efriedma added a comment.
So you want int128_t for compiler-rt itself, so you can use the soft-float
implementation, but you want to make int128_t opt-in to avoid the possibility
of someone getting a link error trying to link code built with clang against
libgcc.a? That seems a little convoluted, but I guess it's okay.
Not sure I like the name "-fuse-int128"; doesn't really indicate what it's
doing. Maybe "-fforce-enable-int128".
cfe-commits mailing list