ref: ee5be0d4d45549d727f46c720158a75b02d53ade dir: /sys/src/libc/386/387/sqrt.s/
TEXT sqrt(SB), $0 FMOVD a+0(FP), F0 FTST WAIT FSTSW AX SAHF JLO bad FSQRT RET bad: FMOVDP F0, F0 CALL NaN(SB) RET