Add original unix v6

source/s3/log.s

@@ -0,0 +1,105 @@
+.globl log, _log
+ldfps = 170100^tst
+stfps = 170200^tst
+ldexp = 176400^movif
+stexp = 175000^movfi
+/
+/	log accepts its argument and returns its result
+/	in fr0.  The carry bit is set if the argument is
+/	zero or negative.
+/	The coefficients are #2705 from Hart & Cheney.
+/
+/	movf	arg,fr0
+/	jsr	pc,log
+/	movf	fr0,...
+/
+_log:
+	mov	r5,-(sp)
+	mov	sp,r5
+	movf	4(r5),fr0
+	jsr	pc,log
+	mov	(sp)+,r5
+	rts	pc
+
+log:
+	tstf	fr0
+	cfcc
+	bgt	1f
+	movf	$bigneg,fr0	/return -(big) on error
+	sec
+	rts	pc
+1:
+	stfps	-(sp)
+	ldfps	$200		/di mode
+	movf	fr2,-(sp)
+	movf	fr1,-(sp)
+/
+	stexp	fr0,-(sp)	/scale
+	ldexp	$0,fr0
+	cmpf	sqrt2o2,fr0
+	cfcc
+	blt	1f
+	ldexp	$1,fr0
+	dec	(sp)
+1:
+	movf	fr0,fr1		/(1/2)^(1/2) < x < 2^(1/2)
+	subf	$one,fr0
+	addf	$one,fr1
+	divf	fr1,fr0		/z = (x-1)/(x+1)
+	movf	fr0,fr1
+	mulf	fr0,fr1		/z^2
+/
+	movf	p3,fr2
+	mulf	fr1,fr2
+	addf	p2,fr2
+	mulf	fr1,fr2
+	addf	p1,fr2
+	mulf	fr1,fr2
+	addf	p0,fr2
+	mulf	fr2,fr0		/zP(z)
+/
+	movf	fr1,fr2
+	addf	q2,fr2
+	mulf	fr1,fr2
+	addf	q1,fr2
+	mulf	fr1,fr2
+	addf	q0,fr2		/Q(z)
+/
+	divf	fr2,fr0		/zP(z)/Q(z)
+	movif	(sp)+,fr1
+	mulf	log2,fr1
+	addf	fr1,fr0
+/
+	movf	(sp)+,fr1
+	movf	(sp)+,fr2
+	ldfps	(sp)+
+	rts	pc
+/
+/
+one	= 40200
+bigneg	= 177777
+/
+.data
+sqrt2o2: 40065; 02363; 31771; 157145
+log2:	 40061; 71027;173721;147572
+/
+p0:	141300; 16201; 02154; 10216
+p1:	 41367;124211; 21611;114442
+p2:	141032; 31773; 64222; 40261
+p3:	 37727;114303;110107;114145
+/
+q0:	141100; 16201; 02154; 10216
+q1:	 41233;154404;136454; 22153
+q2:	141016;111747; 07541; 52530
+/
+/
+/p0 = -.24013 91795 59210 50986 8484  d2
+/p1 =  .30957 29282 15376 50062 264   d2
+/p2 = -.96376 90933 68686 59324       d1
+/p3 =  .42108 73712 17979 7145        d0
+/
+/q0 = -.12006 95897 79605 25471 7525  d2
+/q1 =  .19480 96607 00889 73051 623   d2
+/q2 = -.89111 09027 93783 12337       d1
+/q3 =  .1                             d1
+/