Ta-Wei Tu via llvm-dev
2020-Jul-18 11:38 UTC
[llvm-dev] Regarding the project "Create LoopNestPass"
Hi, Thanks for your help! I've checked the sources that you mentioned. Currently, I think that I would need to implement a FunctionToLoopNestPassAdaptor which is essentially the same as the FunctionToLoopPassAdaptor but operates only on LI.getTopLevelLoops(). We might also need a LNPMUpdater (LoopNestPassManagerUpdater) which disallows adding inner-loops back into the pipeline, and LoopNestPassManager will simply be PassManager<Loop, LoopAnalysisManager, LoopStandardAnalysisResult &, LNPMUpdater &>. One question I have is whether the IRUnit LoopNestPass operates on should be Loop or LoopNest, since I'm not quite sure about the usage of LoopNest and why it should be constructed with a ScalarEvolution. Also, it is stated that "we want to create a LoopNestPass, where transformations intended for loop nest can inherit from it" in the original GSoC project description, but I believe that inheriting from a Pass subclass is no longer required in the New Pass Manager. So should we also implement a LoopNestPass subclass that allows implementing loop-nest-passes for the Legacy Pass Manager? Finally, I have some questions that might not be very relevant to the project. But currently, how does the LegacyPassManager and the NewPassManager interact? Also, is it possible to add passes designed for LegacyPassManager into the NewPassManager and vice versa? What do you think about the plan? I'm quite likely to miss something important, so please kindly correct me if I'm in the wrong direction. Thank you very much! Sincerely, Ta-Wei Tu Whitney Tsang <whitney.uwaterloo at gmail.com> 於 2020年7月15日 週三 下午6:14寫道：> Hi Wayne, > > As far as I know, no one is working on this project. Your contribution is > always appreciated. > > This project aims to create LoopNestPass in the new pass manager (NPM). > In https://www.youtube.com/watch?v=3pRhvQi7Z10 > <https://urldefense.proofpoint.com/v2/url?u=https-3A__www.youtube.com_watch-3Fv-3D3pRhvQi7Z10&d=DwMFaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=p0DGcdtx8-l1bvwJTLSk1zBTXpb78Y1slqHKTsTpRTE&m=PzTQj0kzu8kuCmHOMYatYGxUnZCBLnJ5ynt0qqlYoSE&s=nDqZ-LcpFAgM1uK4RSlRYDlhQE60FUZmOPjgdW5aTuo&e=> , > you can try to follow along to create a LLVM loop pass in NPM. > > There exist different kinds of passes in the NPM, e.g. ModulePass, > FunctionPass, LoopPass. > One or more loop passes can be added in a LoopPassManager, which then can > be added in FunctionPassManager through createFunctionToLoopPassAdaptor. > Examples can be found in llvm/lib/Passes/PassBuilder.cpp. > There exist passes that best operate as a loop nest, e.g. LoopInterchange. > For those passes, currently can be written as either FunctionPass or > LoopPass. > However, choosing one or the other needs to sacrifice the ability of the > other. > The idea of a LoopNestPass is to combine the benefits of FunctionPass and > LoopPass needed for a loop nest. > > On top of LoopNest I would suggest to also get familiar with different > PassAdaptor classes (e.g. FunctionToLoopPassAdaptor). > - llvm/include/llvm/Transforms/Scalar/LoopPassManager.h > > I am happy to provide feedback once you have a plan of how to proceed, or > review your patches on Phabricator. > > Regards, > Whitney Tsang > > On Wed, Jul 15, 2020 at 5:49 AM Wayne Tu via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> Hi, >> >> I'm a college student who is quite new to the community and is interested >> in contributing to the LLVM project. Although I haven't applied to GSoC, I >> notice that the project "Create LoopNestPass" seems to be unassigned. >> So I'm curious whether anyone is currently working on it, and if not, is >> it possible for me to work on it as a side-project? >> >> I've been programming in C++ for quite a while, and I've walked through >> the `LoopPass`, `LoopNest`, and some other LLVM classes that I think would >> probably be related to this project. I've also watched some of the videos >> in the llvm-dev conference regarding loops, so I now have a rough idea on >> how to implement the LoopNestPass. >> >> I'm looking forward to working on this project. >> >> Thank you very much. >> >> Sincerely, >> Ta-Wei Tu >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200718/bbd0aa6a/attachment.html>
Whitney T Tsang via llvm-dev
2020-Jul-18 19:32 UTC
[llvm-dev] Regarding the project "Create LoopNestPass"
