Interpreter.h

//===-- Interpreter.h ------------------------------------------*- 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 header file defines the interpreter structure
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_LIB_EXECUTIONENGINE_INTERPRETER_INTERPRETER_H
#define LLVM_LIB_EXECUTIONENGINE_INTERPRETER_INTERPRETER_H

#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstVisitor.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
namespace llvm {

class IntrinsicLowering;
template<typename T> class generic_gep_type_iterator;
class ConstantExpr;
typedef generic_gep_type_iterator<User::const_op_iterator> gep_type_iterator;


// AllocaHolder - Object to track all of the blocks of memory allocated by
// alloca.  When the function returns, this object is popped off the execution
// stack, which causes the dtor to be run, which frees all the alloca'd memory.
//
class AllocaHolder {
  std::vector<void *> Allocations;

public:
  AllocaHolder() = default;

  // Make this type move-only.
  AllocaHolder(AllocaHolder &&) = default;
  AllocaHolder &operator=(AllocaHolder &&RHS) = default;

  ~AllocaHolder() {
    for (void *Allocation : Allocations)
      free(Allocation);
  }

  void add(void *Mem) { Allocations.push_back(Mem); }
};

typedef std::vector<GenericValue> ValuePlaneTy;

// ExecutionContext struct - This struct represents one stack frame currently
// executing.
//
struct ExecutionContext {
  Function             *CurFunction;// The currently executing function
  BasicBlock           *CurBB;      // The currently executing BB
  BasicBlock::iterator  CurInst;    // The next instruction to execute
  CallBase             *Caller;     // Holds the call that called subframes.
                                    // NULL if main func or debugger invoked fn
  std::map<Value *, GenericValue> Values; // LLVM values used in this invocation
  std::vector<GenericValue>  VarArgs; // Values passed through an ellipsis
  AllocaHolder Allocas;            // Track memory allocated by alloca

  ExecutionContext() : CurFunction(nullptr), CurBB(nullptr), CurInst(nullptr) {}
};

// Interpreter - This class represents the entirety of the interpreter.
//
class Interpreter : public ExecutionEngine, public InstVisitor<Interpreter> {
  GenericValue ExitValue;          // The return value of the called function
  IntrinsicLowering *IL;

  // The runtime stack of executing code.  The top of the stack is the current
  // function record.
  std::vector<ExecutionContext> ECStack;

  // AtExitHandlers - List of functions to call when the program exits,
  // registered with the atexit() library function.
  std::vector<Function*> AtExitHandlers;

public:
  explicit Interpreter(std::unique_ptr<Module> M);
  ~Interpreter() override;

  /// runAtExitHandlers - Run any functions registered by the program's calls to
  /// atexit(3), which we intercept and store in AtExitHandlers.
  ///
  void runAtExitHandlers();

  static void Register() {
    InterpCtor = create;
  }

  /// Create an interpreter ExecutionEngine.
  ///
  static ExecutionEngine *create(std::unique_ptr<Module> M,
                                 std::string *ErrorStr = nullptr);

  /// run - Start execution with the specified function and arguments.
  ///
  GenericValue runFunction(Function *F,
                           ArrayRef<GenericValue> ArgValues) override;

  void *getPointerToNamedFunction(StringRef Name,
                                  bool AbortOnFailure = true) override {
    // FIXME: not implemented.
    return nullptr;
  }

  // Methods used to execute code:
  // Place a call on the stack
  void callFunction(Function *F, ArrayRef<GenericValue> ArgVals);
  void run();                // Execute instructions until nothing left to do

  // Opcode Implementations
  void visitReturnInst(ReturnInst &I);
  void visitBranchInst(BranchInst &I);
  void visitSwitchInst(SwitchInst &I);
  void visitIndirectBrInst(IndirectBrInst &I);

