[Bug c++/71240] ICE on valid code at -O2 and above on x86_64-linux-gnu: verify_gimple failed

[rogero at howzatt dot demon.co.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71240

--- Comment #1 from Roger Orr <rogero at howzatt dot demon.co.uk> ---
(The example code compiles with gcc revision 236175, dated 20160512)