<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="">This would only be enabled when optimizations are enabled, correct?<div class=""><br class=""></div><div class="">For GDB and LLDB debug info tuning mode, this sounds good to me. I don't know if, e.g., the Sony debugger supports entry values. Out of curiosity, does anyone know if GCC enable entry values by default?</div><div class=""><br class=""></div><div class="">-- adrian<br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Feb 7, 2020, at 12:09 PM, Vedant Kumar <<a href="mailto:vedant_kumar@apple.com" class="">vedant_kumar@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html; charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">(trying to add back folks dropped by Mail.app...)<div class=""><br class=""></div><div class="">+ David Blaikie, David Stenberg, Adrian, Jeremy, and Fred<br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Feb 7, 2020, at 12:04 PM, Vedant Kumar via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html; charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" 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" class="">[DebugInfo] Enable the debug entry values feature by default</a></div><div class="">[2] <a href="https://reviews.llvm.org/D73700" class="">[CallSiteInfo] Fix the assertions regarding updating the CallSiteInfo</a>, <a href="https://reviews.llvm.org/D74122" 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" 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" class="">https://gist.github.com/vedantk/7602b20a9e1d44c42d32dcca36591cc0</a></div></div>_______________________________________________<br class="">LLVM Developers mailing list<br class=""><a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a><br class=""><a href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev" class="">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><br class=""></div></blockquote></div><br class=""></div></div></div></blockquote></div><br class=""></div></body></html>