Messages in this thread | | | Date | Fri, 05 Sep 2003 15:19:09 -0700 | From | George Anzinger <> | Subject | Re: [PATCHSET][2.6-test4][0/6]Support for HPET based timer - Take 2 |
| |
Erik Andersen wrote: > On Fri Aug 29, 2003 at 11:23:47AM -0700, Andrew Morton wrote: > >>"Pallipadi, Venkatesh" <venkatesh.pallipadi@intel.com> wrote: >> >>>Resending the patch. >> >>Thanks, I'll include these in the next -mm kernel. >> >>Reading the code, the only thing which leaps out is: >> >>+/* Use our own asm for 64 bit multiply/divide */ >>+#define ASM_MUL64_REG(eax_out,edx_out,reg_in,eax_in) \ >>+ __asm__ __volatile__("mull %2" \ >>+ :"=a" (eax_out), "=d" (edx_out) \ >>+ :"r" (reg_in), "0" (eax_in))
This can be done in standard C. If you want an inline, how about (from .../kernel/posix-timers.c):
static inline u64 mpy_l_X_l_ll(unsigned long mpy1,unsigned long mpy2) { return (u64)mpy1 * mpy2; }
>>+ >>+#define ASM_DIV64_REG(eax_out,edx_out,reg_in,eax_in,edx_in) \ >>+ __asm__ __volatile__("divl %2" \ >>+ :"=a" (eax_out), "=d" (edx_out) \ >>+ :"r" (reg_in), "0" (eax_in), "1" (edx_in))
This appears to be the same as (from .../include/asm-i386/div64.h):
#define div_long_long_rem(a,b,c) div_ll_X_l_rem(a,b,c)
extern inline long div_ll_X_l_rem(long long divs, long div, long *rem) { long dum2; __asm__("divl %2":"=a"(dum2), "=d"(*rem) : "rm"(div), "A"(divs));
return dum2;
}
-g
>> >>We seem to keep on proliferating home-grown x86 64-bit math functions. >> >>Do you really need these? Is it possible to use do_div() and the C 64x64 >>`*' operator instead? > > > > The fundamental reason these are proliferating is that given > some random bit of code such as: > > u64 foo=9, bar=3, baz; > baz = foo / bar; > baz = foo % bar; > > gcc then generates code calling __udivdi3 and __umoddi3. Since > the kernel does not provide these, people keep reinventing them. > Perhaps it is time to kill off do_div and all its little friends > and simply copy __udivdi3 and __umoddi3 from libgcc..... > > -Erik > > -- > Erik B. Andersen http://codepoet-consulting.com/ > --This message was written using 73% post-consumer electrons-- > - > 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/ >
-- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
- 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/
| |