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

[Jim Brain]

My understanding was that C only promotes to integer when doing negation 
or when other operands are integer.  I've never seen constants promoted 
to int in a normal (1<<X) mode.

I dislike _BV, as I don't think it adds enough value.  My opinion, of 
course.

I would agree that 1<<3 is not maintainable code.  For AVR flags, I use:

(1<<TIMSK) type nomenclature

For data pins, I tend to do:

#define PORT_ADDR_OUT   PORTD
#define ADDR_CLK               (1<<PIN2)

And then code is:

PORT_ADDR_OUT |= ADDR_CLK;

I find that expressing it this way provides lots of value for 
portability, etc.

And, when I negate, I do:

PORT &=(unsigned char)~ADDR_CLK;

to cancel the promotion.

Jim





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