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<meta http-equiv="Content-Type" content="text/html; charset=Windows-1252">
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<body>
<p>Thanks, everyone. It looks like we do have a time that works for
almost everyone.</p>
<p><br>
</p>
<p>Let's plan to meet on Tuesday, July 14th @ 12-1 central time /
10-11 pacific time / 6-7pm in London, and at that time on Tuesday
every four weeks.</p>
<p><br>
</p>
<p>Please use the Google doc linked below to add agenda items for
the next call (or, if you cannot access a Google doc, send me a
note and I'll add them for you).</p>
<p><br>
</p>
<p><a class="moz-txt-link-freetext" href="https://docs.google.com/document/d/1ybwEKDVtIbhIhK50qYtwKsL50K-NvB6LfuBsfepBZ9Y/edit?usp=sharing">https://docs.google.com/document/d/1ybwEKDVtIbhIhK50qYtwKsL50K-NvB6LfuBsfepBZ9Y/edit?usp=sharing</a><br>
</p>
<p><br>
</p>
<p>Meeting URL<br>
<a class="moz-txt-link-freetext" href="https://bluejeans.com/101176001?src=join_info">https://bluejeans.com/101176001?src=join_info</a><br>
<br>
Meeting ID<br>
101 176 001<br>
<br>
Want to dial in from a phone?<br>
<br>
Dial one of the following numbers:<br>
+1.312.216.0325 (US (Chicago))<br>
+1.408.740.7256 (US (San Jose))<br>
+1.866.226.4650 (US Toll Free)<br>
(see all numbers - <a class="moz-txt-link-freetext" href="https://www.bluejeans.com/premium-numbers">https://www.bluejeans.com/premium-numbers</a>)<br>
<br>
Enter the meeting ID and passcode followed by #<br>
<br>
Connecting from a room system?<br>
Dial: bjn.vc or 199.48.152.152 and enter your meeting ID &
passcode</p>
<p><br>
</p>
<p>Thanks again,</p>
<p>Hal<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 6/24/20 10:33 AM, Finkel, Hal J.
wrote:<br>
</div>
<blockquote type="cite" cite="mid:SN6PR09MB3805FE9883D5DEC4629A3E62A2950@SN6PR09MB3805.namprd09.prod.outlook.com">
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<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
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Hi, everyone,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
We had a great call last month, and progress is definitely being
made on several fronts. The notes from our last call are
available here:</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<a href="https://docs.google.com/document/d/1ybwEKDVtIbhIhK50qYtwKsL50K-NvB6LfuBsfepBZ9Y/edit#heading=h.vpxs8lkuxy79" id="LPlnk603524" moz-do-not-send="true">https://docs.google.com/document/d/1ybwEKDVtIbhIhK50qYtwKsL50K-NvB6LfuBsfepBZ9Y/edit#heading=h.vpxs8lkuxy79</a></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
and, also, pasted below.</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
DOODLE POLL:</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
As we discussed on our last call, I would like to schedule a
regular call to discuss alias-analysis issues within LLVM. I've
put together an initial Doodle poll to pick a time for this
call: <a href="https://doodle.com/poll/9iqfaqttvvic5rfp" id="LPlnk462928" moz-do-not-send="true">https://doodle.com/poll/9iqfaqttvvic5rfp</a></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
Please fill out this poll with the understanding that the
meeting will recur every four weeks. If you're interested in
participating, but none of the times on the poll would work for
you, please let me know.</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
Notes from our last call:</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
****</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<b style="font-weight:normal">
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="font-size:11pt; font-family:Arial;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span style="font-size:12pt;
font-family:Calibri,sans-serif">Scalability challenges
and other issues discovered with the current
infrastructure (especially, perhaps, with the noalias
metadata).<br>
</span></p>
</li>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Issue #1: MDNode::intersect
uses O(n^2) algorithm. The operation does not scale
for large NoAlias sets.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Issue #2:
ScopedNoAliasAAResult::mayAliasInScopes includes
overhead (per query) of partitioning the input set
based on the domain metadata.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Issue #3: Memory footprint of
the flattened Alias.Scope or NoAlias set can be
large.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Issue #4: correctness:
current implementation has problems after inlining
in a loop. </span></p>
</li>
</ul>
</ul>
<br>
<p dir="ltr" style="line-height:1.38; margin-left: 36pt;
margin-top:0pt; margin-bottom:0pt">
<span style="font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">Notes:</span></p>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Jeroen notes that he has not
observed scalability issues with the
</span><span><br>
</span><span>“full restrict” implementation.</span></p>
</li>
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Michael notes that part of the
scalability challenge comes from the fact that the
noalias scheme marks all those things with which you
don’t alias, but for restrict-like pointers, that’s
the default for everything in that scope.</span></p>
</li>
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Tarique notes that there may
still be a need for AA from the frontend, e.g., for
Fortran, above what the C-like restrict provides.</span></p>
</li>
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Eric asks if anyone is
considering a ground-up design to support Fortran?</span></p>
</li>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Troy notes that we would
prefer one representation to cover Fortran, C, etc.
