Is it possible to use EE within optimization pass?

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1

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?

Please help me out here!
Thanks,
Bhavani

2

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.

3

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.

thanks,
Bhavani

4

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.

5

I think so. I am using the name try.

6

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.

I hope the question is clear now. Sorry for repeating so many times.
thanks,
Bhavani

7

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

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Thanks Nick and others who replied. I just fixed the issue. I compiled opt by linking executionengine into it and now I am able to create jit from within the optimization pass.