// FIXME: This might have been relevant for the old JIT but the MCJIT
// has a completly different implementation so this comment below is
// likely irrelevant and misleading.
//
// For performance purposes we construct the stub in such a way that the
// arguments pointer is passed through the static global variable gTheArgsP in
// this file. This is done so that the stub function prototype trivially matches
// the special cases that the JIT knows how to directly call. If this is not
// done, then the jit will end up generating a nullary stub just to call our
// stub, for every single function call.
Function *ExternalDispatcherImpl::createDispatcher(Function *target,
Instruction *inst,
Module *module) {
if (!resolveSymbol(target->getName()))
return 0;
CallSite cs;
if (inst->getOpcode() == Instruction::Call) {
cs = CallSite(cast<CallInst>(inst));
} else {
cs = CallSite(cast<InvokeInst>(inst));
}
Value **args = new Value *[cs.arg_size()];
std::vector<Type *> nullary;
// MCJIT functions need unique names, or wrong function can be called.
// The module identifier is included because for the MCJIT we need
// unique function names across all `llvm::Modules`s.
std::string fnName =
"dispatcher_" + target->getName().str() + module->getModuleIdentifier();
Function *dispatcher =
Function::Create(FunctionType::get(Type::getVoidTy(ctx), nullary, false),
GlobalVariable::ExternalLinkage, fnName, module);
BasicBlock *dBB = BasicBlock::Create(ctx, "entry", dispatcher);
// Get a Value* for &gTheArgsP, as an i64**.
Instruction *argI64sp = new IntToPtrInst(
ConstantInt::get(Type::getInt64Ty(ctx), (uintptr_t)(void *)&gTheArgsP),
PointerType::getUnqual(PointerType::getUnqual(Type::getInt64Ty(ctx))),
"argsp", dBB);
Instruction *argI64s = new LoadInst(argI64sp, "args", dBB);
// Get the target function type.
FunctionType *FTy = cast<FunctionType>(
cast<PointerType>(target->getType())->getElementType());
// Each argument will be passed by writing it into gTheArgsP[i].
unsigned i = 0, idx = 2;
for (CallSite::arg_iterator ai = cs.arg_begin(), ae = cs.arg_end(); ai != ae;
++ai, ++i) {
// Determine the type the argument will be passed as. This accomodates for
// the corresponding code in Executor.cpp for handling calls to bitcasted
// functions.
Type *argTy =
(i < FTy->getNumParams() ? FTy->getParamType(i) : (*ai)->getType());
Instruction *argI64p = GetElementPtrInst::Create(
KLEE_LLVM_GEP_TYPE(nullptr)
argI64s, ConstantInt::get(Type::getInt32Ty(ctx), idx), "", dBB);
Instruction *argp =
new BitCastInst(argI64p, PointerType::getUnqual(argTy), "", dBB);
args[i] = new LoadInst(argp, "", dBB);
unsigned argSize = argTy->getPrimitiveSizeInBits();
idx += ((!!argSize ? argSize : 64) + 63) / 64;
}
Constant *dispatchTarget = module->getOrInsertFunction(
target->getName(), FTy, target->getAttributes());
Instruction *result = CallInst::Create(
dispatchTarget, llvm::ArrayRef<Value *>(args, args + i), "", dBB);
if (result->getType() != Type::getVoidTy(ctx)) {
Instruction *resp = new BitCastInst(
argI64s, PointerType::getUnqual(result->getType()), "", dBB);
new StoreInst(result, resp, dBB);
}
ReturnInst::Create(ctx, dBB);
delete[] args;
return dispatcher;
}
inline String parseExpression(QStringRef const &expression) const
{
// Presently the expression consists of a single symbol.
return resolveSymbol(expression);
}