Fortran is, in some sense, simpler than C/C++. Also
notes that language-specific AA can be a useful
technique as well.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Johannes notes that other
languages, e.g., Rust, can also benefit, and we
might need something where we can have universes,
negated aliasing edges, etc.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Michael notes that we can
chain AA, and so it’s possible to have something
more domain specific.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400; margin-left: 72pt">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Hal notes that if we have
language-specific MD, we need to figure out how to
maintain it (otherwise, all of the passes will drop
it, but maintaining it means that enough of the
semantics must be available). Jeroen notes that
reusing in-tree passes maximally reuses correct
implementation in combination with loop unrolling,
etc.</span></p>
</li>
</ul>
</ul>
<br>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="font-size:11pt; font-family:Arial;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span style="font-size:12pt;
font-family:Calibri,sans-serif">Proposed solutions:
progress, outstanding challenges, how to make progress
going forward.<br>
</span></p>
</li>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Proposal #1: (Related to both
Issue #1 and Issue #2) In the MDNode class,
pre-partition the set of Metadata operands where
each partition is an ordered set of Metadata
operands belonging to a specific domain.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Proposal #2: (Related to
Issue #3) Design a hierarchical representation for
the metadata operands in Alias.Scope and NoAlias
sets.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Proposal #3:
</span><a href="https://reviews.llvm.org/D68484" moz-do-not-send="true"><span style="color:#1155cc;
text-decoration:underline;
text-decoration-skip-ink:none">https://reviews.llvm.org/D68484</span></a><span>
provides the infrastructure to fix issue #4. It
might also help with issue #1 and issue #3 as it
makes it possible to share scopes.<br>
</span></p>
</li>
</ul>
</ul>
<br>
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400">Notes</span></p>
<br>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Tarique presented challenges
with the current prototype, including that there’s
currently no way to differentiate noalias MD from
other kinds of metadata, so it’s hard to keep a useful
cache in the generic MDNode implementation.</span></p>
</li>
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Jeroen presented some slides on
the full-restrict implementation, noted how this
scheme might solve/mitigate some of the scalability
challenges associated with the pure-metadata solution.</span></p>
</li>
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>The full-restrict
implementation is being used, and Jerone is currently
updating this implementation based on feedback from
that usage, he also will update the implementation to
use provenance instead of sidechannel and repost.</span></p>
</li>
<li dir="ltr" style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400">
<p dir="ltr" style="line-height:1.38; margin-top:0pt;
margin-bottom:0pt"><span>Johannes notes that we need
more reviewers for this patch set.</span></p>
</li>
</ul>
</b><br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
****</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
Thanks again,</div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
Hal</div>
<div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div id="Signature">
<div>
<div class="BodyFragment"><font size="2"><span style="font-size:10pt;">
<div class="PlainText">Hal Finkel<br>
Lead, Compiler Technology and Programming Languages<br>
Leadership Computing Facility<br>
Argonne National Laboratory</div>
</span></font></div>
</div>
</div>
</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b>
llvm-dev <a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev-bounces@lists.llvm.org"><llvm-dev-bounces@lists.llvm.org></a> on behalf
of Finkel, Hal J. via llvm-dev
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a><br>
<b>Sent:</b> Thursday, May 28, 2020 7:35 AM<br>
<b>To:</b> Jeroen Dobbelaere
<a class="moz-txt-link-rfc2396E" href="mailto:Jeroen.Dobbelaere@synopsys.com"><Jeroen.Dobbelaere@synopsys.com></a>; Alina Sbirlea
