LLVM API Documentation

JIT.cpp

Go to the documentation of this file.
00001 //===-- JIT.cpp - LLVM Just in Time Compiler ------------------------------===//
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 tool implements a just-in-time compiler for LLVM, allowing direct
00011 // execution of LLVM bytecode in an efficient manner.
00012 //
00013 //===----------------------------------------------------------------------===//
00014 
00015 #include "JIT.h"
00016 #include "llvm/Constants.h"
00017 #include "llvm/DerivedTypes.h"
00018 #include "llvm/Function.h"
00019 #include "llvm/GlobalVariable.h"
00020 #include "llvm/Instructions.h"
00021 #include "llvm/ModuleProvider.h"
00022 #include "llvm/CodeGen/MachineCodeEmitter.h"
00023 #include "llvm/CodeGen/MachineFunction.h"
00024 #include "llvm/ExecutionEngine/GenericValue.h"
00025 #include "llvm/System/DynamicLibrary.h"
00026 #include "llvm/Target/TargetMachine.h"
00027 #include "llvm/Target/TargetJITInfo.h"
00028 #include <iostream>
00029 using namespace llvm;
00030 
00031 static struct RegisterJIT {
00032   RegisterJIT() { JIT::Register(); }
00033 } JITRegistrator;
00034 
00035 namespace llvm {
00036   void LinkInJIT() {
00037   }
00038 }
00039 
00040 JIT::JIT(ModuleProvider *MP, TargetMachine &tm, TargetJITInfo &tji)
00041   : ExecutionEngine(MP), TM(tm), TJI(tji), state(MP) {
00042   setTargetData(TM.getTargetData());
00043 
00044   // Initialize MCE
00045   MCE = createEmitter(*this);
00046 
00047   // Add target data
00048   MutexGuard locked(lock);
00049   FunctionPassManager& PM = state.getPM(locked);
00050   PM.add(new TargetData(TM.getTargetData()));
00051 
00052   // Compile LLVM Code down to machine code in the intermediate representation
00053   TJI.addPassesToJITCompile(PM);
00054 
00055   // Turn the machine code intermediate representation into bytes in memory that
00056   // may be executed.
00057   if (TM.addPassesToEmitMachineCode(PM, *MCE)) {
00058     std::cerr << "Target '" << TM.getName()
00059               << "' doesn't support machine code emission!\n";
00060     abort();
00061   }
00062 }
00063 
00064 JIT::~JIT() {
00065   delete MCE;
00066   delete &TM;
00067 }
00068 
00069 /// run - Start execution with the specified function and arguments.
00070 ///
00071 GenericValue JIT::runFunction(Function *F,
00072                               const std::vector<GenericValue> &ArgValues) {
00073   assert(F && "Function *F was null at entry to run()");
00074 
00075   void *FPtr = getPointerToFunction(F);
00076   assert(FPtr && "Pointer to fn's code was null after getPointerToFunction");
00077   const FunctionType *FTy = F->getFunctionType();
00078   const Type *RetTy = FTy->getReturnType();
00079 
00080   assert((FTy->getNumParams() <= ArgValues.size() || FTy->isVarArg()) &&
00081          "Too many arguments passed into function!");
00082   assert(FTy->getNumParams() == ArgValues.size() &&
00083          "This doesn't support passing arguments through varargs (yet)!");
00084 
00085   // Handle some common cases first.  These cases correspond to common `main'
00086   // prototypes.
00087   if (RetTy == Type::IntTy || RetTy == Type::UIntTy || RetTy == Type::VoidTy) {
00088     switch (ArgValues.size()) {
00089     case 3:
00090       if ((FTy->getParamType(0) == Type::IntTy ||
00091            FTy->getParamType(0) == Type::UIntTy) &&
00092           isa<PointerType>(FTy->getParamType(1)) &&
00093           isa<PointerType>(FTy->getParamType(2))) {
00094         int (*PF)(int, char **, const char **) =
00095           (int(*)(int, char **, const char **))FPtr;
00096 
00097         // Call the function.
00098         GenericValue rv;
00099         rv.IntVal = PF(ArgValues[0].IntVal, (char **)GVTOP(ArgValues[1]),
00100                        (const char **)GVTOP(ArgValues[2]));
00101         return rv;
00102       }
00103       break;
00104     case 2:
00105       if ((FTy->getParamType(0) == Type::IntTy ||
00106            FTy->getParamType(0) == Type::UIntTy) &&
00107           isa<PointerType>(FTy->getParamType(1))) {
00108         int (*PF)(int, char **) = (int(*)(int, char **))FPtr;
00109 
00110         // Call the function.
00111         GenericValue rv;
00112         rv.IntVal = PF(ArgValues[0].IntVal, (char **)GVTOP(ArgValues[1]));
00113         return rv;
00114       }
00115       break;
00116     case 1:
00117       if (FTy->getNumParams() == 1 &&
00118           (FTy->getParamType(0) == Type::IntTy ||
00119            FTy->getParamType(0) == Type::UIntTy)) {
00120         GenericValue rv;
00121         int (*PF)(int) = (int(*)(int))FPtr;
00122         rv.IntVal = PF(ArgValues[0].IntVal);
00123         return rv;
00124       }
00125       break;
00126     }
00127   }
00128 
00129   // Handle cases where no arguments are passed first.
