xref: /llvm-project/llvm/lib/ExecutionEngine/ExecutionEngine.cpp (revision faae50b66bea90f4f5c0cbdb09378e7a66dcb2b5)
1 //===-- ExecutionEngine.cpp - Common Implementation shared by EEs ---------===//
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 defines the common interface used by the various execution engine
11 // subclasses.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #define DEBUG_TYPE "jit"
16 #include "Interpreter/Interpreter.h"
17 #include "JIT/JIT.h"
18 #include "llvm/Constants.h"
19 #include "llvm/DerivedTypes.h"
20 #include "llvm/Module.h"
21 #include "llvm/ModuleProvider.h"
22 #include "llvm/ADT/Statistic.h"
23 #include "llvm/CodeGen/IntrinsicLowering.h"
24 #include "llvm/ExecutionEngine/ExecutionEngine.h"
25 #include "llvm/ExecutionEngine/GenericValue.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/System/DynamicLibrary.h"
28 #include "llvm/Target/TargetData.h"
29 using namespace llvm;
30 
31 namespace {
32   Statistic<> NumInitBytes("lli", "Number of bytes of global vars initialized");
33   Statistic<> NumGlobals  ("lli", "Number of global vars initialized");
34 }
35 
36 ExecutionEngine::ExecutionEngine(ModuleProvider *P) :
37   CurMod(*P->getModule()), MP(P) {
38   assert(P && "ModuleProvider is null?");
39 }
40 
41 ExecutionEngine::ExecutionEngine(Module *M) : CurMod(*M), MP(0) {
42   assert(M && "Module is null?");
43 }
44 
45 ExecutionEngine::~ExecutionEngine() {
46   delete MP;
47 }
48 
49 /// getGlobalValueAtAddress - Return the LLVM global value object that starts
50 /// at the specified address.
51 ///
52 const GlobalValue *ExecutionEngine::getGlobalValueAtAddress(void *Addr) {
53   MutexGuard locked(lock);
54 
55   // If we haven't computed the reverse mapping yet, do so first.
56   if (state.getGlobalAddressReverseMap(locked).empty()) {
57     for (std::map<const GlobalValue*, void *>::iterator I =
58            state.getGlobalAddressMap(locked).begin(), E = state.getGlobalAddressMap(locked).end(); I != E; ++I)
59       state.getGlobalAddressReverseMap(locked).insert(std::make_pair(I->second, I->first));
60   }
61 
62   std::map<void *, const GlobalValue*>::iterator I =
63     state.getGlobalAddressReverseMap(locked).find(Addr);
64   return I != state.getGlobalAddressReverseMap(locked).end() ? I->second : 0;
65 }
66 
67 // CreateArgv - Turn a vector of strings into a nice argv style array of
68 // pointers to null terminated strings.
69 //
70 static void *CreateArgv(ExecutionEngine *EE,
71                         const std::vector<std::string> &InputArgv) {
72   unsigned PtrSize = EE->getTargetData().getPointerSize();
73   char *Result = new char[(InputArgv.size()+1)*PtrSize];
74 
75   DEBUG(std::cerr << "ARGV = " << (void*)Result << "\n");
76   const Type *SBytePtr = PointerType::get(Type::SByteTy);
77 
78   for (unsigned i = 0; i != InputArgv.size(); ++i) {
79     unsigned Size = InputArgv[i].size()+1;
80     char *Dest = new char[Size];
81     DEBUG(std::cerr << "ARGV[" << i << "] = " << (void*)Dest << "\n");
82 
83     std::copy(InputArgv[i].begin(), InputArgv[i].end(), Dest);
84     Dest[Size-1] = 0;
85 
86     // Endian safe: Result[i] = (PointerTy)Dest;
87     EE->StoreValueToMemory(PTOGV(Dest), (GenericValue*)(Result+i*PtrSize),
88                            SBytePtr);
89   }
90 
91   // Null terminate it
92   EE->StoreValueToMemory(PTOGV(0),
93                          (GenericValue*)(Result+InputArgv.size()*PtrSize),
94                          SBytePtr);
95   return Result;
96 }
97 
98 
99 /// runStaticConstructorsDestructors - This method is used to execute all of
100 /// the static constructors or destructors for a module, depending on the
101 /// value of isDtors.
