<div dir="ltr">Oh, and yeah - I'm all for turnaround time, though different situations put the costs for that in different places - for Google a distributed build means file sizes are important because they delay sending content between builders and from the builders down to the developers machine.</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Mar 16, 2020 at 10:56 AM David Blaikie <<a href="mailto:dblaikie@gmail.com">dblaikie@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div dir="ltr">On Mon, Mar 16, 2020 at 10:50 AM Robinson, Paul <<a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div lang="EN-US">
<div>
<p class="MsoNormal">SCE tuning does turn on the .debug_aranges section. Our debugger team really cares about startup cost. Turnaround time in general is huge for our licensees, to the point where we support edit-and-continue (minimal rebuild, live-patch the
running process).</p></div></div></blockquote><div><br>Ah, good to know! I'd be curious to know about the performance tradeoff when they're disabled if you ever happen to have data around that.</div><div>I guess a related question: Does SCE use the non-.text entries (or otherwise have an opinion on having them) in debug_aranges?<br> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div lang="EN-US"><div><p class="MsoNormal"><u></u><u></u></p>
<p class="MsoNormal">--paulr<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<div style="border-top:none;border-right:none;border-bottom:none;border-left:1.5pt solid blue;padding:0in 0in 0in 4pt">
<div>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in">
<p class="MsoNormal"><b>From:</b> David Blaikie <<a href="mailto:dblaikie@gmail.com" target="_blank">dblaikie@gmail.com</a>> <br>
<b>Sent:</b> Monday, March 16, 2020 1:20 PM<br>
<b>To:</b> Robinson, Paul <<a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>><br>
<b>Cc:</b> Dylan McKay <<a href="mailto:me@dylanmckay.io" target="_blank">me@dylanmckay.io</a>>; <a href="mailto:llvm-dev@lists.llvm.org" target="_blank">llvm-dev@lists.llvm.org</a><br>
<b>Subject:</b> Re: [llvm-dev] DWARF .debug_aranges data objects and address spaces<u></u><u></u></p>
</div>
</div>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<div>
<p class="MsoNormal">On Mon, Mar 16, 2020 at 9:31 AM Robinson, Paul <<a href="mailto:paul.robinson@sony.com" target="_blank">paul.robinson@sony.com</a>> wrote:<u></u><u></u></p>
</div>
<div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin-left:4.8pt;margin-right:0in">
<div>
<div>
<p class="MsoNormal">With AVR being affected, upstreaming a patch to put segment selectors into .debug_aranges becomes completely reasonable. There would likely want to be a target hook somewhere to
return a value saying what size to use, with the default implementation returning zero.<u></u><u></u></p>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">*nod* something along those lines<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"> <u></u><u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin-left:4.8pt;margin-right:0in">
<div>
<div>
<p class="MsoNormal"> > If the producer has put ranges on the CU it's not a lot of work - it's parsing one DIE & looking for a couple of attributes.<u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal">It’s walking through all the CUs, picking up the associated abbrevs, trolling down the list of attributes… “not a lot” indeed, but not as trivial as running through a single section
linearly, which is what .debug_aranges gets you. I’ve been lectured by @clayborg on what consumers really want for performance gains.<u></u><u></u></p>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal"><br>
Sure enough - though I don't believe aranges is used by default on any target/platform LLVM supports, so this time/space tradeoff doesn't seem to have been important to any of them? <br>
<u></u><u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin-left:4.8pt;margin-right:0in">
<div>
<div>
<p class="MsoNormal"> > It's enough at least at Google for us to not use them & use CU ranges for the same purpose.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Google is much more seriously concerned about debug-info size than about debugger performance, IIRC. This is not universally the preferred tradeoff. Just sayin’.<u></u><u></u></p>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal" style="margin-left:4.8pt"><br>
Sure enough.<br>
<br>
I've just had a couple of people ask about aranges recently (~year or so) & when pressing a little further, using the CU's address ranges turned out to be sufficient for their needs without having to change Clang's defaults or have their users specify extra
flags to explicitly request them, etc.<br>
<br>
Out of curiosity/for data/usage/etc - does Sony use aranges? (changing the default when targeting SCE or the like)<br>
<br>
- Dave<br>
<u></u><u></u></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin-left:4.8pt;margin-right:0in">
<div>
<div>
<div style="border-top:none;border-right:none;border-bottom:none;border-left:1.5pt solid blue;padding:0in 0in 0in 4pt">
<div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin:5pt 0in 5pt 4.8pt">
<p class="MsoNormal"><u></u> <u></u></p>
</blockquote>
</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
</div>
</div>
</blockquote></div></div>
</blockquote></div>