https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69132
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Wang Xuancong from comment #2) > I assume rcp(b)=1/b, so a/b=a*(1/b)=a*rcp(b). That assumption is wrong. The VRCPPS instruction does not compute reciprocal of the operand, but just an approximation thereof, see the ISA documentation. In particular, |Relative Error| < 1.5 *2^ -12 Such an error is too much even for -Ofast.
