[llvm-dev] GN build roundtable summary; adding GN build files to the repo (original) (raw)

Dean Michael Berris via llvm-dev llvm-dev at lists.llvm.org
Wed Oct 31 15:44:03 PDT 2018

FWIW, this is consistent with my experience as well.

I also wrote a presubmit script that I run locally to build/test the cross-product of:

COMPILER={gcc+gold, clang+lld} MODE={debug, release-with-assertions} TARGETS={llvm+clang+lld+compiler-rt, compiler-rt(standalone)}

While the build/test times are helped by using ninja, the CMake config times are less than optimal.

It’s bad enough that I think I’ll give gn a whirl if the files were in the project(s) too.

On 1 Nov 2018, at 09:33, Zachary Turner via llvm-dev <llvm-dev at lists.llvm.org> wrote:

And by the way, that is with my cache already populated. Here it is on a fresh build directory where it has to generate everything. (this time release build) $ timecmd cmake -G Ninja -DLLVMENABLEPROJECTS=clang;lld;lldb -DLLVMTARGETSTOBUILD=X86 -DCMAKEBUILDTYPE=Release ........\llvm-mono\llvm command took 0:0:57.42 (57.42s total) This is on a 48-core machine btw, with an SSD. On Wed, Oct 31, 2018 at 3:29 PM Zachary Turner <zturner at google.com> wrote: On Wed, Oct 31, 2018 at 3:11 PM Nicolai Hähnle via llvm-dev <llvm-dev at lists.llvm.org> wrote:

Besides, how on earth are you using LLVM that cmake times are an issue? Given that cmake times seem to be the only argument you have in favor of GN... I just measured the typical case (for LLVM only, debug build, all non-experimental targets enabled) by touching all files. cmake takes 5 seconds to run, while the build as a whole takes about 5 minutes. (This is on Ubuntu 18.10, in case that matters.) I am using CMake with LLVM with all targets OFF except for x86. Only clang, lldb, and lld enabled. $ timecmd cmake ........\llvm-mono\llvm command took 0:0:34.05 (34.05s total)

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-- Dean

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