floating-point compare
An instruction that compares two floats and sets flags - with an extra "unordered" outcome when either one is NaN.
x86-64 ucomisd/ucomiss set ZF, PF and CF (as an unsigned comparison would; unordered sets all three); ARM64 fcmp sets NZCV (unordered = 0011); RISC-V feq/flt/fle write 0 or 1 to an integer register.
See also