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 a new interpreter object.
34 ///
35 ExecutionEngine *Interpreter::create(std::unique_ptr<Module> M,
36                                      std::string *ErrStr) {
37   // Tell this Module to materialize everything and release the GVMaterializer.
38   if (std::error_code EC = M->materializeAllPermanently()) {
39     if (ErrStr)
40       *ErrStr = EC.message();
41     // We got an error, just return 0
42     return nullptr;
43   }
44 
45   return new Interpreter(std::move(M));
46 }
47 
48 //===----------------------------------------------------------------------===//
49 // Interpreter ctor - Initialize stuff
50 //
51 Interpreter::Interpreter(std::unique_ptr<Module> M)
52   : ExecutionEngine(std::move(M)), TD(Modules.back().get()) {
53 
54   memset(&ExitValue.Untyped, 0, sizeof(ExitValue.Untyped));
55   setDataLayout(&TD);
56   // Initialize the "backend"
57   initializeExecutionEngine();
58   initializeExternalFunctions();
59   emitGlobals();
60 
61   IL = new IntrinsicLowering(TD);
62 }
63 
64 Interpreter::~Interpreter() {
65   delete IL;
66 }
67 
68 void Interpreter::runAtExitHandlers () {
69   while (!AtExitHandlers.empty()) {
70     callFunction(AtExitHandlers.back(), None);
71     AtExitHandlers.pop_back();
72     run();
73   }
74 }
75 
76 /// run - Start execution with the specified function and arguments.
77 ///
78 GenericValue Interpreter::runFunction(Function *F,
79                                       ArrayRef<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   const size_t ArgCount = F->getFunctionType()->getNumParams();
90   ArrayRef<GenericValue> ActualArgs =
91       ArgValues.slice(0, std::min(ArgValues.size(), ArgCount));
92 
93   // Set up the function call.
94   callFunction(F, ActualArgs);
95 
96   // Start executing the function.
97   run();
98 
99   return ExitValue;
100 }
101