https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65979
--- Comment #12 from Kazumoto Kojima <kkojima at gcc dot gnu.org> --- I've looked into which stage2 object was miscompiled with bisecting on objects for 5.1.0 and found tree-cfg.o is the one of them. 5.1.0 cross compiler miscompiles it too and I've got which change causes the problem with bisecting on changes. Surprisingly, it's r220922 for PR target/65153. With reverting it and applying the patch in the trail #c7 in PR65153, stage2 compiler can pass conftest.c issues during configuring target libraries. That patch simply removes a peephole and looked to be safe from wrong code problem. It means that there is another problem elsewhere. I've compared the outputs for tree-cfg.c w/wo that peephole and found that is_ctrl_stmt was miscompiled without that peephole. I'll attach a reduced testcase.