Hi Ta-Wei,> We might also need a LNPMUpdater (LoopNestPassManagerUpdater) whichdisallows adding inner-loops back into the pipeline, and LoopNestPassManager will simply be PassManager<Loop, LoopAnalysisManager, LoopStandardAnalysisResult &, LNPMUpdater &>. LNPMUpdater should have some functionalities of LPMUpdater, e.g. adding sibling loop nest, revisit the current loop nest, etc.> One question I have is whether the IRUnit LoopNestPass operates on shouldbe Loop or LoopNest, since I'm not quite sure about the usage of LoopNest and why it should be constructed with a ScalarEvolution. That's a good point, we can make ScalarEvolution optional for LoopNest. Currently, the only use case is to check if the loop nest is perfect, which can provide a more conservative result if ScalarEvolution is not given. Having said that, ScalarEvolution is one of the analyses in LoopStandardAnalysisResults, so all LoopPasses already have access to ScalarEvolution. LoopNest provides some useful utilities, although it is still not at a manual phrase. My personal opinion is all the mechanism of the LoopNest, e.g. LoopNestPassManager, LPMUpdater, etc, should operates on Loop. While IRUnitT which is used by loop nest transformations/analyses should operates on LoopNest. @etiotto What's your opinion on that?> Also, it is stated that "we want to create a LoopNestPass, wheretransformations intended for loop nest can inherit from it" in the original GSoC project description, but I believe that inheriting from a Pass subclass is no longer required in the New Pass Manager. So should we also implement a LoopNestPass subclass that allows implementing loop-nest-passes for the Legacy Pass Manager? Right, the wording should be corrected. Given that the New Pass Manager will soon be the default Pass Manager, we should not spend extra effort to create LoopNestPass in Legacy Pass Manager.> Finally, I have some questions that might not be very relevant to theproject. But currently, how does the LegacyPassManager and the NewPassManager interact? Also, is it possible to add passes designed for LegacyPassManager into the NewPassManager and vice versa? Most transformations have both for LegacyPassManager and NewPassManager, and have the actual implementation of the transformations in a separate class, or a static function that can be call by both. e.g. LoopFuseLegacy is for LegacyPassManager , LoopFusePass is for NewPassManager, and both create LoopFuser and do the transformation there. Looking forward to your first patch! Regards, Whitney Tsang From: Ta-Wei Tu <tu.da.wei at gmail.com> To: Whitney Tsang <whitney.uwaterloo at gmail.com> Cc: llvm-dev <llvm-dev at lists.llvm.org>, whitneyt at ca.ibm.com Date: 2020/07/18 07:38 AM Subject: [EXTERNAL] Re: [llvm-dev] Regarding the project "Create LoopNestPass" Hi, Thanks for your help! I've checked the sources that you mentioned. Currently, I think that I would need to implement a FunctionToLoopNestPassAdaptor which is essentially the same as the FunctionToLoopPassAdaptor but operates only on LI.getTopLevelLoops(). We might also need a LNPMUpdater (LoopNestPassManagerUpdater) which disallows adding inner-loops back into the pipeline, and LoopNestPassManager will simply be PassManager<Loop, LoopAnalysisManager, LoopStandardAnalysisResult &, LNPMUpdater &>. One question I have is whether the IRUnit LoopNestPass operates on should be Loop or LoopNest, since I'm not quite sure about the usage of LoopNest and why it should be constructed with a ScalarEvolution. Also, it is stated that "we want to create a LoopNestPass, where transformations intended for loop nest can inherit from it" in the original GSoC project description, but I believe that inheriting from a Pass subclass is no longer required in the New Pass Manager. So should we also implement a LoopNestPass subclass that allows implementing loop-nest-passes for the Legacy Pass Manager? Finally, I have some questions that might not be very relevant to the project. But currently, how does the LegacyPassManager and the NewPassManager interact? Also, is it possible to add passes designed for LegacyPassManager into the NewPassManager and vice versa? What do you think about the plan? I'm quite likely to miss something important, so please kindly correct me if I'm in the wrong direction. Thank you very much! Sincerely, Ta-Wei Tu Whitney Tsang <whitney.uwaterloo at gmail.com> 於 2020年7月15日 週三 下午6:14 寫道： Hi Wayne, As far as I know, no one is working on this project. Your contribution is always appreciated. This project aims to create LoopNestPass in the new pass manager (NPM). In https://www.youtube.com/watch?v=3pRhvQi7Z10 , you can try to follow along to create a LLVM loop pass in NPM. There exist different kinds of passes in the NPM, e.g. ModulePass, FunctionPass, LoopPass. One or more loop passes can be added in a LoopPassManager, which then can be added in FunctionPassManager through createFunctionToLoopPassAdaptor. Examples can be found in llvm/lib/Passes/PassBuilder.cpp. There exist passes that best operate as a loop nest, e.g. LoopInterchange. For those passes, currently can be written as either FunctionPass or LoopPass. However, choosing one or the other needs to sacrifice the ability of the other. The idea of a LoopNestPass is to combine the benefits of FunctionPass and LoopPass needed for a loop nest. On top of LoopNest I would suggest to also get familiar with different PassAdaptor classes (e.g. FunctionToLoopPassAdaptor). - llvm/include/llvm/Transforms/Scalar/LoopPassManager.h I am happy to provide feedback once you have a plan of how to proceed, or review your patches on Phabricator. Regards, Whitney Tsang On Wed, Jul 15, 2020 at 5:49 AM Wayne Tu via llvm-dev < llvm-dev at lists.llvm.org> wrote: Hi, I'm a college student who is quite new to the community and is interested in contributing to the LLVM project. Although I haven't applied to GSoC, I notice that the project "Create LoopNestPass" seems to be unassigned. So I'm curious