102 void ExecutionEngine::runStaticConstructorsDestructors(bool isDtors) {
103   const char *Name = isDtors ? "llvm.global_dtors" : "llvm.global_ctors";
104   GlobalVariable *GV = CurMod.getNamedGlobal(Name);
105   if (!GV || GV->isExternal() || !GV->hasInternalLinkage()) return;
106 
107   // Should be an array of '{ int, void ()* }' structs.  The first value is the
108   // init priority, which we ignore.
109   ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
110   if (!InitList) return;
111   for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
112     if (ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i))){
113       if (CS->getNumOperands() != 2) return;  // Not array of 2-element structs.
114 
115       Constant *FP = CS->getOperand(1);
116       if (FP->isNullValue())
117         return;  // Found a null terminator, exit.
118 
119       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
120         if (CE->getOpcode() == Instruction::Cast)
121           FP = CE->getOperand(0);
122       if (Function *F = dyn_cast<Function>(FP)) {
123         // Execute the ctor/dtor function!
124         runFunction(F, std::vector<GenericValue>());
125       }
126     }
127 }
128 
129 /// runFunctionAsMain - This is a helper function which wraps runFunction to
130 /// handle the common task of starting up main with the specified argc, argv,
131 /// and envp parameters.
132 int ExecutionEngine::runFunctionAsMain(Function *Fn,
133                                        const std::vector<std::string> &argv,
134                                        const char * const * envp) {
135   std::vector<GenericValue> GVArgs;
136   GenericValue GVArgc;
137   GVArgc.IntVal = argv.size();
138   unsigned NumArgs = Fn->getFunctionType()->getNumParams();
139   if (NumArgs) {
140     GVArgs.push_back(GVArgc); // Arg #0 = argc.
141     if (NumArgs > 1) {
142       GVArgs.push_back(PTOGV(CreateArgv(this, argv))); // Arg #1 = argv.
143       assert(((char **)GVTOP(GVArgs[1]))[0] &&
144              "argv[0] was null after CreateArgv");
145       if (NumArgs > 2) {
146         std::vector<std::string> EnvVars;
147         for (unsigned i = 0; envp[i]; ++i)
148           EnvVars.push_back(envp[i]);
149         GVArgs.push_back(PTOGV(CreateArgv(this, EnvVars))); // Arg #2 = envp.
150       }
151     }
152   }
153   return runFunction(Fn, GVArgs).IntVal;
154 }
155 
156 /// If possible, create a JIT, unless the caller specifically requests an
157 /// Interpreter or there's an error. If even an Interpreter cannot be created,
158 /// NULL is returned.
159 ///
160 ExecutionEngine *ExecutionEngine::create(ModuleProvider *MP,
161                                          bool ForceInterpreter,
162                                          IntrinsicLowering *IL) {
163   ExecutionEngine *EE = 0;
164 
165   // Unless the interpreter was explicitly selected, try making a JIT.
166   if (!ForceInterpreter)
167     EE = JIT::create(MP, IL);
168 
169   // If we can't make a JIT, make an interpreter instead.
170   if (EE == 0) {
171     try {
172       Module *M = MP->materializeModule();
173       try {
174         EE = Interpreter::create(M, IL);
175       } catch (...) {
176         std::cerr << "Error creating the interpreter!\n";
177       }
178     } catch (std::string& errmsg) {
179       std::cerr << "Error reading the bytecode file: " << errmsg << "\n";
180     } catch (...) {
181       std::cerr << "Error reading the bytecode file!\n";
182     }
183   }
184 
185   if (EE == 0)
186     delete IL;
187   else
188     // Make sure we can resolve symbols in the program as well. The zero arg
189     // to the function tells DynamicLibrary to load the program, not a library.
