[flang-dev] Comparing build times for flang

[Michael Kruse via flang-dev]

Thank you for the comparison. Could you provide some more details? How
many threads/cores does the "powerful lab machine have"? How much
memory does the build use? What version of gcc?

Michael

Am Fr., 11. Dez. 2020 um 12:43 Uhr schrieb Peter Steinfeld via
flang-dev <flang-dev at lists.llvm.org>:
>
> I've been playing around with the scripts I use to build flang in and out of tree.  I don't think I used to be able to do this, but I can now build the front end by only specifying "flang" in the define for "DLLVM_ENABLE_PROJECTS".  Here's my full build script for doing in in-tree build of the front end:
>
>
>
> #!/bin/bash
>
> cmake -G Ninja ../llvm \
>
>   -DCMAKE_BUILD_TYPE=Release \
>
>   -DFLANG_ENABLE_WERROR=On \
>
>   -DLLVM_ENABLE_PROJECTS="flang" \
>
>   -DCMAKE_CXX_STANDARD=17 \
>
>   -DLLVM_TARGETS_TO_BUILD=host \
>
>   -DLLVM_LIT_ARGS=-v \
>
>   -DLLVM_INSTALL_UTILS=On \
>
>   -DCMAKE_INSTALL_PREFIX=../install
>
>
>
> When I build clang, flang, and mlir, it takes 6 minutes, 8 seconds and produces an install area of 1.9 GB.  When I do in in-tree build of just the flang front end, it takes 4 minutes, 33 seconds and produces an install area of 1.3 GB.  When I do an out-of-tree build, it takes 1 minute 52 seconds, and produces a build area of 651 MB.
>
>
>
> All of these times are running on a powerful lab machine using the GNU C++ compiler.
>
>
>
> Pete
>
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