Re: [avr-gcc-list] Need help compiling testcase with gcc 3.3.5 or 3.4.3

[Andy Hutchinson]

Oh thats bad !

It looks like loop is changed so loop counter goes from 0 to -x

- think that needs a bug report


address@hidden wrote:

> Another interesting case (-Os used):
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> int foo (int x)
> {
>     int i= x;
>     do {
>         x *= 2;
>     } while (--i);
>     return x;
> }
>
> Result with 3.3.4:
> ~~~~~~~~~~~~~~~~~~
> foo:
> /* prologue: frame size=0 */
> /* prologue end (size=0) */
>         mov r18,r24
>         mov r19,r25
> .L2:
>         add r24,r24
>         adc r25,r25
>         subi r18,lo8(-(-1))
>         sbci r19,hi8(-(-1))
>         brne .L2
> /* epilogue: frame size=0 */
>         ret
>
> Result with 4.0:
> ~~~~~~~~~~~~~~~~
> foo:
> /* prologue: frame size=0 */
> /* prologue end (size=0) */
>         ldi r18,lo8(0)
>         ldi r19,hi8(0)
>         clr r20
>         clr r21
>         sub r20,r24
>         sbc r21,r25
> .L2:
>         add r24,r24
>         adc r25,r25
>         subi r18,lo8(-(-1))
>         sbci r19,hi8(-(-1))
>         cp r18,r20
>         cpc r19,r21
>         brne .L2
> /* epilogue: frame size=0 */
>         ret
>
>
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