190     sys::DynamicLibrary::LoadLibraryPermanently(0);
191 
192   return EE;
193 }
194 
195 /// getPointerToGlobal - This returns the address of the specified global
196 /// value.  This may involve code generation if it's a function.
197 ///
198 void *ExecutionEngine::getPointerToGlobal(const GlobalValue *GV) {
199   if (Function *F = const_cast<Function*>(dyn_cast<Function>(GV)))
200     return getPointerToFunction(F);
201 
202   MutexGuard locked(lock);
203   void *p = state.getGlobalAddressMap(locked)[GV];
204   if (p)
205     return p;
206 
207   // Global variable might have been added since interpreter started.
208   if (GlobalVariable *GVar =
209           const_cast<GlobalVariable *>(dyn_cast<GlobalVariable>(GV)))
210     EmitGlobalVariable(GVar);
211   else
212     assert("Global hasn't had an address allocated yet!");
213   return state.getGlobalAddressMap(locked)[GV];
214 }
215 
216 /// FIXME: document
217 ///
218 GenericValue ExecutionEngine::getConstantValue(const Constant *C) {
219   GenericValue Result;
220   if (isa<UndefValue>(C)) return Result;
221 
222   if (ConstantExpr *CE = const_cast<ConstantExpr*>(dyn_cast<ConstantExpr>(C))) {
223     switch (CE->getOpcode()) {
224     case Instruction::GetElementPtr: {
225       Result = getConstantValue(CE->getOperand(0));
226       std::vector<Value*> Indexes(CE->op_begin()+1, CE->op_end());
227       uint64_t Offset =
228         TD->getIndexedOffset(CE->getOperand(0)->getType(), Indexes);
229 
230       if (getTargetData().getPointerSize() == 4)
231         Result.IntVal += Offset;
232       else
233         Result.LongVal += Offset;
234       return Result;
235     }
236     case Instruction::Cast: {
237       // We only need to handle a few cases here.  Almost all casts will
238       // automatically fold, just the ones involving pointers won't.
239       //
240       Constant *Op = CE->getOperand(0);
241       GenericValue GV = getConstantValue(Op);
242 
243       // Handle cast of pointer to pointer...
244       if (Op->getType()->getTypeID() == C->getType()->getTypeID())
245         return GV;
246 
247       // Handle a cast of pointer to any integral type...
248       if (isa<PointerType>(Op->getType()) && C->getType()->isIntegral())
249         return GV;
250 
251       // Handle cast of integer to a pointer...
252       if (isa<PointerType>(C->getType()) && Op->getType()->isIntegral())
253         switch (Op->getType()->getTypeID()) {
254         case Type::BoolTyID:    return PTOGV((void*)(uintptr_t)GV.BoolVal);
255         case Type::SByteTyID:   return PTOGV((void*)( intptr_t)GV.SByteVal);
256         case Type::UByteTyID:   return PTOGV((void*)(uintptr_t)GV.UByteVal);
257         case Type::ShortTyID:   return PTOGV((void*)( intptr_t)GV.ShortVal);
258         case Type::UShortTyID:  return PTOGV((void*)(uintptr_t)GV.UShortVal);
259         case Type::IntTyID:     return PTOGV((void*)( intptr_t)GV.IntVal);
260         case Type::UIntTyID:    return PTOGV((void*)(uintptr_t)GV.UIntVal);
261         case Type::LongTyID:    return PTOGV((void*)( intptr_t)GV.LongVal);
262         case Type::ULongTyID:   return PTOGV((void*)(uintptr_t)GV.ULongVal);
263         default: assert(0 && "Unknown integral type!");
264         }
265       break;
266     }
267 
268     case Instruction::Add:
269       switch (CE->getOperand(0)->getType()->getTypeID()) {
270       default: assert(0 && "Bad add type!"); abort();
271       case Type::LongTyID:
272       case Type::ULongTyID:
273         Result.LongVal = getConstantValue(CE->getOperand(0)).LongVal +
