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

[Dmitry K.]

On Saturday 29 January 2005 11:41, Andy Hutchinson wrote:
> Many Thanks to summarize 3.4.3 has same response as WINAVR 3.3.1
>
> I've filed bug report on 4.0 for lack of loop reversal - but it will be
> treated as missed optimisation unless other ports take a big hit.
>
> gcc-avr has problem with pattern matching - This happens at least back
> to 3.3.1
>
> The AVR.MD RTL peephole turns sign status tests (Rx<=0) + jump into (RX
> & -32768) +jump. Then  "*sbrx_and_branchhi" turns this into SBRS.
> Unfortunately this occurs before  the potentially more efficient code
> peephole ((Rx=Rx-1)<=0)+jump is tried.
>
> Somehow I have to figure out how to catch things before 1st peephole
> grabs the sign test. Probabley another RTL peephole and delete the old
> code ones.

Interesting thing with avr-gcc 4.0 -- wrong size in comment.
Look:
        ...
testloop1:
/* prologue: frame size=0 */
        push r28
        push r29
/* prologue end (size=2) */
        ldi r28,lo8(10)
        ldi r29,hi8(10)
.L2:
        call foo
        sbiw r28,1
        brne .L2
/* epilogue: frame size=0 */
        pop r29
        pop r28
        ret
/* epilogue end (size=3) */
/* function testloop1 size 12 (7) */

Similar error is in 3.3.4 also.

I have send a message to gcc bug-list (#19684).