Messages in this thread | | | Date | Tue, 7 Sep 2021 09:29:34 -0500 | From | Segher Boessenkool <> | Subject | Re: [GIT PULL v2] Kbuild updates for v5.15-rc1 |
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On Mon, Sep 06, 2021 at 02:08:58PM -0700, Linus Torvalds wrote: > On Mon, Sep 6, 2021 at 1:14 PM Jakub Jelinek <jakub@redhat.com> wrote: > > > > the only guaranteed APIs are > > those provided by the headers (x86intrin.h/*mmintrin.h etc. on x86, > > arm_{neon,sve}.h etc. on arm*, ...) > > You guys realize we don't use those, do you?
Linux does use the Arm and Power vector intrinsics (arm_neon.h and altivec.h).
> And you don't seem to realize that you are actively arguing *AGAINST* > what you think you argue for.
I have no idea what you think we are arguing for, only what we are.
> That "immintrin.h" file, for example, is simply not usable for the > kernel. I just checked.
Yes. It cannot be used in freestanding environments; it includes a header file we don't ship (<mm_malloc.h>, via <xmmintrin.h>). Or perhaps we do ship it, but only on native systems? Same issue, anyway.
The top comment in the latter says /* Implemented from the specification included in the Intel C++ Compiler User Guide and Reference, version 9.0. */ so the shortcoming exists there already probably?
> 27 | #include <stdlib.h> > | ^~~~~~~~~~ > > Oops.
Yup, that is not a (freestanding) standard C header.
> Very similar things happens if you try to use that <stdint.h> file > that somebody mentioned earlier.
Not at all. <stdint.h> *is* a standard C header, and we ship it, it always works. If you find problems with it, please report them!
> You also don't seem to realize how hard it is to separate out the > user-land crap that we really cannot use, and must not use.
We have worked very hard for many years to make this better. For the freestanding headers only <limits.h> is still problematic, and you do not need that one anyway, it is legacy more than anything else.
Segher
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