<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<p>I'm quite confident jump threading and the like easily capture
what's captured by D36287. In other words, I'm confident JT/GVN
isn't missing anything that D36287 is trying to do, so it's
difficult to assess the value of adding a predicateinfo based
pass. The patch itself removed on the order of 10-15 static
instruction from each of the impacted benchmarks and again that
was only about 1/3 of SPEC20XX and maybe 10-15 of the llvmts tests
(i.e., not very exciting).</p>
<p>I'm much much more interested in solving
<a class="moz-txt-link-freetext" href="http://lists.llvm.org/pipermail/llvm-dev/2017-August/116183.html">http://lists.llvm.org/pipermail/llvm-dev/2017-August/116183.html</a>,
which is where is idea of this patch came from..<br>
</p>
<br>
<div class="moz-cite-prefix">On 8/4/2017 1:18 PM, Daniel Berlin via
llvm-commits wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAF4BwTU1gKCtbdZDei47XhbT=-rNhx8P1xyK1xbUbM9YF4pH2g@mail.gmail.com">
<div dir="ltr">If you do discover testcases where these passes are
actually *missing* optimization, we'd love to see them.
<div>(as you surmise, there's little we can do about the ones
that come after ;P).</div>
<div><br>
</div>
<div>Otherwise, it would be pretty easy to build a predicateinfo
based pass to clean up here if it's valuable.</div>
<div>Predicateinfo takes < 600ms on > 1 million
blocks/conditionals (where even constructing the dominator
tree takes 700-800ms), so it's unlikely to affect compile time
in any real way.</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Fri, Aug 4, 2017 at 9:41 AM, Chad
Rosier via Phabricator <span dir="ltr"><<a
href="mailto:reviews@reviews.llvm.org" target="_blank"
moz-do-not-send="true">reviews@reviews.llvm.org</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">mcrosier
added a comment.<br>
<span class=""><br>
In <a href="https://reviews.llvm.org/D36287#831132"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://reviews.llvm.org/<wbr>D36287#831132</a>,
@efriedma wrote:<br>
<br>
> We already have a couple other passes which can do
optimize your testcase (JumpThreading and GVN); what do we
gain from doing this analysis here specifically?<br>
<br>
<br>
</span>Just to follow up on your question, Eli. I suspect
the fact that SimplifyCFG runs more frequently than JT and
GVN result in a few additional cases being captured (perhaps
cases exposed after JT/GVN). However, I honestly haven't
done the full investigation to get a definitive answer.
Again, this is just derivative work and I'm not particularly
set on getting this committed.<br>
<br>
<br>
<a href="https://reviews.llvm.org/D36287" rel="noreferrer"
target="_blank" moz-do-not-send="true">https://reviews.llvm.org/<wbr>D36287</a><br>
<br>
<br>
<br>
</blockquote>
</div>
<br>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
llvm-commits mailing list
<a class="moz-txt-link-abbreviated" href="mailto:llvm-commits@lists.llvm.org">llvm-commits@lists.llvm.org</a>
<a class="moz-txt-link-freetext" href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits</a>
</pre>
</blockquote>
<br>
</body>
</html>