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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> </div>
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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.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> 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</font>
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+ Evgeny</div>
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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.<br>
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<div id="x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> 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</font>
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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.</p>
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-Eli</p>
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<b>From:</b> 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</p>
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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:</p>
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<a href="https://bugs.llvm.org/show_bug.cgi?id=42313">https://bugs.llvm.org/show_bug.cgi?id=42313</a></p>
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It appears that GCC improved support for jump threading in 2015 along the same lines:</p>
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<a href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54742">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54742</a></p>
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Is anyone aware of any plan to do improve LLVM jump-threading along the same lines for LLVM?</p>
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Thanks!</p>
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Alan Phipps</p>
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