whether anyone is currently working on it, and if not, is it possible for me to work on it as a side-project? I've been programming in C++ for quite a while, and I've walked through the `LoopPass`, `LoopNest`, and some other LLVM classes that I think would probably be related to this project. I've also watched some of the videos in the llvm-dev conference regarding loops, so I now have a rough idea on how to implement the LoopNestPass. I'm looking forward to working on this project. Thank you very much. Sincerely, Ta-Wei Tu _______________________________________________ LLVM Developers mailing list llvm-dev at lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200718/48f05473/attachment.html> -------------- next part -------------- A non-text attachment was scrubbed... Name: graycol.gif Type: image/gif Size: 105 bytes Desc: not available URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200718/48f05473/attachment.gif>
Ettore Tiotto via llvm-dev
2020-Jul-21 12:43 UTC
[llvm-dev] Regarding the project "Create LoopNestPass"
<div class="socmaildefaultfont" dir="ltr"
style="font-family:Arial, Helvetica, sans-serif;font-size:10pt"
><div dir="ltr" ><div><div
class="socmaildefaultfont" dir="ltr"
style="font-family: Arial, Helvetica, sans-serif;" ><div
class="socmaildefaultfont" dir="ltr" style="font-size:
10.5pt; font-family: Arial;" ><font size="3" >>
</font><font size="3" >One question I have is whether the
IRUnit LoopNestPass operates on should be Loop or LoopNest, since I'm not
quite sure about the usage of LoopNest and why it should be constructed with a
ScalarEvolution.</font><br><br><font size="3"
>That's a good point, we can make ScalarEvolution optional for LoopNest.
Currently, the only use case is to check if the loop nest is perfect, which can
provide a more conservative result if ScalarEvolution is not given.
</font><br><font size="3" >Having said that,
</font><font size="3" >ScalarEvolution is one of the
analyses in </font><font size="3"
>LoopStandardAnalysisResults</font><font size="3" >, so
all LoopPasses already have access to
ScalarEvolution.</font><br><font size="3" >LoopNest
provides some useful utilities, although it is still not at a manual phrase.
</font><br><font size="3" >My personal opinion is
all the mechanism of the LoopNest, e.g.</font><font size="3"
> LoopNestPassManager, </font><font size="3"
>LPMUpdater</font><font size="3" >, etc, should
operates on Loop. While IRUnitT which is used by loop nest
transformations/analyses should operates on
LoopNest.</font><br><font size="3" >@etiotto
What's your opinion on that?</font></div>
<div class="socmaildefaultfont" dir="ltr"
style="font-size: 10.5pt; font-family: Arial;" > </div>
<div class="socmaildefaultfont" dir="ltr"
style="font-family: Arial;" ><font size="3"
>Determining whether a loop nest is perfect is a fundamental feature for
LoopNest analysis, and ScalarEvolution is required to catch not-trivial cases. I
agree that SE should be always available to a LoopNest pass. The LoopNest
analysis should be available to a LoopNest pass manager, and a LoopNest pass IMO
should operate on a LoopNest IR unit rather than a Loop.
</font></div>
<div class="socmaildefaultfont" dir="ltr"
style="font-family: Arial;" >
</div></div></div></div>
<div class="mail-signature-container" dir="ltr"
><div class="socmaildefaultfont" dir="ltr"
style="font-family:Arial, Helvetica, sans-serif;font-size:10.5pt"
><div class="socmaildefaultfont" dir="ltr"
style="font-family:Arial;font-size:10.5pt" ><div
dir="ltr" >Ettore Tiotto<br>IBM Canada Laboratory, 8200
Warden Ave, Markham, ON L6G 1C7, Canada<br>etiotto@ca.ibm.com -- Phone:
(905) 413-2387<br><br>“No great discovery was ever made without a
bold guess.” - Isaac Newton</div></div></div></div>
<div dir="ltr" > </div>
<div dir="ltr" > </div>
<blockquote data-history-content-modified="1"
data-history-expanded="1" dir="ltr"
style="border-left:solid #aaaaaa 2px; margin-left:5px; padding-left:5px;
direction:ltr; margin-right:0px" >----- Original message
-----<br>From: Whitney T Tsang/Toronto/IBM<br>To: Ta-Wei Tu
<tu.da.wei@gmail.com><br>Cc: llvm-dev
<llvm-dev@lists.llvm.org>, Whitney Tsang
<whitney.uwaterloo@gmail.com>, Ettore
Tiotto/Toronto/IBM@IBMCA<br>Subject: Re: [EXTERNAL] Re: [llvm-dev]
Regarding the project "Create LoopNestPass"<br>Date: Sat, Jul
18, 2020 3:32 PM<br> <br><font size="3" >Hi
Ta-Wei,</font><br><br><font size="3" >>
</font><font size="3" >We might also need a LNPMUpdater
(LoopNestPassManagerUpdater) which disallows adding inner-loops back into the
pipeline, and LoopNestPassManager will simply be PassManager<Loop,
LoopAnalysisManager, LoopStandardAnalysisResult &, LNPMUpdater
&>.</font><br><br><font size="3"
>LNPMUpdater </font><font size="3" >should have some
functionalities of LPMUpdater, e.g. adding sibling loop nest, revisit the
current loop nest, etc. </font><br><br><font
size="3" >> </font><font size="3" >One
question I have is whether the IRUnit LoopNestPass operates on should be Loop or
LoopNest, since I'm not quite sure about the usage of LoopNest and why it
should be constructed with a
ScalarEvolution.</font><br><br><font size="3"
>That's a good point, we can make ScalarEvolution optional for LoopNest.
