Re: [patch/rfc 2/4] pcf875x I2C GPIO expander driver

[Bill Gatliff]

Jean Delvare wrote:
> Hi Bill,
>
> On Fri, 30 Nov 2007 07:04:10 -0600, Bill Gatliff wrote:
>   
> > Jean Delvare wrote:
> >     
> > > !!(value & (1 << offset))
> > > is more efficiently written
> > > (value >> offset) & 1
> > >       
> > ... but not more efficiently implemented.
> >
> > Your version requires code to do the shift on live data at runtime.  
> > David's version lets the compiler create the mask once, at compile-time.
> >     
>
> I don't understand. How could the compiler create the mask at
> compile-time when "offset" is only known at runtime?
>   

Oops.  :)  I was thinking of some different code.  Disregard.

/me got up too early this morning, after working too late last night!


b.g.

--
Bill Gatliff
bgat@xxxxxxxxxxxxxxx

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