the pass), and
  38 /// analyses that the pass PRESERVES (the pass does not invalidate the results
  39 /// of these analyses).  This information is provided by a pass to the Pass
  40 /// infrastructure through the getAnalysisUsage virtual function.
  41 ///
  42 class AnalysisUsage {
  43 public:
  44   using VectorType = SmallVectorImpl<AnalysisID>;
  45
  46 private:
  47   /// Sets of analyses required and preserved by a pass
  48   // TODO: It's not clear that SmallVector is an appropriate data structure for
  49   // this usecase.  The sizes were picked to minimize wasted space, but are
  50   // otherwise fairly meaningless.
  51   SmallVector<AnalysisID, 8> Required;
  52   SmallVector<AnalysisID, 2> RequiredTransitive;
  53   SmallVector<AnalysisID, 2> Preserved;
  54   SmallVector<AnalysisID, 0> Used;
  55   bool PreservesAll = false;
  56
  57 public:
  58   AnalysisUsage() = default;
  59
  60   ///@{
  61   /// Add the specified ID to the required set of the usage info for a pass.
  62   AnalysisUsage &addRequiredID(const void *ID);
  63   AnalysisUsage &addRequiredID(char &ID);
  64   template<class PassClass>
  65   AnalysisUsage &addRequired() {
  66     return addRequiredID(PassClass::ID);
  67   }
  68
  69   AnalysisUsage &addRequiredTransitiveID(char &ID);
  70   template<class PassClass>
  71   AnalysisUsage &addRequiredTransitive() {
  72     return addRequiredTransitiveID(PassClass::ID);
  73   }
  74   ///@}
  75
  76   ///@{
  77   /// Add the specified ID to the set of analyses preserved by this pass.
  78   AnalysisUsage &addPreservedID(const void *ID) {
  79     Preserved.push_back(ID);
  80     return *this;
  81   }
  82   AnalysisUsage &addPreservedID(char &ID) {
  83     Preserved.push_back(&ID);
  84     return *this;
  85   }
  86   /// Add the specified Pass class to the set of analyses preserved by this pass.
  87   template<class PassClass>
  88   AnalysisUsage &addPreserved() {
  89     Preserved.push_back(&PassClass::ID);
  90     return *this;
  91   }
  92   ///@}
  93
  94   ///@{
  95   /// Add the specified ID to the set of analyses used by this pass if they are
  96   /// available..
  97   AnalysisUsage &addUsedIfAvailableID(const void *ID) {
  98     Used.push_back(ID);
  99     return *this;
 100   }
 101   AnalysisUsage &addUsedIfAvailableID(char &ID) {
 102     Used.push_back(&ID);
 103     return *this;
 104   }
 105   /// Add the specified Pass class to the set of analyses used by this pass.
 106   template<class PassClass>
 107   AnalysisUsage &addUsedIfAvailable() {
 108     Used.push_back(&PassClass::ID);
 109     return *this;
 110   }
 111   ///@}
 112
 113   /// Add the Pass with the specified argument string to the set of analyses
 114   /// preserved by this pass. If no such Pass exists, do nothing. This can be
 115   /// useful when a pass is trivially preserved, but may not be linked in. Be
 116   /// careful about spelling!
 117   AnalysisUsage &addPreserved(StringRef Arg);
 118
 119   /// Set by analyses that do not transform their input at all
 120   void setPreservesAll() { PreservesAll = true; }
 121
 122   /// Determine whether a pass said it does not transform its input at all
 123   bool getPreservesAll() const { return PreservesAll; }
 124
 125   /// This function should be called by the pass, iff they do not:
 126   ///
 127   ///  1. Add or remove basic blocks from the function
 128   ///  2. Modify terminator instructions in any way.
 129   ///
 130   /// This function annotates the AnalysisUsage info object to say that analyses
 131   /// that only depend on the CFG are preserved by this pass.
 132   void setPreservesCFG();
 133
 134   const VectorType &getRequiredSet() const { return Required; }
 135   const VectorType &getRequiredTransitiveSet() const {
 136     return RequiredTransitive;
 137   }
 138   const VectorType &getPreservedSet() const { return Preserved; }
 139   const VectorType &getUsedSet() const { return Used; }
 140 };
 141
 142 //===----------------------------------------------------------------------===//
 143 /// AnalysisResolver - Simple interface used by Pass objects to pull all
 144 /// analysis information out of pass manager that is responsible to manage
 145 /// the pass.
 146 ///
 147 class AnalysisResolver {
 148 public:
 149   AnalysisResolver() = delete;
 150   explicit AnalysisResolver(PMDataManager &P) : PM(P) {}
 151
 152   PMDataManager &getPMDataManager() { return PM; }
 153
 154   /// Find pass that is implementing PI.
 155   Pass *findImplPass(AnalysisID PI) {
 156     Pass *ResultPass = nullptr;
 157     for (const auto &AnalysisImpl : AnalysisImpls) {
 158       if (AnalysisImpl.first == PI) {
 159         ResultPass = AnalysisImpl.second;
 160         break;
 161       }
 162     }
 163     return ResultPass;
 164   }
 165
 166   /// Find pass that is implementing PI. Initialize pass for Function F.
