Re: [avr-gcc-list] How to (efficeiently !!!) test a bit within a multi-byte integer ?

[Vincent Trouilliez]

On Fri, 2005-11-04 at 15:20 +0800, Ian Caddy wrote:
> Hi Vince,
> 
> All your new code is doing is checking that address is non-zero as it is 
> a logical AND with a non-zero number, which would get optimised out.
> 
> I haven't tried this, but it might be better:
> 
> unsigned char temp;
> 
> temp = (address >> 16) & 0xFF;
> 
> if(temp & 0x04)


Thank you very much Ian, your code is highly efficient, and does work
perfectly, unlike && or &.  :o) I am in heaven :

                temp = (address >> 16) & 0xFF;
    28bc:       ca 01           movw    r24, r20
    28be:       aa 27           eor     r26, r26
    28c0:       bb 27           eor     r27, r27
                if (temp & 0x04)
    28c2:       82 ff           sbrs    r24, 2
    28c4:       02 c0           rjmp    .+4             ; 0x28ca

can't get any better than that really :o)))


Thanks again


--
Vince