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? -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120307/bc52aa4e/attachment.html>
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? >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120307/78118dad/attachment.html> -------------- next part -------------- A non-text attachment was scrubbed... Name: BasicBlock Type: application/octet-stream Size: 42180 bytes Desc: not available URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20120307/78118dad/attachment.obj>
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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It sounds like Transforms/Utils/SSAUpdater may be what you are looking for. A good example of how to use it -- one that sounds very similar to what you're doing -- can be found in Transforms/Scalar/LoopRotation.cpp On Wed, Mar 7, 2012 at 2:03 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? > > _______________________________________________ > LLVM Developers mailing list > 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/20120308/3532603d/attachment.html>
I think the SSAupdater might do the trick. The issue with replaceUses is that it would work great for the current block but what about the PHIs in continuing blocks, think that would be a problem. Thanks. On Thu, Mar 8, 2012 at 1:28 PM, Marc de Kruijf <dekruijf at cs.wisc.edu> wrote:> It sounds like Transforms/Utils/SSAUpdater may be what you are looking > for. > A good example of how to use it -- one that sounds very similar to what > you're doing -- can be found in Transforms/Scalar/LoopRotation.cpp > > On Wed, Mar 7, 2012 at 2:03 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? >> >> _______________________________________________ >> LLVM Developers mailing list >> 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/20120309/019a3109/attachment.html>