[LLVMdev] CFG Manipulation is LLVM

[Rohith Goparaju]

  Hi Duncan,

    Does llvm have any specific methods to build dependenece graphs ?

  Thanks,
  Rohith.

On Fri, Mar 26, 2010 at 4:50 AM, Duncan Sands <baldrick at free.fr> wrote:

> Hi Rohith,
>
>
>      I'm actually working on building a dependence graph . I'm not able
>> to find the methods which llvm uses to build the CFG. Is it possible to
>> use the same functions do build a dependence graph ( i Know the CFG
>> nodes are basicblocks where as dependence graph nodes will be variables)?.
>>
>
> LLVM does not have explicit methods to build the CFG because it is created
> automatically when you build the IR.  For example, each basic block must
> finish with a "terminator" instruction (branch, return, invoke, etc).  Each
> terminator instruction specifies which other basic blocks control can
> reach.
> Thus to find the successor nodes of a basic block, you look at the last
> instruction of the basic block, and see where it says control flows to.
> There are of course helper methods that do this for you.  Predecessors are
> also automatically set up.
>
> Similarly, the list of uses of "variables" (aka instructions) is maintained
> automatically.
>
> Ciao,
>
> Duncan.
>
> PS: Please reply to the list rather than me personally.  I've CC'd the
> list.
>
>
>> Thanks,
>> Rohith.
>>
>> On Thu, Mar 18, 2010 at 4:55 PM, Rohith Goparaju <rgoparaj at umail.iu.edu
>> <mailto:rgoparaj at umail.iu.edu>> wrote:
>>
>>      Thanks Duncan...That was helpful.
>>
>>
>>    On Thu, Mar 18, 2010 at 4:54 AM, Duncan Sands <baldrick at free.fr
>>    <mailto:baldrick at free.fr>> wrote:
>>
>>        Hi Rohith,
>>
>>         >     Is there any API within llvm that provides methods to
>>        access the CFG
>>         > and do some manipulations on the CFG.
>>
>>        the CFG is built into the LLVM IR: given a basic block (i.e. a
>>        node of the
>>        CFG) you can iterate over its successors and predecessors using
>>        the methods
>>        in include/llvm/Support/CFG.h.  To modify the CFG you have to
>>        modify the
>>        basic blocks, usually by changing the basic block terminator.
>>
>>        Ciao,
>>
>>        Duncan.
>>        _______________________________________________
>>        LLVM Developers mailing list
>>        LLVMdev at cs.uiuc.edu <mailto: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/20100326/62dad05c/attachment.html>