Currently, the only use case is to check if the loop nest is perfect, which can
provide a more conservative result if ScalarEvolution is not given.
</font><br><font size="3" >Having said that,
</font><font size="3" >ScalarEvolution is one of the
analyses in </font><font size="3"
>LoopStandardAnalysisResults</font><font size="3" >, so
all LoopPasses already have access to
ScalarEvolution.</font><br><font size="3" >LoopNest
provides some useful utilities, although it is still not at a manual phrase.
</font><br><font size="3" >My personal opinion is
all the mechanism of the LoopNest, e.g.</font><font size="3"
> LoopNestPassManager, </font><font size="3"
>LPMUpdater</font><font size="3" >, etc, should
operates on Loop. While IRUnitT which is used by loop nest
transformations/analyses should operates on
LoopNest.</font><br><font size="3" >@etiotto
What's your opinion on that?</font><br><br><font
size="3" >> Also, it is stated that "we want to create a
LoopNestPass, where transformations intended for loop nest can inherit from
it" in the original GSoC project description, but I believe that inheriting
from a Pass subclass is no longer required in the New Pass Manager. So should we
also implement a LoopNestPass subclass that allows implementing loop-nest-passes
for the Legacy Pass Manager?</font><br><br><font
size="3" >Right, the wording should be corrected. Given that the
New Pass Manager will soon be the default Pass Manager, we should not spend
extra effort to create LoopNestPass in Legacy Pass
Manager.</font><br><br><font size="3" >>
Finally, I have some questions that might not be very relevant to the project.
But currently, how does the LegacyPassManager and the NewPassManager interact?
Also, is it possible to add passes designed for LegacyPassManager into the
NewPassManager and vice versa? </font><br><br><font
size="3" >Most transformations have both for LegacyPassManager and
NewPassManager, and have the actual implementation of the transformations in a
separate class, or a static function that can be call by
both.</font><br><font size="3" >e.g.
</font><font size="3" >LoopFuseLegacy</font><font
size="3" > is for LegacyPassManager , </font><a
href="https://llvm.org/doxygen/classllvm_1_1LoopFusePass.html#a971f40ada3f1410759faede02bfbace7"
target="_blank"><u><font color="#4665A2"
size="3" >LoopFusePass</font></u></a><font
size="3" > is for NewPassManager, and both create
</font><font size="3" >LoopFuser</font><font
size="3" > and do the transformation
there.</font><br><br><font size="3" >Looking
forward to your first patch!</font><br><br><font
size="3" >Regards,</font><br><font
size="3" >Whitney
Tsang</font><br><br><br><img alt="Inactive hide
details for Ta-Wei Tu ---2020/07/18 07:38:44 AM---Hi, Thanks for your help!
I've checked the sources that you men" border="0"
height="16" src="/icons/graycol.gif" width="16"
><font color="#424282" size="2" >Ta-Wei Tu
---2020/07/18 07:38:44 AM---Hi, Thanks for your help! I've checked the
sources that you mentioned.</font><br><br><font
color="#5F5F5F" size="2" >From: </font><font
size="2" >Ta-Wei Tu
<tu.da.wei@gmail.com></font><br><font
color="#5F5F5F" size="2" >To: </font><font
size="2" >Whitney Tsang
<whitney.uwaterloo@gmail.com></font><br><font
color="#5F5F5F" size="2" >Cc: </font><font
size="2" >llvm-dev <llvm-dev@lists.llvm.org>,
whitneyt@ca.ibm.com</font><br><font color="#5F5F5F"
size="2" >Date: </font><font size="2"
>2020/07/18 07:38 AM</font><br><font color="#5F5F5F"
size="2" >Subject: </font><font size="2"
>[EXTERNAL] Re: [llvm-dev] Regarding the project "Create
LoopNestPass"</font>
<hr align="left" size="2" style="color:#8091A5;
" width="100%" ><br><br><br><font
size="3" >Hi,</font><br><br><font
size="3" >Thanks for your help! I've checked the sources that
you mentioned. Currently, I think that I would need to implement a
FunctionToLoopNestPassAdaptor which is essentially the same as the
FunctionToLoopPassAdaptor but operates only on LI.getTopLevelLoops().
