[Bug middle-end/126153] [13/14/15/16/17 Regression] [csmith] runtime crash with -O3 -ftrivial-auto-var-init=zero

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126153

--- Comment #16 from Richard Biener <rguenth at gcc dot gnu.org> ---
Seems to be some interaction between DSE of

  l_59.f3.f7 = 1;

because of the later

  MEM <char> [(struct S1 *)&l_59 + 13B] = 4;

and following analysis figuring l_59.f3.f7 is now uninitialized.
Digging further.