<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<br>
<br>
<div class="moz-cite-prefix">On 3/15/20 11:12 PM, Benson Bin Bin Li
via llvm-dev wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAH6L9ak+6mtOb7F6siJo6R0cEpguS=UMt_5tARN8KaZ2qCSu4Q@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">
<div>Hi Stefanos,</div>
<div><br>
</div>
<div>First, thanks a lot for the very detailed response! I
watched both of the videos, and I seem to have a rough idea
now of how each of the different pieces of software maps onto
the compilation process. Though I found blogs such as these
two: <a
href="https://jonasdevlieghere.com/understanding-the-clang-ast/"
moz-do-not-send="true">https://jonasdevlieghere.com/understanding-the-clang-ast/</a>,
<a
href="https://releases.llvm.org/2.6/docs/tutorial/JITTutorial1.html"
moz-do-not-send="true">https://releases.llvm.org/2.6/docs/tutorial/JITTutorial1.html</a>
to be better for a more in-depth understanding. Anyways, in
response to your answers:</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>The latter can even be problematic if you start applying
C++ craziness while the first is pretty much always needed
when working in a team project.</div>
</blockquote>
<div>Ok, that makes sense as you would want the style to be
consistent throughout. <br>
</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>running the LLVM suite is super easy</div>
</blockquote>
<div>Yeah, everything went fine from following your
instructions. I do have a question though: How do I diagnose
failed tests? I found the files that correspond to them, and
they seem to be 1 line scripts rather than "code" per say. <br>
</div>
<div><br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div> But I think every good GSoC proposal includes a
biography-like section</div>
</blockquote>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>Then, try to study it, understand the context and the
problem. <br>
</div>
</blockquote>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>But because submitting good patches is one of the best
indicators <br>
</div>
</blockquote>
<div>Ok, so for the application process, basically try to get
more info on the projects I am interested in and from there
submit a proposal? Given the whole coronavirus situation and
the time remaining for the application, I probably do not have
the time to get a patch through. Regarding the projects I am
interested in, I have narrowed it down to two(mostly because I
don't think I have the ability to tackle PostDominatorTree
project as of now), and have the following questions about
them:</div>
<div><br>
</div>
<div>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"
id="gmail-docs-internal-guid-48482a0b-7fff-e7f0-4627-fb046bcc2e7f"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline;white-space:pre-wrap">LLVM Pass</span></p>
<ol style="margin-top:0px;margin-bottom:0px">
<li dir="ltr" style="list-style-type:decimal;font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre"><p dir="ltr" style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">I am following the guide to create a LLVM pass following this guide(<a href="https://llvm.org/docs/WritingAnLLVMPass.html" moz-do-not-send="true">https://llvm.org/docs/WritingAnLLVMPass.html</a>), but it appears “add_llvm_library” is a macro and not a built-in command. So I have two questions. 1) In comparing the online repo I found this macro in and my local, it appears I don’t have the file. Do I need to build it then? 2) How do I tell CMake to look for this macro?</span></p></li>
<li dir="ltr" style="list-style-type:decimal;font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre"><p dir="ltr" style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Is there a specific section of the dragon book that I should read so that I can at least understand theoretically what it means to create a LoopNestPass?</span></p></li>
</ol>
</div>
</div>
</blockquote>
Stefanos can speak to this more but in order to create a
LoopNestPass after reading what they are talking about requires
information from the call graph<br>
for a function or the loop hierarchy in LLVM IR. I'm not sure of the
internal classes for this so Stefanos is there a way currently to
get the info in IR about<br>
the outer loop or from the call graph? That seems to be the biggest
problem getting the outer loop in the IR or the call graph. After
that you would<br>
basically check if the loop is the outer loop and if so you can add
dynamically to the pipeline. <br>
<br>
Sorry if I'm not much help as I'm not sure if the call graph API
supports this but I'm pretty sure LLVM IR doesn't make this easy,<br>
Nick<br>
<blockquote type="cite"
cite="mid:CAH6L9ak+6mtOb7F6siJo6R0cEpguS=UMt_5tARN8KaZ2qCSu4Q@mail.gmail.com">
<div dir="ltr">
<div><br>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:underline;vertical-align:baseline;white-space:pre-wrap">LLDB Tab Completion</span></p>
<ol style="margin-top:0px;margin-bottom:0px">
<li style="list-style-type:decimal;font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre"><p style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Is there any resource I can read that explains how lldb is able to “pause” the executable and map it to a certain line in the source file/in general how lldb represents the state of the executable?</span></p></li>
<li style="list-style-type:decimal;font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre"><p style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Where in the source code can I go to see how existing tab completions are implemented?</span></p></li>
<li style="list-style-type:decimal;font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">I built lldb and check-lldb, but it seems that the call path to clang got messed up, as it is trying to call "Example=Code/llvm-project" rather than my actual name for the directory "Example-Code/llvm-project". Should I just clone the repo into a parent directory that doesn't use hyphen?
