llvm dev - May 2011 - [LLVMdev] difficulty in replicating a sequence of instructions + inserting at a different location -- "instruction doesn't dominate all uses"

I am having difficulty in replicating a sequence of instructions (2+, 
with def-use dependencies within) and inserting them at a different 
location.

I have tried a few different approaches (IRBuilder, new Instruction(), 
I->clone(), insertBefore/insertAfter,etc.), all leading to the same 
error msg:
"Instruction doesn't dominate all uses"

The DevList has a few previous discussions on this, but not much of 
hints I can get from there.

Could somebody point me a code template or an existing LLVM source file 
that does similar things?


Thank you very much

Chuck


-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20110502/88a3ff6f/attachment.html>

hi,

Do you have a example for the code generated by your pass?

best regards
ether

On Tue, May 3, 2011 at 12:59 AM, Chuck Zhao <czhao at eecg.toronto.edu>
wrote:
> I am having difficulty in replicating a sequence of instructions (2+, with
> def-use dependencies within) and inserting them at a different location.
>
> I have tried a few different approaches (IRBuilder, new Instruction(),
> I->clone(), insertBefore/insertAfter,etc.), all leading to the same
error
> msg:
> "Instruction doesn't dominate all uses"
>
> The DevList has a few previous discussions on this, but not much of hints I
> can get from there.
>
> Could somebody point me a code template or an existing LLVM source file
that
> does similar things?
>
>
> Thank you very much
>
> Chuck
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>

On 5/2/11 11:59 AM, Chuck Zhao wrote:
> I am having difficulty in replicating a sequence of instructions (2+, 
> with def-use dependencies within) and inserting them at a different 
> location.
>
> I have tried a few different approaches (IRBuilder, new Instruction(), 
> I->clone(), insertBefore/insertAfter,etc.), all leading to the same 
> error msg:
> "Instruction doesn't dominate all uses"
In LLVM IR, an instruction must dominate all of its uses.  What this 
means is that an instruction must be inserted into a basic block that 
dominates the basic blocks of all instructions that use the inserted 
instruction's result.  In other words, it must be the case that the 
inserted instruction is always executed once before any instruction that 
uses its result.

I'm not sure what you are doing wrong that is causing the above problem 
to occur.  It might be that you're not adjusting the def-use chains 
after replication or you might be inserting instructions in the wrong 
order in a basic block (defs must come before uses).

The above error comes from the verifier pass, so you can disable the 
verifier pass, save the bitcode, and disassemble it to see what IR 
you're building that is incorrect.  Alternatively, you can have your 
transform dump the new instructions to stdout or stderr to see what IR 
it is generating.

-- John T.
>
> The DevList has a few previous discussions on this, but not much of 
> hints I can get from there.
>
> Could somebody point me a code template or an existing LLVM source 
> file that does similar things?
>
>
> Thank you very much
>
> Chuck
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20110502/c053ad65/attachment.html>

John, Ether,

Thank you for the reply.

The root of the problem is exactly as what John described --
"there are attempted uses of instruction(s) before its/their respective 
definition(s)", so the LLVM Verify pass complains as "Instruction 
doesn't dominate all uses".

This unveils the problem, but I haven't come up with a proper solution yet.
I will address in a different question.

Thank you for the help.

Chuck

On 5/2/2011 2:29 PM, John Criswell wrote:
> On 5/2/11 11:59 AM, Chuck Zhao wrote:
>> I am having difficulty in replicating a sequence of instructions (2+, 
>> with def-use dependencies within) and inserting them at a different 
>> location.
>>
>> I have tried a few different approaches (IRBuilder, new 
>> Instruction(), I->clone(), insertBefore/insertAfter,etc.), all 
>> leading to the same error msg:
>> "Instruction doesn't dominate all uses"
>
> In LLVM IR, an instruction must dominate all of its uses.  What this 
> means is that an instruction must be inserted into a basic block that 
> dominates the basic blocks of all instructions that use the inserted 
> instruction's result.  In other words, it must be the case that the 
> inserted instruction is always executed once before any instruction 
> that uses its result.
>
> I'm not sure what you are doing wrong that is causing the above 
> problem to occur.  It might be that you're not adjusting the def-use 
> chains after replication or you might be inserting instructions in the 
> wrong order in a basic block (defs must come before uses).
>
> The above error comes from the verifier pass, so you can disable the 
> verifier pass, save the bitcode, and disassemble it to see what IR 
> you're building that is incorrect.  Alternatively, you can have your 
> transform dump the new instructions to stdout or stderr to see what IR 
> it is generating.
>
> -- John T.
>
>>
>> The DevList has a few previous discussions on this, but not much of 
>> hints I can get from there.
>>
>> Could somebody point me a code template or an existing LLVM source 
>> file that does similar things?
>>
>>
>> Thank you very much
>>
>> Chuck
>>
>>
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu          http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.llvm.org/pipermail/llvm-dev/attachments/20110504/c056928d/attachment.html>