00130   if (ArgValues.empty()) {
00131     GenericValue rv;
00132     switch (RetTy->getTypeID()) {
00133     default: assert(0 && "Unknown return type for function call!");
00134     case Type::BoolTyID:
00135       rv.BoolVal = ((bool(*)())FPtr)();
00136       return rv;
00137     case Type::SByteTyID:
00138     case Type::UByteTyID:
00139       rv.SByteVal = ((char(*)())FPtr)();
00140       return rv;
00141     case Type::ShortTyID:
00142     case Type::UShortTyID:
00143       rv.ShortVal = ((short(*)())FPtr)();
00144       return rv;
00145     case Type::VoidTyID:
00146     case Type::IntTyID:
00147     case Type::UIntTyID:
00148       rv.IntVal = ((int(*)())FPtr)();
00149       return rv;
00150     case Type::LongTyID:
00151     case Type::ULongTyID:
00152       rv.LongVal = ((int64_t(*)())FPtr)();
00153       return rv;
00154     case Type::FloatTyID:
00155       rv.FloatVal = ((float(*)())FPtr)();
00156       return rv;
00157     case Type::DoubleTyID:
00158       rv.DoubleVal = ((double(*)())FPtr)();
00159       return rv;
00160     case Type::PointerTyID:
00161       return PTOGV(((void*(*)())FPtr)());
00162     }
00163   }
00164 
00165   // Okay, this is not one of our quick and easy cases.  Because we don't have a
00166   // full FFI, we have to codegen a nullary stub function that just calls the
00167   // function we are interested in, passing in constants for all of the
00168   // arguments.  Make this function and return.
00169 
00170   // First, create the function.
00171   FunctionType *STy=FunctionType::get(RetTy, std::vector<const Type*>(), false);
00172   Function *Stub = new Function(STy, Function::InternalLinkage, "",
00173                                 F->getParent());
00174 
00175   // Insert a basic block.
00176   BasicBlock *StubBB = new BasicBlock("", Stub);
00177 
00178   // Convert all of the GenericValue arguments over to constants.  Note that we
00179   // currently don't support varargs.
00180   std::vector<Value*> Args;
00181   for (unsigned i = 0, e = ArgValues.size(); i != e; ++i) {
00182     Constant *C = 0;
00183     const Type *ArgTy = FTy->getParamType(i);
00184     const GenericValue &AV = ArgValues[i];
00185     switch (ArgTy->getTypeID()) {
00186     default: assert(0 && "Unknown argument type for function call!");
00187     case Type::BoolTyID:   C = ConstantBool::get(AV.BoolVal); break;
00188     case Type::SByteTyID:  C = ConstantSInt::get(ArgTy, AV.SByteVal);  break;
00189     case Type::UByteTyID:  C = ConstantUInt::get(ArgTy, AV.UByteVal);  break;
00190     case Type::ShortTyID:  C = ConstantSInt::get(ArgTy, AV.ShortVal);  break;
00191     case Type::UShortTyID: C = ConstantUInt::get(ArgTy, AV.UShortVal); break;
00192     case Type::IntTyID:    C = ConstantSInt::get(ArgTy, AV.IntVal);    break;
00193     case Type::UIntTyID:   C = ConstantUInt::get(ArgTy, AV.UIntVal);   break;
00194     case Type::LongTyID:   C = ConstantSInt::get(ArgTy, AV.LongVal);   break;
00195     case Type::ULongTyID:  C = ConstantUInt::get(ArgTy, AV.ULongVal);  break;
00196     case Type::FloatTyID:  C = ConstantFP  ::get(ArgTy, AV.FloatVal);  break;
00197     case Type::DoubleTyID: C = ConstantFP  ::get(ArgTy, AV.DoubleVal); break;
00198     case Type::PointerTyID:
00199       void *ArgPtr = GVTOP(AV);
00200       if (sizeof(void*) == 4) {
00201         C = ConstantSInt::get(Type::IntTy, (int)(intptr_t)ArgPtr);
00202       } else {
00203         C = ConstantSInt::get(Type::LongTy, (intptr_t)ArgPtr);
00204       }
00205       C = ConstantExpr::getCast(C, ArgTy);  // Cast the integer to pointer
00206       break;
00207     }
00208     Args.push_back(C);
00209   }
00210 
00211   CallInst *TheCall = new CallInst(F, Args, "", StubBB);
00212   TheCall->setTailCall();
00213   if (TheCall->getType() != Type::VoidTy)
00214     new ReturnInst(TheCall, StubBB);             // Return result of the call.
00215   else
00216     new ReturnInst(StubBB);                      // Just return void.
00217 
00218   // Finally, return the value returned by our nullary stub function.
00219   return runFunction(Stub, std::vector<GenericValue>());
00220 }
00221 
00222 /// runJITOnFunction - Run the FunctionPassManager full of
00223 /// just-in-time compilation passes on F, hopefully filling in
00224 /// GlobalAddress[F] with the address of F's machine code.