</span></li>
</ol>
</div>
<div><br>
</div>
<div>(Would it be better if I posted this on the forum?)</div>
<div><br>
</div>
<div>Best regards,</div>
<div>Benson<br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, Mar 14, 2020 at 11:10
AM Stefanos Baziotis <<a
href="mailto:stefanos.baziotis@gmail.com"
moz-do-not-send="true">stefanos.baziotis@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">Hi Benson,<br>
<br>
You're welcome to the LLVM community!<br>
<br>
I'll try to help but note that I'm no formal position to
talk about how LLVM decides about GSoC (I'm a LLVM newcomer
anyway).<br>
With that said, the rest is _my_ opinion which is partially
formed from my experience as a GSoC student.<br>
<br>
> <span style="color:rgb(0,0,0);font-family:Arial;font-size:14.6667px;white-space:pre-wrap">But to be up front about this, I have not done any full scale C++ project
</span><br>
Depending on how you define "full-scale", a lot of amazing
LLVM contributors have not done a full-scale C++. So, I
think no problem there, it's just good to have a relatively
good knowledge of C++.<br>
Talking about C++ skills, I think they're more important if
you want to contribute to Clang than say LLVM middle or
back-end. Because for Clang, you have to know a lot of
details of the language<br>
in order to parse it, type-check it and generate LLVM IR. In
most other parts of LLVM, you're only using the language.<br>
As a matter of fact, if you have a good knowledge of C++, I
believe it's more important to be able to understand and
adapt to "nearby" code, than to be an expert in C++.<br>
The latter can even be problematic if you start applying C++
craziness while the first is pretty much always needed when
working in a team project.<br>
<br>
> <span style="color:rgb(0,0,0);font-family:Arial;font-size:14.6667px;white-space:pre-wrap">1. Do I need to submit a resume/screening/patches?
</span><br>
As far as the resume, in the way that you may usually apply
to jobs, no. But I think every good GSoC proposal includes a
biography-like section<br>
where you basically tell your story in programming and how
you fit into the project (in our case, LLVM).<br>
<br>
I'm not sure what you mean by screening.<br>
<br>
As for patches, I don't think they're required but they're
super useful. Not because they're some part of unrelated
logistics (like "you have to have X patches to be
considered").<br>
But because submitting good patches is one of the best
indicators (if not the best) that you are able to do useful
work in this project. :)<br>
And they don't only show your technical skills. But also
communication skills, independence etc.<br>
<br>
> 2. <span style="color:rgb(0,0,0);font-family:Arial;font-size:14.6667px;white-space:pre-wrap">Although I do have interests in certain projects posted on you website(Implement missing tab completion, createLoopPass, and PostDominatorTree), I am uncertain if I have enough expertise to decide what would be an appropriate project to contribute to given my current knowledge and experience.
</span><br>
This is kind of a generic sentence.<br>
I'd say, start with finding a project that you're truly
interested in. Then, try to study it, understand the context
and the problem.<br>
You don't need to get very far, that's totally ok. You can
then do a post (either here or on Discourse: <a
href="https://llvm.discourse.group/c/community/gsoc/32"
target="_blank" moz-do-not-send="true">https://llvm.discourse.group/c/community/gsoc/32</a>)<br>
for this specific project (you can do posts for multiple
projects).<br>
Hopefully, by discussing with people (and mentors) and
understanding what the project is asking better,<br>
you can find if you want to do it or not. Certainly, the
mentors of the project can guide you through.<br>
<br>
<span style="color:rgb(0,0,0);font-family:Arial;font-size:14.6667px;white-space:pre-wrap">3. The GCC GSoC website suggested checking out their source code, compiling and running their test suite. Can I do something similar for LLVM?
</span><br>
Yes, totally. I'm not familiar with GCC internals but
running the LLVM suite is super easy (so easy that you don't
really learn anything by doing it :P )<br>
So, the LLVM project has moved to a common repository: <a
href="https://github.com/llvm/llvm-project"
target="_blank" moz-do-not-send="true">https://github.com/llvm/llvm-project</a><br>
You can clone the project and then use CMake to build it.
