<div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Mar 2, 2019 at 2:13 AM Fedor Sergeev <<a href="mailto:fedor.sergeev@azul.com">fedor.sergeev@azul.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">
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On 3/2/19 2:38 AM, Hiroshi Yamauchi wrote:<br>
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<div> Conditional BFI<br>
We could consider adding a
conditional BFI analysis that is a
wrapper around BFI and computes
BFI only if profiles are available
(either checking the module has
profile summary or depend on the
PSI.) With this, we wouldn’t need
to conditionally build pass
pipelines and may work for the new
pass manager. But a similar
wouldn’t work for the old pass
manager because we cannot
conditionally depend on an
analysis under it.<br>
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There is LazyBlockFrequencyInfo.<br>
Not sure how well it fits this idea.<br>
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<div><font face="arial, helvetica, sans-serif">Good
point. LazyBlockFrequencyInfo seems
usable with the old pass manager (save
unnecessary BFI/BPI) and would work for
function passes. I think t</font><span style="font-family:arial,helvetica,sans-serif">he </span><span style="font-family:arial,helvetica,sans-serif">restriction still applies
- </span><span style="font-family:arial,helvetica,sans-serif">a
loop pass cannot still request
(outer-scope) BFI, lazy or not, new or
old (pass manager). </span></div>
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You would need to explicitly require it (or/and add to
LoopStandardAnalysisResult) and teach loop passes to preserve it.<br>
Preserving LazyBFI might be as simple as resetting it all, yet the
overall idea of this LAzyBFI thing seems to be more or<br>
less duplicating what analysis managers are doing in new pass
manager.<br>
<br>
Here is a comment from LazyBFI's header:<br>
/// Note that it is expected that we wouldn't need this
functionality for the<br>
/// new PM since with the new PM, analyses are executed on demand.<br>
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:)<br></div></blockquote><div><br></div><div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif">Yes, we could actually request LazyBFI from a loop pass under the old pass manager.</div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div bgcolor="#FFFFFF">
<br>
regards,<br>
Fedor.<br>
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<div><span style="font-family:arial,helvetica,sans-serif">Another
assumption is that </span><span style="font-family:arial,helvetica,sans-serif">it'd
be cheap and safe to unconditionally
depend on PSI or check the module's
profile summary.</span></div>
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<div bgcolor="#FFFFFF"> <br>
regards,<br>
Fedor.<br>
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[1] We cannot call
AnalysisManager::getResult for an
outer scope but only
getCachedResult. Probably because
of potential pipelining or
concurrency issues.<br>
[2] For example, potentially
breaking up multiple pipelined
loop passes and insert
RequireAnalysisPass<BlockFrequencyAnalysis>
in front of each of them.<br>
[3] For example,
-fprofile-instr-use and
-fprofile-sample-use aren’t
present in ThinLTO post link
builds.<br>
[4] For example, we could check
whether the module has the profile
summary metadata annotated when
building pass pipelines but we
don’t always pass the module down
to the place where we build pass
pipelines.<br>
[5] By inserting
RequireAnalysisPass<ProfileSummaryInfo>
after the PGOInstrumentationUse
and the SampleProfileLoaderPass
passes (and around the
PGOIndirectCallPromotion pass for
the Thin LTO post link pipeline.)<br>
[6] For example, the
context-sensitive PGO<span class="gmail_default" style="font-family:arial,helvetica,sans-serif">.</span><br>
[7] Directly calling its
constructor along with the
dependent analyses results, eg.
the jump threading pass.</div>
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