274                          getConstantValue(CE->getOperand(1)).LongVal;
275         break;
276       case Type::IntTyID:
277       case Type::UIntTyID:
278         Result.IntVal = getConstantValue(CE->getOperand(0)).IntVal +
279                         getConstantValue(CE->getOperand(1)).IntVal;
280         break;
281       case Type::ShortTyID:
282       case Type::UShortTyID:
283         Result.ShortVal = getConstantValue(CE->getOperand(0)).ShortVal +
284                           getConstantValue(CE->getOperand(1)).ShortVal;
285         break;
286       case Type::SByteTyID:
287       case Type::UByteTyID:
288         Result.SByteVal = getConstantValue(CE->getOperand(0)).SByteVal +
289                           getConstantValue(CE->getOperand(1)).SByteVal;
290         break;
291       case Type::FloatTyID:
292         Result.FloatVal = getConstantValue(CE->getOperand(0)).FloatVal +
293                           getConstantValue(CE->getOperand(1)).FloatVal;
294         break;
295       case Type::DoubleTyID:
296         Result.DoubleVal = getConstantValue(CE->getOperand(0)).DoubleVal +
297                            getConstantValue(CE->getOperand(1)).DoubleVal;
298         break;
299       }
300       return Result;
301     default:
302       break;
303     }
304     std::cerr << "ConstantExpr not handled as global var init: " << *CE << "\n";
305     abort();
306   }
307 
308   switch (C->getType()->getTypeID()) {
309 #define GET_CONST_VAL(TY, CTY, CLASS) \
310   case Type::TY##TyID: Result.TY##Val = (CTY)cast<CLASS>(C)->getValue(); break
311     GET_CONST_VAL(Bool   , bool          , ConstantBool);
312     GET_CONST_VAL(UByte  , unsigned char , ConstantUInt);
313     GET_CONST_VAL(SByte  , signed char   , ConstantSInt);
314     GET_CONST_VAL(UShort , unsigned short, ConstantUInt);
315     GET_CONST_VAL(Short  , signed short  , ConstantSInt);
316     GET_CONST_VAL(UInt   , unsigned int  , ConstantUInt);
317     GET_CONST_VAL(Int    , signed int    , ConstantSInt);
318     GET_CONST_VAL(ULong  , uint64_t      , ConstantUInt);
319     GET_CONST_VAL(Long   , int64_t       , ConstantSInt);
320     GET_CONST_VAL(Float  , float         , ConstantFP);
321     GET_CONST_VAL(Double , double        , ConstantFP);
322 #undef GET_CONST_VAL
323   case Type::PointerTyID:
324     if (isa<ConstantPointerNull>(C))
325       Result.PointerVal = 0;
326     else if (const Function *F = dyn_cast<Function>(C))
327       Result = PTOGV(getPointerToFunctionOrStub(const_cast<Function*>(F)));
328     else if (const GlobalVariable* GV = dyn_cast<GlobalVariable>(C))
329       Result = PTOGV(getOrEmitGlobalVariable(const_cast<GlobalVariable*>(GV)));
330     else
331       assert(0 && "Unknown constant pointer type!");
332     break;
333   default:
334     std::cout << "ERROR: Constant unimp for type: " << *C->getType() << "\n";
335     abort();
336   }
337   return Result;
338 }
339 
340 /// FIXME: document
341 ///
342 void ExecutionEngine::StoreValueToMemory(GenericValue Val, GenericValue *Ptr,
343                                          const Type *Ty) {
344   if (getTargetData().isLittleEndian()) {
345     switch (Ty->getTypeID()) {
346     case Type::BoolTyID:
347     case Type::UByteTyID:
348     case Type::SByteTyID:   Ptr->Untyped[0] = Val.UByteVal; break;
349     case Type::UShortTyID:
350     case Type::ShortTyID:   Ptr->Untyped[0] = Val.UShortVal & 255;
351                             Ptr->Untyped[1] = (Val.UShortVal >> 8) & 255;
352                             break;
353     Store4BytesLittleEndian:
354     case Type::FloatTyID:
