如何使用LLVM IRBuilder从外部DLL调用函数? [英] How to call functions from external DLL using LLVM IRBuilder?

问题描述

如何从LLVM的外部DLL调用函数?如何从LLVM代码调用DLL文件中定义的函数?

How to call functions from external DLL from LLVM? How to call a function defined in a DLL file from a LLVM code?

推荐答案

由于您的问题缺少重要信息，我想您可能想要实现以下目标.我猜您将使用c/c ++接口，并且该函数具有签名void fun(void).我还猜想您将使用LLVM Builder创建对此功能的调用(而不是clang等).

As your question is missing vital information, I can guess that you want to achieve the following. I am guessing you will be using the c/c++ interface and that the function has a signature void fun(void). I also guess that you will be using LLVM Builder to create calls to this very function (and not clang or the like).

首先使用dlopen/loadlibrary动态加载函数并获取函数指针fnPtr.

Start by using dlopen / loadlibrary to dynamically load the function and get the function pointer fnPtr.

为函数的返回值创建Type*

Type* voidType[1];
voidType[0] = Type::getVoidTy(getGlobalContext());
ArrayRef<Type*> voidTypeARef (voidType, 1);

为此功能创建一个Function*.在初始化阶段，您应该已经有一个Module* TheModule.

Create a Function* for the function. You should have a Module* TheModule already from initialization phase.

FunctionType* signature = FunctionType::get(voidTypeARef, false);
Function* func = Function::Create(signature, Function::ExternalLinkage, "fun", TheModule);

使用addGlobalMapping创建到该功能的映射.在初始化阶段，您应该有一个ExecutionEngine* TheExecutionEngine.

Use addGlobalMapping to create a Mapping to the function. You should have a ExecutionEngine* TheExecutionEngine from initialization phase.

TheExecutionEngine->addGlobalMapping(func, const_cast<void*>(fnPtr));

现在，在您要调用的适当位置，您现在可以像这样使用IRBuilder插入对函数的调用.

Now, at the appropiate place where you want to call, you can now insert calls to the function using IRBuilder like this.

Function *FuncToCall= TheModule->getFunction("fun");
std::vector<Value*> Args; // This is empty since void parameters of function
Value *Result = IRBuilder->CreateCall(FuncToCall, Args, "calltmp"); // Result is void

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