On Wed, Apr 06, 2016 at 05:14:45PM +0800, [email protected] wrote:
> From: Zhaoxiu Zeng <[email protected]>
>
> Use alternatives, lifted from arch_hweight
>
> Signed-off-by: Zhaoxiu Zeng <[email protected]>
> ---
> arch/x86/include/asm/arch_hweight.h | 5 ++
> arch/x86/include/asm/arch_parity.h | 102
> ++++++++++++++++++++++++++++++++++++
> arch/x86/include/asm/bitops.h | 4 +-
> arch/x86/lib/Makefile | 8 +++
> arch/x86/lib/parity.c | 32 ++++++++++++
> 5 files changed, 150 insertions(+), 1 deletion(-)
> create mode 100644 arch/x86/include/asm/arch_parity.h
> create mode 100644 arch/x86/lib/parity.c
...
> +static __always_inline unsigned int __arch_parity32(unsigned int w)
> +{
> + unsigned int res;
> +
> + asm(ALTERNATIVE("call __sw_parity32", POPCNT32 "; and $1, %0",
> X86_FEATURE_POPCNT)
> + : "="REG_OUT (res)
> + : REG_IN (w)
> + : "cc");
So why all that churn instead of simply doing:
static __always_inline unsigned int __arch_parity32(unsigned int w)
{
return hweight32(w) & 1;
}
Ditto for the 64-bit version.
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284
(AG Nürnberg)
--