</font><br><br><font size="3" >We might also
need a LNPMUpdater (LoopNestPassManagerUpdater) which disallows adding
inner-loops back into the pipeline, and LoopNestPassManager will simply be
PassManager<Loop, LoopAnalysisManager, LoopStandardAnalysisResult &,
LNPMUpdater &>.</font><br><br><font
size="3" >One question I have is whether the IRUnit LoopNestPass
operates on should be Loop or LoopNest, since I'm not quite sure about the
usage of LoopNest and why it should be constructed with a
ScalarEvolution.</font><br><br><font size="3"
>Also, it is stated that "we want to create a LoopNestPass, where
transformations intended for loop nest can inherit from it" in the original
GSoC project description, but I believe that inheriting from a Pass subclass is
no longer required in the New Pass Manager. So should we also implement a
LoopNestPass subclass that allows implementing loop-nest-passes for the Legacy
Pass Manager?</font><br><br><font size="3"
>Finally, I have some questions that might not be very relevant to the
project. But currently, how does the LegacyPassManager and the NewPassManager
interact? Also, is it possible to add passes designed for LegacyPassManager into
the NewPassManager and vice versa? </font><br><br><font
size="3" >What do you think about the plan? I'm quite likely to
miss something important, so please kindly correct me if I'm in the wrong
direction.</font><br><br><font size="3" >Thank
you very much!</font><br><font size="3" >Sincerely,
Ta-Wei Tu</font><br><br><font size="3"
>Whitney Tsang <</font><a
href="mailto:whitney.uwaterloo@gmail.com"
target="_blank"><u><font color="#0000FF"
size="3"
>whitney.uwaterloo@gmail.com</font></u></a><font
size="3" >> 於 2020年7月15日 週三 下午6:14寫道：</font>
<ul style="padding-left: 9pt; margin-left: 0px; list-style-type:
none;" > <li><font color="#121212"
face="Helvetica Neue" size="3" >Hi
Wayne,</font><br> <br> <font
color="#121212" face="Helvetica Neue" size="3"
>As far as I know, no one is working on this project. Your contribution is
always appreciated.</font><br> <br> <font
color="#121212" face="Helvetica Neue" size="3"
>This project aims to create LoopNestPass in the new pass manager
(NPM).</font><br> <font color="#121212"
face="Helvetica Neue" size="3" >In </font><a
href="https://www.youtube.com/watch?v=3pRhvQi7Z10"
target="_blank"><u><font color="#4178BE"
face="Helvetica Neue" size="3"
>https://www.youtube.com/watch?v=3pRhvQi7Z10</font></u></a><font
color="#121212" face="Helvetica Neue" size="3"
> , you can try to follow along to create a LLVM loop pass in
NPM.</font><br> <br> <font
color="#121212" face="Helvetica Neue" size="3"
>There exist different kinds of passes in the NPM, e.g. ModulePass,
FunctionPass, LoopPass. </font><br> <font
color="#121212" face="Helvetica Neue" size="3"
>One or more loop passes can be added in a LoopPassManager, which then can be
added in FunctionPassManager through createFunctionToLoopPassAdaptor.
</font><br> <font color="#121212"
face="Helvetica Neue" size="3" >Examples can be found in
llvm/lib/Passes/PassBuilder.cpp. </font><br> <font
color="#121212" face="Helvetica Neue" size="3"
>There exist passes that best operate as a loop nest, e.g. LoopInterchange.
For those passes, currently can be written as either FunctionPass or
LoopPass.</font><br> <font color="#121212"
face="Helvetica Neue" size="3" >However, choosing one or
the other needs to sacrifice the ability of the other. </font><br>
<font color="#121212" face="Helvetica Neue"
size="3" >The idea of a LoopNestPass is to combine the benefits of
FunctionPass and LoopPass needed for a loop nest.</font><br>
<br> <font color="#121212" face="Helvetica
Neue" size="3" >On top of LoopNest I would suggest to also get
familiar with different PassAdaptor classes (e.g.
