Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 10 Jul 2003 22:19:39 +0200 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] Fix do_div() for all architectures |
| |
On Thu, Jul 10, 2003 at 09:31:45PM +0200, Bernardo Innocenti wrote: > On Thursday 10 July 2003 18:39, Richard Henderson wrote: > > > On Thu, Jul 10, 2003 at 06:18:59PM +0200, Andrea Arcangeli wrote: > > > On Thu, Jul 10, 2003 at 08:40:19AM -0700, Richard Henderson wrote: > > > > On Tue, Jul 08, 2003 at 08:27:26PM +0200, Bernardo Innocenti wrote: > > > > > +extern uint32_t __div64_32(uint64_t *dividend, uint32_t > > > > > divisor) __attribute_pure__; > > > > > > > > ... > > > > > > > > > + __rem = __div64_32(&(n), __base); \ > > > > > > > > The pure declaration is very incorrect. You're writing to N. > > > > > > now pure sounds more reasonable, I wondered how could gcc keep track > > > of the stuff pointed by the parameters (especially if this stuff > > > points to other stuff etc.. ;). > > The compiler could easily tell what memory can be clobbered by a pointer > by applying type-based aliasing rules. For example, a function taking a > "char *" can't clobber memory objects declared as "long bar" or > "struct foo". > > Without type based alias analysis, the compiler is forced to flush > all registers containing copies of memory objects before function > call and reloading values from memory afterwards.
the kernel isn't complaint with the alias analysis, that's why it has to be turned off (-fnostrict-aliasing) or stuff would break.
> Boy, that's ugly! It's too bad C can't do it the Perl way: > > (n,rem) = __div64_32(n, base);
or the python way:
n, rem = __div64_32(n, base)
;)
Andrea - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| ![\](/images/icornerr.gif) |