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

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?

Anyway, I just checked and gcc (4.1.2 on x86_86) generates the same
code for both expressions, so there's not much to argue about. David,
feel free to ignore my comment if you prefer your implementation :)

--
Jean Delvare
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