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Interpreter.cpp

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00001 //===- Interpreter.cpp - Top-Level LLVM Interpreter Implementation --------===//
00002 // 
00003 //                     The LLVM Compiler Infrastructure
00004 //
00005 // This file was developed by the LLVM research group and is distributed under
00006 // the University of Illinois Open Source License. See LICENSE.TXT for details.
00007 // 
00008 //===----------------------------------------------------------------------===//
00009 //
00010 // This file implements the top-level functionality for the LLVM interpreter.
00011 // This interpreter is designed to be a very simple, portable, inefficient
00012 // interpreter.
00013 //
00014 //===----------------------------------------------------------------------===//
00015 
00016 #include "Interpreter.h"
00017 #include "llvm/CodeGen/IntrinsicLowering.h"
00018 #include "llvm/DerivedTypes.h"
00019 #include "llvm/Module.h"
00020 using namespace llvm;
00021 
00022 /// create - Create a new interpreter object.  This can never fail.
00023 ///
00024 ExecutionEngine *Interpreter::create(Module *M, IntrinsicLowering *IL) {
00025   bool isLittleEndian = false;
00026   switch (M->getEndianness()) {
00027   case Module::LittleEndian: isLittleEndian = true; break;
00028   case Module::BigEndian:    isLittleEndian = false; break;
00029   case Module::AnyPointerSize:
00030     int Test = 0;
00031     *(char*)&Test = 1;    // Return true if the host is little endian
00032     isLittleEndian = (Test == 1);
00033     break;
00034   }
00035 
00036   bool isLongPointer = false;
00037   switch (M->getPointerSize()) {
00038   case Module::Pointer32: isLongPointer = false; break;
00039   case Module::Pointer64: isLongPointer = true; break;
00040   case Module::AnyPointerSize:
00041     isLongPointer = (sizeof(void*) == 8);  // Follow host
00042     break;
00043   }
00044 
00045   return new Interpreter(M, isLittleEndian, isLongPointer, IL);
00046 }
00047 
00048 //===----------------------------------------------------------------------===//
00049 // Interpreter ctor - Initialize stuff
00050 //
00051 Interpreter::Interpreter(Module *M, bool isLittleEndian, bool isLongPointer,
00052                          IntrinsicLowering *il)
00053   : ExecutionEngine(M), ExitCode(0), 
00054     TD("lli", isLittleEndian, isLongPointer ? 8 : 4, isLongPointer ? 8 : 4,
00055        isLongPointer ? 8 : 4), IL(il) {
00056 
00057   setTargetData(TD);
00058   // Initialize the "backend"
00059   initializeExecutionEngine();
00060   initializeExternalFunctions();
00061   emitGlobals();
00062 
00063   if (IL == 0) IL = new DefaultIntrinsicLowering();
00064 }
00065 
00066 Interpreter::~Interpreter() {
00067   delete IL;
00068 }
00069 
00070 void Interpreter::runAtExitHandlers () {
00071   while (!AtExitHandlers.empty()) {
00072     callFunction(AtExitHandlers.back(), std::vector<GenericValue>());
00073     AtExitHandlers.pop_back();
00074     run();
00075   }
00076 }
00077 
00078 /// run - Start execution with the specified function and arguments.
00079 ///
00080 GenericValue Interpreter::runFunction(Function *F,
00081             const std::vector<GenericValue> &ArgValues) {
00082   assert (F && "Function *F was null at entry to run()");
00083 
00084   // Try extra hard not to pass extra args to a function that isn't
00085   // expecting them.  C programmers frequently bend the rules and
00086   // declare main() with fewer parameters than it actually gets
00087   // passed, and the interpreter barfs if you pass a function more
00088   // parameters than it is declared to take. This does not attempt to
00089   // take into account gratuitous differences in declared types,
00090   // though.
00091   std::vector<GenericValue> ActualArgs;
00092   const unsigned ArgCount = F->getFunctionType()->getNumParams();
00093   for (unsigned i = 0; i < ArgCount; ++i)
00094     ActualArgs.push_back(ArgValues[i]);
00095   
00096   // Set up the function call.
00097   callFunction(F, ActualArgs);
00098 
00099   // Start executing the function.
00100   run();
00101   
00102   GenericValue rv;
00103   rv.IntVal = ExitCode;
00104   return rv;
00105 }
00106