clang vs gcc build performance (executable not build time)

[Arnaud Versini]

Hi everyone,

I just tested libreoffice performance between GCC + gold + libstdc++, clang
+ lld + libstdc++ and clang + lld + libc++ and noticed that gcc builds are
slower (at least in this case). I will write a blog article with all the
process to reproduce but small version, it just converts openDocument
standart files (ODF 1.0 to 1.3) to PDF. There is no significant difference
between both clang builds (changing lib C++ from libstdc++ to libc++) but
gcc is slower than clang. Of course all builds don't use system libraries
in this case to compare between lib C++, and builds are optimised and use
LTO.


OpenSUSE 7.2 Clang + libc++ Clang + std Gcc + std
Run 1 50,923045275 45,456441587 45,878275287 49,487550577
Run 2 50,360027388 43,83441037 44,303120572 47,898307652
Run 3 50,258628137 43,552443057 44,332110013 47,596628518
Run 4 50,062155622 43,587905602 44,616728628 47,430735675
Run 5 53,567235331 43,548408389 44,561502427 47,727024813
Run 6 50,354870307 43,877387065 44,107891362 47,444552655
Run 7 49,663738973 43,92048805 44,583599634 47,293633635
Run 8 49,780141995 43,843555496 44,055990454 47,561677627
Run 9 49,763425026 43,398042427 44,011950682 47,65275752
Run 10 50,197944032 44,153460819 44,303763557 47,974880802
Average 50,4931212086 43,9172542862 44,4754932616 47,8067749474

For information I use openSUSE Tumbleweed latest release.

I also noticed that libengine12 is really bigger with GCC but I've not have
that data on me now.

I hope this could be an idea of improvement ! Next crazy test I would like
to do is between MSVC and clang on windows ! But it seems harder !
-- 
Arnaud Versini
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