Interpreter.cpp revision 726c1ef2bdd72975f41e3188371bb7d6f40401be 
1//===- Interpreter.cpp - Top-Level LLVM Interpreter Implementation --------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the top-level functionality for the LLVM interpreter.
11// This interpreter is designed to be a very simple, portable, inefficient
12// interpreter.
13//
14//===----------------------------------------------------------------------===//
15
16#include "Interpreter.h"
17#include "llvm/CodeGen/IntrinsicLowering.h"
18#include "llvm/DerivedTypes.h"
19#include "llvm/Module.h"
20#include "llvm/ModuleProvider.h"
21using namespace llvm;
22
23static struct RegisterInterp {
24  RegisterInterp() { Interpreter::Register(); }
25} InterpRegistrator;
26
27/// create - Create a new interpreter object.  This can never fail.
28///
29ExecutionEngine *Interpreter::create(ModuleProvider *MP) {
30  Module *M;
31  try {
32    M = MP->materializeModule();
33  } catch (...) {
34    return 0;  // error materializing the module.
35  }
36
37  bool isLittleEndian = false;
38  switch (M->getEndianness()) {
39  case Module::LittleEndian: isLittleEndian = true; break;
40  case Module::BigEndian:    isLittleEndian = false; break;
41  case Module::AnyPointerSize:
42    int Test = 0;
43    *(char*)&Test = 1;    // Return true if the host is little endian
44    isLittleEndian = (Test == 1);
45    break;
46  }
47
48  bool isLongPointer = false;
49  switch (M->getPointerSize()) {
50  case Module::Pointer32: isLongPointer = false; break;
51  case Module::Pointer64: isLongPointer = true; break;
52  case Module::AnyPointerSize:
53    isLongPointer = (sizeof(void*) == 8);  // Follow host
54    break;
55  }
56
57  return new Interpreter(M, isLittleEndian, isLongPointer);
58}
59
60//===----------------------------------------------------------------------===//
61// Interpreter ctor - Initialize stuff
62//
63Interpreter::Interpreter(Module *M, bool isLittleEndian, bool isLongPointer)
64  : ExecutionEngine(M),
65    TD("lli", isLittleEndian, isLongPointer ? 8 : 4, isLongPointer ? 8 : 4,
66       isLongPointer ? 8 : 4) {
67
68  memset(&ExitValue, 0, sizeof(ExitValue));
69  setTargetData(TD);
70  // Initialize the "backend"
71  initializeExecutionEngine();
72  initializeExternalFunctions();
73  emitGlobals();
74
75  IL = new DefaultIntrinsicLowering();
76}
77
78Interpreter::~Interpreter() {
79  delete IL;
80}
81
82void Interpreter::runAtExitHandlers () {
83  while (!AtExitHandlers.empty()) {
84    callFunction(AtExitHandlers.back(), std::vector<GenericValue>());
85    AtExitHandlers.pop_back();
86    run();
87  }
88}
89
90/// run - Start execution with the specified function and arguments.
91///
92GenericValue
93Interpreter::runFunction(Function *F,
94                         const std::vector<GenericValue> &ArgValues) {
95  assert (F && "Function *F was null at entry to run()");
96
97  // Try extra hard not to pass extra args to a function that isn't
98  // expecting them.  C programmers frequently bend the rules and
99  // declare main() with fewer parameters than it actually gets
100  // passed, and the interpreter barfs if you pass a function more
101  // parameters than it is declared to take. This does not attempt to
102  // take into account gratuitous differences in declared types,
103  // though.
104  std::vector<GenericValue> ActualArgs;
105  const unsigned ArgCount = F->getFunctionType()->getNumParams();
106  for (unsigned i = 0; i < ArgCount; ++i)
107    ActualArgs.push_back(ArgValues[i]);
108
109  // Set up the function call.
110  callFunction(F, ActualArgs);
111
112  // Start executing the function.
113  run();
114
115  return ExitValue;
116}
117
118