https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58416
--- Comment #16 from Paul Eggert <eggert at cs dot ucla.edu> --- (In reply to Richard Biener from comment #13) > Paul - can you test if this patch resolves the emacs issue? Unfortunately not. Although the generated code differs, it's still the same bad pattern. GDB's command 'disas decode_lisp_time' reports this: ... 0x082a924c <+876>: call 0x82a8140 <decode_ticks_hz> => 0x082a9251 <+881>: fldl 0x8c(%esp) 0x082a9258 <+888>: add $0x10,%esp 0x082a925b <+891>: fstpl 0x7c(%esp) ... where the 8-byte quantity being copied comes from the leading bytes of this union: union c_time { struct ticks_hz { long long ticks; long long hz; } th; struct timespec ts; double d; }; and this union happens to contain th (of type struct ticks_hz) not d (of type double).