Re: [PATCH] x86: support i386 with Clang

[Linus Torvalds]

On Mon, May 11, 2020 at 10:24 AM Nick Desaulniers
<ndesaulniers@xxxxxxxxxx> wrote:
>
> Bumping for comment+review.
>
> On Mon, May 4, 2020 at 4:03 PM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:
> >
> > -                   : "qi" ((pto_T__)(val)));           \
> > +                   : "qi" ((unsigned char)(unsigned long)(val))); \

I find the extra casts really annoying and illogical.

I kind of see why they happen: just casting to 'unsigned char' can
cause warnings, when this case isn't even taken, and the sizeof(var)
is something else (and you cast a pointer to a char without going
through the 'unsigned long' first.

But that doesn't make this change any more sensible or readable.

Would using "__builtin_choose_expr()" be able to avoid this whole issue?

Because I'd rather re-write the whole thing with a different model
that doesn't have this issue, than make the code look insane.

And it does look insane, because that whole thing makes for a very
natural question: "why do we cast to unsigned long and then to char,
when we just checked that the size of the type is 1"?

                 Linus