<a class="moz-txt-link-rfc2396E" href="mailto:alina.sbirlea@gmail.com"><alina.sbirlea@gmail.com></a><br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a>; Doerfert, Johannes
<a class="moz-txt-link-rfc2396E" href="mailto:jdoerfert@anl.gov"><jdoerfert@anl.gov></a><br>
<b>Subject:</b> Re: [llvm-dev] LLVM Alias Analysis Technical
Call - Doodle Poll</font>
<div> </div>
</div>
<div dir="ltr">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
Hi, everyone,</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
Just a quick reminder, this call starts in approximately 1.5
hours.</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
At the present time, our agenda has:</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<b style="font-weight:normal">
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="font-size:11pt; font-family:Arial;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span style="font-size:12pt;
font-family:Calibri,sans-serif">Scalability
challenges and other issues discovered with the
current infrastructure (especially, perhaps, with
the noalias metadata).</span></p>
</li>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
Issue #1: MDNode::intersect uses O(n^2) algorithm.
The operation does not scale for large NoAlias
sets.<br>
</p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span>Issue #2:
ScopedNoAliasAAResult::mayAliasInScopes includes
overhead (per query) of partitioning the input
set based on the domain metadata.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span>Issue #3: Memory footprint of the flattened
Alias.Scope or NoAlias set can be large.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span>Issue #4: correctness: current
implementation has problems after inlining in a
loop. </span></p>
</li>
</ul>
<li dir="ltr" style="font-size:11pt; font-family:Arial;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span style="font-size:12pt;
font-family:Calibri,sans-serif">Proposed
solutions: progress, outstanding challenges, how
to make progress going forward.</span></p>
</li>
<ul style="margin-top:0; margin-bottom:0">
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
Proposal #1: (Related to both Issue #1 and Issue
#2) In the MDNode class, pre-partition the set of
Metadata operands where each partition is an
ordered set of Metadata operands belonging to a
specific domain.<br>
</p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span>Proposal #2: (Related to Issue #3) Design a
hierarchical representation for the metadata
operands in Alias.Scope and NoAlias sets.</span></p>
</li>
<li dir="ltr" style="list-style-type:circle;
font-size:12pt; font-family:Calibri,sans-serif;
color:#000000; font-weight:400">
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span style="color:rgb(0,0,0);
font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; font-weight:normal"><span style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400">Proposal #3:
</span><a href="https://reviews.llvm.org/D68484" moz-do-not-send="true"><span style="font-size:12pt;
font-family:Calibri,sans-serif;
color:rgb(17,85,204); font-weight:400">https://reviews.llvm.org/D68484</span></a><span style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400"> provides the infrastructure
to fix issue #4. It might also help with issue
#1 and issue #3 as it makes it possible to
share scopes.</span></span></p>
</li>
</ul>
</ul>
<div>
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span style="color:rgb(0,0,0);
font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; font-weight:normal"><span style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400"><br>
</span></span></p>
<p dir="ltr" style="margin-top: 0px; margin-bottom:
0px;line-height:1.38; margin-top:0pt;
margin-bottom:0pt">
<span style="color:rgb(0,0,0);
font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; font-weight:normal"><span style="font-size:12pt;
font-family:Calibri,sans-serif; color:#000000;
font-weight:400"> -Hal</span></span></p>
</div>
</b></div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div id="x_Signature">
<div class="x_BodyFragment"><font size="2"><span style="font-size:10pt">
<div class="x_PlainText">Hal Finkel<br>
Lead, Compiler Technology and Programming
Languages<br>
Leadership Computing Facility<br>
Argonne National Laboratory</div>
</span></font></div>
</div>
</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> Finkel, Hal J.