355     case Type::UIntTyID:
356     case Type::IntTyID:     Ptr->Untyped[0] =  Val.UIntVal        & 255;
357                             Ptr->Untyped[1] = (Val.UIntVal >>  8) & 255;
358                             Ptr->Untyped[2] = (Val.UIntVal >> 16) & 255;
359                             Ptr->Untyped[3] = (Val.UIntVal >> 24) & 255;
360                             break;
361     case Type::PointerTyID: if (getTargetData().getPointerSize() == 4)
362                               goto Store4BytesLittleEndian;
363     case Type::DoubleTyID:
364     case Type::ULongTyID:
365     case Type::LongTyID:
366       Ptr->Untyped[0] = (unsigned char)(Val.ULongVal      );
367       Ptr->Untyped[1] = (unsigned char)(Val.ULongVal >>  8);
368       Ptr->Untyped[2] = (unsigned char)(Val.ULongVal >> 16);
369       Ptr->Untyped[3] = (unsigned char)(Val.ULongVal >> 24);
370       Ptr->Untyped[4] = (unsigned char)(Val.ULongVal >> 32);
371       Ptr->Untyped[5] = (unsigned char)(Val.ULongVal >> 40);
372       Ptr->Untyped[6] = (unsigned char)(Val.ULongVal >> 48);
373       Ptr->Untyped[7] = (unsigned char)(Val.ULongVal >> 56);
374       break;
375     default:
376       std::cout << "Cannot store value of type " << *Ty << "!\n";
377     }
378   } else {
379     switch (Ty->getTypeID()) {
380     case Type::BoolTyID:
381     case Type::UByteTyID:
382     case Type::SByteTyID:   Ptr->Untyped[0] = Val.UByteVal; break;
383     case Type::UShortTyID:
384     case Type::ShortTyID:   Ptr->Untyped[1] = Val.UShortVal & 255;
385                             Ptr->Untyped[0] = (Val.UShortVal >> 8) & 255;
386                             break;
387     Store4BytesBigEndian:
388     case Type::FloatTyID:
389     case Type::UIntTyID:
390     case Type::IntTyID:     Ptr->Untyped[3] =  Val.UIntVal        & 255;
391                             Ptr->Untyped[2] = (Val.UIntVal >>  8) & 255;
392                             Ptr->Untyped[1] = (Val.UIntVal >> 16) & 255;
393                             Ptr->Untyped[0] = (Val.UIntVal >> 24) & 255;
394                             break;
395     case Type::PointerTyID: if (getTargetData().getPointerSize() == 4)
396                               goto Store4BytesBigEndian;
397     case Type::DoubleTyID:
398     case Type::ULongTyID:
399     case Type::LongTyID:
400       Ptr->Untyped[7] = (unsigned char)(Val.ULongVal      );
401       Ptr->Untyped[6] = (unsigned char)(Val.ULongVal >>  8);
402       Ptr->Untyped[5] = (unsigned char)(Val.ULongVal >> 16);
403       Ptr->Untyped[4] = (unsigned char)(Val.ULongVal >> 24);
404       Ptr->Untyped[3] = (unsigned char)(Val.ULongVal >> 32);
405       Ptr->Untyped[2] = (unsigned char)(Val.ULongVal >> 40);
406       Ptr->Untyped[1] = (unsigned char)(Val.ULongVal >> 48);
407       Ptr->Untyped[0] = (unsigned char)(Val.ULongVal >> 56);
408       break;
409     default:
410       std::cout << "Cannot store value of type " << *Ty << "!\n";
411     }
412   }
413 }
414 
415 /// FIXME: document
416 ///
417 GenericValue ExecutionEngine::LoadValueFromMemory(GenericValue *Ptr,
418                                                   const Type *Ty) {
419   GenericValue Result;
420   if (getTargetData().isLittleEndian()) {
421     switch (Ty->getTypeID()) {
422     case Type::BoolTyID:
423     case Type::UByteTyID:
424     case Type::SByteTyID:   Result.UByteVal = Ptr->Untyped[0]; break;
425     case Type::UShortTyID:
426     case Type::ShortTyID:   Result.UShortVal = (unsigned)Ptr->Untyped[0] |
427                                               ((unsigned)Ptr->Untyped[1] << 8);
