StackSafetyAnalysis.h

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//===- StackSafetyAnalysis.h - Stack memory safety 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
//
//===----------------------------------------------------------------------===//
//
// Stack Safety Analysis detects allocas and arguments with safe access.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_ANALYSIS_STACKSAFETYANALYSIS_H
#define LLVM_ANALYSIS_STACKSAFETYANALYSIS_H
 
#include "llvm/IR/ModuleSummaryIndex.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"
 
namespace llvm {
 
class AllocaInst;
class ScalarEvolution;
 
/// Interface to access stack safety analysis results for single function.
class StackSafetyInfo {
public:
  struct InfoTy;
 
private:
  Function *F = nullptr;
  std::function<ScalarEvolution &()> GetSE;
  mutable std::unique_ptr<InfoTy> Info;
 
public:
  StackSafetyInfo();
  StackSafetyInfo(Function *F, std::function<ScalarEvolution &()> GetSE);
  StackSafetyInfo(StackSafetyInfo &&);
  StackSafetyInfo &operator=(StackSafetyInfo &&);
  ~StackSafetyInfo();
 
  const InfoTy &getInfo() const;
 
  // TODO: Add useful for client methods.
  void print(raw_ostream &O) const;
 
  /// Parameters use for a FunctionSummary.
  /// Function collects access information of all pointer parameters.
  /// Information includes a range of direct access of parameters by the
  /// functions and all call sites accepting the parameter.
  /// StackSafety assumes that missing parameter information means possibility
  /// of access to the parameter with any offset, so we can correctly link
  /// code without StackSafety information, e.g. non-ThinLTO.
  std::vector<FunctionSummary::ParamAccess>
  getParamAccesses(ModuleSummaryIndex &Index) const;
};
 
class StackSafetyGlobalInfo {
public:
  struct InfoTy;
 
private:
  Module *M = nullptr;
  std::function<const StackSafetyInfo &(Function &F)> GetSSI;
  const ModuleSummaryIndex *Index = nullptr;
  mutable std::unique_ptr<InfoTy> Info;
  const InfoTy &getInfo() const;
 
public:
  StackSafetyGlobalInfo();
  StackSafetyGlobalInfo(
      Module *M, std::function<const StackSafetyInfo &(Function &F)> GetSSI,
      const ModuleSummaryIndex *Index);
  StackSafetyGlobalInfo(StackSafetyGlobalInfo &&);
  StackSafetyGlobalInfo &operator=(StackSafetyGlobalInfo &&);
  ~StackSafetyGlobalInfo();
 
  // Whether we can prove that all accesses to this Alloca are in-range and
  // during its lifetime.
  bool isSafe(const AllocaInst &AI) const;
 
  // Returns true if the instruction can be proven to do only two types of
  // memory accesses:
  //  (1) live stack locations in-bounds or
  //  (2) non-stack locations.
  bool stackAccessIsSafe(const Instruction &I) const;
  void print(raw_ostream &O) const;
  void dump() const;
};
 
/// StackSafetyInfo wrapper for the new pass manager.
class StackSafetyAnalysis : public AnalysisInfoMixin<StackSafetyAnalysis> {
  friend AnalysisInfoMixin<StackSafetyAnalysis>;
  static AnalysisKey Key;
 
public:
  using Result = StackSafetyInfo;
  StackSafetyInfo run(Function &F, FunctionAnalysisManager &AM);
};
 
/// Printer pass for the \c StackSafetyAnalysis results.
class StackSafetyPrinterPass : public PassInfoMixin<StackSafetyPrinterPass> {
  raw_ostream &OS;
 
public:
  explicit StackSafetyPrinterPass(raw_ostream &OS) : OS(OS) {}
  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
  static bool isRequired() { return true; }
};
 
/// StackSafetyInfo wrapper for the legacy pass manager
class StackSafetyInfoWrapperPass : public FunctionPass {
  StackSafetyInfo SSI;
 
public:
  static char ID;
  StackSafetyInfoWrapperPass();
 
  const StackSafetyInfo &getResult() const { return SSI; }
 
  void print(raw_ostream &O, const Module *M) const override;
  void getAnalysisUsage(AnalysisUsage &AU) const override;
 
  bool runOnFunction(Function &F) override;
};
 
/// This pass performs the global (interprocedural) stack safety analysis (new
/// pass manager).
class StackSafetyGlobalAnalysis
    : public AnalysisInfoMixin<StackSafetyGlobalAnalysis> {
  friend AnalysisInfoMixin<StackSafetyGlobalAnalysis>;
  static AnalysisKey Key;
 
public:
  using Result = StackSafetyGlobalInfo;
  Result run(Module &M, ModuleAnalysisManager &AM);
};
 
/// Printer pass for the \c StackSafetyGlobalAnalysis results.
class StackSafetyGlobalPrinterPass
    : public PassInfoMixin<StackSafetyGlobalPrinterPass> {
  raw_ostream &OS;
 
public:
  explicit StackSafetyGlobalPrinterPass(raw_ostream &OS) : OS(OS) {}
  PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
  static bool isRequired() { return true; }
};
 
/// This pass performs the global (interprocedural) stack safety analysis
/// (legacy pass manager).
class StackSafetyGlobalInfoWrapperPass : public ModulePass {
  StackSafetyGlobalInfo SSGI;
 
public:
  static char ID;
 
  StackSafetyGlobalInfoWrapperPass();
  ~StackSafetyGlobalInfoWrapperPass();
 
  const StackSafetyGlobalInfo &getResult() const { return SSGI; }
 
  void print(raw_ostream &O, const Module *M) const override;
  void getAnalysisUsage(AnalysisUsage &AU) const override;
 
  bool runOnModule(Module &M) override;
};
 
bool needsParamAccessSummary(const Module &M);
 
void generateParamAccessSummary(ModuleSummaryIndex &Index);
 
} // end namespace llvm
 
#endif // LLVM_ANALYSIS_STACKSAFETYANALYSIS_H