[Bug debug/80629] Missing .loc for a function in the presence of -O2

[matt at godbolt dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80629

--- Comment #1 from Matt Godbolt <matt at godbolt dot org> ---
This bug is noticeable in Compiler Explorer: https://godbolt.org/g/scFj7A for
example; the function is not colourised as CE uses the .locs to track how the
source lines map to asm. One can also see how the bug has changed between
compiler revisions, in the 5.x and 6.x series it was the first function that
suffered the loc loss, and in 4.9.4 there's no such issue. (the older compilers
need the addition of the -std=c++0x flag)