[cfe-dev] speed up clang build after modifying checker code of static analyzer
Artem Dergachev via cfe-dev
cfe-dev at lists.llvm.org
Wed Sep 19 18:50:16 PDT 2018
(whoops re-adding cfe-dev)
clang-3.8 is ancient. I guess you'll need a newer clang (and probably a
newer libc++ if you're using it instead of libstdc++, because lack of
std::atomic support might be a standard library problem).
But for me on linux the -DBUILD_SHARED_LIBS=1 flag was pretty much the
answer. So i don't think you should dig too much into compiling with
clang unless you care about compilation time as much as linking time,
which is unlikely.
Also see if you're running out of memory while linking. If you're
swapping, it will be slow. Linking is the only memory-intensive part of
the build.
On 9/19/18 2:44 PM, Lou Wynn via cfe-dev wrote:
>
> ~/work/git-repos/llvm/release-git$ which clang
> /usr/bin/clang
>
> ~/work/git-repos/llvm/release-git$ clang -###
> clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
> Target: x86_64-pc-linux-gnu
> Thread model: posix
> InstalledDir: /usr/bin
>
>
> I also tried with a self-built clang, and got the same error.
>
>
> Thanks,
> Lou
>
> On 09/19/2018 02:41 PM, Kristóf Umann wrote:
>> Are you using a prebuild binary? Are you sure you're using the clang
>> you'd like to compile with? (`which clang`?)
>>
>> On 19 Sep 2018 23:38, "Lou Wynn" <lewisurn at gmail.com
>> <mailto:lewisurn at gmail.com>> wrote:
>>
>> When I use clang to compile (gcc is fine), I got cmake error:
>>
>> -- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB
>> -- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB - Failed
>> -- Looking for __atomic_fetch_add_4 in atomic
>> -- Looking for __atomic_fetch_add_4 in atomic - found
>> -- Performing Test HAVE_CXX_ATOMICS_WITH_LIB
>> -- Performing Test HAVE_CXX_ATOMICS_WITH_LIB - Failed
>> CMake Error at cmake/modules/CheckAtomic.cmake:50 (message):
>> Host compiler must support std::atomic!
>> Call Stack (most recent call first):
>> cmake/config-ix.cmake:323 (include)
>> CMakeLists.txt:577 (include)
>>
>>
>> How can I fix it? I checkout source code from the git mirror. I'm
>> running ubuntu 16.04.1 LTS.
>>
>>
>> Thanks,
>> Lou
>>
>>
>> On 09/19/2018 12:02 AM, Kristóf Umann 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 <mailto: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 <mailto: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
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>>
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>>
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