[llvm-dev] Incrementally compiling LLVM

[David Blaikie via llvm-dev]

Sounds like something's going wrong for sure. How are you measuring
the time? (how much time is it taking) and what are you testing by
"partial recompilation"? Touching an ADT .h file is likely to
recompile nearly everything so might not be much better than a clean
build - but touching a .cpp file (especially a .cpp file for a single
tool, rather than a library) might be quite quick. So try timing a
full clean build (ninja -t clean, ninja clang) and then incrementally
touching just a .cpp file (eg: clang/tools/driver/driver.cpp  ) and
see how they compare

On Wed, Apr 14, 2021 at 11:21 AM Francesco Bertolaccini via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> Hi all,
> I noticed that doing a partial recompilation on Windows (I tried
> compiling with both MSVC and clang, in both cases using ninja generated
> by CMake) does not seem to be any faster than compiling from scratch.
>
> Is there any way to improve the situation? Is partial recompilation
> supported at all, or am I doing something wrong?
>
> Thanks,
> Francesco Bertolaccini
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