[LLVMdev] [LLVMDEV]How could I get function name in this situation?

[songlh at cs.wisc.edu]

> On 1/26/11 3:00 PM, songlh at cs.wisc.edu wrote:
>>> On 1/26/11 2:40 PM, songlh at cs.wisc.edu wrote:
>>>> thanks!
>>>>
>>>> After I check the ll file, I find this:
>>>>
>>>> %1 = load %struct.nsAString** %aBuf_addr, align 4, !dbg !2048
>>>> %2 = getelementptr inbounds %struct.nsAString* %1, i32 0, i32 0, !dbg
>>>> !2048
>>>> %3 = getelementptr inbounds %struct.nsISupports* %2, i32 0, i32 0,
>>>> !dbg
>>>> !2048
>>>> %4 = load i32 (...)*** %3, align 4, !dbg !2048
>>>> %5 = getelementptr inbounds i32 (...)** %4, i32 10, !dbg !2048
>>>> %6 = load i32 (...)** %5, align 1, !dbg !2048
>>>> %7 = bitcast i32 (...)* %6 to void (%struct.nsAString*, i32)*, !dbg
>>>> !2048
>>>> %8 = load %struct.nsAString** %aBuf_addr, align 4, !dbg !2048
>>>> call void %7(%struct.nsAString* %8, i32 0) nounwind, !dbg !2048
>>>>
>>>> The last line is the CallInst I find.
>>>>
>>>> I feel it is using memory address to get the function. Is there
>>>> someway
>>>> I
>>>> can do this in my c++ code??
>>> Yes, the code is loading a pointer to a function from memory and
>>> calling
>>> it.
>>>
>>> I don't understand your question, though.
>>>
>>> -- John T.
>>>
>> I mean how do I realize this in a c++ pass code?
>
> You're still not making sense.  Are you asking what sort of C++ code
> will generate the use of a function pointer when compiled into LLVM IR,
> or are you asking how to determine, within an LLVM pass, what the
> possible target(s) of an indirect function call might be?
>
> -- John T.

Sorry, I am asking the second question.
"
how to determine, within an LLVM pass, what the
possible target(s) of an indirect function call might be?
"

thanks a lot!

Linhai
>
>> thanks a lot!
>>
>>             Linhai
>>
>>>> thanks a lot!
>>>>
>>>>> On 1/26/11 2:07 PM, songlh at cs.wisc.edu wrote:
>>>>>> Hi:
>>>>>>
>>>>>>      My llvm code is:
>>>>>>
>>>>>>      for( BasicBlock::iterator i = b->begin() , ie = b->end();
>>>>>>           b != be ; b ++ ){
>>>>>>           if( CallInst * pCall = dyn_cast<CallInst>(i)){
>>>>>>
>>>>>>              pCall->dump(); //
>>>>>>              Function * pFunction = pCall->getCalledFunction();
>>>>>>              if( !pFunction ){
>>>>>>
>>>>>>              }
>>>>>>              std::string fname = pFunction->getName();
>>>>>>           }
>>>>>>      }
>>>>>>
>>>>>>      The dump result of the function call I want to find is :
>>>>>>
>>>>>>      call void %7(%struct.nsAString* %8, i32 0) nounwind, !dbg !1565
>>>>> This is a call using a function pointer.  There is no function name
>>>>> to
>>>>> retrieve.  You can check the called value (pcall->getCalledValue())
>>>>> and
>>>>> see if it's something like a cast instruction that casts a constant
>>>>> function value, but that case is probably unlikely.
>>>>>
>>>>> -- John T.
>>>>>
>>>>>>      it returns null from pCall->getCalledFunction(), and I cannot
>>>>>> get
>>>>>> the
>>>>>> function name.
>>>>>>
>>>>>>      How could I get the function name in this situation?
>>>>>>
>>>>>>      thanks a lot!
>>>>>>
>>>>>>                                            Linhai
>>>>>>
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>>>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>>>
>>
>
>