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<div class="moz-cite-prefix">On 6/22/16 1:15 AM, Yuxi Chen wrote:<br>
</div>
<blockquote
cite="mid:83E2887150EB424E8D7877B912AE1FF167C3F268@xm-mbx-07-prod"
type="cite">
<meta http-equiv="Context-Type" content="text/html;
charset=Windows-1252">
<div>1. If I don't use getAnalysisUsage, are there other ways to
implement invocation of different passes.
<br>
</div>
</blockquote>
<br>
As Mehdi stated, you must explicitly run the other passes by
scheduling them in the pass manager. If you're using opt to run
your pass, you just tell opt to run the transform passes before your
passes. If you're writing a tool, you have code that creates a
PassManager object and adds passes to the PassManager object. In
that case, you just add the tranform passes to the PassManager
object in the correct order.<br>
<br>
<blockquote
cite="mid:83E2887150EB424E8D7877B912AE1FF167C3F268@xm-mbx-07-prod"
type="cite">
<div>
2. Transform pass can't rely on other transform passes, if we
really want to do that, what can we do?<br>
</div>
</blockquote>
<br>
To clarify, transform passes can depend upon *analysis* passes
(i.e., passes that don't change the program). All passes should
avoid using addRequired<>() in their
getAnalysisUsage<>() methods to depend upon transform passes.<br>
<br>
Regards,<br>
<br>
John Criswell<br>
<br>
<blockquote
cite="mid:83E2887150EB424E8D7877B912AE1FF167C3F268@xm-mbx-07-prod"
type="cite">
<div>
<br>
Best,<br>
Yuxi<br>
<div>
<hr tabindex="-1">
<div id="divRpF161158"><b>From:</b> John Criswell
[<a class="moz-txt-link-abbreviated" href="mailto:jtcriswel@gmail.com">jtcriswel@gmail.com</a>]<br>
<b>Sent:</b> Tuesday, June 21, 2016 11:01 AM<br>
<b>To:</b> Yuxi Chen<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-abbreviated" href="mailto:llvmdev-bounces@cs.uiuc.edu">llvmdev-bounces@cs.uiuc.edu</a>; <a class="moz-txt-link-abbreviated" href="mailto:llvmdev@cs.uiuc.edu">llvmdev@cs.uiuc.edu</a><br>
<b>Subject:</b> Re: [llvm-dev] pass invalidation<br>
<br>
</div>
<div>
<div class="moz-cite-prefix">On 6/20/16 3:46 PM, Yuxi Chen
wrote:<br>
</div>
<blockquote type="cite">
<div>Hi, <br>
<br>
Thanks for your reply. <br>
But I still don't know how a transform pass updates a
new analysis pass after it modifies the IR. Can you
explain it clearly? I am not familiar with pass
management and invocation.
<br>
</div>
</blockquote>
<br>
Passes can have methods that allow their internal state to
be updated by other passes (the same way that their state
can be queried by other passes). For example, the alias
analysis passes have methods for querying alias information
as well as methods that allow other passes to update the
aliasing information when they make changes to the IR (so
that friendly optimization passes don't invalidate alias
analysis information when they make simple changes).<br>
<br>
Right now, your transform pass has a method which your other
passes are using to query information (I am guessing that
your transform pass is recording information on what it has
done). I am suggesting that you create a new pass (call it
"RK" for "Record Keeper") that implements this method (call
it getInfo()). Additionally, the RK pass also implements a
method called setInfo() which the transform pass uses to
record any information that later passes will need. In
their getAnalysisUsage<>() method, your passes
preserve the results of the RK pass.<br>
<br>
In this way, your transform pass modifies the IR and dumps
any information needed by your analysis passes into the RK
pass. The RK pass does not modify the IR, so it doesn't
create an impossible-to-schedule pass pipeline like your
transform pass does.<br>
<br>
If this isn't clear, please let me know. I see that you're
from UChicago, so I'm guessing that you need this for a
research project.<br>
<br>
Regards,<br>
<br>
John Criswell<br>
<br>
<br>
<blockquote type="cite">
<div><br>
Best,<br>
Yuxi<br>
<div>
<hr tabindex="-1">
<div id="divRpF16799"><b>From:</b> John Criswell [<a
moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:jtcriswel@gmail.com" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:jtcriswel@gmail.com">jtcriswel@gmail.com</a></a>]<br>
<b>Sent:</b> Sunday, June 19, 2016 10:05 AM<br>
<b>To:</b> Mehdi Amini; Yuxi Chen<br>
<b>Cc:</b> <a moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:llvm-dev@lists.llvm.org"
target="_blank">
llvm-dev@lists.llvm.org</a>; <a
moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:llvmdev-bounces@cs.uiuc.edu"
target="_blank">
<a class="moz-txt-link-abbreviated" href="mailto:llvmdev-bounces@cs.uiuc.edu">llvmdev-bounces@cs.uiuc.edu</a></a>; <a
moz-do-not-send="true"
class="moz-txt-link-abbreviated"
href="mailto:llvmdev@cs.uiuc.edu" target="_blank">
<a class="moz-txt-link-abbreviated" href="mailto:llvmdev@cs.uiuc.edu">llvmdev@cs.uiuc.edu</a></a><br>
<b>Subject:</b> Re: [llvm-dev] pass invalidation<br>
<br>
</div>
<div>
<div class="moz-cite-prefix">On 6/19/16 4:28 AM,
Mehdi Amini via llvm-dev wrote:<br>
</div>
<blockquote type="cite"><br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Jun 18, 2016, at 10:44 PM,
Yuxi Chen via llvm-dev <<a
moz-do-not-send="true"
href="mailto:llvm-dev@lists.llvm.org"
class="" target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a></a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="">Hi All,
<div class=""><br class="">
</div>
<div class="">When I use llvm, I encounter
a problem like "unable to schedule pass
A required by C"</div>
<div class="">I investigated deeper. It's
like:</div>
<div class="">I have three passes, say A,
B, C(all are on function level)</div>
<div class="">A would modify IR code.
