[LLVMdev] Extract operations as function

[Manish Gupta]

Thanks again Duncan.
As you said just prototype is enough. So in mypass.c I write my pass and
declare func(x,y,op) and in mypass.h I write my definition for func(x,y,op).
Kindly let me know my understanding is correct? So next when ever i replace
instruction with op uses with this func automatically correct code in
intermediate llvm IR representation would be inserted.

Writing function definition for func(x,y,op) using IR builder will be
painful I guess.

Regards,
Manish

On Thu, May 12, 2011 at 2:05 AM, Duncan Sands <baldrick at free.fr> wrote:

> Hi Manish,
>
>
>  Great!! Thanks Duncan.
>> By step 1 that you mentioned it seems I can write my function func(x,y,op)
>> in
>> mypass.cpp itself. Please elaborate how can add it to the module?
>>
>
> the minimum is to add a prototype for "func" to the module.  For that you
> can
> use getOrInsertFunction.  If you want to insert the code defining "func"
> too,
> then insert the prototype, add a basic block to it, use an IRBuilder to add
> instructions to the basic block.
>
> Ciao, Duncan.
>
>
>>
>> On Thu, May 12, 2011 at 1:22 AM, Duncan Sands <baldrick at free.fr
>> <mailto:baldrick at free.fr>> wrote:
>>
>>    Hi Manish,
>>
>>     > I am planning to extract every operation as function.
>>     >
>>     > eg. z=x+y; ==> z=func(x,y,op);
>>     >
>>     > I wish to write a custom definition of op. Which I would like to
>> define
>>    in func.
>>     >
>>     > It would be really helpful if someone could suggest passes already
>>    available in
>>     > llvm to look for or point some references how should one proceed on
>> it.
>>
>>    I think you should write your own pass that
>>    (1) adds a declaration of "func" to the module
>>    (2) iterates over all functions, and all instructions in the function.
>>  When it
>>    sees a binary operator ("isa<BinaryOperator>(Instruction)") it needs to
>> first
>>    insert a call just in front of the instruction (see an IRBuilder to do
>> this;
>>    use "SetInsertPoint(Instruction)" to tell it where to add the call; use
>>    CreateCall3 to create the call).  Then use replaceAllUsesWith to
>> replace every
>>    use of the binary operator with the call you just created.  Finally,
>> delete the
>>    original instruction (eraseFromParent).
>>
>>    Ciao, Duncan.
>>
>>     >
>>     > Is codeExtractor.cpp useful for this. I was also thinking of going
>> like
>>     > loop-extract way. any other suggestion would be extremely helpful
>>     >
>>     >
>>     >
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