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+|
+|	satanh.sa 3.3 12/19/90
+|
+|	The entry point satanh computes the inverse
+|	hyperbolic tangent of
+|	an input argument; satanhd does the same except for denormalized
+|	input.
+|
+|	Input: Double-extended number X in location pointed to
+|		by address register a0.
+|
+|	Output: The value arctanh(X) returned in floating-point register Fp0.
+|
+|	Accuracy and Monotonicity: The returned result is within 3 ulps in
+|		64 significant bit, i.e. within 0.5001 ulp to 53 bits if the
+|		result is subsequently rounded to double precision. The
+|		result is provably monotonic in double precision.
+|
+|	Speed: The program satanh takes approximately 270 cycles.
+|
+|	Algorithm:
+|
+|	ATANH
+|	1. If |X| >= 1, go to 3.
+|
+|	2. (|X| < 1) Calculate atanh(X) by
+|		sgn := sign(X)
+|		y := |X|
+|		z := 2y/(1-y)
+|		atanh(X) := sgn * (1/2) * logp1(z)
+|		Exit.
+|
+|	3. If |X| > 1, go to 5.
+|
+|	4. (|X| = 1) Generate infinity with an appropriate sign and
+|		divide-by-zero by
+|		sgn := sign(X)
+|		atan(X) := sgn / (+0).
+|		Exit.
+|
+|	5. (|X| > 1) Generate an invalid operation by 0 * infinity.
+|		Exit.
+|
+
+|		Copyright (C) Motorola, Inc. 1990
+|			All Rights Reserved
+|
+|       For details on the license for this file, please see the
+|       file, README, in this same directory.
+
+|satanh	idnt	2,1 | Motorola 040 Floating Point Software Package
+
+	|section	8
+
+	|xref	t_dz
+	|xref	t_operr
+	|xref	t_frcinx
+	|xref	t_extdnrm
+	|xref	slognp1
+
+	.global	satanhd
+satanhd:
+|--ATANH(X) = X FOR DENORMALIZED X
+
+	bra		t_extdnrm
+
+	.global	satanh
+satanh:
+	movel		(%a0),%d0
+	movew		4(%a0),%d0
+	andil		#0x7FFFFFFF,%d0
+	cmpil		#0x3FFF8000,%d0
+	bges		ATANHBIG
+
+|--THIS IS THE USUAL CASE, |X| < 1
+|--Y = |X|, Z = 2Y/(1-Y), ATANH(X) = SIGN(X) * (1/2) * LOG1P(Z).
+
+	fabsx		(%a0),%fp0	| ...Y = |X|
+	fmovex		%fp0,%fp1
+	fnegx		%fp1		| ...-Y
+	faddx		%fp0,%fp0		| ...2Y
+	fadds		#0x3F800000,%fp1	| ...1-Y
+	fdivx		%fp1,%fp0		| ...2Y/(1-Y)
+	movel		(%a0),%d0
+	andil		#0x80000000,%d0
+	oril		#0x3F000000,%d0	| ...SIGN(X)*HALF
+	movel		%d0,-(%sp)
+
+	fmovemx	%fp0-%fp0,(%a0)	| ...overwrite input
+	movel		%d1,-(%sp)
+	clrl		%d1
+	bsr		slognp1		| ...LOG1P(Z)
+	fmovel		(%sp)+,%fpcr
+	fmuls		(%sp)+,%fp0
+	bra		t_frcinx
+
+ATANHBIG:
+	fabsx		(%a0),%fp0	| ...|X|
+	fcmps		#0x3F800000,%fp0
+	fbgt		t_operr
+	bra		t_dz
+
+	|end