[alsa-devel] [PATCH 11/39] firewire-lib: Add support for channel mapping

[Takashi Sakamoto]

(Mar 11 2014 17:23), Clemens Ladisch wrote:
> In code like this:
>
>          for (... s->channels ...)
>              buffer[i] = ...;
>
> it is, as far as the compiler knows, possible that &buffer[i] and
> &s->channels actually point to the same variable, so s->channels must
> be reloaded in every loop iteration.  A local variable avoids that.
>
> (Whether this optimization is worth it is another question ...)

As long as I test with simple codes and gcc, this optimization reduce 
one opcode in a loop. Codes with your way compares address content to a 
register, but codes with my way once push address content to another 
register and compare the two registers.

The read/write functions are called the most freqently, so shorter codes 
are preferable. I realize I should keep it what you wrote. Thanks for 
your indication.


Thanks

Takashi Sakamoto
o-takashi at sakamocchi.jp