(change instruction order)</div>
<div class=""><br class="">
</div>
<div class="">For pass B, </div>
<div class="">I would use the result of
pass A, I use addRequired<B>(),
and &getAnalysis<B>(), it
works. </div>
<div class=""><br class="">
</div>
<div class="">void getAnalysisUsage(AU){</div>
<div class=""><span class="Apple-tab-span"></span>AU.addRequired<A>();</div>
<div class="">}</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class="">For pass C, it will use the
results of pass A and B. </div>
<div class="">I use the way as used for
pass B, but it failed, even for LoopInfo
analysis pass(which is the built-in
analysis pass).</div>
<div class="">void getAnalysisUsage(AU){</div>
<div class=""><span class=""><span
class="Apple-tab-span"></span>AU.addRequired<A>();</span></div>
<div class=""><span class=""><span
class="Apple-tab-span"></span>AU.addRequired<B>();</span></div>
<div class=""><span class="">}</span></div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class="">It seems because A would
modify IR code, so for pass C, I need
first load pass A then pass B, otherwise
it will be invalidated. </div>
<div class="">However, when I change the
using order, I still got error "unable
to schedule pass A required by C".</div>
<div class=""><br class="">
</div>
<div class="">Does anyone encounter the
same problem before and have a solution?</div>
</div>
</div>
</blockquote>
<blockquote type="cite" class="">
<div class="">
<div class="">
<div class="">Any help is appreciated. </div>
</div>
</div>
</blockquote>
<div><br class="">
</div>
<div>Depending on other transformations isn’t
recommended, and isn’t supported by the
soon-new-passmanager I believe.</div>
<div>The expectation is that the passes are
added in order to the pass manager by the
client.</div>
</div>
</blockquote>
<br>
Depending on transformation passes isn't supported
by the legacy PassManager, either. Occasionally
some passes can get away with it, but it often
results in unschedule-able pass pipelines as above.<br>
<br>
If your transform pass does something to the code,
other passes should either infer what it did by
examining the IR. the IR contains the definitive
information about the program (because it is the
program).<br>
<br>
Alternatively, you could create an analysis pass
upon which both your transform and analysis passes
depend. The transform pass would update this new
analysis pass with information on what it
transformed; your later analysis passes could then
query this information. This approach is fragile,
but it could work.<br>
<br>
Regards,<br>
<br>
John Criswell<br>
<br>
<blockquote type="cite">
<div>
<div><br class="">
</div>
<div>In you case, I expect that it would “work”
by removing the dependency from C to A. If C
requires B and B requires A, by scheduling C
you’ll get A, B, C in sequence.</div>
<div><br class="">
</div>
<div>— </div>
<div>Mehdi</div>
<div><br class="">
</div>
<div><br class="">
</div>
<br class="">
<blockquote type="cite" class="">
<div class="">
<div class="">
<div class=""><br class="">
</div>
<div class="">Best,</div>
<div class="">Yuxi</div>
</div>
<span class="">_______________________________________________</span><br
class="">
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class="" target="_blank">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a></div>
</blockquote>
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<pre class="moz-signature" cols="72">--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.cs.rochester.edu/u/criswell" target="_blank">http://www.cs.rochester.edu/u/criswell</a></pre>
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</p>
<pre class="moz-signature" cols="72">--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://www.cs.rochester.edu/u/criswell" target="_blank">http://www.cs.rochester.edu/u/criswell</a></pre>
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<p><br>
</p>
<pre class="moz-signature" cols="72">--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
<a class="moz-txt-link-freetext" href="http://www.cs.rochester.edu/u/criswell">http://www.cs.rochester.edu/u/criswell</a></pre>
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