[cfe-dev] Fwd: clang++ vs g++ compilation speed for ace-tao servants

[Richard Smith]

We may also be able to pick out an 'obvious winner' (perhaps looking for
one that only requires standard conversions) before trying to build
conversion sequences for all candidates.


On Thu, Oct 31, 2013 at 12:19 PM, Richard Smith <richard at metafoo.co.uk>wrote:

> I suspect the problem is overload resolution for the several hundred
> overloads of each of 'operator<<', 'operator<<=', 'operator>>', and
> 'operator>>=' that are present here. Many of these have the same LHS
> parameter type; we could probably improve performance here by caching the
> computation of an implicit conversion sequence for a given (argument,
> parameter type) pair.
>
>
> On Thu, Oct 31, 2013 at 10:05 AM, David Blaikie <dblaikie at gmail.com>wrote:
>
>>
>>
>>
>> On Wed, Oct 30, 2013 at 11:59 PM, Igor Vagulin <igor.vagulin at gmail.com>wrote:
>>
>>> Hi All,
>>>
>>> We are evaluating switch to clang from gcc for our c++ application.
>>> Main focus is compilation speed, but we also look at address/memory
>>> sanitizer, c++11 support and c++ modules. I've tried to compile our
>>> project with clang++ but resulting compilation time is more than with
>>> gcc. Can someone give me a hint where might be a problem?
>>>
>>> Our project is bunch of ace-tao corba servants. Overall time with
>>> clang++ is about twice more than with gcc. To reproduce problem I
>>> preprocesssed one file and then compile it, result same - twice longer
>>> compilation. Don't know where to look further.
>>>
>>
>> If you're lucky, someone might look for you if you attach (or link to, if
>> it's too big to attach) an example of the problem.
>>
>> Otherwise, you might want to get started with a profiler and see where
>> the hot parts of Clang/LLVM are in your example.
>>
>> (also, consider trying with Clang top of tree (straight from svn/git) -
>> the project moves fairly quickly)
>>
>>
>>> [root at ivagulin-pc ~]# time clang++ -c RemoveClusterObserverClang.cpp
>>> real    0m1.283s
>>> user    0m1.254s
>>> sys    0m0.024s
>>> [root at ivagulin-pc ~]# time g++ -c RemoveClusterObserverGcc.cpp
>>> real    0m0.576s
>>> user    0m0.524s
>>> sys    0m0.048s
>>>
>>> I use llvm-3.3 and cfe-3.3 compiled with folowing options. Sources of
>>> RemoveClusterObserver*cpp attached.
>>> + cmake -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=Release
>>> '-DCMAKE_CXX_FLAGS_RELEASE=-O3 -g -mtune=amdfam10 -march=i686'
>>> '-DCMAKE_C_FLAGS_RELEASE=-O3 -g -mtune=amdfam10 -march=i686'
>>> -DCMAKE_EXE_LINKER_FLAGS_RELEASE=-Wl,--as-needed -Wl,--strip-all'
>>> '-DCMAKE_MODULE_LINKER_FLAGS_RELEASE=-Wl,--as-needed -Wl,--strip-all'
>>> '-DCMAKE_SHARED_LINKER_FLAGS_RELEASE=-Wl,--as-needed -Wl,--strip-all
>>> -shared' -DCMAKE_SKIP_RPATH=YES -DBUILD_SHARED_LIBS=YES
>>> -DLLVM_ENABLE_TIMESTAMPS=NO ..
>>>
>>> Igor Vagulin
>>>
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at cs.uiuc.edu
>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>
>>>
>>
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>>
>
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