[LLVMdev] How to insert a basic block in an edge

[Olivier Meurant]

See http://llvm.org/docs/WritingAnLLVMPass.html
If you are inside MyPass::runOn{Module,Function,Loop,BasicBlock}(),
just use the "this" pointer.

Olivier

On Wed, Jul 21, 2010 at 7:35 PM, Chayan Sarkar <chayan.ju at gmail.com> wrote:
> Hi,
>
> I could not figure out, how to declare a Pass*. Can anyone give me an
> example, how to use SplitEdge() function ?
>
> Please help me out.
>
> Regards,
> Chayan
>
> On Tue, Jul 20, 2010 at 10:12 AM, Chayan Sarkar <chayan.ju at gmail.com> wrote:
>> Hi All,
>>
>> Still I could not figure out how to use Pass* while calling
>> SplitEdge() function. Can anyone provide me some example?
>>
>> Regards,
>> Chayan
>>
>> On Sun, Jul 18, 2010 at 11:49 PM, Nick Lewycky <nicholas at mxc.ca> wrote:
>>> Chayan Sarkar wrote:
>>>>
>>>> Hi,
>>>>
>>>> I have tried to use SplitEdge function, but failed. Actually the third
>>>> parameter is a variable of type Pass and it need to be non-null. But I
>>>> could not figure out how to use it. Please help me out.
>>>
>>> The only reason it needs a non-NULL Pass* is to call llvm::SplitBlock which
>>> uses P->getAnalysisIfAvailable unconditionally. Feel free to wrap those
>>> calls in 'if (P) { ... }' and send us a patch.
>>>
>>> Of course, the obvious question is why aren't you doing your transforms
>>> inside of a Pass?
>>>
>>> Nick
>>>
>>>> Regards,
>>>> Chayan
>>>>
>>>> On Sat, Jul 17, 2010 at 10:16 PM, Nick Lewycky<nicholas at mxc.ca>  wrote:
>>>>>
>>>>> Chayan Sarkar wrote:
>>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> Suppose in a CFG bb1 has two succesor bb3 and bb4, and bb3 has two
>>>>>> predecessor bb1 and bb2. Now how can I insert a basic block between
>>>>>> bb1 and bb3 that at the edge bb1-->bb3 .
>>>>>>
>>>>>> In general how can I insert a basic block on an edge?
>>>>>
>>>>> Use llvm::SplitEdge in Transforms/Utils/BasicBlockUtils.h.
>>>>>
>>>>> The technique is to create a new bb with a single branch to bb3, then
>>>>> modify
>>>>> bb1's use of bb3 to point to 'new bb' instead, then fix up any phi nodes
>>>>> in
>>>>> bb3 by replacing uses of bb1 with 'new bb'.
>>>>>
>>>>> Nick
>>>>>
>>>>
>>>
>>>
>>
>
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