Re: [PATCH] x86: merge the simple bitops and move them to bitops.h

[Andi Kleen]

The CMOV define should probably be dependent on what CPU the kernel
is tuned for. It was originally written for when x86-64 was only
K8 which has fast CMOV, but e.g. on P4 CMOV is actually deprecated
over jumps.

> Both define fls64(), but i386 uses a generic one and x86_64 defines
> one all by itself. The generic one is currently not suitable for
> use by 64-bit archs... that can change.

It is very unlikely a generic one will ever be able to compete
with a single instruction.

> x86_64 defines ARCH_HAS_FAST_MULTIPLIER, i386 not. This affects a
> choice of generated code in the (generic) hweight function. It would
> be nice if that could move to some other file.

It depends on the CPU, but it can be probably safely set on pretty much
all modern x86 cores.

> x86_64 has a mysterious inline function set_bit_string, which is
> only used by pci-calgary_64.c and pci-gart_64.c. Not sure what to
> do with it.

It's generic and could really live in linux/bitops.h

-Andi

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/