Re: [avr-gcc-list] efficiency of assigning bits

[Jim Brain]

Graham Davies wrote:

> This has nothing to do with what the ANSI C specification requires.  This
> just indicates that the optimizer has determined that the result will be the
> same whether the operands are processed as integers or at their declared
>  
I'll rephrase my statement.  In my avr object code produced by GNU GCC 
concerning the (1<<X) construct, I've only seen the need to explicitly 
cast ~(1<<X) statements in order to force the optimizer/compiler to not 
generate integer based code in that circumstance.

> You can't "cancel" promotions.  All you can do it take the result of an
> operand or expression evaluation and cast (perform an explicit conversion)
> to some type.  This is what you are doing here.
>  
Which effectively "cancels" the promotion.  I apologize for not using 
the pedantically correct terminology.  I hope other readers were able to 
understand the essence of the statement.

Jim

--
Jim Brain, Brain Innovations
address@hidden                                http://www.jbrain.com
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!