Re: TBAA bug?

[Richard Biener <richard.guenther@gmail.com>]

On Sun, Jul 25, 2021 at 1:58 PM Uecker, Martin
<Martin.Uecker@med.uni-goettingen.de> wrote:
>
>
>
> Hi Richard,
>
> here is another case where it seems that TBAA goes
> wrong. Since this is not in a loop, it seems this
> is something else than what we discussed. Is
> this a known issue?

No, it's not known and it is a bug.  It seems to be
related to doing

Value numbering stmt = pu_6(D)->x = xy_7;
Store matched earlier value, value numbering store vdefs to matching vuses.
Setting value number of .MEM_8 to .MEM_5 (changed)

I'm looking into it.

Richard.

> Best,
> Martin
>
>
> #include <stdio.h>
> #include <stdlib.h>
>
> union u {
>   long x;
>   long long y;
> };
>
> __attribute__((noinline,noclone))
> long test(long *px, long long *py, union u *pu)
> {
>   *px = 0;
>   *py = 1;
>
>   long xy = pu->y;
>   pu->x = xy;
>
>   return *px;
> }
>
> int main(void)
> {
>   union u u;
>   printf("%ld\n", test(&u.x, &u.y, &u));
> }
>
> https://godbolt.org/z/a9drezEza
>