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+//===- StackProtector.h - Stack Protector Insertion -------------*- 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 pass inserts stack protectors into functions which need them. A variable
+// with a random value in it is stored onto the stack before the local variables
+// are allocated. Upon exiting the block, the stored value is checked. If it's
+// changed, then there was some sort of violation and the program aborts.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CODEGEN_STACKPROTECTOR_H
+#define LLVM_CODEGEN_STACKPROTECTOR_H
+
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/ValueMap.h"
+#include "llvm/Pass.h"
+
+namespace llvm {
+
+class BasicBlock;
+class DominatorTree;
+class Function;
+class Instruction;
+class Module;
+class TargetLoweringBase;
+class TargetMachine;
+class Type;
+
+class StackProtector : public FunctionPass {
+private:
+  /// A mapping of AllocaInsts to their required SSP layout.
+  using SSPLayoutMap = DenseMap<const AllocaInst *,
+                                MachineFrameInfo::SSPLayoutKind>;
+
+  const TargetMachine *TM = nullptr;
+
+  /// TLI - Keep a pointer of a TargetLowering to consult for determining
+  /// target type sizes.
+  const TargetLoweringBase *TLI = nullptr;
+  Triple Trip;
+
+  Function *F;
+  Module *M;
+
+  DominatorTree *DT;
+
+  /// Layout - Mapping of allocations to the required SSPLayoutKind.
+  /// StackProtector analysis will update this map when determining if an
+  /// AllocaInst triggers a stack protector.
+  SSPLayoutMap Layout;
+
+  /// The minimum size of buffers that will receive stack smashing
+  /// protection when -fstack-protection is used.
+  unsigned SSPBufferSize = 0;
+
+  /// VisitedPHIs - The set of PHI nodes visited when determining
+  /// if a variable's reference has been taken.  This set
+  /// is maintained to ensure we don't visit the same PHI node multiple
+  /// times.
+  SmallPtrSet<const PHINode *, 16> VisitedPHIs;
+
+  // A prologue is generated.
+  bool HasPrologue = false;
+
+  // IR checking code is generated.
+  bool HasIRCheck = false;
+
+  /// InsertStackProtectors - Insert code into the prologue and epilogue of
+  /// the function.
+  ///
+  ///  - The prologue code loads and stores the stack guard onto the stack.
+  ///  - The epilogue checks the value stored in the prologue against the
+  ///    original value. It calls __stack_chk_fail if they differ.
+  bool InsertStackProtectors();
+
+  /// CreateFailBB - Create a basic block to jump to when the stack protector
+  /// check fails.
+  BasicBlock *CreateFailBB();
+
+  /// ContainsProtectableArray - Check whether the type either is an array or
+  /// contains an array of sufficient size so that we need stack protectors
+  /// for it.
+  /// \param [out] IsLarge is set to true if a protectable array is found and
+  /// it is "large" ( >= ssp-buffer-size).  In the case of a structure with
+  /// multiple arrays, this gets set if any of them is large.
+  bool ContainsProtectableArray(Type *Ty, bool &IsLarge, bool Strong = false,
+                                bool InStruct = false) const;
+
+  /// Check whether a stack allocation has its address taken.
+  bool HasAddressTaken(const Instruction *AI);
+
+  /// RequiresStackProtector - Check whether or not this function needs a
+  /// stack protector based upon the stack protector level.
+  bool RequiresStackProtector();
+
+public:
+  static char ID; // Pass identification, replacement for typeid.
+
+  StackProtector() : FunctionPass(ID), SSPBufferSize(8) {
+    initializeStackProtectorPass(*PassRegistry::getPassRegistry());
+  }
+
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
+  // Return true if StackProtector is supposed to be handled by SelectionDAG.
+  bool shouldEmitSDCheck(const BasicBlock &BB) const;
+
+  bool runOnFunction(Function &Fn) override;
+
+  void copyToMachineFrameInfo(MachineFrameInfo &MFI) const;
+};
+
+} // end namespace llvm
+
+#endif // LLVM_CODEGEN_STACKPROTECTOR_H