[Bug middle-end/36770] PowerPC missed autoincrement opportunity

[steven at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36770

Steven Bosscher <steven at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |steven at gcc dot gnu.org

--- Comment #6 from Steven Bosscher <steven at gcc dot gnu.org> ---
(In reply to Gunnar von Boehn from comment #2)
> Correct would be:
> test2:
>         lwz 0,0(3)
>         stwu 0,4(3)
>         blr
> 
> Is you can see the created bad code is just the same.
> This is independent of the register pinning.

At least with gcc 4.7.1 and gcc 4.9.0 (r206195) the register pinning
makes all the difference.

$ cat t.c
register int * src asm("r15");

int test1( ){
    src[1]=src[0];
    src++;
}

int *test2(int *a ){
    a[1]=a[0];
    a++;
    return a;
}

$ ./cc1 -quiet -O2 t.c
$ cat t.s
...
.L.test1:
        lwz 10,0(15)
        mr 9,15
        addi 15,15,4
        stw 10,4(9)
        blr
...
.L.test2:
        lwz 9,0(3)
        stwu 9,4(3)
        blr


This is basically the same as bug 44281.