<a class="moz-txt-link-rfc2396E" href="mailto:hfinkel@anl.gov"><hfinkel@anl.gov></a><br>
<b>Sent:</b> Monday, May 18, 2020 11:40 AM<br>
<b>To:</b> Jeroen Dobbelaere
<a class="moz-txt-link-rfc2396E" href="mailto:Jeroen.Dobbelaere@synopsys.com"><Jeroen.Dobbelaere@synopsys.com></a>; Alina Sbirlea
<a class="moz-txt-link-rfc2396E" href="mailto:alina.sbirlea@gmail.com"><alina.sbirlea@gmail.com></a><br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a>; Doerfert, Johannes
<a class="moz-txt-link-rfc2396E" href="mailto:jdoerfert@anl.gov"><jdoerfert@anl.gov></a><br>
<b>Subject:</b> Re: LLVM Alias Analysis Technical Call -
Doodle Poll</font>
<div> </div>
</div>
<div dir="ltr">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
To join our call on Thursday, May 28th @ <span style="font-family:Calibri,Arial,Helvetica,sans-serif;
background-color:rgb(255,255,255);
display:inline!important">9-10 AM central time / 2-3
PM UTC </span>please use this information:</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<span>Meeting URL<br>
</span>
<div><a class="moz-txt-link-freetext" href="https://bluejeans.com/643493129?src=join_info">https://bluejeans.com/643493129?src=join_info</a><br>
</div>
<div><br>
</div>
<div>Meeting ID<br>
</div>
<div>643 493 129<br>
</div>
<div><br>
</div>
<div>Want to dial in from a phone?<br>
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<div>(see all numbers -
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</div>
<div>Enter the meeting ID and passcode followed by #<br>
</div>
<div><br>
</div>
<div>Connecting from a room system?<br>
</div>
<span>Dial: bjn.vc or 199.48.152.152 and enter your
meeting ID & passcode</span><br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<span><br>
</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<span>On our agenda, we'll have:</span></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<span><br>
</span></div>
<div style=""><font face="Calibri, Arial, Helvetica,
sans-serif" color="#000000"><span style="font-size:12pt"> 1. Scalability
</span>challenges<span style="font-size:12pt"> and
other issues discovered with the current
infrastructure (especially, perhaps, with the
noalias metadata).</span></font></div>
<div style=""><font face="Calibri, Arial, Helvetica,
sans-serif" color="#000000"><span style="font-size:12pt"> 2. Proposed solutions:
progress, outstanding
</span>challenges, how to make progress going forward.</font></div>
<div style=""><font face="Calibri, Arial, Helvetica,
sans-serif" color="#000000"><br>
</font></div>
<div style=""><font face="Calibri, Arial, Helvetica,
sans-serif" color="#000000">We'll formulate the
detailed agenda and take notes from the call using
this Google doc: <a href="https://docs.google.com/document/d/1ybwEKDVtIbhIhK50qYtwKsL50K-NvB6LfuBsfepBZ9Y/edit?usp=sharing" id="LPNoLP538393" moz-do-not-send="true">https://docs.google.com/document/d/1ybwEKDVtIbhIhK50qYtwKsL50K-NvB6LfuBsfepBZ9Y/edit?usp=sharing</a></font></div>
<div style=""><br>
</div>
<div style="">A summary will then be sent to the mailing
list after the call. If you would like to add items to
the agenda, please edit the document (or reply to this
email).</div>
<div style=""><br>
</div>
<div style="">Thanks again,</div>
<div style="">Hal</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div id="x_x_Signature">
<div class="x_x_BodyFragment"><font size="2"><span style="font-size:10pt">
<div class="x_x_PlainText">Hal Finkel<br>
Lead, Compiler Technology and Programming
Languages<br>
Leadership Computing Facility<br>
Argonne National Laboratory</div>
</span></font></div>
</div>
</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<hr tabindex="-1" style="display:inline-block;
width:98%">
<div id="x_x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> Finkel, Hal J.
