Hi Bruce, Brooks, On Sat, Feb 3, 2018 at 3:52 AM, Bruce Evans <b...@optusnet.com.au> wrote: > On Fri, 2 Feb 2018 a bug that doesn't want repl...@freebsd.org wrote: > >> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=225626 >> >> --- Comment #1 from Brooks Davis <bro...@freebsd.org> --- > ... >> Note that memset should be used in preference to bzero as the compiler >> should >> be able to elide most of the cost of the memset since it can emit it >> inline and >> then delete the dead stores.
(To Brooks:) Not in -ffreestanding by default, unfortunately. We can give it that hint back by defining memset() in terms of __builtin_memset(), though. We have done so for some sizes of constant bzero(), but not for bcopy, memcpy, or memmove, unfortunately. > Note that memset() should _not_ be used in preference to bzero() since: > - using memset() in the kernel is a style bug, except possibly with a > nonzero > fill byte > - the existence of memset() in the kernel is an umplementation style bug, > except possibly with a nonzero fill byte. This is total nonsense. > ... > - using memset() instead of bzero() in the kernel is a pessimization. Since > memset() is only compatibilty cruft and should not be used, it is > intentionally not as optimized as bzero(). > ... This can and should be fixed. > Not so simlarly for memcpy(). Its use in the kernel is now just a style > bug, since the compiler is not allowed to inline it (except in my version > of course). This should be fixed. > ... > FreeBSD was changed to use -ffreestanding because without it the compiler > is allowed to inline functions like printf() and gcc started doing that > (it converts printf(3) into puts() galore, and puts() doesn't exist in > the kernel). This broke all inlining, but no one cared (except me of > course). Isn't the other issue that non-freestanding links libgcc (GPL) into the kernel? We could work around puts() by adding a puts() implementation, of course. Conrad _______________________________________________ freebsd-bugs@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "freebsd-bugs-unsubscr...@freebsd.org"
