Re: linux-2.3.4pre1: Adjustments for using gcc builtins

Linus Torvalds (torvalds@transmeta.com)
Sun, 30 May 1999 21:18:24 -0700 (PDT)

On Fri, 28 May 1999, Horst von Brand wrote:
>
> After the recent problems with egcs snapshots, it was suggested that the
> kernel don't use handcrafted mem* and str* functions, it better use the gcc
> builtins. This gives rise to the first patch below: It just blows away the
> redundant definitions in include/asm-i386/string.h and adds the symbols for
> the functions to kernel/ksyms.c (gcc doesn't allways inline them for some
> reason, falling back on the library functions).

Thcc gcc "builtins" are generally noticeably worse than the kernel
headers.

Anyway, there is a really simple choice when it comes to compilers: we
will choose the one that generates better code. For a long time it
_seemed_ that egcs would be the choice, but if we have to disable the new
alias code and/or use ugly tricks like the above then the choice is fairly
clear - gcc-2.7.2 will still continue to generate better code.

I've asked the egcs people to give us some way to tell the compiler what's
going on, but at least so far I haven't had any replies. As I know how
gcc-2.7.2 can be made to generate the code I want, and nobody so far has
told me how to get egcs to do the same, I know which compiler _I_ will
recommend.

Linus

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