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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D;mso-fareast-language:EN-US">Ah! Excellent. This looks like just what I’m looking for, thanks for the pointer!<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri","sans-serif""> Jason Eckhardt [mailto:jeckhardt@nvidia.com]
<br>
<b>Sent:</b> 30 November 2021 17:01<br>
<b>To:</b> llvm-dev@lists.llvm.org; Colin McEwan <colin.mcewan@mediatek.com><br>
<b>Subject:</b> Re: Function register clobber propagation<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Calibri","sans-serif";color:black">There is at least some minimal support for this, see CodeGen/RegUsageInfoPropagate.cpp (and related). This interprocedural register allocation is enabled with "-enable-ipra".
<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 Colin
McEwan via llvm-dev <llvm-dev@lists.llvm.org><br>
<b>Sent:</b> Tuesday, November 30, 2021 9:26 AM<br>
<b>To:</b> llvm-dev@lists.llvm.org <llvm-dev@lists.llvm.org><br>
<b>Subject:</b> [llvm-dev] Function register clobber propagation</span> <o:p></o:p></p>
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<p class="MsoNormal"><b><span style="font-size:7.5pt;font-family:"Verdana","sans-serif";color:black">External email: Use caution opening links or attachments</span></b><span style="font-size:7.5pt;font-family:"Verdana","sans-serif";color:black">
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<p class="xmsonormal">Hi all,<o:p></o:p></p>
<p class="xmsonormal"> <o:p></o:p></p>
<p class="xmsonormal">Does LLVM currently have any way to exploit known register usage of already-compiled callee functions within a module to reduce register pressure in calling functions? GCC does this, but I haven’t seen any sign of this being done (having
checked on a couple of different target architectures), and can’t find any mention of such optimisation in the source.<o:p></o:p></p>
<p class="xmsonormal"> <o:p></o:p></p>
<p class="xmsonormal">Have I overlooked something? Or is there a rationale for not attempting this? (Such as limiting potential parallelism in compiling a module)<o:p></o:p></p>
<p class="xmsonormal"> <o:p></o:p></p>
<p class="xmsonormal">Thanks!<o:p></o:p></p>
<p class="xmsonormal"> <o:p></o:p></p>
<p class="xmsonormal">-- <o:p></o:p></p>
<p class="xmsonormal">Colin <o:p></o:p></p>
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