lib/ExecutionEngine/Interpreter/Interpreter.cpp

   1 //===- Interpreter.cpp - Top-Level LLVM Interpreter Implementation --------===//
   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 implements the top-level functionality for the LLVM interpreter.
  10 // This interpreter is designed to be a very simple, portable, inefficient
  11 // interpreter.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "Interpreter.h"
  16 #include "llvm/CodeGen/IntrinsicLowering.h"
  17 #include "llvm/IR/DerivedTypes.h"
  18 #include "llvm/IR/Module.h"
  19 #include <cstring>
  20 using namespace llvm;
  21
  22 namespace {
  23
  24 static struct RegisterInterp {
  25   RegisterInterp() { Interpreter::Register(); }
  26 } InterpRegistrator;
  27
  28 }
  29
  30 extern "C" void LLVMLinkInInterpreter() { }
  31
  32 /// Create a new interpreter object.
  33 ///
  34 ExecutionEngine *Interpreter::create(std::unique_ptr<Module> M,
  35                                      std::string *ErrStr) {
  36   // Tell this Module to materialize everything and release the GVMaterializer.
  37   if (Error Err = M->materializeAll()) {
  38     std::string Msg;
  39     handleAllErrors(std::move(Err), [&](ErrorInfoBase &EIB) {
  40       Msg = EIB.message();
  41     });
  42     if (ErrStr)
  43       *ErrStr = Msg;
  44     // We got an error, just return 0
  45     return nullptr;
  46   }
  47
  48   return new Interpreter(std::move(M));
  49 }
  50
  51 //===----------------------------------------------------------------------===//
  52 // Interpreter ctor - Initialize stuff
  53 //
  54 Interpreter::Interpreter(std::unique_ptr<Module> M)
  55     : ExecutionEngine(std::move(M)) {
  56
  57   memset(&ExitValue.Untyped, 0, sizeof(ExitValue.Untyped));
  58   // Initialize the "backend"
  59   initializeExecutionEngine();
  60   initializeExternalFunctions();
  61   emitGlobals();
  62
  63   IL = new IntrinsicLowering(getDataLayout());
  64 }
  65
  66 Interpreter::~Interpreter() {
  67   delete IL;
  68 }
  69
  70 void Interpreter::runAtExitHandlers () {
  71   while (!AtExitHandlers.empty()) {
  72     callFunction(AtExitHandlers.back(), None);
  73     AtExitHandlers.pop_back();
  74     run();
  75   }
  76 }
  77
  78 /// run - Start execution with the specified function and arguments.
  79 ///
  80 GenericValue Interpreter::runFunction(Function *F,
  81                                       ArrayRef<GenericValue> ArgValues) {
  82   assert (F && "Function *F was null at entry to run()");
  83
  84   // Try extra hard not to pass extra args to a function that isn't
  85   // expecting them.  C programmers frequently bend the rules and
  86   // declare main() with fewer parameters than it actually gets
  87   // passed, and the interpreter barfs if you pass a function more
  88   // parameters than it is declared to take. This does not attempt to
  89   // take into account gratuitous differences in declared types,
  90   // though.
  91   const size_t ArgCount = F->getFunctionType()->getNumParams();
  92   ArrayRef<GenericValue> ActualArgs =
  93       ArgValues.slice(0, std::min(ArgValues.size(), ArgCount));
  94
  95   // Set up the function call.
  96   callFunction(F, ActualArgs);
  97
  98   // Start executing the function.
  99   run();
 100
 101   return ExitValue;
 102 }