llvm dev - Jan 2011 - [LLVMdev] [LLVMDEV]How could I get function name in this situation?

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??

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
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>

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
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>

> 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?

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
>>>>
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>
>>
>
>