如何从LLVM的中间表示中获取在程序的每个功能中执行的功能调用列表?

问题描述

我正在尝试使用LLVM构建代码分析工具的简单版本.

I am trying to build a simple version of a code analysis tool with LLVM.

我有一些.ll文件，其中包含某些程序的中间LLVM表示形式.

I have a few .ll files which contain the intermediate LLVM representation of certain programs.

如何从LLVM的中间表示中获取在程序的每个功能中执行的功能调用列表?

我拥有的输入参数是LLVM:代表程序的模块类的实例.然后，使用getFunctionList()函数获取程序中存在的函数列表.

The input parameter I have is an instance of the LLVM: Module class which represents the program. Then, I get the list of functions present in the program with the function getFunctionList ().

void getFunctionCalls(const Module *M)
{

  // Iterate functions in program
  for (auto curFref = M->getFunctionList().begin(), endFref = M->getFunctionList().end();
 curFref != endFref; ++curFref) {

        // For each function
        // Get list of function calls

  }

}

推荐答案

这是我们工作代码的一部分此处:

This is a fragment from our working code here:

for (auto &module : Ctx.getModules()) {
  auto &functionList = module->getModule()->getFunctionList();
  for (auto &function : functionList) {
    for (auto &bb : function) {
      for (auto &instruction : bb) {
        if (CallInst *callInst = dyn_cast<CallInst>(&instruction)) {
          if (Function *calledFunction = callInst->getCalledFunction()) {
            if (calledFunction->getName().startswith("llvm.dbg.declare")) {

还请记住，还有一些调用指令InvokeInst，它们可以通过类似的方式获得.

Also keep in mind that there are also invoke instructions InvokeInst which may be obtained in a similar way.

Google CallInst vs InvokeInst，还可以了解带有或不带有被调用函数的函数.如果一个函数没有被调用的函数，则这是间接调用.当源代码而不是直接调用函数而是调用函数指针时，间接调用会出现在LLVM IR中.在C ++中，当某些类通过抽象接口(多态)进行操作时，通常会发生这种情况.因此请记住，即使有调用指令，也不总是能够100％跟踪被调用的函数.

Google CallInst vs InvokeInst and also learn about the functions with or without a called function. If a function does not have a called function this is indirect call. Indirect calls appear in LLVM IR when the source code instead of calling a function directly, calls a function pointer. In C++ this often happens when some class operates through an abstract interface (polymorphism). So keep in mind that it is not 100% always possible to trace a called function even though you have a call instruction in place.

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