<a class="moz-txt-link-rfc2396E" href="mailto:hfinkel@anl.gov"><hfinkel@anl.gov></a><br>
<b>Sent:</b> Monday, May 18, 2020 10:24 AM<br>
<b>To:</b> Jeroen Dobbelaere
<a class="moz-txt-link-rfc2396E" href="mailto:Jeroen.Dobbelaere@synopsys.com"><Jeroen.Dobbelaere@synopsys.com></a>; Alina
Sbirlea <a class="moz-txt-link-rfc2396E" href="mailto:alina.sbirlea@gmail.com"><alina.sbirlea@gmail.com></a>; Finkel, Hal
J. <a class="moz-txt-link-rfc2396E" href="mailto:hfinkel@anl.gov"><hfinkel@anl.gov></a><br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a>; Doerfert, Johannes
<a class="moz-txt-link-rfc2396E" href="mailto:jdoerfert@anl.gov"><jdoerfert@anl.gov></a><br>
<b>Subject:</b> Re: LLVM Alias Analysis Technical
Call - Doodle Poll</font>
<div> </div>
</div>
<div dir="ltr">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
Thanks to everyone who participated in the poll. The
time that maximizes availability is:</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
Thursday, May 28th @ 9-10 AM central time / 2-3 PM
UTC.</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
I'll send out meeting information shortly.</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
-Hal</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div id="x_x_x_Signature">
<div class="x_x_x_BodyFragment"><font size="2"><span style="font-size:10pt">
<div class="x_x_x_PlainText">Hal Finkel<br>
Lead, Compiler Technology and Programming
Languages<br>
Leadership Computing Facility<br>
Argonne National Laboratory</div>
</span></font></div>
</div>
</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<hr tabindex="-1" style="display:inline-block;
width:98%">
<div id="x_x_x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri,
sans-serif" color="#000000"><b>From:</b>
llvm-dev <a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev-bounces@lists.llvm.org"><llvm-dev-bounces@lists.llvm.org></a>
on behalf of Finkel, Hal J. via llvm-dev
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a><br>
<b>Sent:</b> Wednesday, May 13, 2020 11:14 AM<br>
<b>To:</b> Jeroen Dobbelaere
<a class="moz-txt-link-rfc2396E" href="mailto:Jeroen.Dobbelaere@synopsys.com"><Jeroen.Dobbelaere@synopsys.com></a>; Alina
Sbirlea <a class="moz-txt-link-rfc2396E" href="mailto:alina.sbirlea@gmail.com"><alina.sbirlea@gmail.com></a><br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a>; Doerfert,
Johannes <a class="moz-txt-link-rfc2396E" href="mailto:jdoerfert@anl.gov"><jdoerfert@anl.gov></a><br>
<b>Subject:</b> [llvm-dev] LLVM Alias Analysis
Technical Call - Doodle Poll</font>
<div> </div>
</div>
<div dir="ltr">
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
Hi, everyone,</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
We've had a number of discussions recently,
including on the Flang technical call, about
potential improvements to LLVM's alias analysis
to support handling restrict and restrict-like
semantics.</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
We would like to try having a call to discuss
these issues further. Please, if you're
interested in joining, indicate your
availability (prior to the end of this week):</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<a href="https://doodle.com/poll/evhwr2eyfvcf8ib3" id="LPlnk510266" moz-do-not-send="true">https://doodle.com/poll/evhwr2eyfvcf8ib3</a></div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
Thanks again,</div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
Hal</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<div id="x_x_x_x_Signature">
<div class="x_x_x_x_BodyFragment"><font size="2"><span style="font-size:10pt">
<div class="x_x_x_x_PlainText">Hal
Finkel<br>
