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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">David,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks for the reply. That makes sense.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A couple of further thoughts … In the LTO implementation that I am working on, when -flto is specified to the compiler, the compiler embeds the IR in the compiler generated object file. The linker can then read the IR out of the incoming
object file if LTO is enabled at link time or just ignore the IR if LTO is disabled at link time.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I would agree that having -S write out the IR content for -flto provides a good way to see what is being fed into the LTO link in a human readable form.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">For our LTO implementation, the linker can be told to keep the IR that it extracts from the incoming object files. You can then run llvm-dis over the extracted IR to see the .ll version.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">~ Todd<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b>From:</b> David Blaikie <dblaikie@gmail.com> <br>
<b>Sent:</b> Monday, October 18, 2021 4:21 PM<br>
<b>To:</b> Snider, Todd <t-snider@ti.com><br>
<b>Cc:</b> llvm-dev@lists.llvm.org<br>
<b>Subject:</b> [EXTERNAL] Re: [llvm-dev] Question about -flto behavior<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Yeah, sounds expected to me - flto produces object files that aren't really object files - instead they're LLVM IR (bitcode) that the linker identifies, then calls back into LLVM to link the IR, optimize on that IR, then produce object
code/assembly/whatever).<br>
<br>
So the "assembly" form of an "object" (really LLVM bitcode) file is LLVM textual IR.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Mon, Oct 18, 2021 at 1:56 PM Snider, Todd via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Hi All,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">When -flto is combined with -S on the clang command line, the output .s file contains IR content instead of target assembly language.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Is this expected/correct behavior? I was anticipating that the output .s file would contain target assembly code.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">~ Todd Snider<o:p></o:p></p>
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<p class="MsoNormal">_______________________________________________<br>
LLVM Developers mailing list<br>
<a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a><br>
<a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" target="_blank">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><o:p></o:p></p>
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