00225 ///
00226 void JIT::runJITOnFunction(Function *F) {
00227   static bool isAlreadyCodeGenerating = false;
00228   assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
00229 
00230   MutexGuard locked(lock);
00231 
00232   // JIT the function
00233   isAlreadyCodeGenerating = true;
00234   state.getPM(locked).run(*F);
00235   isAlreadyCodeGenerating = false;
00236 
00237   // If the function referred to a global variable that had not yet been
00238   // emitted, it allocates memory for the global, but doesn't emit it yet.  Emit
00239   // all of these globals now.
00240   while (!state.getPendingGlobals(locked).empty()) {
00241     const GlobalVariable *GV = state.getPendingGlobals(locked).back();
00242     state.getPendingGlobals(locked).pop_back();
00243     EmitGlobalVariable(GV);
00244   }
00245 }
00246 
00247 /// getPointerToFunction - This method is used to get the address of the
00248 /// specified function, compiling it if neccesary.
00249 ///
00250 void *JIT::getPointerToFunction(Function *F) {
00251   MutexGuard locked(lock);
00252 
00253   if (void *Addr = getPointerToGlobalIfAvailable(F))
00254     return Addr;   // Check if function already code gen'd
00255 
00256   // Make sure we read in the function if it exists in this Module
00257   if (F->hasNotBeenReadFromBytecode())
00258     try {
00259       MP->materializeFunction(F);
00260     } catch ( std::string& errmsg ) {
00261       std::cerr << "Error reading function '" << F->getName()
00262                 << "' from bytecode file: " << errmsg << "\n";
00263       abort();
00264     } catch (...) {
00265       std::cerr << "Error reading function '" << F->getName()
00266                 << "from bytecode file!\n";
00267       abort();
00268     }
00269 
00270   if (F->isExternal()) {
00271     void *Addr = getPointerToNamedFunction(F->getName());
00272     addGlobalMapping(F, Addr);
00273     return Addr;
00274   }
00275 
00276   runJITOnFunction(F);
00277 
00278   void *Addr = getPointerToGlobalIfAvailable(F);
00279   assert(Addr && "Code generation didn't add function to GlobalAddress table!");
00280   return Addr;
00281 }
00282 
00283 /// getOrEmitGlobalVariable - Return the address of the specified global
00284 /// variable, possibly emitting it to memory if needed.  This is used by the
00285 /// Emitter.
00286 void *JIT::getOrEmitGlobalVariable(const GlobalVariable *GV) {
00287   MutexGuard locked(lock);
00288 
00289   void *Ptr = getPointerToGlobalIfAvailable(GV);
00290   if (Ptr) return Ptr;
00291 
00292   // If the global is external, just remember the address.
00293   if (GV->isExternal()) {
00294     Ptr = sys::DynamicLibrary::SearchForAddressOfSymbol(GV->getName().c_str());
00295     if (Ptr == 0) {
00296       std::cerr << "Could not resolve external global address: "
00297                 << GV->getName() << "\n";
00298       abort();
00299     }
00300   } else {
00301     // If the global hasn't been emitted to memory yet, allocate space.  We will
00302     // actually initialize the global after current function has finished
00303     // compilation.
00304     uint64_t S = getTargetData().getTypeSize(GV->getType()->getElementType());
00305     unsigned char A =
00306       getTargetData().getTypeAlignment(GV->getType()->getElementType());
00307     Ptr = MCE->allocateGlobal(S, A);
00308     state.getPendingGlobals(locked).push_back(GV);
00309   }
00310   addGlobalMapping(GV, Ptr);
00311   return Ptr;
00312 }
00313 
00314 
00315 /// recompileAndRelinkFunction - This method is used to force a function
00316 /// which has already been compiled, to be compiled again, possibly
00317 /// after it has been modified. Then the entry to the old copy is overwritten
00318 /// with a branch to the new copy. If there was no old copy, this acts
00319 /// just like JIT::getPointerToFunction().
00320 ///
00321 void *JIT::recompileAndRelinkFunction(Function *F) {
00322   void *OldAddr = getPointerToGlobalIfAvailable(F);
00323 
00324   // If it's not already compiled there is no reason to patch it up.
00325   if (OldAddr == 0) { return getPointerToFunction(F); }
00326 
00327   // Delete the old function mapping.
00328   addGlobalMapping(F, 0);
00329 
00330   // Recodegen the function
00331   runJITOnFunction(F);
00332 
00333   // Update state, forward the old function to the new function.
00334   void *Addr = getPointerToGlobalIfAvailable(F);
00335   assert(Addr && "Code generation didn't add function to GlobalAddress table!");
00336   TJI.replaceMachineCodeForFunction(OldAddr, Addr);
00337   return Addr;
00338 }
00339 
00340 /// freeMachineCodeForFunction - release machine code memory for given Function
00341 ///
00342 void JIT::freeMachineCodeForFunction(Function *F) {
00343   // currently a no-op
00344 }