Lead, Compiler Technology and
Programming Languages<br>
Leadership Computing Facility<br>
Argonne National Laboratory</div>
</span></font></div>
</div>
</div>
<div>
<div style="font-family:Calibri,Arial,Helvetica,sans-serif;
font-size:12pt; color:rgb(0,0,0)">
<br>
</div>
<hr tabindex="-1" style="display:inline-block;
width:98%">
<div id="x_x_x_x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri,
sans-serif" color="#000000"><b>From:</b>
llvm-dev
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev-bounces@lists.llvm.org"><llvm-dev-bounces@lists.llvm.org></a> on
behalf of Alina Sbirlea via llvm-dev
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a><br>
<b>Sent:</b> Monday, May 11, 2020 9:49 AM<br>
<b>To:</b> Jeroen Dobbelaere
<a class="moz-txt-link-rfc2396E" href="mailto:Jeroen.Dobbelaere@synopsys.com"><Jeroen.Dobbelaere@synopsys.com></a><br>
<b>Cc:</b> <a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:llvm-dev@lists.llvm.org"><llvm-dev@lists.llvm.org></a>; Doerfert,
Johannes <a class="moz-txt-link-rfc2396E" href="mailto:jdoerfert@anl.gov"><jdoerfert@anl.gov></a><br>
<b>Subject:</b> Re: [llvm-dev] Full restrict
support - status update</font>
<div> </div>
</div>
<div>
<div dir="ltr">Hi Johannes et al,<br>
<div><br>
</div>
<div>Trying to revive this discussion, as
the restrict support is relevant for one
of our teams.</div>
<div><br>
</div>
<div>Thank you,</div>
<div>Alina</div>
</div>
<br>
<div class="x_x_x_x_x_gmail_quote">
<div dir="ltr" class="x_x_x_x_x_gmail_attr">On
Tue, Nov 12, 2019 at 1:16 PM Jeroen
Dobbelaere via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
wrote:<br>
</div>
<blockquote class="x_x_x_x_x_gmail_quote" style="margin:0px 0px 0px 0.8ex;
border-left:1px solid rgb(204,204,204);
padding-left:1ex">
Hi Johannes et al,<br>
<br>
> -----Original Message-----<br>
> From: Doerfert, Johannes <<a href="mailto:jdoerfert@anl.gov" target="_blank" moz-do-not-send="true">jdoerfert@anl.gov</a>><br>
[..]<br>
> On 11/06, Jeroen Dobbelaere wrote:<br>
> > >From: Alexey Zhikhartsev<br>
> > [..]<br>
> > > We would love to see your
patches merged as soon as possible, so I
was<br>
> wondering: do you think the lack of
bitcode support will prevent that from<br>
> happening?<br>
> ><br>
> > Yes, I think that the lack of
bitcode support will prevent it.<br>
> ><br>
> > During the Developers meeting, I
also talked with Hal and Johannes.<br>
> > They had some extra remarks:<br>
> > - (1) the restrict
implementation deserves a separate
document. (I am<br>
> working on that one)<br>
> > - (2) they don't like the naming
of 'noalias_sidechannel'.<br>
> > - (3) they also have some other
mechanisms in mind to add the
'sidechannel'<br>
> to the load/store instructions<br>
> > (and maybe to function
calls, intrinsics; currently that is
handled through<br>
> llvm.noalias.arg.guard)<br>
> ><br>
> > For (2) and (3), I am waiting
for a proposal from them ;)<br>
> <br>
> I would like to see the restrict
support be merged but, as Jeroen<br>
> mentions above, I feel there are two
design choices we have to<br>
> overthink. Here are short
descriptions to get some feedback from the<br>
> community:<br>
> <br>
> (A) Naming and restriction<br>
> <br>
> The name "sidechannel" is
unfortunate, it has various negative<br>
> connotations, e.g., the release notes
that read:<br>
> "LLVM 10.0 now has sidechannel
support for your restrict pointer"<br>
> will raise a lot of follow up
questions.<br>
> <br>
> What I think we actually do, and what
we should call it, is "provenance"<br>
> tracking.<br>
> <br>
> Now beyond the pure renaming of
"sidechannel" into "provenance" (or sth.<br>
> similar) I want us to decouple
