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<p>I've put my changes to EarlyCSE that trigger this case up on phab
here: <a class="moz-txt-link-freetext" href="http://reviews.llvm.org/D19821">http://reviews.llvm.org/D19821</a>. These changes depend on
<a class="moz-txt-link-freetext" href="http://reviews.llvm.org/D19664">http://reviews.llvm.org/D19664</a> so that will need to be applied
first. With these changes applied, the original attached .ll file
should trigger this bug when compiled with opt -early-cse
-early-cse-use-memoryssa<br>
</p>
<div class="moz-cite-prefix">On 5/2/2016 2:34 PM, Daniel Berlin
wrote:<br>
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<blockquote
cite="mid:CAF4BwTVzbNhGBNTtwS0RBBmw8tP-vkJR6d_qy1p99gGaTYn8-w@mail.gmail.com"
type="cite">
<div dir="ltr">(IE the thing we cache has to be the same no matter
which version is called. If it can't be for some reason, we
can't cache results from both in the same cache. If it can be, i
suspect there is a bug in making that work :P)
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<div>I suspect the latter, and not the former.</div>
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<div class="gmail_extra"><br>
<div class="gmail_quote">On Mon, May 2, 2016 at 11:32 AM, Daniel
Berlin <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:dberlin@dberlin.org" target="_blank">dberlin@dberlin.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">I suspect something is pulling the RHS of the
memorydef and caching it for calls it should not be used
for.
<div>In particular, i suspect we are about to discover we
can't cache the results from both versions of
getClobberingMemoryAccess together, or that the cache is
not always getting consistently written.</div>
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<div class="HOEnZb">
<div class="h5">
<div class="gmail_extra"><br>
<div class="gmail_quote">On Mon, May 2, 2016 at 11:16
AM, George Burgess IV <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:george.burgess.iv@gmail.com"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:george.burgess.iv@gmail.com">george.burgess.iv@gmail.com</a></a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr">Yeah, that sounds like a fun bug.
I'll take a look later today and see what I can
find out. :)
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<div class="gmail_extra"><br>
<div class="gmail_quote">On Fri, Apr 29,
2016 at 2:55 PM, Geoff Berry <span
dir="ltr"><<a
moz-do-not-send="true"
href="mailto:gberry@codeaurora.org"
target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:gberry@codeaurora.org">gberry@codeaurora.org</a></a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex">
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<p>Hi guys,</p>
<p>I think I have run into another
CachingMemorySSAWalker cache bug.
It's a bit tricky to reproduce, so
I'd like to start by trying to
show you what is happening when
running EarlyCSE with my local
changes to use MemorySSA. I've
attached a debug log that shows
that the value returned by
getClobberingMemoryAccess(Inst)
after a call to removeMemoryAccess
is wrong. The MemorySSA node in
question is MemoryUse(7), and the
corruption happens after a call to
remove MemoryUse(2), at which
point its clobber value changes to
'1 = MemoryDef(liveOnEntry)'. The
interesting thing is that is
doesn't seem to be the first call
to getClobberingMemoryAccess after
the removal that causes the
corruption, but rather the
second. You'll notice that I
added calls to
getClobberingMemoryAccess when
doing MSSA.dump(), which is what
I'm using to attempt to figure out
when the cache gets corrupted.<br>
</p>
Hopefully this is enough information
to debug the problem. If not
perhaps we can look at getting my
EarlyCSE changes checked in in a
disabled state so you can reproduce
the problem directly. I'm also
happy to help debug it farther.<span><font
color="#888888"><br>
<pre cols="72">--
Geoff Berry
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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<pre class="moz-signature" cols="72">--
Geoff Berry
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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