ref: 2a531d444cf53419e8d4af716b9937d14ca5b08c dir: /sys/src/libc/386/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