[Bug middle-end/105654] transparent_union, function pointer and different types arguments causes null pointer to be passed

[max.ferger at gmx dot de via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105654

--- Comment #6 from Max Ferger <max.ferger at gmx dot de> ---
Versions of GCC that experience the bug:

- x86-64 gcc 12.1 ... 14.2  `-O1` ... `-O6`

Non-affected version of GCC:

- x86-64 gcc 12.1 ... 14.2  `-O0 -fno-tree-dse` ... `-O6 -fno-tree-dse`
- x86-64 gcc 3.4.6 ... 11.4  `-O1` ... `-O6`

Findings for GCC:

1. x86-64 gcc 12.1 introduced the bug.
2. The bug is triggered by a conglomerate of the optimizations under `-O1`.
3. The bug can be circumvented via `-fno-tree-dse` (and possibly others).