<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 Mar 8, 2017, at 3:08 PM, Hal Finkel <<a href="mailto:hfinkel@anl.gov" class="">hfinkel@anl.gov</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="moz-cite-prefix" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><br class="Apple-interchange-newline">On 03/08/2017 04:55 PM, Chris Bieneman via llvm-dev wrote:<br class=""></div><blockquote cite="mid:110A9441-D0C4-4B23-843B-404E8BDBC08C@apple.com" type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class="">David,<div class=""><br class=""></div><div class="">This is an area that has had a lot of development over the last two years.</div><div class=""><br class=""></div><div class="">There are two supported ways in the LLVM build system to build compiler-rt with the just-built compiler.<div class=""><br class=""></div><div class="">1) The legacy way is for if compiler-rt is under LLVM/projects. You can specify -DLLVM_BUILD_EXTERNAL_COMPILER_RT=On, which will configure compiler-rt using the just-built clang after clang is built.</div></div></blockquote><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); float: none; display: inline !important;" class="">Why is this not the default?</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""></div></blockquote><div><br class=""></div><div>Two reasons. (1) It is buggy, and nobody fixed the issues because (2) the long-term plan is to not support building compiler-rt (or any other runtime library) under llvm/projects. The goal is to migrate entirely to llvm/runtimes where the support is more complete.</div><div><br class=""></div><div>-Chris</div><br class=""><blockquote type="cite" class=""><div class=""><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); float: none; display: inline !important;" class="">Thanks again,</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); float: none; display: inline !important;" class="">Hal</span><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""><blockquote cite="mid:110A9441-D0C4-4B23-843B-404E8BDBC08C@apple.com" type="cite" style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""><div class=""><div class=""><br class=""></div><div class="">2) The new way, is to place compiler-rt under LLVM/runtimes. In this path the build system will automatically build with the just-built compiler. This path also splits compiler-rt into two separate build steps, one that configures and builds the builtins with the just-built compiler, and a second that configures and builds the sanitizer libraries.</div><div class=""><br class=""></div><div class="">The second path also works for many (but not all) of our other runtime library projects. I know it works for libcxx, libcxxabi, and libunwind. Petr Hosek (CC'd) has also been working on support for multi-arch builtin and runtime library builds so that you can generate full cross-compilers from a single cmake invocation.</div><div class=""><br class=""></div><div class="">-Chris</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><div class=""><blockquote type="cite" class=""><div class="">On Mar 8, 2017, at 2:35 PM, David Blaikie via llvm-dev <<a moz-do-not-send="true" 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" class=""><br class=""><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Wed, Mar 8, 2017 at 2:03 PM Sterling Augustine <<a moz-do-not-send="true" href="mailto:saugustine@google.com" class="">saugustine@google.com</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div dir="ltr" class="gmail_msg">Yes, this is a aspect of the larger problem that clang bootstrap doesn't work for a cross-compiler. The build (mostly?) assumes that host==target during the build of clang itself, and then if you want another architecture also, you run a second build of the target libraries, and manually merge the trees.</div></blockquote><div class=""><br class="">I kind of roughly follow that, but not too well.<br class=""> </div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div dir="ltr" class="gmail_msg"><div class="gmail_msg">If you think about compiler-rt as being compiled for the target rather than the host, the problem you describe here is exactly the same one, and we have been getting lucky.<br class=""></div></div></blockquote><div class=""><br class="">Sure - if a PPC clang is being built from an x86 host, how would compiler-rt be built (OK, it could be built with the just-built clang, which it isn't at the moment) and tested (can't really be tested because the host can't run PPC binaries).<br class=""> </div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div dir="ltr" class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg">At the moment, the blaze builds of clang do exactly the procedure described above, so this hasn't been a terrible problem for Google, but I do think it is something that should be fixed (I'm working on another aspect of compiler-rt bringup at the moment, so won't solve this in the immediate future.)<br class=""></div></div></div></blockquote><div class=""><br class=""></div><div class="">Rightio</div><div class=""> </div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div dir="ltr" class="gmail_msg"><div class="gmail_msg"><div class="gmail_msg"><br class="gmail_msg"></div><div class="gmail_msg">gnu systems have a make variable, "CC_FOR_TARGET" that addresses this problem. I imagine llvm should adopt a similar mechanism inside cmake.</div></div></div></blockquote><div class=""><br class="">Not sure I follow on the need/use of CC_FOR_TARGET compared to using the just-built clang as the CC_FOR_TARGET (which it seems we have some plumbing for already - the just-built clang is used for building the compiler-rt tests, but not for building the library. I /think/ it should be used for both)<br class=""><br class="">- Dave<br class=""> </div><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div class="gmail_extra gmail_msg"><br class="gmail_msg"><div class="gmail_quote gmail_msg">On Wed, Mar 8, 2017 at 1:54 PM, David Blaikie<span class="Apple-converted-space"> </span><span dir="ltr" class="gmail_msg"><<a moz-do-not-send="true" href="mailto:dblaikie@gmail.com" class="gmail_msg" target="_blank">dblaikie@gmail.com</a>></span><span class="Apple-converted-space"> </span>wrote:<br class="gmail_msg"><blockquote class="gmail_quote gmail_msg" style="margin: 0px 0px 0px 0.8ex; border-left-width: 1px; border-left-color: rgb(204, 204, 204); border-left-style: solid; padding-left: 1ex;"><div dir="ltr" class="gmail_msg">I stumbled across what seems to be a bug (to me) in the compiler-rt build:<br class="gmail_msg"><br class="gmail_msg">The compiler-rt libraries themselves are built with the host compiler while the tests are built and then linked with the just-built clang.<br class="gmail_msg"><br class="gmail_msg">It was my understanding that the goal/intent/need was to have the compiler-rt library build with the just-built clang? Did I misunderstand that?*<br class="gmail_msg"><br class="gmail_msg">Sterling: Chandler seemed to think you might be interested in this issue & possibly addressing it given you're working on compiler-rt bring-up? It'd probably be useful to have compiler-rt built with the just-built clang for performance reasons.<br class="gmail_msg"><br class="gmail_msg">Evgeniy - not sure if you're interested in this or have much context? Know if this is right/wrong/neutral, etc?<br class="gmail_msg"><br class="gmail_msg">* reasons include performance, ABI compatibility, etc (I thought this was necessary for correctness in some way) - also, otherwise it seems excessive to hold up the whole build on waiting for just-built clang to finish, then use that to compile some tests. (well, I realize some of the tests are end-to-end, so they do need the just-built compiler)</div></blockquote></div><br class="gmail_msg"></div></blockquote></div></div>_______________________________________________<br class="">LLVM Developers mailing list<br class=""><a moz-do-not-send="true" href="mailto:llvm-dev@lists.llvm.org" class="">llvm-dev@lists.llvm.org</a><br class=""><a class="moz-txt-link-freetext" href="http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev">http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><br class=""></div></blockquote></div><br class=""></div></div><br class=""><fieldset class="mimeAttachmentHeader"></fieldset><br class=""><pre wrap="" class="">_______________________________________________
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</pre></blockquote><br style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);" class=""><pre class="moz-signature" cols="72" style="font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);">--
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory</pre></div></blockquote></div><br class=""></body></html>