[Bug middle-end/63273] atomic operations lead to inefficient code

[dvyukov at google dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63273

--- Comment #6 from Dmitry Vyukov <dvyukov at google dot com> ---
The real world situation is:
replace atomic_load/store implementation with relaxed atomic builtins here:
https://gcc.gnu.org/viewcvs/gcc/trunk/libsanitizer/sanitizer_common/sanitizer_atomic_clang_x86.h?view=markup
then build tsan runtime and compare generated code for __tsan_read8 before and
after the change. They should be roughly identical.