Re: [Qemu-devel] [PATCH v3 5/6] bitops: add BITNR macro

[Paolo Bonzini]

Il 13/11/2013 03:40, Alexey Kardashevskiy ha scritto:
> I looked further and did not find any use of ffs/clz so I wonder what did
> you mean about bitops.h and what did I miss? I am confused.

It's host-utils.h actually.  The reason for the wrappers is twofold:

(1) provide 32/64-bit functions instead of int/long/longlong;

(2) support GCC <3.4.

The wrappers are not usable where you have constant expressions as in
your case.  So your original patch is good IMO, except for the __ at the
beginning of __BITNR.

Paolo

> So I would suggest the following instead (if I really needed this BITNR but
> I really do not :) )
> 
> ===
>     bitops: add BITNR macro
> 
>     This adds a macro to calculate the highest single bit set. If more than
>     one bit is set, returns -1.