1 //===- Interpreter.cpp - Top-Level LLVM Interpreter Implementation --------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // 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/IR/DerivedTypes.h"
19 #include "llvm/IR/Module.h"
20 #include <cstring>
21 using namespace llvm;
22 
23 namespace {
24 
25 static struct RegisterInterp {
26   RegisterInterp() { Interpreter::Register(); }
27 } InterpRegistrator;
28 
29 }
30 
31 extern "C" void LLVMLinkInInterpreter() { }
32 
33 /// create - Create a new interpreter object.  This can never fail.
34 ///
35 ExecutionEngine *Interpreter::create(Module *M, std::string* ErrStr) {
36   // Tell this Module to materialize everything and release the GVMaterializer.
37   if (error_code EC = M->materializeAllPermanently()) {
38     if (ErrStr)
39       *ErrStr = EC.message();
40     // We got an error, just return 0
41     return nullptr;
42   }
43 
44   return new Interpreter(M);
45 }
46 
47 //===----------------------------------------------------------------------===//
48 // Interpreter ctor - Initialize stuff
49 //
50 Interpreter::Interpreter(Module *M)
51   : ExecutionEngine(M), TD(M) {
52 
53   memset(&ExitValue.Untyped, 0, sizeof(ExitValue.Untyped));
54   setDataLayout(&TD);
55   // Initialize the "backend"
56   initializeExecutionEngine();
57   initializeExternalFunctions();
58   emitGlobals();
59 
60   IL = new IntrinsicLowering(TD);
61 }
62 
63 Interpreter::~Interpreter() {
64   delete IL;
65 }
66 
67 void Interpreter::runAtExitHandlers () {
68   while (!AtExitHandlers.empty()) {
69     callFunction(AtExitHandlers.back(), std::vector<GenericValue>());
70     AtExitHandlers.pop_back();
71     run();
72   }
73 }
74 
75 /// run - Start execution with the specified function and arguments.
76 ///
77 GenericValue
78 Interpreter::runFunction(Function *F,
79                          const std::vector<GenericValue> &ArgValues) {
80   assert (F && "Function *F was null at entry to run()");
81 
82   // Try extra hard not to pass extra args to a function that isn't
83   // expecting them.  C programmers frequently bend the rules and
84   // declare main() with fewer parameters than it actually gets
85   // passed, and the interpreter barfs if you pass a function more
86   // parameters than it is declared to take. This does not attempt to
87   // take into account gratuitous differences in declared types,
88   // though.
89   std::vector<GenericValue> ActualArgs;
90   const unsigned ArgCount = F->getFunctionType()->getNumParams();
91   for (unsigned i = 0; i < ArgCount; ++i)
92     ActualArgs.push_back(ArgValues[i]);
93 
94   // Set up the function call.
95   callFunction(F, ActualArgs);
96 
97   // Start executing the function.
98   run();
99 
100   return ExitValue;
101 }
102