/arch/m68k/fpsp040/scosh.S

https://bitbucket.org/evzijst/gittest
Assembly | 132 lines | 109 code | 23 blank | 0 comment | 2 complexity | 095922c71b23da4b7d9277a84bc54222 MD5 | raw file
```  1|
2|	scosh.sa 3.1 12/10/90
3|
4|	The entry point sCosh computes the hyperbolic cosine of
5|	an input argument; sCoshd does the same except for denormalized
6|	input.
7|
8|	Input: Double-extended number X in location pointed to
10|
11|	Output: The value cosh(X) returned in floating-point register Fp0.
12|
13|	Accuracy and Monotonicity: The returned result is within 3 ulps in
14|		64 significant bit, i.e. within 0.5001 ulp to 53 bits if the
15|		result is subsequently rounded to double precision. The
16|		result is provably monotonic in double precision.
17|
18|	Speed: The program sCOSH takes approximately 250 cycles.
19|
20|	Algorithm:
21|
22|	COSH
23|	1. If |X| > 16380 log2, go to 3.
24|
25|	2. (|X| <= 16380 log2) Cosh(X) is obtained by the formulae
26|		y = |X|, z = exp(Y), and
27|		cosh(X) = (1/2)*( z + 1/z ).
28|		Exit.
29|
30|	3. (|X| > 16380 log2). If |X| > 16480 log2, go to 5.
31|
32|	4. (16380 log2 < |X| <= 16480 log2)
33|		cosh(X) = sign(X) * exp(|X|)/2.
34|		However, invoking exp(|X|) may cause premature overflow.
35|		Thus, we calculate sinh(X) as follows:
36|		Y	:= |X|
37|		Fact	:=	2**(16380)
38|		Y'	:= Y - 16381 log2
39|		cosh(X) := Fact * exp(Y').
40|		Exit.
41|
42|	5. (|X| > 16480 log2) sinh(X) must overflow. Return
43|		Huge*Huge to generate overflow and an infinity with
44|		the appropriate sign. Huge is the largest finite number in
45|		extended format. Exit.
46|
47|
48
49|		Copyright (C) Motorola, Inc. 1990
51|
52|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
53|	The copyright notice above does not evidence any
54|	actual or intended publication of such source code.
55
56|SCOSH	idnt	2,1 | Motorola 040 Floating Point Software Package
57
58	|section	8
59
60	|xref	t_ovfl
61	|xref	t_frcinx
62	|xref	setox
63
64T1:	.long 0x40C62D38,0xD3D64634 | ... 16381 LOG2 LEAD
65T2:	.long 0x3D6F90AE,0xB1E75CC7 | ... 16381 LOG2 TRAIL
66
67TWO16380: .long 0x7FFB0000,0x80000000,0x00000000,0x00000000
68
69	.global	scoshd
70scoshd:
71|--COSH(X) = 1 FOR DENORMALIZED X
72
73	fmoves		#0x3F800000,%fp0
74
75	fmovel		%d1,%FPCR
77	bra		t_frcinx
78
79	.global	scosh
80scosh:
81	fmovex		(%a0),%fp0	| ...LOAD INPUT
82
83	movel		(%a0),%d0
84	movew		4(%a0),%d0
85	andil		#0x7FFFFFFF,%d0
86	cmpil		#0x400CB167,%d0
87	bgts		COSHBIG
88
89|--THIS IS THE USUAL CASE, |X| < 16380 LOG2
90|--COSH(X) = (1/2) * ( EXP(X) + 1/EXP(X) )
91
92	fabsx		%fp0		| ...|X|
93
94	movel		%d1,-(%sp)
95	clrl		%d1
96	fmovemx	%fp0-%fp0,(%a0)	|pass parameter to setox
97	bsr		setox		| ...FP0 IS EXP(|X|)
98	fmuls		#0x3F000000,%fp0	| ...(1/2)EXP(|X|)
99	movel		(%sp)+,%d1
100
101	fmoves		#0x3E800000,%fp1	| ...(1/4)
102	fdivx		%fp0,%fp1		| ...1/(2 EXP(|X|))
103
104	fmovel		%d1,%FPCR
106
107	bra		t_frcinx
108
109COSHBIG:
110	cmpil		#0x400CB2B3,%d0
111	bgts		COSHHUGE
112
113	fabsx		%fp0
115	fsubd		T2(%pc),%fp0		| ...|X| - 16381 LOG2, ACCURATE
116
117	movel		%d1,-(%sp)
118	clrl		%d1
119	fmovemx	%fp0-%fp0,(%a0)
120	bsr		setox
121	fmovel		(%sp)+,%fpcr
122
123	fmulx		TWO16380(%pc),%fp0
124	bra		t_frcinx
125
126COSHHUGE:
127	fmovel		#0,%fpsr		|clr N bit if set by source
128	bclrb		#7,(%a0)		|always return positive value
129	fmovemx	(%a0),%fp0-%fp0
130	bra		t_ovfl
131
132	|end
```