https://gcc.gnu.org/bugzilla/show_bug.cgi?id=34040
--- Comment #18 from Georg-Johann Lay <gjl at gcc dot gnu.org> --- (In reply to Francois-Xavier Coudert from comment #11) > As far as I can say, the targets with this problem are: avr, bfin, h8300, > picochip and sh (for some subtargets of sh). > > On avr, bfin, h8300 and picochip, we're doomed anyway because there is no > double-sized type at all. On sh, we could use long double math calls. > > I'm making this into an enhancement; it will probably be very painful, > because most of the front-end assumes FLOAT_TYPE_SIZE == 32 and > DOUBLE_TYPE_SIZE == 64. At least for AVR, the situation changed with v10, see https://gcc.gnu.org/gcc-10/changes.html#avr https://gcc.gnu.org/install/configure.html#avr In order to keep v10 compatible with older versions of avr-gcc, double still defaults to 32 bits, though. To get 64-bit double, you'll have to configure using --with-double=64 (or use --with-double=64,32 so you can which to 32-bit double with -mdouble=32 at compile-time). The default for this option is --with-double=32,64; hence what's also possible is to use default configuraton, but provide -mdouble=64 for every translation unit. FYI, the 64-bit double support is provided by LibF7, which is a part of avr-libgcc. For details and shortcomings, see https://gcc.gnu.org/wiki/avr-gcc#Libf7 https://gcc.gnu.org/git/?p=gcc.git;a=tree;f=libgcc/config/avr/libf7