FunctionToLoopPassAdaptor).<br> -
llvm/include/llvm/Transforms/Scalar/LoopPassManager.h</font><br>
<br> <font color="#121212" face="Helvetica
Neue" size="3" >I am happy to provide feedback once you have a
plan of how to proceed, or review your patches on
Phabricator.</font><br> <br> <font
color="#121212" face="Helvetica Neue" size="3"
>Regards,</font><br> <font color="#121212"
face="Helvetica Neue" size="3" >Whitney
Tsang</font><br> <br> <font
size="3" >On Wed, Jul 15, 2020 at 5:49 AM Wayne Tu via llvm-dev
<</font><a href="mailto:llvm-dev@lists.llvm.org"
target="_blank"><u><font color="#0000FF"
size="3"
>llvm-dev@lists.llvm.org</font></u></a><font
size="3" >> wrote:</font>
<ul style="padding-left: 9pt; margin-left: 0px; list-style-type:
none;" > <li><font size="3"
>Hi,</font><br> <br> <font
size="3" >I'm a college student who is quite new to the
community and is interested in contributing to the LLVM project. Although I
haven't applied to GSoC, I notice that the project "Create
LoopNestPass" seems to be unassigned. </font><br>
<font size="3" >So I'm curious whether anyone is currently
working on it, and if not, is it possible for me to work on it as a
side-project?</font><br> <br>
<font size="3" >I've been programming in C++ for quite a
while, and I've walked through the `LoopPass`, `LoopNest`, and some other
LLVM classes that I think would probably be related to this project. I've
also watched some of the videos in the llvm-dev conference regarding loops, so I
now have a rough idea on how to implement the
LoopNestPass.</font><br> <br>
<font size="3" >I'm looking forward to working on this
project. </font><br> <br>
<font size="3" >Thank you very much.</font><br>
<br> <font size="3"
>Sincerely,</font><br> <font size="3"
>Ta-Wei Tu</font><br> <font size="3"
>_______________________________________________<br>
LLVM Developers mailing list</font><br> <a
href="mailto:llvm-dev@lists.llvm.org"
target="_blank"><u><font color="#0000FF"
size="3"
>llvm-dev@lists.llvm.org</font></u></a><br>
<a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev"
target="_blank"><u><font color="#0000FF"
size="3"
>https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</font></u></a></li>
</ul> </li></ul></blockquote>
<div dir="ltr" > </div></div><BR>
Ta-Wei Tu via llvm-dev
2020-Jul-24 05:27 UTC
[llvm-dev] Regarding the project "Create LoopNestPass"
Hi, I would like to give a quick update on what my current design and implementation go like. Basically, the `FunctionToLoopPassAdaptor` is now modified to a generic version `FunctionToLoopUnitPassAdaptor`, which allows re-using the existing codes to implement `FunctionToLoopNestPassAdaptor`, with the help of additional metadata associated with `Loop` and `LoopNest`. Both `FunctionToLoopPassAdaptor` and `FunctionToLoopNestPassAdaptor` are aliases to `FunctionToLoopUnitPassAdaptor` and they operates on `Loop`, and the `FunctionToLoopNestPassAdaptor` will construct the `LoopNest` object lazily for the given `LoopNestPass` to run on. The `LNPMUpdater` only support `revisitCurrentLoopNest()` and `markLoopNestAsDeleted()` since other functionalities like `addChildLoops()` and `addSiblingLoops()` that `LPMUpdater` provide don't seem to be meaningful since we're dealing with outer-most `LoopNest`s. Still, an analogy of `addSiblingLoops()` can be implemented as something like `addAllLoopNests()`. What's your opinion on that? Currently, `LoopNestToLoopPassAdaptor` is also implemented to allow injecting a `LoopPassManager` into a `LoopNestPassManager`. The reason why I think this is useful is that both `LoopPass` and `LoopNestPass` requires loop canonicalization passes to be run first, and composing both of them and promoting them into a single `FunctionPass` can reduce unnecessary runs of the canonicalization phases. With these, the pipeline can be built like: ``` FunctionPassManager FPM; LoopNestPassManager LNPM; LoopPassManager LPM; LNPM.addPass(SomeLoopNestPass()); LPM.addPass(SomeLoopPass()); LNPM.addPass(createLoopNestToLoopPassAdaptor(LPM)); FPM.addPass(createFunctionToLoopNestPassAdaptor(LNPM)); // This still works, but the loop canonicalization passes will be run twice: // FPM.addPass(createFunctionToLoopPassAdaptor(LPM)); // FPM.addPass(createFunctionToLoopNestPassAdaptor(LNPM)); ``` `LoopNestAnalysisManager` and the proxies between `LoopAnalysis`, `LoopNestAnalysis` and `FunctionAnalysis` are also implemented. One of the problems now is on parsing the pipeline. In the current `PassBuilder`, a function pass is implicitly created and wrapping the subsequent loop passes. If we allow putting `LoopPass` into `LoopNestPass` in the future as described above, what would be a good way to distinguish whether we should choose "function - loopnest - loop" or "function - loop" in this case? As this is my first patch to LLVM, I would also like to ask what would generally be a good time to submit a patch like this. As most of the functionalities are completed but not tested, should I submit the