include/llvm/Analysis/LazyValueInfo.h

   1 //===- LazyValueInfo.h - Value constraint analysis --------------*- 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 the interface for lazy computation of value constraint
  10 // information.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_ANALYSIS_LAZYVALUEINFO_H
  15 #define LLVM_ANALYSIS_LAZYVALUEINFO_H
  16
  17 #include "llvm/IR/PassManager.h"
  18 #include "llvm/Pass.h"
  19
  20 namespace llvm {
  21   class AssumptionCache;
  22   class Constant;
  23   class ConstantRange;
  24   class DataLayout;
  25   class DominatorTree;
  26   class Instruction;
  27   class TargetLibraryInfo;
  28   class Value;
  29
  30 /// This pass computes, caches, and vends lazy value constraint information.
  31 class LazyValueInfo {
  32   friend class LazyValueInfoWrapperPass;
  33   AssumptionCache *AC = nullptr;
  34   const DataLayout *DL = nullptr;
  35   class TargetLibraryInfo *TLI = nullptr;
  36   DominatorTree *DT = nullptr;
  37   void *PImpl = nullptr;
  38   LazyValueInfo(const LazyValueInfo&) = delete;
  39   void operator=(const LazyValueInfo&) = delete;
  40 public:
  41   ~LazyValueInfo();
  42   LazyValueInfo() {}
  43   LazyValueInfo(AssumptionCache *AC_, const DataLayout *DL_, TargetLibraryInfo *TLI_,
  44                 DominatorTree *DT_)
  45       : AC(AC_), DL(DL_), TLI(TLI_), DT(DT_) {}
  46   LazyValueInfo(LazyValueInfo &&Arg)
  47       : AC(Arg.AC), DL(Arg.DL), TLI(Arg.TLI), DT(Arg.DT), PImpl(Arg.PImpl) {
  48     Arg.PImpl = nullptr;
  49   }
  50   LazyValueInfo &operator=(LazyValueInfo &&Arg) {
  51     releaseMemory();
  52     AC = Arg.AC;
  53     DL = Arg.DL;
  54     TLI = Arg.TLI;
  55     DT = Arg.DT;
  56     PImpl = Arg.PImpl;
  57     Arg.PImpl = nullptr;
  58     return *this;
  59   }
  60
  61   /// This is used to return true/false/dunno results.
  62   enum Tristate {
  63     Unknown = -1, False = 0, True = 1
  64   };
  65
  66   // Public query interface.
  67
  68   /// Determine whether the specified value comparison with a constant is known
  69   /// to be true or false on the specified CFG edge.
  70   /// Pred is a CmpInst predicate.
  71   Tristate getPredicateOnEdge(unsigned Pred, Value *V, Constant *C,
  72                               BasicBlock *FromBB, BasicBlock *ToBB,
  73                               Instruction *CxtI = nullptr);
  74
  75   /// Determine whether the specified value comparison with a constant is known
  76   /// to be true or false at the specified instruction
  77   /// (from an assume intrinsic). Pred is a CmpInst predicate.
  78   Tristate getPredicateAt(unsigned Pred, Value *V, Constant *C,
  79                           Instruction *CxtI);
  80
  81   /// Determine whether the specified value is known to be a
  82   /// constant at the end of the specified block.  Return null if not.
  83   Constant *getConstant(Value *V, BasicBlock *BB, Instruction *CxtI = nullptr);
  84
  85   /// Return the ConstantRange constraint that is known to hold for the
  86   /// specified value at the end of the specified block. This may only be called
  87   /// on integer-typed Values.
  88   ConstantRange getConstantRange(Value *V, BasicBlock *BB, Instruction *CxtI = nullptr);
  89
  90   /// Determine whether the specified value is known to be a
  91   /// constant on the specified edge.  Return null if not.
  92   Constant *getConstantOnEdge(Value *V, BasicBlock *FromBB, BasicBlock *ToBB,
  93                               Instruction *CxtI = nullptr);
  94
  95   /// Return the ConstantRage constraint that is known to hold for the
  96   /// specified value on the specified edge. This may be only be called
  97   /// on integer-typed Values.
  98   ConstantRange getConstantRangeOnEdge(Value *V, BasicBlock *FromBB,
  99                                        BasicBlock *ToBB,
 100                                        Instruction *CxtI = nullptr);
 101
 102   /// Inform the analysis cache that we have threaded an edge from
 103   /// PredBB to OldSucc to be from PredBB to NewSucc instead.
 104   void threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc, BasicBlock *NewSucc);
 105
 106   /// Inform the analysis cache that we have erased a block.
 107   void eraseBlock(BasicBlock *BB);
 108
 109   /// Print the \LazyValueInfo Analysis.
 110   /// We pass in the DTree that is required for identifying which basic blocks
 111   /// we can solve/print for, in the LVIPrinter. The DT is optional
 112   /// in LVI, so we need to pass it here as an argument.
 113   void printLVI(Function &F, DominatorTree &DTree, raw_ostream &OS);
 114
 115   /// Disables use of the DominatorTree within LVI.
 116   void disableDT();
 117
 118   /// Enables use of the DominatorTree within LVI. Does nothing if the class
 119   /// instance was initialized without a DT pointer.
 120   void enableDT();
 121
 122   // For old PM pass. Delete once LazyValueInfoWrapperPass is gone.
 123   void releaseMemory();
 124
 125   /// Handle invalidation events in the new pass manager.
 126   bool invalidate(Function &F, const PreservedAnalyses &PA,
 127                   FunctionAnalysisManager::Invalidator &Inv);
 128 };
 129
 130 /// Analysis to compute lazy value information.
 131 class LazyValueAnalysis : public AnalysisInfoMixin<LazyValueAnalysis> {
 132 public:
 133   typedef LazyValueInfo Result;
 134   Result run(Function &F, FunctionAnalysisManager &FAM);
 135
 136 private:
 137   static AnalysisKey Key;
 138   friend struct AnalysisInfoMixin<LazyValueAnalysis>;
 139 };
 140
 141 /// Wrapper around LazyValueInfo.
 142 class LazyValueInfoWrapperPass : public FunctionPass {
 143   LazyValueInfoWrapperPass(const LazyValueInfoWrapperPass&) = delete;
 144   void operator=(const LazyValueInfoWrapperPass&) = delete;
 145 public:
 146   static char ID;
 147   LazyValueInfoWrapperPass() : FunctionPass(ID) {
 148     initializeLazyValueInfoWrapperPassPass(*PassRegistry::getPassRegistry());
 149   }
 150   ~LazyValueInfoWrapperPass() override {
 151     assert(!Info.PImpl && "releaseMemory not called");
 152   }
 153
 154   LazyValueInfo &getLVI();
 155
 156   void getAnalysisUsage(AnalysisUsage &AU) const override;
 157   void releaseMemory() override;
 158   bool runOnFunction(Function &F) override;
 159 private:
 160   LazyValueInfo Info;
 161 };
 162
 163 }  // end namespace llvm
 164
 165 #endif
 166