[PATCH 2/2] PowerPC - Add a faster way to read the Time Base register

[Ryan S. Arnold]

On Wed, Apr 4, 2012 at 3:41 PM, Tulio Magno Quites Machado Filho
<tuliom@linux.vnet.ibm.com> wrote:

> diff --git a/sysdeps/powerpc/sys/platform/ppc.h b/sysdeps/powerpc/sys/platform/ppc.h
> index b4bf7c8..cdfcba5 100644
> --- a/sysdeps/powerpc/sys/platform/ppc.h
> +++ b/sysdeps/powerpc/sys/platform/ppc.h
> @@ -19,5 +19,40 @@
>
>  #define _SYS_PLATFORM_PPC_H    1
>
> +typedef unsigned long long int __ppc_timebase;
> +
> +/* Read the Time Base Register
> +   The Time Base Register is a 64-bit register that stores a monotonically
> +   incremented value updated at a system dependent frequency that may be
> +   different of processor frequency.
> +   More information in Power ISA 2.06b - Book II - Section 5.2   */
> +#ifdef __powerpc64__
> +static inline __ppc_timebase
> +__ppc_get_timebase (void)
> +{
> +  __ppc_timebase __tb;
> +  __asm__ volatile (
> +                   "mfspr %0, 268\n"
> +                   : "=r" (__tb)
> +                   : );
> +  return __tb;
> +}
> +#else  /* not __powerpc64__ */
> +static inline __ppc_timebase
> +__ppc_get_timebase (void)
> +{
> +  register unsigned long __tbu, __tbl, __tmp; \
> +  __asm__ volatile (
> +                   "0:\n"
> +                   "mftbu %0\n"
> +                   "mftbl %1\n"
> +                   "mftbu %2\n"
> +                   "cmpw %0, %2\n"
> +                   "bne- 0b\n"
> +                   : "=r" (__tbu), "=r" (__tbl), "=r" (__tmp)
> +                   : );
> +  return (( (__ppc_timebase) __tbu << 32) | __tbl);
> +}
> +#endif  /* not __powerpc64__ */
>
>  #endif  /* sys/platform/ppc.h */

Per Roland's response to [PATCH 1/2], merge this with the creation of
ppc.h, thus creating ppc.h and adding these inline functions at the
same time.

And, I think that ppc.h should be added to this patchset [PATCH 2/2]
rather than [PATCH 1/2].

Ryan