Re: 8/16bit oddities on avr-gcc

[Michael Kukat <michael at kukat dot de>]

Hi again,

Andrew Haley schrieb:
> For -O2 gcc 4.3 does:
>
> ;; Function test (test)
>
> Analyzing Edge Insertions.
> test ()
> {
>   uint8_t ctr;
>
> <bb 2>:
>   xx = 0;
>   xx = 1;
>   ctr = 2;
>
> <L0>:;
>   xx = ctr;
>   ctr = ctr + 1;
>   if (ctr != 64) goto <L0>; else goto <L1>;
>
> <L1>:;
>   return;

okay, i just tested 4.2-20070228 and voila - i can reproduce what you 
have seen in 4.3, here is the assembler equivalent of this:

test:
/* prologue: frame size=0 */
/* prologue end (size=0) */
        sts var,__zero_reg__
        ldi r24,lo8(1)
        sts var,r24
        ldi r24,lo8(2)
.L2:
        sts var,r24
        subi r24,lo8(-(1))
        cpi r24,lo8(64)
        brne .L2
/* epilogue: frame size=0 */
        ret

So the uint8_t versus unsigned int problem seems to be gone in 4.2. But 
only for this special case, as in the function where i have seen the 
"problem" yesterday, i see this "unsigned int" stuff again now and it 
again compiles to a 16 bit counter. I'll try to find out what triggers 
the problem this time.

...Michael