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

[John Criswell]

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.

> 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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>>
>