[cfe-dev] speed up clang build after modifying checker code of static analyzer

[David Blaikie via cfe-dev]

Consider using Split DWARF (there's a cake option for it) if your debugging
use cases can handle it. It'll reduce the size of object files and the
final binary, should help out the linker a bit.

On Wed., 19 Sep. 2018, 12:03 am Kristóf Umann via cfe-dev, <
cfe-dev at lists.llvm.org> wrote:

> Hi!
>
> A couple tips I can give:
>   * Compile with clang. Make sure you use a release build for this
> purpose, optimized with LTO. I usually just download a prebuild binary and
> go with that. Clang tends to be about 2-3 times faster than gcc.
>   * For linking, use LLD, a linker part of the LLVM family. Especially
> with -j8, it will make a significant difference. Your next best option is
> gnu gold.
>
> Great to hear about a new checker! I'd encourage you to upload your work
> in progress early on to phabricator, even if it only contains an empty
> callback, because an entire working solution (if lengthy enough) can
> drastically increase the time it takes to review it.
>
> I know because I made that mistake :).
>
> Cheers,
> Kristóf Umann
>
>
> On 19 Sep 2018 04:06, "Lou Wynn via cfe-dev" <cfe-dev at lists.llvm.org>
> wrote:
>
> I do need debug information because tracing code is a great way for me to
> get familiarized with clang and the static analyzer.
>
> I've managed to run "make -j8 clang" at the top of the build directory.
> However, the final linking process takes too long now. Is there a way to
> build a thin version that only runs the static analyzer? I think that I can
> at least cut the code gen part out of the build process but have no idea
> how. The only command I run is "clang -cc1 -analyze -analyzer-checker=xxx"
> It'd be great if I could reduce the final object file to few hundred
> megabytes.
>
> [ 96%] Built target clangStaticAnalyzerCore
>
> Scanning dependencies of target clangStaticAnalyzerCheckers
> [ 96%] Building CXX object
> tools/clang/lib/StaticAnalyzer/Checkers/CMakeFiles/clangStaticAnalyzerCheckers.dir/IntegerOverflowChecker.cpp.o
> [ 96%] Linking CXX static library
> ../../../../../lib/libclangStaticAnalyzerCheckers.a
> [100%] Built target clangStaticAnalyzerCheckers
> [100%] Linking CXX executable ../../../../bin/clang  <-- this take most
> time now
> [100%] Built target clang
>
> real    2m22.707s
> user    2m10.812s
> sys     0m14.936s
>
> Thanks,
> Lou
>
> On 09/18/2018 06:25 PM, Reid Kleckner wrote:
>
> If the clang binary is 2GB, I would recommend building in Release mode
> with assertions enabled. Linking binaries without debug information is
> dramatically faster. This means passing -DCMAKE_BUILD_TYPE=Release
> -DLLVM_ENABLE_ASSERTIONS=ON to cmake.
>
> If you use debug information, I recommend explicitly building one target,
> the target you are testing (usually clang), until you feel the need to run
> the complete clang test suite.
>
> On Tue, Sep 18, 2018 at 5:42 PM Lou Wynn via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> Hi,
>>
>> I'm writing my first clang static analyzer checker. I wrote the scaffold
>> code to add the checker into clang. But every time when I change the
>> checker implementation code, the build process after generating the
>> checker object file is very slow. It's over 4 minutes in my laptop,
>> which has the i7-6820HQ four core CPU and 32G memory. The generated
>> clang binary is over 2G. The affected artifacts are as follows:
>>
>> ---------------------
>>
>> Scanning dependencies of target clangStaticAnalyzerCheckers
>> [ 95%] Building CXX object
>>
>> tools/clang/lib/StaticAnalyzer/Checkers/CMakeFiles/clangStaticAnalyzerCheckers.dir/IntegerOverflowChecker.cpp.o
>> [ 95%] Linking CXX static library
>> ../../../../../lib/libclangStaticAnalyzerCheckers.a
>> [ 98%] Built target clangStaticAnalyzerCheckers
>> [ 98%] Linking CXX executable ../../../../bin/arcmt-test
>> [ 98%] Linking CXX executable ../../../../bin/clang-check
>> [ 98%] Linking CXX executable ../../../../bin/clang
>> [ 98%] Linking CXX shared library ../../../../lib/libclang.so
>> [ 98%] Built target arcmt-test   <--- this seems to take the most time
>> [ 98%] Built target libclang
>> [ 98%] Linking CXX executable ../../../../bin/c-arcmt-test
>> [ 98%] Linking CXX executable ../../../../bin/c-index-test
>> [ 98%] Built target c-arcmt-test
>> [ 98%] Built target clang-check
>> [ 98%] Built target clang
>> [100%] Built target c-index-test
>>
>> real    4m23.014s
>> user    8m4.032s
>> sys     0m51.992s
>>
>> ---------------------
>>
>> How can I speed up the build process so that I don't have to wait for
>> almost 4.5 minute for a single change in the implementation code? I only
>> work on the checker of the static analyzer.
>>
>> --
>> Thanks,
>> Lou
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>
>
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