[LLVMdev] Updating value from PHI

[Ryan Taylor]

I guess I thought that once I redirected the branches and created new PHIs
that LLVM would correct the variable usage when I return true (changed CFG)
from the pass. Is this not the case?

On Wed, Mar 7, 2012 at 4:08 PM, Ryan Taylor <ryta1203 at gmail.com> wrote:

> Here is the code snippet that I am using to create the PHIs in the loop
> according to the PHIs in the new preheader. At this point I have already
> redirected the loop backedge and removed the preheader from the loop.
>
>             for (BasicBlock::iterator II = loopHeaderBB->begin();
> (PN=dyn_cast<PHINode>(II)); ++II) {
>                // remove loop back PHI and add it to split BB
>                errs()<<*II<<"\n";
>                PHINode *newPHIvalue = PHINode::Create(PN->getType(), 2,
> PN->getName().str(), splitBB->getFirstInsertionPt());
>                int IDX = PN->getBasicBlockIndex(splitBB);
>                while (IDX != -1) {
>                   Value *oldValue = PN->getIncomingValue((unsigned(IDX)));
>                   PN->removeIncomingValue(IDX, false);
>                   newPHIvalue->addIncoming(oldValue, loopLatchBB);
>                   newPHIvalue->addIncoming(PN, loopHeaderBB);
>                   IDX = PN->getBasicBlockIndex(splitBB);
>
>                }
>             }
>
> On Wed, Mar 7, 2012 at 4:04 PM, Ryan Taylor <ryta1203 at gmail.com> wrote:
>
>> I have attached a case of what I am trying to do, I'm pretty sure I'm
>> just missing some simple API call. In the cfg you can see that although Im
>> setting "lsr.iv441" as "lsr.iv44" from for.body.387.i it's not propagating
>> that through the block or graph.
>>
>>
>> On Wed, Mar 7, 2012 at 12:03 PM, Ryan Taylor <ryta1203 at gmail.com> wrote:
>>
>>> I am splitting a one BB loop into two BB.
>>>
>>> Basically, the one loop BB has 3 incoming values, one form back edge two
>>> from other edges. I want to extract the PHIs from the other two edges out
>>> into it's own BB and delete that from the loop, then redirect the backedge
>>> to the loopbody (non extracted portion) and create a new PHI coming from
>>> the extracted BB and the backedge.
>>>
>>> I can do this; however, the PHIs following in all the other BBs are not
>>> getting updated, neither are the statements in the loopbody.
>>>
>>> What is the easieset way to propagate these changes downward?
>>>
>>
>>
>
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