ref: 30b7ca54c38e7229c32ec80df2c56bae9a5e5263 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