The cmake configuration for LLVM has a bunch of flags: <a
href="https://llvm.org/docs/CMake.html" target="_blank"
moz-do-not-send="true">https://llvm.org/docs/CMake.html</a><br>
and you may get lost. So, I'll say start simple:<br>
Go to the llvm-project dir (the one you cloned) and do:<br>
cmake ./llvm -DLLVM_ENABLE_PROJECTS="clang"
-DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=ON
-DLLVM_TARGETS_TO_BUILD="X86"<br>
<br>
In the link above you can read what the flags do. llvm
middle / back-end (i.e. opt / llc, ask if you don't know
what these mean) is always built. But to build clang<br>
we have to enable it explicitly. We set build type to
release because doing a debug build will take a lot of time
and a lot of space. Also, when starting out,<br>
you probably don't need it. We enable assertions mostly
because you can use the -debug option say in opt and see
debug prints.<br>
Finally, we only build for x86 arch because that's probably
what you have and you don't need any other for now.<br>
<br>
Hit enter and once the configuration is complete you can do:<br>
make<br>
or<br>
make -j<number of threads> <-- this is faster
but limit it depending on your systemS<br>
<br>
When that's finished, the llvm-project/bin/ dir will have
executables like clang, clang++, opt, llc etc.<br>
Which you can run (also ask if you don't know what to do
with them. With clang you probably will know, it's like
invoking<br>
most compilers like gcc to compile .c / .cpp files).<br>
<br>
To run the test suite, you can go to llvm-project/llvm/test
and do:<br>
<dir of llvm-project>/bin/llvm-lit .<br>
That will run only llvm's test suite but you'll get an idea.<br>
<br>
Also, you can watch these videos:<br>
<a href="https://www.youtube.com/watch?v=J5xExRGaIIY"
target="_blank" moz-do-not-send="true">https://www.youtube.com/watch?v=J5xExRGaIIY</a><br>
<a href="https://www.youtube.com/watch?v=5kkMpJpIGYU"
target="_blank" moz-do-not-send="true">https://www.youtube.com/watch?v=5kkMpJpIGYU</a><br>
<br>
Hope this helped!<br>
<br>
Kind regards,<br>
Stefanos Baziotis</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Στις Σάβ, 14 Μαρ 2020 στις
2:04 π.μ., ο/η Benson Bin Bin Li via llvm-dev <<a
href="mailto:llvm-dev@lists.llvm.org" target="_blank"
moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
έγραψε:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"
id="gmail-m_-4313643294865233574gmail-m_-8466928840379538763gmail-docs-internal-guid-2a0d31dc-7fff-9297-e699-ad2df8792b10"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Dear LLVM Team,</span></p>
<br>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">I would like to contribute to/participate in LLVM’s GSOC, because I would very much like to combine my knowledge of graph theory/algorithms and my interest in C++ together. Contributing to the LLVM code seems like a fantastic challenge and learning experience for these two interests of mine, as well as computer science in general (For example, the use of a new syntactic category to disambiguate a grammar demonstrates 1) indirection 2) the power of naming things).</span></p>
<br>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">But to be up front about this, I have not done any full scale C++ project(Although we had to modify the Linux kernel in my OS class, that was in C). However, I do believe my C++ skills are at an intermediate level, as C++, like Python, is a language in which I will spend my free time learning more about. Like vim, there is always more to learn in C++, and to that end I will watch CppCon Videos or peruse blogs such as Fluent C++(which is a treasure trove of material to nerd out on) in my free time. I also have a layman’s knowledge of CMake, from using it to configure ccls to lint C++ code with specific flags, and am aware of Google’s Test framework. Finally, I am currently taking Professor Stroustrap’s C++ class, and the compilers course here at Columbia.</span></p>
<br>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Regarding the logistics:</span></p>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">1. Do I need to submit a resume/screening/patches? </span></p>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">2. Although I do have interests in certain projects posted on you website(Implement missing tab completion, createLoopPass, and PostDominatorTree), I am uncertain if I have enough expertise to decide what would be an appropriate project to contribute to given my current knowledge and experience. </span></p>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">3. The GCC GSoC website suggested checking out their source code, compiling and running their test suite. Can I do something similar for LLVM?</span></p>
<br>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Anyways, thank you for taking the time to read this email, and I hope to hear back!</span></p>
<br>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Best regards,</span></p>
<p dir="ltr"
style="line-height:1.38;margin-top:0pt;margin-bottom:0pt"><span style="font-size:11pt;font-family:Arial;color:rgb(0,0,0);background-color:transparent;font-weight:400;font-style:normal;font-variant:normal;text-decoration:none;vertical-align:baseline;white-space:pre-wrap">Benson Li</span></p>
</div>
_______________________________________________<br>
LLVM Developers mailing list<br>
<a href="mailto:llvm-dev@lists.llvm.org" target="_blank"
moz-do-not-send="true">llvm-dev@lists.llvm.org</a><br>
<a
href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><br>
</blockquote>
</div>
</blockquote>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
LLVM Developers mailing list
<a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-freetext" href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a>
</pre>
</blockquote>
<br>
</body>
</html>