[LLVMdev] Is it possible to use EE within optimization pass?

[Nick Lewycky]

bhavani krishnan wrote:
> I realize my questions may not have been so clear. To give more details. I am writing a fuction pass. I want to interpret some of the instructions within the function pass. In order to do so, I need to create an EE object within the function pass. Now, If I compile and execute using opt. I get an error(Error loading symbol) at the line where I am creating EE. 
> opt: symbol lookup error: ../../../build/Release/lib/Try.so: undefined symbol: _ZN4llvm15ExecutionEngine6createEPNS_14ModuleProviderEbPSs

> So, I thought I need to link the EE library files as it is not able to load EE. In order to do so, I added the line LINK_COMPONENTS=engine to the Makefile. Now, when I execute using opt, I get the error that the pass is registered multiple times. I know that there has to be a way out of this. Please let me know how I should link/load the EE library files with my optimization pass.

Make sure you aren't linking both your pass against the EE and the opt 
program against the EE.

> I hope the question is clear now. Sorry for repeating so many times.

If you're in a rush, I suggest that you just drop 'opt' and build your 
own standalone opt-like program which is linked against the execution 
engine and your optimization pass (ie., not using -load) and whatever 
other things you need. I also suggest linking with LINK_COMPONENTS=all, 
since that mysteriously seems to avoid all linker errors.

Otherwise, you may want to try tracking down which pass is being 
registered multiple times, and work backwards to find out which file is 
getting linked twice. I wouldn't approach this from the angle that 
you're doing anything wrong. Rather, assume that LLVM's dependencies and 
LINK_COMPONENTS system is buggy and try to figure out how and why.

Hope that helps.
Nick Lewycky

> thanks,
> Bhavani
> 
> 
> --- On Mon, 10/27/08, John Criswell <criswell at cs.uiuc.edu> wrote:
> 
>> From: John Criswell <criswell at cs.uiuc.edu>
>> Subject: Re: [LLVMdev] Is it possible to use EE within optimization pass?
>> To: "bhavi63 at yahoo.com" <bhavi63 at yahoo.com>
>> Cc: "LLVM Developers Mailing List" <llvmdev at cs.uiuc.edu>
>> Date: Monday, October 27, 2008, 3:22 PM
>> bhavani krishnan wrote:
>>> Thanks John! My pass is registered only in 1 cpp file.
>> It registers and executes fine without the EE.
>>> I only get the Pass registered multiple times error
>> when I try to link to the EE by using LINK_COMPONENTS=engine
>> in the Makefile. Without that line in the Makefile, my pass
>> gets registered fine but it is not able to create EE(Error
>> reading Symbol). So, how do I link LLVMExecutionEngine.o
>> without causing the multiple registration error.
>>>   
>> Just to make sure we've covered all the obvious stuff,
>> are you sure that 
>> the name of your pass (the name you use when you execute it
>> with the opt 
>> command) is unique?  Is the class name of your pass unique?
>>
>> -- John T.
>>
>>> thanks,
>>> Bhavani
>>>
>>> --- On Mon, 10/27/08, John Criswell
>> <criswell at cs.uiuc.edu> wrote:
>>>   
>>>> From: John Criswell <criswell at cs.uiuc.edu>
>>>> Subject: Re: [LLVMdev] Is it possible to use EE
>> within optimization pass?
>>>> To: "bhavi63 at yahoo.com"
>> <bhavi63 at yahoo.com>, "LLVM Developers Mailing
>> List" <llvmdev at cs.uiuc.edu>
>>>> Date: Monday, October 27, 2008, 3:01 PM
>>>> bhavani krishnan wrote:
>>>>     
>>>>> Hi all,
>>>>>
>>>>> I am repeating my question from yesterday coz
>> I need
>>>>>       
>>>> to find a solution to this ASAP. 
>>>>     
>>>>> How do I link the executionengine to an
>> optimization
>>>>>       
>>>> pass. If I use LINK_COMPONENTS=engine in the
>> Makefile, I get
>>>> the Pass registered multiple times error. And if i
>> dont use
>>>> anything, it is not able to load the EE. It gives
>> error
>>>> loading symbol error. So,
>>>>     
>>>>> 1. Is it possible to use the EE within an
>> optimization
>>>>>       
>>>> pass?
>>>>     
>>>>> 2. If it is possible, how do I do it?
>>>>>   
>>>>>       
>>>> I have a hunch that I know what your problem is.
>>>>
>>>> You said that your pass is getting registered
>> twice.  Are
>>>> you sure that 
>>>> your RegisterPass declaration is only being called
>> once?  A
>>>> common error 
>>>> is to put the RegisterPass<MyPass> Foo
>> variable
>>>> inside a header file 
>>>> that gets included by multiple .cpp files
>> implementing your
>>>> pass (I'm 
>>>> assuming you've written a custom pass here). 
>> This will
>>>> cause your pass 
>>>> to get registered multiple times, which will make
>> the LLVM
>>>> pass manager 
>>>> unhappy.
>>>>
>>>> I believe this is because the RegisterPass<>
>>>> constructor does pass 
>>>> registration, so if it's declared multiple
>> times, it
>>>> registers the pass 
>>>> multiple times.
>>>>
>>>> To fix it, put RegisterPass<YourPassName>
>> inside one
>>>> of the .cpp files 
>>>> implementing your pass.
>>>>
>>>> Regarding your more specific questions, I suspect
>> that EE
>>>> can be used 
>>>> with the Pass Manager to run optimization passes,
>> but
>>>> that's just a 
>>>> guess on my part; I have never done it myself.  I
>> suspect
>>>> the issue is 
>>>> just getting the right libraries listed in
>> LINK_COMPONENTS
>>>> and making 
>>>> sure your pass isn't registered twice.
>>>>
>>>> Please let us know if the RegisterPass thing is
>> the problem
>>>> and whether 
>>>> the solution above fixes it.
>>>>
>>>> Regards,
>>>>
>>>> -- John T.
>>>>
>>>>
>>>>     
>>>>> Please help me out here!
>>>>> Thanks,
>>>>> Bhavani
>>>>>
>>>>>
>>>>>
>>>>>       
>>>>>
>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> LLVMdev at cs.uiuc.edu        
>> http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>>>       
>>>
>>>       
>>>
> 
> 
>       
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