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

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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
[email protected]

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