[LLVMdev] Extract operations as function

[Duncan Sands]

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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