<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On May 30, 2017, at 1:16 PM, David Blaikie 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=""><div dir="ltr" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br class=""><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Tue, May 30, 2017 at 12:52 PM Bob Haarman via llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-style: solid; border-left-color: rgb(204, 204, 204); padding-left: 1ex;"><u class=""></u><div class=""><div style="font-size: 10pt; font-family: Verdana, Arial, Helvetica, sans-serif;" class=""><div class="">I would like to better understand how you came to conclude that the tablegen re-runs based on changes in Support are what's causing your build to be slow and what part specifically is taking all that time. I can do a clean release + assertions build of LLVM, Clang, compiler-rt and lld in about 5 minutes, plus 40 seconds to run cmake, on what I think is similar hardware to what Zach is using. If I swap Ptr += ret and Size -= Ret in raw_fd_ostream::write_impl so that Support changes, I can do an incremental build in about 10 seconds, including the regeneration of various .inc files. How do we get from there to 10 minutes for an incremental build?<br class=""></div></div></div></blockquote><div class=""><br class="">Which build system are you using?<br class=""><br class="">On my build config (16 core/32 thread, 128GB RAM) it takes 47 user seconds to rebuild the clang binary after making the change you mentioned - with ninja and lld, host compiler is a recent release build of clang. Ninja reports building 377 things.<br class=""></div></div></div></div></blockquote><div><br class=""></div><div>At least for me ninja starts with a high estimated number of files needing a rebuild. But the number of targets immediately jumps down by several hundreds as soon as ninja realizes that the tablegen output didn't actually change.</div><div><br class=""></div><div>- Matthias</div><div><br class=""></div></div></body></html>