Hi,

On Fri, Aug 21, 2015 at 11:01:41AM +0300, Tomi Valkeinen wrote:

quoted

quoted

Possibly the patches are still good for x86 also, but that needs to be
proven.

not exactly, because x86_64 don’t have hardware instruction to do rbit OP,
i compile by test :

For old drivers i386 may be more relevant than x86_64.

It seems asm bit reversal is supported in Kernel on arm & arm64 only,
not sure whether any other arch even provide asm bit reversal
instruction.

These kind of optimizations should have some real world measurements,

Not for this case, but once measured on ARM, iirc, a 32-bit asm bit
reversal as compared to doing it in C was taking 1 cycle as opposed to
~225 cycles!, of course writing optimized C could have made it fare
better, but still would reach no-way near asm bit reversal.

Regards
Afzal