gcc will become the best optimizing x86 compiler

[Tim Prince]

Agner Fog wrote:
>  I have tested a few of the most important functions in 
> libc and compared them with other available libraries (MS, Borland, 
> Intel, Mac). The comparison does not look good for gnu libc. See my test 
> results in http://www.agner.org/optimize/optimizing_cpp.pdf section 2.6. 
As far as I can see, you identify the library you tested only as "ubuntu 
g++ 4.2.3."  Presumably, that implies some version of glibc?  On my x86-64 
system where I have glibc-2.6.1-18.3, some of the functions perform much 
better than those provided with earlier glibc versions.
Speaking of the one case where I have looked into it, the builtin_memcpy 
of gcc for 32-bit linux uses a string move which performs well only for 
certain cases of short non-aligned strings.  The corresponding 64-bit 
linux will see vastly different levels of performance, depending on the 
glibc version, as it doesn't use a builtin string move.
Certain newer CPUs aim to improve performance of the 32-bit gcc builtin 
string moves, but don't entirely eliminate the situations where it isn't 
optimum.
The machinery for getting good performing versions in glibc isn't visible 
on this list.