428                             break;
429     Load4BytesLittleEndian:
430     case Type::FloatTyID:
431     case Type::UIntTyID:
432     case Type::IntTyID:     Result.UIntVal = (unsigned)Ptr->Untyped[0] |
433                                             ((unsigned)Ptr->Untyped[1] <<  8) |
434                                             ((unsigned)Ptr->Untyped[2] << 16) |
435                                             ((unsigned)Ptr->Untyped[3] << 24);
436                             break;
437     case Type::PointerTyID: if (getTargetData().getPointerSize() == 4)
438                               goto Load4BytesLittleEndian;
439     case Type::DoubleTyID:
440     case Type::ULongTyID:
441     case Type::LongTyID:    Result.ULongVal = (uint64_t)Ptr->Untyped[0] |
442                                              ((uint64_t)Ptr->Untyped[1] <<  8) |
443                                              ((uint64_t)Ptr->Untyped[2] << 16) |
444                                              ((uint64_t)Ptr->Untyped[3] << 24) |
445                                              ((uint64_t)Ptr->Untyped[4] << 32) |
446                                              ((uint64_t)Ptr->Untyped[5] << 40) |
447                                              ((uint64_t)Ptr->Untyped[6] << 48) |
448                                              ((uint64_t)Ptr->Untyped[7] << 56);
449                             break;
450     default:
451       std::cout << "Cannot load value of type " << *Ty << "!\n";
452       abort();
453     }
454   } else {
455     switch (Ty->getTypeID()) {
456     case Type::BoolTyID:
457     case Type::UByteTyID:
458     case Type::SByteTyID:   Result.UByteVal = Ptr->Untyped[0]; break;
459     case Type::UShortTyID:
460     case Type::ShortTyID:   Result.UShortVal = (unsigned)Ptr->Untyped[1] |
461                                               ((unsigned)Ptr->Untyped[0] << 8);
462                             break;
463     Load4BytesBigEndian:
464     case Type::FloatTyID:
465     case Type::UIntTyID:
466     case Type::IntTyID:     Result.UIntVal = (unsigned)Ptr->Untyped[3] |
467                                             ((unsigned)Ptr->Untyped[2] <<  8) |
468                                             ((unsigned)Ptr->Untyped[1] << 16) |
469                                             ((unsigned)Ptr->Untyped[0] << 24);
470                             break;
471     case Type::PointerTyID: if (getTargetData().getPointerSize() == 4)
472                               goto Load4BytesBigEndian;
473     case Type::DoubleTyID:
474     case Type::ULongTyID:
475     case Type::LongTyID:    Result.ULongVal = (uint64_t)Ptr->Untyped[7] |
476                                              ((uint64_t)Ptr->Untyped[6] <<  8) |
477                                              ((uint64_t)Ptr->Untyped[5] << 16) |
478                                              ((uint64_t)Ptr->Untyped[4] << 24) |
479                                              ((uint64_t)Ptr->Untyped[3] << 32) |
480                                              ((uint64_t)Ptr->Untyped[2] << 40) |
481                                              ((uint64_t)Ptr->Untyped[1] << 48) |
482                                              ((uint64_t)Ptr->Untyped[0] << 56);
483                             break;
484     default:
485       std::cout << "Cannot load value of type " << *Ty << "!\n";
486       abort();
487     }
488   }
489   return Result;
490 }
491 
492 // InitializeMemory - Recursive function to apply a Constant value into the
493 // specified memory location...
