[cfe-dev] Clang on Windows targteing gcc compiles very slowly

Reid Kleckner rnk at google.com
Sat May 30 07:30:36 PDT 2015

You said you configured in release mode, but assertions might still be on.
That accounts for a 2x slowdown. Otherwise I'd say that we haven't profiled
and optimized clang on windows very much.

Sent from phone
On May 29, 2015 4:51 PM, "Edward Diener" <eldlistmailingz at tropicsoft.com>

> I test Boost libraries mostly on Windows using various version of gcc 4.3
> and up, VC++ 8.0 and up, and the latest version of clang which I build from
> source using mingw/gcc-4.8.1 in release mode.
> While clang is a great compiler when it comes to testing code, getting
> intelligent error message, and implementing the latest C++ standard, it is
> noticably slower ( 2x or 3x at minimum ) than the other compilers I use.
> The clang command line parameters usually being used are usually along the
> lines of:
> -c -x c++ -O0 -g -fno-inline -Wall -g -march=i686 -m32
> with the addition of 'std=c++11' occasionally depending on the test.
> Does anybody have any idea why clang is so much slower than any of the
> other compilers I use ? It does not seem to matter whether it is in C++03
> mode or C++11 mode, it is noticeably slower than the other compilers.
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