m68k: Implement ndelay() based on the existing udelay() logic
[linux-3.10.git] / arch / m68k / fpsp040 / sacos.S
1 |
2 |       sacos.sa 3.3 12/19/90
3 |
4 |       Description: The entry point sAcos computes the inverse cosine of
5 |               an input argument; sAcosd does the same except for denormalized
6 |               input.
7 |
8 |       Input: Double-extended number X in location pointed to
9 |               by address register a0.
10 |
11 |       Output: The value arccos(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 sCOS takes approximately 310 cycles.
19 |
20 |       Algorithm:
21 |
22 |       ACOS
23 |       1. If |X| >= 1, go to 3.
24 |
25 |       2. (|X| < 1) Calculate acos(X) by
26 |               z := (1-X) / (1+X)
27 |               acos(X) = 2 * atan( sqrt(z) ).
28 |               Exit.
29 |
30 |       3. If |X| > 1, go to 5.
31 |
32 |       4. (|X| = 1) If X > 0, return 0. Otherwise, return Pi. Exit.
33 |
34 |       5. (|X| > 1) Generate an invalid operation by 0 * infinity.
35 |               Exit.
36 |
37
38 |               Copyright (C) Motorola, Inc. 1990
39 |                       All Rights Reserved
40 |
41 |       For details on the license for this file, please see the
42 |       file, README, in this same directory.
43
44 |SACOS  idnt    2,1 | Motorola 040 Floating Point Software Package
45
46         |section        8
47
48 PI:     .long 0x40000000,0xC90FDAA2,0x2168C235,0x00000000
49 PIBY2:  .long 0x3FFF0000,0xC90FDAA2,0x2168C235,0x00000000
50
51         |xref   t_operr
52         |xref   t_frcinx
53         |xref   satan
54
55         .global sacosd
56 sacosd:
57 |--ACOS(X) = PI/2 FOR DENORMALIZED X
58         fmovel          %d1,%fpcr               | ...load user's rounding mode/precision
59         fmovex          PIBY2,%fp0
60         bra             t_frcinx
61
62         .global sacos
63 sacos:
64         fmovex          (%a0),%fp0      | ...LOAD INPUT
65
66         movel           (%a0),%d0               | ...pack exponent with upper 16 fraction
67         movew           4(%a0),%d0
68         andil           #0x7FFFFFFF,%d0
69         cmpil           #0x3FFF8000,%d0
70         bges            ACOSBIG
71
72 |--THIS IS THE USUAL CASE, |X| < 1
73 |--ACOS(X) = 2 * ATAN(  SQRT( (1-X)/(1+X) )     )
74
75         fmoves          #0x3F800000,%fp1
76         faddx           %fp0,%fp1               | ...1+X
77         fnegx           %fp0            | ... -X
78         fadds           #0x3F800000,%fp0        | ...1-X
79         fdivx           %fp1,%fp0               | ...(1-X)/(1+X)
80         fsqrtx          %fp0            | ...SQRT((1-X)/(1+X))
81         fmovemx %fp0-%fp0,(%a0) | ...overwrite input
82         movel           %d1,-(%sp)      |save original users fpcr
83         clrl            %d1
84         bsr             satan           | ...ATAN(SQRT([1-X]/[1+X]))
85         fmovel          (%sp)+,%fpcr    |restore users exceptions
86         faddx           %fp0,%fp0               | ...2 * ATAN( STUFF )
87         bra             t_frcinx
88
89 ACOSBIG:
90         fabsx           %fp0
91         fcmps           #0x3F800000,%fp0
92         fbgt            t_operr         |cause an operr exception
93
94 |--|X| = 1, ACOS(X) = 0 OR PI
95         movel           (%a0),%d0               | ...pack exponent with upper 16 fraction
96         movew           4(%a0),%d0
97         cmpl            #0,%d0          |D0 has original exponent+fraction
98         bgts            ACOSP1
99
100 |--X = -1
101 |Returns PI and inexact exception
102         fmovex          PI,%fp0
103         fmovel          %d1,%FPCR
104         fadds           #0x00800000,%fp0        |cause an inexact exception to be put
105 |                                       ;into the 040 - will not trap until next
106 |                                       ;fp inst.
107         bra             t_frcinx
108
109 ACOSP1:
110         fmovel          %d1,%FPCR
111         fmoves          #0x00000000,%fp0
112         rts                             |Facos ; of +1 is exact
113
114         |end