[Bug tree-optimization/128217] [14/15 Regression] std::pair members incorrectly compare equal with -O2 -mavx2

[satotasukuweb at toki dot waseda.jp via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128217

--- Comment #6 from Tasuku Sato <satotasukuweb at toki dot waseda.jp> ---
Adding -fno-tree-ch to -O2 -mavx2 also makes both testcases pass.

repro.cpp: GCC 15.1-15.3
break4.cpp: GCC 14.1-14.4, 15.1-15.3