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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">This is great to hear, thanks for the update! Can you provide a timeline for when you expect to have the jump-threading update in review?
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The loop-flattening pass also looks very useful. I’m sure we could help with the review -- I don’t know about taking ownership of it, at least right now.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Alan<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Sjoerd Meijer [mailto:Sjoerd.Meijer@arm.com]
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<b>Sent:</b> Wednesday, September 23, 2020 2:14 PM<br>
<b>To:</b> Phipps, Alan; llvm-dev@lists.llvm.org; Eli Friedman; Evgeny Astigeevich; Sjoerd Meijer; David Green<br>
<b>Subject:</b> [EXTERNAL] Re: [llvm-dev] Improved jump-threading in LLVM for finite state automata<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black">And related while we are at it, i.e. the coremark specials, we have this sitting in upstream review: <a href="https://reviews.llvm.org/D42365" id="LPlnk359956">https://reviews.llvm.org/D42365</a> <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black">That should help a bit too. It needs a little bit of work, but I thought Dave didn't mind if someone commandeers and finishes it.<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> llvm-dev <llvm-dev-bounces@lists.llvm.org> on behalf of Sjoerd
Meijer via llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Sent:</b> 23 September 2020 20:03<br>
<b>To:</b> Phipps, Alan <a-phipps@ti.com>; llvm-dev@lists.llvm.org <llvm-dev@lists.llvm.org>; Eli Friedman <efriedma@quicinc.com>; Evgeny Astigeevich <Evgeny.Astigeevich@arm.com><br>
<b>Subject:</b> Re: [llvm-dev] Improved jump-threading in LLVM for finite state automata</span>
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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black">+ Evgeny<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black">We have a jump threading pass downstream for this that we would love to upstream. I believe Evgeny was working on exactly this, i.e. preparing it for upstreaming.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black"> llvm-dev <llvm-dev-bounces@lists.llvm.org> on behalf of Eli
Friedman via llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Sent:</b> 23 September 2020 19:16<br>
<b>To:</b> Phipps, Alan <a-phipps@ti.com>; llvm-dev@lists.llvm.org <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> Re: [llvm-dev] Improved jump-threading in LLVM for finite state automata</span>
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<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Nobody is currently working on this, as far as I know. If you’re interested in looking into it, I’ll try to answer any questions.<o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">-Eli<o:p></o:p></span></p>
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<p class="xxmsonormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> llvm-dev <llvm-dev-bounces@lists.llvm.org>
<b>On Behalf Of </b>Phipps, Alan via llvm-dev<br>
<b>Sent:</b> Wednesday, September 23, 2020 7:34 AM<br>
<b>To:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [EXT] [llvm-dev] Improved jump-threading in LLVM for finite state automata<o:p></o:p></span></p>
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<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">It is my understanding that the implementation for jump-threading in LLVM is not presently able to effectively optimize code containing a state-machine implemented using
a loop + switch. This is the case, for example, with the Coremark benchmark function core_state_transition(). Bug 42313 was filed to address this in 2019:<o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="https://bugs.llvm.org/show_bug.cgi?id=42313">https://bugs.llvm.org/show_bug.cgi?id=42313</a><o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">It appears that GCC improved support for jump threading in 2015 along the same lines:<o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54742">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54742</a><o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Is anyone aware of any plan to do improve LLVM jump-threading along the same lines for LLVM?<o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Thanks!<o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Alan Phipps<o:p></o:p></span></p>
<p class="xxmsonormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
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