494 //
495 void ExecutionEngine::InitializeMemory(const Constant *Init, void *Addr) {
496   if (isa<UndefValue>(Init)) {
497     return;
498   } else if (const ConstantPacked *CP = dyn_cast<ConstantPacked>(Init)) {
499     unsigned ElementSize =
500       getTargetData().getTypeSize(CP->getType()->getElementType());
501     for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
502       InitializeMemory(CP->getOperand(i), (char*)Addr+i*ElementSize);
503     return;
504   } else if (Init->getType()->isFirstClassType()) {
505     GenericValue Val = getConstantValue(Init);
506     StoreValueToMemory(Val, (GenericValue*)Addr, Init->getType());
507     return;
508   } else if (isa<ConstantAggregateZero>(Init)) {
509     memset(Addr, 0, (size_t)getTargetData().getTypeSize(Init->getType()));
510     return;
511   }
512 
513   switch (Init->getType()->getTypeID()) {
514   case Type::ArrayTyID: {
515     const ConstantArray *CPA = cast<ConstantArray>(Init);
516     unsigned ElementSize =
517       getTargetData().getTypeSize(CPA->getType()->getElementType());
518     for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
519       InitializeMemory(CPA->getOperand(i), (char*)Addr+i*ElementSize);
520     return;
521   }
522 
523   case Type::StructTyID: {
524     const ConstantStruct *CPS = cast<ConstantStruct>(Init);
525     const StructLayout *SL =
526       getTargetData().getStructLayout(cast<StructType>(CPS->getType()));
527     for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i)
528       InitializeMemory(CPS->getOperand(i), (char*)Addr+SL->MemberOffsets[i]);
529     return;
530   }
531 
532   default:
533     std::cerr << "Bad Type: " << *Init->getType() << "\n";
534     assert(0 && "Unknown constant type to initialize memory with!");
535   }
536 }
537 
538 /// EmitGlobals - Emit all of the global variables to memory, storing their
539 /// addresses into GlobalAddress.  This must make sure to copy the contents of
540 /// their initializers into the memory.
541 ///
542 void ExecutionEngine::emitGlobals() {
543   const TargetData &TD = getTargetData();
544 
545   // Loop over all of the global variables in the program, allocating the memory
546   // to hold them.
547   Module &M = getModule();
548   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
549        I != E; ++I)
550     if (!I->isExternal()) {
551       // Get the type of the global...
552       const Type *Ty = I->getType()->getElementType();
553 
554       // Allocate some memory for it!
555       unsigned Size = TD.getTypeSize(Ty);
556       addGlobalMapping(I, new char[Size]);
557     } else {
558       // External variable reference. Try to use the dynamic loader to
559       // get a pointer to it.
560       if (void *SymAddr = sys::DynamicLibrary::SearchForAddressOfSymbol(
561                             I->getName().c_str()))
562         addGlobalMapping(I, SymAddr);
563       else {
564         std::cerr << "Could not resolve external global address: "
565                   << I->getName() << "\n";
566         abort();
567       }
568     }
569 
570   // Now that all of the globals are set up in memory, loop through them all and
571   // initialize their contents.
572   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
573        I != E; ++I)
574     if (!I->isExternal())
575       EmitGlobalVariable(I);
576 }
577 
578 // EmitGlobalVariable - This method emits the specified global variable to the
579 // address specified in GlobalAddresses, or allocates new memory if it's not
580 // already in the map.
581 void ExecutionEngine::EmitGlobalVariable(const GlobalVariable *GV) {
582   void *GA = getPointerToGlobalIfAvailable(GV);
583   DEBUG(std::cerr << "Global '" << GV->getName() << "' -> " << GA << "\n");
584 
585   const Type *ElTy = GV->getType()->getElementType();
586   size_t GVSize = (size_t)getTargetData().getTypeSize(ElTy);
587   if (GA == 0) {
588     // If it's not already specified, allocate memory for the global.
589     GA = new char[GVSize];
590     addGlobalMapping(GV, GA);
591   }
592 
593   InitializeMemory(GV->getInitializer(), GA);
594   NumInitBytes += (unsigned)GVSize;
595   ++NumGlobals;
596 }
597