clang vs gcc build performance (executable not build time)

[Arnaud Versini]

Hi Stephan,

Sorry i didn't wrote all explanation yet, it's execution time in seconds to
convert the ODT standart from odt to pdf, I know that's not a complete
performance test but i will add more test.

I didn' measure build time, i guess clang is better but not sure and that's
not what i was checking

Le mar. 23 nov. 2021 à 17:58, Stephan Bergmann <sbergman at redhat.com> a
écrit :

> On 22/11/2021 17:28, Arnaud Versini wrote:
> > 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
>
> What are you even measuring here, wall-clock time to build LO with the
> various toolchains, or wall-clock time to execute something from the
> resulting buils, or...?  (And what is the unit for those numbers?)
>
>
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