Re: [avr-gcc-list] mass stupidity with registers and longs

[E. Weddington]

Curtis Maloney wrote:

> I give up.  I've been trying to shift 4 chars into an unsigned long, 
> but can't stop GCC 3.4.1 (what's shipped with the latest WinAVR) from 
> sign extending values, let alone producing sane code.
>
> I've tried -Os, -O2, -O3, with and without -fnew-ra... the asm varies, 
> but is generaly crap.
>
> now, if I have:
>     extern char a[4];
>     unsigned long ul;
>
>     ul = ( (unsigned)a[0] << 8 ) | (unsigned)a[1];
>
> why would it be sign extending a[0] and a[1] when they're cast to 
> unsigneds?
> And then why doesn't the code optimiser see to just mov rX, a[1]; mov 
> rX+1,a[0] ?
>
> I tried casts on casts on casts... everything I could think of to get 
> better code, and it just did not improve.
Other have given very good advice on this, that I can't really add to.

> Am I missing something, or do I just need to get gcc 3.4.3?  If so, is 
> anyone lurking here involved with WinAVR, and can tell me when the 
> next update might happen?
Well, I doubt the next update will help you in this situation, but, to 
answer your question, hopefully by the end of the month.

Eric