https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64992
--- Comment #3 from Ishiura Lab Compiler Team <ishiura-compiler at ml dot kwansei.ac.jp> --- Looking only from outside, the two programs are virtually equal, so we just wondered what hinders the optimization on one of the programs. The Optimization on "opt.c" seems very strong, so we think it would be nice if the same transformation would work on "org.c."