/arch/m68k/fpsp040/sasin.S

https://bitbucket.org/evzijst/gittest
Assembly | 104 lines | 89 code | 15 blank | 0 comment | 1 complexity | 512783df7e22336de229dc0206ebb25b MD5 | raw file
```  1|
2|	sasin.sa 3.3 12/19/90
3|
4|	Description: The entry point sAsin computes the inverse sine of
5|		an input argument; sAsind does the same except for denormalized
6|		input.
7|
8|	Input: Double-extended number X in location pointed to
10|
11|	Output: The value arcsin(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 sASIN takes approximately 310 cycles.
19|
20|	Algorithm:
21|
22|	ASIN
23|	1. If |X| >= 1, go to 3.
24|
25|	2. (|X| < 1) Calculate asin(X) by
26|		z := sqrt( [1-X][1+X] )
27|		asin(X) = atan( x / z ).
28|		Exit.
29|
30|	3. If |X| > 1, go to 5.
31|
32|	4. (|X| = 1) sgn := sign(X), return asin(X) := sgn * Pi/2. Exit.
33|
34|	5. (|X| > 1) Generate an invalid operation by 0 * infinity.
35|		Exit.
36|
37
38|		Copyright (C) Motorola, Inc. 1990
40|
41|	THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF MOTOROLA
42|	The copyright notice above does not evidence any
43|	actual or intended publication of such source code.
44
45|SASIN	idnt	2,1 | Motorola 040 Floating Point Software Package
46
47	|section	8
48
49PIBY2:	.long 0x3FFF0000,0xC90FDAA2,0x2168C235,0x00000000
50
51	|xref	t_operr
52	|xref	t_frcinx
53	|xref	t_extdnrm
54	|xref	satan
55
56	.global	sasind
57sasind:
58|--ASIN(X) = X FOR DENORMALIZED X
59
60	bra		t_extdnrm
61
62	.global	sasin
63sasin:
64	fmovex		(%a0),%fp0	| ...LOAD INPUT
65
66	movel		(%a0),%d0
67	movew		4(%a0),%d0
68	andil		#0x7FFFFFFF,%d0
69	cmpil		#0x3FFF8000,%d0
70	bges		asinbig
71
72|--THIS IS THE USUAL CASE, |X| < 1
73|--ASIN(X) = ATAN( X / SQRT( (1-X)(1+X) ) )
74
75	fmoves		#0x3F800000,%fp1
76	fsubx		%fp0,%fp1		| ...1-X
77	fmovemx	%fp2-%fp2,-(%a7)
78	fmoves		#0x3F800000,%fp2
80	fmulx		%fp2,%fp1		| ...(1+X)(1-X)
81	fmovemx	(%a7)+,%fp2-%fp2
82	fsqrtx		%fp1		| ...SQRT([1-X][1+X])
83	fdivx		%fp1,%fp0		| ...X/SQRT([1-X][1+X])
84	fmovemx	%fp0-%fp0,(%a0)
85	bsr		satan
86	bra		t_frcinx
87
88asinbig:
89	fabsx		%fp0	 | ...|X|
90	fcmps		#0x3F800000,%fp0
91	fbgt		t_operr		|cause an operr exception
92
93|--|X| = 1, ASIN(X) = +- PI/2.
94
95	fmovex		PIBY2,%fp0
96	movel		(%a0),%d0
97	andil		#0x80000000,%d0	| ...SIGN BIT OF X
98	oril		#0x3F800000,%d0	| ...+-1 IN SGL FORMAT
99	movel		%d0,-(%sp)	| ...push SIGN(X) IN SGL-FMT
100	fmovel		%d1,%FPCR
101	fmuls		(%sp)+,%fp0
102	bra		t_frcinx
103
104	|end
```