Date: Fri, 1 Jun 2018 15:42:33 -0700 From: Conrad Meyer <cem@freebsd.org> To: lev@freebsd.org Cc: "freebsd-arch@freebsd.org" <freebsd-arch@freebsd.org> Subject: Re: Building and Iterating Message-ID: <CAG6CVpXEwRbL_6Vx3tApRGnB-KEFrc9XGNUNctHoBBnxvMbs=w@mail.gmail.com> In-Reply-To: <5d855fdd-f471-b9cf-de30-b6ef69945a9e@FreeBSD.org> References: <cd5d5e25-34e8-5b1b-c764-affbeabf2ea8@freebsd.org> <CAFMmRNwJuQy2QO_BR4B_AT6u=dF_BTJAmgFrtp4gJd0jnNefXw@mail.gmail.com> <5d855fdd-f471-b9cf-de30-b6ef69945a9e@FreeBSD.org>
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On Fri, Jun 1, 2018 at 1:59 PM, Lev Serebryakov <lev@freebsd.org> wrote: > On 01.06.2018 23:02, Ryan Stone wrote: > >>> 3. If the boostrap toolchain needs to be built in the normal case, onl= y >>> target the ARCH being requested. I understand that we "want" a CC >>> installed that targets all architectures and this is something I agree = with. >> >> Has anybody instrumented the build to determine how much time this >> would actually save? Before trying to optimize the build we need to >> be sure that we're actually targetting the right optimizations. > LLVM build could easily take one hour to be built on rather modern syste= m. > > My VM to build NanoBSD images has 8GiB of RAM (1/4 of total physical > RAM), 4 cores of i7 (out of 4 cores / 8 threads) and resides on SSD > (SATA one). Build WITH cross-toolchain AND world toolchain is about 2.5 > hours and build WITHOUT ANY toolchain (using host's one as > cross-compiler) is less than a hour. Unfortunately, you aren't actually measuring the impact of Sean's #3 =E2=80= =94 which proposes eliminating cross-compilers from Clang *when building Clang is actually desired or required.* It isn't clear that the additional cross-compiler backends add significant overhead to the total Clang build time, which includes a lot of shared code, like C and C++ parsing, generic optimization code, etc. Ryan's just asking for someone to measure that to justify the change. Best, Conrad
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