https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83460
--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> --- I suspect this is the result of r255753. The test searches the dump of code that depends on <vector> which changed in the revision to both avoid warnings and improve the emitted code. To avoid these kinds of effects the test should instead include a test case that's independent of libstdc++ (e.g., a translation unit obtained from a snapshot of <vector> that still exhibits the problem). I only ran libstdc++ tests for this change, in addition to the one GCC regression test I added, so I saw it only after I committed it.
