log.s

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

TEXT	log(SB), $0
	FMOVD	$0.69314718055994530941, F0
	FMOVD	a+0(FP), F0

	FTST
	WAIT
	FSTSW	AX
	SAHF
	JLO	bad

	FYL2X
	RET

TEXT	log10(SB), $0
	FMOVD	$0.30102999566398119521, F0
	FMOVD	a+0(FP), F0

	FTST
	WAIT
	FSTSW	AX
	SAHF
	JLO	bad

	FYL2X
	RET

bad:
	FMOVDP	F0, F0
	FMOVDP	F0, F0
	CALL	NaN(SB)
	RET