[LLVMdev] Problem about the type of Function's arguement in llvm

[Jianfei Hu]

in the  tutorial of official llvm doc, chapter 3, it deals with arguement
of function as follow:

for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
       ++AI, ++Idx) {
    AI->setName(Args[Idx]);

    // NamedValues is map<string, Value*>
    NamedValues[Args[Idx]] = AI;

and when it try to get the value of arguement, it simply does:

Value *VariableExprAST::Codegen() {
  Value *V = NamedValues[Name];
  return V ? V : ErrorV("Unknown variable name");
}

It means that we can access value of arguement directly.

However, in llvm.org/demo and the chapter 6 of tutorial, it deals with
arguemnt:
1. allocate memory for arguement
2. then store the arguemnt into the memory.
3. CreateLoad() to load the arguement when accessing the value of arguement.

I have several problems:
Which way should I follow to get the vale of arguement?

When I tried to use CreateLoad(arguement), the program gives a segmentation
error.
Does this result from the wrong type of argument, unsuitable to be the
params of CreateLoad()?
If it is, what's the type of Function->arg_begin() ? (The source code is
too nested for me to find the original type of that)
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