<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Yep, TAG_call_site_parameter and its children shouldn't require any extra relocations. Thanks!<div class=""><br class=""></div><div class="">vedant<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Feb 7, 2020, at 2:01 PM, David Blaikie <<a href="mailto:dblaikie@gmail.com" class="">dblaikie@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">For that sort of small growth, if it doesn't add more relocations (I think the call sites need them (but they're already emitted/that's not what we're discussing enabling here), but call value descriptions don't), sounds good to me :)</div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, Feb 7, 2020 at 12:04 PM Vedant Kumar <<a href="mailto:vedant_kumar@apple.com" class="">vedant_kumar@apple.com</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;" class=""><div class="">Hi all,</div><div class=""><br class=""></div><div class="">I think we've reached a state where we're ready to enable debug entry value production by default for the x86_64, ARM, and AArch64 targets. For context, this is a debug info feature that allows debuggers to recover the value of unmodified optimized-out parameters by 'going up' a stack frame and interpreting spilled values, constants, etc. to work out what was passed to the callee. There's a nice write-up about the impact of this feature in [3]. A big thank you to all of contributors who've helped us get here (I've tried to CC everyone, sincere apologies if I've accidentally left you out).</div><div class=""><br class=""></div><div class="">I believe Djordje and I have shown that there isn't an outsized binary size or compile time impact of enabling this feature. The aggregate size of DWARF in a stage2 x86_64 RelWithDebInfo clang build grows by under 0.2%, and we didn't find a significant compile time impact. We've shared CTMark results (both compile-time & DWARF section size numbers), as well as a size analysis of stage2 builds of {llc, clang, lldb} in [1].</div><div class=""><br class=""></div><div class="">Djordje has also shared a nice location statistics comparison chart in [1], showing increased variable availability with entry values enabled.</div><div class=""><br class=""></div><div class="">For my part, I instrumented lldb's DWARFExpression::Evaluate method to log instances in which a variable location is unavailable. I then used a script [4] to single-step through a stage2 RelWithDebInfo+entryvals clang binary as it was compiling sqlite3.c, printing local variables at each stop. Without entry values, lldb reported "variable not available" 883,918 times. With entry values lldb reported "variable not available" 687,899 times (a 22% drop).</div><div class=""><br class=""></div><div class="">Does anyone have concerns about enabling this feature?</div><div class=""><br class=""></div><div class="">thanks,</div><div class="">vedant</div><div class=""><br class=""></div><div class="">[1] <a href="https://reviews.llvm.org/D73534" target="_blank" class="">[DebugInfo] Enable the debug entry values feature by default</a></div><div class="">[2] <a href="https://reviews.llvm.org/D73700" target="_blank" class="">[CallSiteInfo] Fix the assertions regarding updating the CallSiteInfo</a>, <a href="https://reviews.llvm.org/D74122" target="_blank" class="">[CallSiteInfo] Use the isCandidateForCallSiteEntry() when update the cs info</a></div>[3] <a href="https://robert.ocallahan.org/2018/11/comparing-quality-of-debug-information.html" target="_blank" class="">https://robert.ocallahan.org/2018/11/comparing-quality-of-debug-information.html</a><div class="">[4] <a href="https://gist.github.com/vedantk/7602b20a9e1d44c42d32dcca36591cc0" target="_blank" class="">https://gist.github.com/vedantk/7602b20a9e1d44c42d32dcca36591cc0</a></div></div></blockquote></div>
</div></blockquote></div><br class=""></div></body></html>