https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77405
--- Comment #10 from John Marino <gnugcc at marino dot st> --- Okay, I bisected this. SVN r239376 (August 11) is the last commit that works I confirmed that r239378, the next commit on the TRUNK, fails to build, resulting with the SIGBUS error. The log for that commit is: Use TImode for piecewise move in 64-bit mode. We should use TImode in 32-bit mode and use OImode or XImode if they are available. But since by_pieces_ninsns determines the widest mode with MAX_FIXED_MODE_SIZE, we can only use TImode in 64-bit mode. gcc/ * config/i386/i386.h (MOVE_MAX_PIECES): Use TImode in 64-bit mode if unaligned SSE load and store are optimal.