patch as soon as all the existing tests pass and add tests specific to the `LoopNestPass` later so that people can provide feedback on the overall design first, or should I submit the patch after implementing fine-grained tests? What are your thoughts on the design? Thank you very much! Sincerely, Ta-Wei Tu Ettore Tiotto <etiotto at ca.ibm.com> 於 2020年7月21日 週二 下午8:43寫道：> > One question I have is whether the IRUnit LoopNestPass operates on > should be Loop or LoopNest, since I'm not quite sure about the usage of > LoopNest and why it should be constructed with a ScalarEvolution. > > That's a good point, we can make ScalarEvolution optional for LoopNest. > Currently, the only use case is to check if the loop nest is perfect, which > can provide a more conservative result if ScalarEvolution is not given. > Having said that, ScalarEvolution is one of the analyses in > LoopStandardAnalysisResults, so all LoopPasses already have access to > ScalarEvolution. > LoopNest provides some useful utilities, although it is still not at a > manual phrase. > My personal opinion is all the mechanism of the LoopNest, e.g. LoopNestPassManager, > LPMUpdater, etc, should operates on Loop. While IRUnitT which is used by > loop nest transformations/analyses should operates on LoopNest. > @etiotto What's your opinion on that? > > Determining whether a loop nest is perfect is a fundamental feature > for LoopNest analysis, and ScalarEvolution is required to catch not-trivial > cases. I agree that SE should be always available to a LoopNest pass. The > LoopNest analysis should be available to a LoopNest pass manager, and a > LoopNest pass IMO should operate on a LoopNest IR unit rather than a Loop. > > Ettore Tiotto > IBM Canada Laboratory, 8200 Warden Ave, Markham, ON L6G 1C7, Canada > etiotto at ca.ibm.com -- Phone: (905) 413-2387 > > “No great discovery was ever made without a bold guess.” - Isaac Newton > > > > ----- Original message ----- > From: Whitney T Tsang/Toronto/IBM > To: Ta-Wei Tu <tu.da.wei at gmail.com> > Cc: llvm-dev <llvm-dev at lists.llvm.org>, Whitney Tsang < > whitney.uwaterloo at gmail.com>, Ettore Tiotto/Toronto/IBM at IBMCA > Subject: Re: [EXTERNAL] Re: [llvm-dev] Regarding the project "Create > LoopNestPass" > Date: Sat, Jul 18, 2020 3:32 PM > > Hi Ta-Wei, > > > We might also need a LNPMUpdater (LoopNestPassManagerUpdater) which > disallows adding inner-loops back into the pipeline, and > LoopNestPassManager will simply be PassManager<Loop, LoopAnalysisManager, > LoopStandardAnalysisResult &, LNPMUpdater &>. > > LNPMUpdater should have some functionalities of LPMUpdater, e.g. adding > sibling loop nest, revisit the current loop nest, etc. > > > One question I have is whether the IRUnit LoopNestPass operates on > should be Loop or LoopNest, since I'm not quite sure about the usage of > LoopNest and why it should be constructed with a ScalarEvolution. > > That's a good point, we can make ScalarEvolution optional for LoopNest. > Currently, the only use case is to check if the loop nest is perfect, which > can provide a more conservative result if ScalarEvolution is not given. > Having said that, ScalarEvolution is one of the analyses in > LoopStandardAnalysisResults, so all LoopPasses already have access to > ScalarEvolution. > LoopNest provides some useful utilities, although it is still not at a > manual phrase. > My personal opinion is all the mechanism of the LoopNest, e.g. LoopNestPassManager, > LPMUpdater, etc, should operates on Loop. While IRUnitT which is used by > loop nest transformations/analyses should operates on LoopNest. > @etiotto What's your opinion on that? > > > Also, it is stated that "we want to create a LoopNestPass, where > transformations intended for loop nest can inherit from it" in the original > GSoC project description, but I believe that inheriting from a Pass > subclass is no longer required in the New Pass Manager. So should we also > implement a LoopNestPass subclass that allows implementing loop-nest-passes > for the Legacy Pass Manager? > > Right, the wording should be corrected. Given that the New Pass Manager > will soon be the default Pass Manager, we should not spend extra effort to > create LoopNestPass in Legacy Pass Manager. > > > Finally, I have some questions that might not be very relevant to the > project. But currently, how does the LegacyPassManager and the > NewPassManager interact? Also, is it possible to add passes designed for > LegacyPassManager into the NewPassManager and vice versa? > > Most transformations have both for LegacyPassManager and NewPassManager, > and have the actual implementation of the transformations in a separate > class, or a static function that can be call by both. > e.g. LoopFuseLegacy is for LegacyPassManager , *LoopFusePass* > <https://llvm.org/doxygen/classllvm_1_1LoopFusePass.html#a971f40ada3f1410759faede02bfbace7> is > for NewPassManager, and both create LoopFuser and do the transformation > there. > > Looking forward to your first