 167   Pass *findImplPass(Pass *P, AnalysisID PI, Function &F);
 168
 169   void addAnalysisImplsPair(AnalysisID PI, Pass *P) {
 170     if (findImplPass(PI) == P)
 171       return;
 172     std::pair<AnalysisID, Pass*> pir = std::make_pair(PI,P);
 173     AnalysisImpls.push_back(pir);
 174   }
 175
 176   /// Clear cache that is used to connect a pass to the analysis (PassInfo).
 177   void clearAnalysisImpls() {
 178     AnalysisImpls.clear();
 179   }
 180
 181   /// Return analysis result or null if it doesn't exist.
 182   Pass *getAnalysisIfAvailable(AnalysisID ID, bool Direction) const;
 183
 184 private:
 185   /// This keeps track of which passes implements the interfaces that are
 186   /// required by the current pass (to implement getAnalysis()).
 187   std::vector<std::pair<AnalysisID, Pass *>> AnalysisImpls;
 188
 189   /// PassManager that is used to resolve analysis info
 190   PMDataManager &PM;
 191 };
 192
 193 /// getAnalysisIfAvailable<AnalysisType>() - Subclasses use this function to
 194 /// get analysis information that might be around, for example to update it.
 195 /// This is different than getAnalysis in that it can fail (if the analysis
 196 /// results haven't been computed), so should only be used if you can handle
 197 /// the case when the analysis is not available.  This method is often used by
 198 /// transformation APIs to update analysis results for a pass automatically as
 199 /// the transform is performed.
 200 template<typename AnalysisType>
 201 AnalysisType *Pass::getAnalysisIfAvailable() const {
 202   assert(Resolver && "Pass not resident in a PassManager object!");
 203
 204   const void *PI = &AnalysisType::ID;
 205
 206   Pass *ResultPass = Resolver->getAnalysisIfAvailable(PI, true);
 207   if (!ResultPass) return nullptr;
 208
 209   // Because the AnalysisType may not be a subclass of pass (for
 210   // AnalysisGroups), we use getAdjustedAnalysisPointer here to potentially
 211   // adjust the return pointer (because the class may multiply inherit, once
 212   // from pass, once from AnalysisType).
 213   return (AnalysisType*)ResultPass->getAdjustedAnalysisPointer(PI);
 214 }
 215
 216 /// getAnalysis<AnalysisType>() - This function is used by subclasses to get
 217 /// to the analysis information that they claim to use by overriding the
 218 /// getAnalysisUsage function.
 219 template<typename AnalysisType>
 220 AnalysisType &Pass::getAnalysis() const {
 221   assert(Resolver && "Pass has not been inserted into a PassManager object!");
 222   return getAnalysisID<AnalysisType>(&AnalysisType::ID);
 223 }
 224
 225 template<typename AnalysisType>
 226 AnalysisType &Pass::getAnalysisID(AnalysisID PI) const {
 227   assert(PI && "getAnalysis for unregistered pass!");
 228   assert(Resolver&&"Pass has not been inserted into a PassManager object!");
 229   // PI *must* appear in AnalysisImpls.  Because the number of passes used
 230   // should be a small number, we just do a linear search over a (dense)
 231   // vector.
 232   Pass *ResultPass = Resolver->findImplPass(PI);
 233   assert(ResultPass &&
 234          "getAnalysis*() called on an analysis that was not "
 235          "'required' by pass!");
 236
 237   // Because the AnalysisType may not be a subclass of pass (for
 238   // AnalysisGroups), we use getAdjustedAnalysisPointer here to potentially
 239   // adjust the return pointer (because the class may multiply inherit, once
 240   // from pass, once from AnalysisType).
 241   return *(AnalysisType*)ResultPass->getAdjustedAnalysisPointer(PI);
 242 }
 243
 244 /// getAnalysis<AnalysisType>() - This function is used by subclasses to get
 245 /// to the analysis information that they claim to use by overriding the
 246 /// getAnalysisUsage function.
 247 template<typename AnalysisType>
 248 AnalysisType &Pass::getAnalysis(Function &F) {
 249   assert(Resolver &&"Pass has not been inserted into a PassManager object!");
 250
 251   return getAnalysisID<AnalysisType>(&AnalysisType::ID, F);
 252 }
 253
 254 template<typename AnalysisType>
 255 AnalysisType &Pass::getAnalysisID(AnalysisID PI, Function &F) {
 256   assert(PI && "getAnalysis for unregistered pass!");
 257   assert(Resolver && "Pass has not been inserted into a PassManager object!");
 258   // PI *must* appear in AnalysisImpls.  Because the number of passes used
 259   // should be a small number, we just do a linear search over a (dense)
 260   // vector.
 261   Pass *ResultPass = Resolver->findImplPass(this, PI, F);
 262   assert(ResultPass && "Unable to find requested analysis info");
 263
 264   // Because the AnalysisType may not be a subclass of pass (for
 265   // AnalysisGroups), we use getAdjustedAnalysisPointer here to potentially
 266   // adjust the return pointer (because the class may multiply inherit, once
 267   // from pass, once from AnalysisType).
 268   return *(AnalysisType*)ResultPass->getAdjustedAnalysisPointer(PI);
 269 }
 270
 271 } // end namespace llvm
 272
 273 #endif // LLVM_PASSANALYSISSUPPORT_H