<div dir="ltr">-fdump-passes? The dump result can be misleading. For instance, the post ipa optimization is grouped under *all_optimization or *all_optimization_g groups. With -Og, *all_optimization is off, but all the nested optimizations that are turned on normally under opt level 1 is still marked as 'ON' -- that is why you don't see many difference. The optimizations included in *all_optimization_g group is a much smaller set.<div><br></div><div>The early optimization pipelines are very similar. WIth -Og, early SRA pass is disabled.</div><div><br></div><div>David</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jul 31, 2015 at 3:28 PM, Robinson, Paul <span dir="ltr"><<a href="mailto:Paul_Robinson@playstation.sony.com" target="_blank">Paul_Robinson@playstation.sony.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I remember using gcc's "tell me what optimizations you ran" flag, which does something like print out the list of –f switches you would need to use to get the
same effect as the optimization flags you actually provided. Comparing –O1 to –Og I saw only one difference. Hence my statement that gcc's –O1 and –Og are 99% equivalent. It is a very black-box experiment but I think it's indicative. Or at least instructive.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">--paulr<u></u><u></u></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Xinliang David Li [mailto:<a href="mailto:xinliangli@gmail.com" target="_blank">xinliangli@gmail.com</a>]
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<b>Sent:</b> Friday, July 31, 2015 11:49 AM<br>
<b>To:</b> Robinson, Paul<br>
<b>Cc:</b> David Blaikie; Dan Walmsley; cfe-dev Developers</span></p><div><div class="h5"><br>
<b>Subject:</b> Re: [cfe-dev] Clangs equivalent to GCCs -Og flag?<u></u><u></u></div></div><p></p>
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<p class="MsoNormal">On Fri, Jul 31, 2015 at 7:27 AM, Robinson, Paul <<a href="mailto:Paul_Robinson@playstation.sony.com" target="_blank">Paul_Robinson@playstation.sony.com</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">People ask about this from time to time, but we've never done anything about it.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">One thing I noticed about GCC –Og is that it's 99% identical to their –O1. </span><u></u><u></u></p>
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<p class="MsoNormal">Not really. The optimization level is set to 1, but the pass pipeline setup is very different between O1 and Og.<u></u><u></u></p>
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<p class="MsoNormal">David<u></u><u></u></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">I'd be curious about people's experience using Clang –O1 –g and whether that experience is somewhere
close to reasonable.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">--paulr</span><u></u><u></u></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:cfe-dev-bounces@cs.uiuc.edu" target="_blank">cfe-dev-bounces@cs.uiuc.edu</a> [mailto:<a href="mailto:cfe-dev-bounces@cs.uiuc.edu" target="_blank">cfe-dev-bounces@cs.uiuc.edu</a>]
<b>On Behalf Of </b>David Blaikie<br>
<b>Sent:</b> Wednesday, July 29, 2015 10:13 AM<br>
<b>To:</b> Dan Walmsley; cfe-dev Developers<br>
<b>Subject:</b> Re: [cfe-dev] Clangs equivalent to GCCs -Og flag?</span><u></u><u></u></p>
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<p class="MsoNormal">On Wed, Jul 29, 2015 at 8:42 AM, Dan Walmsley <<a href="mailto:dan@walms.co.uk" target="_blank">dan@walms.co.uk</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">Thanks,
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<p class="MsoNormal"> Perhaps there might be some documentation somewhere that would give me an idea of which optimizations to enable individually?<u></u><u></u></p>
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Not really - optimized debug info is still pretty lacking in Clang. Even the most common/basic optimizations (SROA, for example) are going to pretty heavily impact debuggability today.<br>
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- Dave<br>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Dan<u></u><u></u></p>
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<p class="MsoNormal">Date: Wed, 29 Jul 2015 06:40:06 -0700<br>
Subject: Re: [cfe-dev] Clangs equivalent to GCCs -Og flag?<br>
From: <a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a><br>
To: <a href="mailto:dan@walms.co.uk" target="_blank">dan@walms.co.uk</a><br>
CC: <a href="mailto:cfe-dev@cs.uiuc.edu" target="_blank">cfe-dev@cs.uiuc.edu</a><u></u><u></u></p>
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On Jul 29, 2015 3:23 AM, "Dan Walmsley" <<a href="mailto:dan@walms.co.uk" target="_blank">dan@walms.co.uk</a>> wrote:<br>
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> GCC has a debug level flag of -Og which enables all optimizers that won't degrade the debugging experience greatly.<br>
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> Does clang have an equivalent?<u></u><u></u></p>
<p>No, clang had no equivalent at this time.<u></u><u></u></p>
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> Thanks in advance.<br>
><br>
> Dan<br>
><br>
> _______________________________________________<br>
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