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<p class="MsoNormal"><span style="font-size:11.0pt">Thanks for the clarification Hal, that’s really useful. We will be sure to upstream any generic work we do on this.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Jamie<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="color:black">From: </span></b><span style="color:black">Hal Finkel <hfinkel@anl.gov><br>
<b>Organization: </b>Argonne National Laboratory<br>
<b>Date: </b>Monday, 23 January 2017 at 14:09<br>
<b>To: </b>Jamie Hanlon <Jamie.Hanlon@graphcore.ai>, "llvm-dev@lists.llvm.org" <llvm-dev@lists.llvm.org><br>
<b>Cc: </b>Jon Chesterfield <jonc@graphcore.ai><br>
<b>Subject: </b>Re: [llvm-dev] Pre/post-increment addressing mode in LSR</span><span style="color:black;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Times New Roman""><o:p> </o:p></span></p>
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<p><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On 01/23/2017 05:52 AM, Jamie Hanlon via llvm-dev wrote:<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Dear all,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">From what I can gather, there is currently no way for loop strength reduction to target pre- and post-increment addressing modes. This is because the target hook `isLegalAddressingMode` in TargetTransformInfo.h
doesn’t allow for pre- and post-increment. There is in fact a comment to that effect on the function prototype: “TODO: handle pre/postinc as well” (see
<a href="http://llvm.org/docs/doxygen/html/TargetTransformInfo_8h_source.html">http://llvm.org/docs/doxygen/html/TargetTransformInfo_8h_source.html</a> line 310).</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">So I was wondering: is there a way to work around this limitation? And are there any plans to add support for pre- and post-increment addressing modes?
</span><o:p></o:p></p>
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<p class="MsoNormal"><span style="font-family:"Times New Roman";mso-fareast-language:EN-GB"><br>
It is, unfortunately, a long-standing deficiency. There are some work-arounds in some targets (e.g. lib/Target/PowerPC/PPCLoopPreIncPrep.cpp), but work on this would be appreciated.<br>
<br>
-Hal<br>
<br>
<br>
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Thanks in advance for any help on this.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Jamie Hanlon (from Graphcore,
<a href="http://www.graphcore.ai">www.graphcore.ai</a>)</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman";mso-fareast-language:EN-GB"><br>
<br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>LLVM Developers mailing list<o:p></o:p></pre>
<pre><a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a><o:p></o:p></pre>
<pre><a href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><o:p></o:p></pre>
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<p class="MsoNormal"><span style="font-family:"Times New Roman";mso-fareast-language:EN-GB"><br>
<br>
<o:p></o:p></span></p>
<pre>-- <o:p></o:p></pre>
<pre>Hal Finkel<o:p></o:p></pre>
<pre>Lead, Compiler Technology and Programming Languages<o:p></o:p></pre>
<pre>Leadership Computing Facility<o:p></o:p></pre>
<pre>Argonne National Laboratory<o:p></o:p></pre>
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