LazyValueInfo.h

Go to the documentation of this file.

//===- LazyValueInfo.h - Value constraint analysis --------------*- 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 the interface for lazy computation of value constraint
// information.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_ANALYSIS_LAZYVALUEINFO_H
#define LLVM_ANALYSIS_LAZYVALUEINFO_H
 
#include "llvm/IR/InstrTypes.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"
 
namespace llvm {
  class AssumptionCache;
  class BasicBlock;
  class Constant;
  class DataLayout;
  class DominatorTree;
  class Instruction;
  class Value;
  class Use;
  class LazyValueInfoImpl;
  /// This pass computes, caches, and vends lazy value constraint information.
  class LazyValueInfo {
    friend class LazyValueInfoWrapperPass;
    Function *F = nullptr;
    AssumptionCache *AC = nullptr;
    LazyValueInfoImpl *PImpl = nullptr;
    LazyValueInfo(const LazyValueInfo &) = delete;
    void operator=(const LazyValueInfo &) = delete;
 
    LazyValueInfoImpl *getImpl();
    LazyValueInfoImpl &getOrCreateImpl();
 
  public:
    LLVM_ABI ~LazyValueInfo();
    LazyValueInfo() = default;
    LazyValueInfo(Function *F, AssumptionCache *AC) : F(F), AC(AC) {}
    LazyValueInfo(LazyValueInfo &&Arg)
        : F(Arg.F), AC(Arg.AC), PImpl(Arg.PImpl) {
      Arg.PImpl = nullptr;
    }
    LazyValueInfo &operator=(LazyValueInfo &&Arg) {
      releaseMemory();
      F = Arg.F;
      AC = Arg.AC;
      PImpl = Arg.PImpl;
      Arg.PImpl = nullptr;
      return *this;
    }
 
    // Public query interface.
 
    /// Determine whether the specified value comparison with a constant is
    /// known to be true or false on the specified CFG edge. Pred is a CmpInst
    /// predicate.
    LLVM_ABI Constant *getPredicateOnEdge(CmpInst::Predicate Pred, Value *V,
                                          Constant *C, BasicBlock *FromBB,
                                          BasicBlock *ToBB,
                                          Instruction *CxtI = nullptr);
 
    /// Determine whether the specified value comparison with a constant is
    /// known to be true or false at the specified instruction. \p Pred is a
    /// CmpInst predicate. If \p UseBlockValue is true, the block value is also
    /// taken into account.
    LLVM_ABI Constant *getPredicateAt(CmpInst::Predicate Pred, Value *V,
                                      Constant *C, Instruction *CxtI,
                                      bool UseBlockValue);
 
    /// Determine whether the specified value comparison is known to be true
    /// or false at the specified instruction. While this takes two Value's,
    /// it still requires that one of them is a constant.
    /// \p Pred is a CmpInst predicate.
    /// If \p UseBlockValue is true, the block value is also taken into account.
    LLVM_ABI Constant *getPredicateAt(CmpInst::Predicate Pred, Value *LHS,
                                      Value *RHS, Instruction *CxtI,
                                      bool UseBlockValue);
 
    /// Determine whether the specified value is known to be a constant at the
    /// specified instruction. Return null if not.
    LLVM_ABI Constant *getConstant(Value *V, Instruction *CxtI);
 
    /// Return the ConstantRange constraint that is known to hold for the
    /// specified value at the specified instruction. This may only be called
    /// on integer-typed Values.
    LLVM_ABI ConstantRange getConstantRange(Value *V, Instruction *CxtI,
                                            bool UndefAllowed);
 
    /// Return the ConstantRange constraint that is known to hold for the value
    /// at a specific use-site.
    LLVM_ABI ConstantRange getConstantRangeAtUse(const Use &U,
                                                 bool UndefAllowed);
 
    /// Determine whether the specified value is known to be a
    /// constant on the specified edge.  Return null if not.
    LLVM_ABI Constant *getConstantOnEdge(Value *V, BasicBlock *FromBB,
                                         BasicBlock *ToBB,
                                         Instruction *CxtI = nullptr);
 
    /// Return the ConstantRage constraint that is known to hold for the
    /// specified value on the specified edge. This may be only be called
    /// on integer-typed Values.
    LLVM_ABI ConstantRange getConstantRangeOnEdge(Value *V, BasicBlock *FromBB,
                                                  BasicBlock *ToBB,
                                                  Instruction *CxtI = nullptr);
 
    /// Inform the analysis cache that we have threaded an edge from
    /// PredBB to OldSucc to be from PredBB to NewSucc instead.
    LLVM_ABI void threadEdge(BasicBlock *PredBB, BasicBlock *OldSucc,
                             BasicBlock *NewSucc);
 
    /// Remove information related to this value from the cache.
    LLVM_ABI void forgetValue(Value *V);
 
    /// Inform the analysis cache that we have erased a block.
    LLVM_ABI void eraseBlock(BasicBlock *BB);
 
    /// Complete flush all previously computed values
    LLVM_ABI void clear();
 
    /// Print the \LazyValueInfo Analysis.
    /// We pass in the DTree that is required for identifying which basic blocks
    /// we can solve/print for, in the LVIPrinter.
    LLVM_ABI void printLVI(Function &F, DominatorTree &DTree, raw_ostream &OS);
 
    // For old PM pass. Delete once LazyValueInfoWrapperPass is gone.
    LLVM_ABI void releaseMemory();
 
    /// Handle invalidation events in the new pass manager.
    LLVM_ABI bool invalidate(Function &F, const PreservedAnalyses &PA,
                             FunctionAnalysisManager::Invalidator &Inv);
  };
 
/// Analysis to compute lazy value information.
class LazyValueAnalysis : public AnalysisInfoMixin<LazyValueAnalysis> {
public:
  typedef LazyValueInfo Result;
  LLVM_ABI Result run(Function &F, FunctionAnalysisManager &FAM);
 
private:
  static AnalysisKey Key;
  friend struct AnalysisInfoMixin<LazyValueAnalysis>;
};
 
/// Printer pass for the LazyValueAnalysis results.
class LazyValueInfoPrinterPass
    : public RequiredPassInfoMixin<LazyValueInfoPrinterPass> {
  raw_ostream &OS;
 
public:
  explicit LazyValueInfoPrinterPass(raw_ostream &OS) : OS(OS) {}
 
  LLVM_ABI PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
};
 
/// Wrapper around LazyValueInfo.
class LLVM_ABI LazyValueInfoWrapperPass : public FunctionPass {
  LazyValueInfoWrapperPass(const LazyValueInfoWrapperPass&) = delete;
  void operator=(const LazyValueInfoWrapperPass&) = delete;
public:
  static char ID;
  LazyValueInfoWrapperPass();
  ~LazyValueInfoWrapperPass() override {
    assert(!Info.PImpl && "releaseMemory not called");
  }
 
  LazyValueInfo &getLVI();
 
  void getAnalysisUsage(AnalysisUsage &AU) const override;
  void releaseMemory() override;
  bool runOnFunction(Function &F) override;
private:
  LazyValueInfo Info;
};
 
}  // end namespace llvm
 
#endif