  void visitUnaryOperator(UnaryOperator &I);
  void visitBinaryOperator(BinaryOperator &I);
  void visitICmpInst(ICmpInst &I);
  void visitFCmpInst(FCmpInst &I);
  void visitAllocaInst(AllocaInst &I);
  void visitLoadInst(LoadInst &I);
  void visitStoreInst(StoreInst &I);
  void visitGetElementPtrInst(GetElementPtrInst &I);
  void visitPHINode(PHINode &PN) {
    llvm_unreachable("PHI nodes already handled!");
  }
  void visitTruncInst(TruncInst &I);
  void visitZExtInst(ZExtInst &I);
  void visitSExtInst(SExtInst &I);
  void visitFPTruncInst(FPTruncInst &I);
  void visitFPExtInst(FPExtInst &I);
  void visitUIToFPInst(UIToFPInst &I);
  void visitSIToFPInst(SIToFPInst &I);
  void visitFPToUIInst(FPToUIInst &I);
  void visitFPToSIInst(FPToSIInst &I);
  void visitPtrToIntInst(PtrToIntInst &I);
  void visitIntToPtrInst(IntToPtrInst &I);
  void visitBitCastInst(BitCastInst &I);
  void visitSelectInst(SelectInst &I);

  void visitVAStartInst(VAStartInst &I);
  void visitVAEndInst(VAEndInst &I);
  void visitVACopyInst(VACopyInst &I);
  void visitIntrinsicInst(IntrinsicInst &I);
  void visitCallBase(CallBase &I);
  void visitUnreachableInst(UnreachableInst &I);

  void visitShl(BinaryOperator &I);
  void visitLShr(BinaryOperator &I);
  void visitAShr(BinaryOperator &I);

  void visitVAArgInst(VAArgInst &I);
  void visitExtractElementInst(ExtractElementInst &I);
  void visitInsertElementInst(InsertElementInst &I);
  void visitShuffleVectorInst(ShuffleVectorInst &I);

  void visitExtractValueInst(ExtractValueInst &I);
  void visitInsertValueInst(InsertValueInst &I);

  void visitInstruction(Instruction &I) {
    errs() << I << "\n";
    llvm_unreachable("Instruction not interpretable yet!");
  }

  GenericValue callExternalFunction(Function *F,
                                    ArrayRef<GenericValue> ArgVals);
  void exitCalled(GenericValue GV);

  void addAtExitHandler(Function *F) {
    AtExitHandlers.push_back(F);
  }

  GenericValue *getFirstVarArg () {
    return &(ECStack.back ().VarArgs[0]);
  }

private:  // Helper functions
  GenericValue executeGEPOperation(Value *Ptr, gep_type_iterator I,
                                   gep_type_iterator E, ExecutionContext &SF);

  // SwitchToNewBasicBlock - Start execution in a new basic block and run any
  // PHI nodes in the top of the block.  This is used for intraprocedural
  // control flow.
  //
  void SwitchToNewBasicBlock(BasicBlock *Dest, ExecutionContext &SF);

  void *getPointerToFunction(Function *F) override { return (void*)F; }

  void initializeExecutionEngine() { }
  void initializeExternalFunctions();
  GenericValue getConstantExprValue(ConstantExpr *CE, ExecutionContext &SF);
  GenericValue getOperandValue(Value *V, ExecutionContext &SF);
  GenericValue executeTruncInst(Value *SrcVal, Type *DstTy,
                                ExecutionContext &SF);
  GenericValue executeSExtInst(Value *SrcVal, Type *DstTy,
                               ExecutionContext &SF);
  GenericValue executeZExtInst(Value *SrcVal, Type *DstTy,
                               ExecutionContext &SF);
  GenericValue executeFPTruncInst(Value *SrcVal, Type *DstTy,
                                  ExecutionContext &SF);
  GenericValue executeFPExtInst(Value *SrcVal, Type *DstTy,
                                ExecutionContext &SF);
  GenericValue executeFPToUIInst(Value *SrcVal, Type *DstTy,
                                 ExecutionContext &SF);
  GenericValue executeFPToSIInst(Value *SrcVal, Type *DstTy,
                                 ExecutionContext &SF);
  GenericValue executeUIToFPInst(Value *SrcVal, Type *DstTy,
                                 ExecutionContext &SF);
  GenericValue executeSIToFPInst(Value *SrcVal, Type *DstTy,
                                 ExecutionContext &SF);
  GenericValue executePtrToIntInst(Value *SrcVal, Type *DstTy,
                                   ExecutionContext &SF);
  GenericValue executeIntToPtrInst(Value *SrcVal, Type *DstTy,
                                   ExecutionContext &SF);
  GenericValue executeBitCastInst(Value *SrcVal, Type *DstTy,
                                  ExecutionContext &SF);
  void popStackAndReturnValueToCaller(Type *RetTy, GenericValue Result);

};

} // End llvm namespace

#endif