patch! > > Regards, > Whitney Tsang > > > [image: Inactive hide details for Ta-Wei Tu ---2020/07/18 07:38:44 > AM---Hi, Thanks for your help! I've checked the sources that you men]Ta-Wei > Tu ---2020/07/18 07:38:44 AM---Hi, Thanks for your help! I've checked the > sources that you mentioned. > > From: Ta-Wei Tu <tu.da.wei at gmail.com> > To: Whitney Tsang <whitney.uwaterloo at gmail.com> > Cc: llvm-dev <llvm-dev at lists.llvm.org>, whitneyt at ca.ibm.com > Date: 2020/07/18 07:38 AM > Subject: [EXTERNAL] Re: [llvm-dev] Regarding the project "Create > LoopNestPass" > ------------------------------ > > > > Hi, > > Thanks for your help! I've checked the sources that you mentioned. > Currently, I think that I would need to implement a > FunctionToLoopNestPassAdaptor which is essentially the same as the > FunctionToLoopPassAdaptor but operates only on LI.getTopLevelLoops(). > > We might also need a LNPMUpdater (LoopNestPassManagerUpdater) which > disallows adding inner-loops back into the pipeline, and > LoopNestPassManager will simply be PassManager<Loop, LoopAnalysisManager, > LoopStandardAnalysisResult &, LNPMUpdater &>. > > One question I have is whether the IRUnit LoopNestPass operates on should > be Loop or LoopNest, since I'm not quite sure about the usage of LoopNest > and why it should be constructed with a ScalarEvolution. > > Also, it is stated that "we want to create a LoopNestPass, where > transformations intended for loop nest can inherit from it" in the original > GSoC project description, but I believe that inheriting from a Pass > subclass is no longer required in the New Pass Manager. So should we also > implement a LoopNestPass subclass that allows implementing loop-nest-passes > for the Legacy Pass Manager? > > Finally, I have some questions that might not be very relevant to the > project. But currently, how does the LegacyPassManager and the > NewPassManager interact? Also, is it possible to add passes designed for > LegacyPassManager into the NewPassManager and vice versa? > > What do you think about the plan? I'm quite likely to miss something > important, so please kindly correct me if I'm in the wrong direction. > > Thank you very much! > Sincerely, Ta-Wei Tu > > Whitney Tsang <*whitney.uwaterloo at gmail.com* <whitney.uwaterloo at gmail.com>> 於 > 2020年7月15日 週三 下午6:14寫道： > > - Hi Wayne, > > As far as I know, no one is working on this project. Your contribution > is always appreciated. > > This project aims to create LoopNestPass in the new pass manager (NPM). > In *https://www.youtube.com/watch?v=3pRhvQi7Z10* > <https://www.youtube.com/watch?v=3pRhvQi7Z10> , you can try to follow > along to create a LLVM loop pass in NPM. > > There exist different kinds of passes in the NPM, e.g. ModulePass, > FunctionPass, LoopPass. > One or more loop passes can be added in a LoopPassManager, which then > can be added in FunctionPassManager through > createFunctionToLoopPassAdaptor. > Examples can be found in llvm/lib/Passes/PassBuilder.cpp. > There exist passes that best operate as a loop nest, e.g. > LoopInterchange. For those passes, currently can be written as either > FunctionPass or LoopPass. > However, choosing one or the other needs to sacrifice the ability of > the other. > The idea of a LoopNestPass is to combine the benefits of FunctionPass > and LoopPass needed for a loop nest. > > On top of LoopNest I would suggest to also get familiar with different > PassAdaptor classes (e.g. FunctionToLoopPassAdaptor). > - llvm/include/llvm/Transforms/Scalar/LoopPassManager.h > > I am happy to provide feedback once you have a plan of how to proceed, > or review your patches on Phabricator. > > Regards, > Whitney Tsang > > On Wed, Jul 15, 2020 at 5:49 AM Wayne Tu via llvm-dev < > *llvm-dev at lists.llvm.org* <llvm-dev at lists.llvm.org>> wrote: > - Hi, > > I'm a college student who is quite new to the community and is > interested in contributing to the LLVM project. Although I haven't applied > to GSoC, I notice that the project "Create LoopNestPass" seems to be > unassigned. > So I'm curious whether anyone is currently working on it, and if > not, is it possible for me to work on it as a side-project? > > I've been programming in C++ for quite a while, and I've walked > through the `LoopPass`, `LoopNest`, and some other LLVM classes that I > think would probably be related to this project. I've also watched some of > the videos in the llvm-dev conference regarding loops, so I now have a > rough idea on how to implement the LoopNestPass. > > I'm looking forward to working on this project. > > Thank you very much. > > Sincerely, > Ta-Wei Tu > _______________________________________________ > LLVM Developers mailing list > *llvm-dev at lists.llvm.org* <llvm-dev at lists.llvm.org> > *https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev* > <https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev> > > > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200724/dc98c2c4/attachment-0001.html>