provenance tracking from the noalias<br>
> logic. Noalias/restrict is one use
case in which (pointer) provenance<br>
> information is useful but not the
only one. If we add some mechanism to<br>
> track provenance, let's make it
generic and reusable. Note that the<br>
> basic ideas are not much different to
what the noalias RFC proposed.<br>
> The major difference would be that we
have provenance information and if<br>
> that originates in an
`llvm.restrict.decl` call we can use it
for<br>
> (no)alias queries.<br>
<br>
"provenance" might indeed be a good name.<br>
<br>
There is a big difference between a
restrict declaration, and a restrict
usage: <br>
- the declaration intrinsic
(llvm.noalias.decl) is used to track in
the cfg the location<br>
where the restrict variable was
declared. This is important to handle code
motion,<br>
merging, duplication in a correct way
(inlining, loop unrolling, ...)<br>
- the restrict usage intrinsics
(llvm.noalias and llvm.side.noalias) are
used to indicate<br>
that from that point on, restrict
(noalias) properties are introduced for
that pointer.<br>
They can exist without an associated
'llvm.noalias.decl' (when the declaration
is outside<br>
the function.)<br>
Given that, I assume that you mean
'llvm.provenance.noalias' (~
llvm.side.noalias) instead<br>
of 'llvm.restrict.decl'.<br>
<br>
> <br>
> <br>
> <br>
> (B) Using operand bundles<br>
> <br>
> Right now, loads and stores are
treated differently and given a new<br>
> operand. Then there are intrinsics to
decode other kinds of information.<br>
> As an alternative, we could allow
operand bundles on all instructions<br>
> and use them to tie information to an
instruction. The "sidechannel"<br>
> operand of a load would then look
something like:<br>
> load i32* %p [
"ptr_provenance"(%p_decl) ]<br>
> and for a store we could have<br>
> store i32** %p.addr, i32* %p [
"ptr_provenance"(%p_decl) ]<br>
> <br>
> The benefit is that we do not change
the operand count (which causes a<br>
> lot of noise) but we still have to
make sure ptr/value uses are not<br>
> confused with operand bundle uses. We
can attach the information to more<br>
> than load/store instructions, also to
remove the need for some of the<br>
> intrinsics.<br>
<br>
To me, operand bundles sound to be more or
less equivalent to the current<br>
solution. It might also make the
'instruction cloning' easier, if we can
omit the<br>
'ptr_provenance' there. The change of the
number of operands caused some<br>
noise, but it is the changes in the amount
of 'uses' of a pointer that refer to the<br>
same instruction that caused the most
problems. Especially when that instruction<br>
was going to be erased. Operand bundles
will still need those code changes.<br>
(like in parts of D68516 and D68518)<br>
<br>
As the 'Call' instruction already supports
operand bundles, it could eliminate the
need<br>
for the 'llvm.noalias.arg.guard'
intrinsic, which combines the normal
pointer with the<br>
side channel (aka provenance). But, after
inlining, we still need to put that
information<br>
somewhere. Or it should be propagated
during inlining.<br>
Care must be taken not to lose that
information when the 'call' is changed by
optimizations<br>
as, after inlining, that might result in
wrong alias analysis conclusions.<br>
<br>
Are you thinking of "operand bundles"
support for just LoadInst/StoreInst, or
for all<br>
instructions ?<br>
<br>
Greetings,<br>
<br>
Jeroen Dobbelaere<br>
<br>
<br>
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<pre class="moz-signature" cols="72">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre>
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