ref: 1a55b8d1f0253b4d39b1972978b469a352f0f94b 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