[Bug c/82078] wrong code at -O3 in both 32-bit and 64-bit modes on x86_64-linux-gnu

[su at cs dot ucdavis.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82078

--- Comment #4 from Zhendong Su <su at cs dot ucdavis.edu> ---
So, it is indeed a bug and appears to be a recent regression.