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There is at least some minimal support for this, see CodeGen/RegUsageInfoPropagate.cpp (and related). This interprocedural register allocation is enabled with "-enable-ipra".
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> 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</font>
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<p class="x_MsoNormal">Hi all,</p>
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<p class="x_MsoNormal">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.</p>
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<p class="x_MsoNormal">Have I overlooked something? Or is there a rationale for not attempting this? (Such as limiting potential parallelism in compiling a module)</p>
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<p class="x_MsoNormal">Thanks!</p>
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<p class="x_MsoNormal">-- </p>
<p class="x_MsoNormal">Colin </p>
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