diff options
author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/i386/math-emu/poly_2xm1.c |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'arch/i386/math-emu/poly_2xm1.c')
-rw-r--r-- | arch/i386/math-emu/poly_2xm1.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/arch/i386/math-emu/poly_2xm1.c b/arch/i386/math-emu/poly_2xm1.c new file mode 100644 index 000000000000..9766ad5e9743 --- /dev/null +++ b/arch/i386/math-emu/poly_2xm1.c | |||
@@ -0,0 +1,156 @@ | |||
1 | /*---------------------------------------------------------------------------+ | ||
2 | | poly_2xm1.c | | ||
3 | | | | ||
4 | | Function to compute 2^x-1 by a polynomial approximation. | | ||
5 | | | | ||
6 | | Copyright (C) 1992,1993,1994,1997 | | ||
7 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia | | ||
8 | | E-mail billm@suburbia.net | | ||
9 | | | | ||
10 | | | | ||
11 | +---------------------------------------------------------------------------*/ | ||
12 | |||
13 | #include "exception.h" | ||
14 | #include "reg_constant.h" | ||
15 | #include "fpu_emu.h" | ||
16 | #include "fpu_system.h" | ||
17 | #include "control_w.h" | ||
18 | #include "poly.h" | ||
19 | |||
20 | |||
21 | #define HIPOWER 11 | ||
22 | static const unsigned long long lterms[HIPOWER] = | ||
23 | { | ||
24 | 0x0000000000000000LL, /* This term done separately as 12 bytes */ | ||
25 | 0xf5fdeffc162c7543LL, | ||
26 | 0x1c6b08d704a0bfa6LL, | ||
27 | 0x0276556df749cc21LL, | ||
28 | 0x002bb0ffcf14f6b8LL, | ||
29 | 0x0002861225ef751cLL, | ||
30 | 0x00001ffcbfcd5422LL, | ||
31 | 0x00000162c005d5f1LL, | ||
32 | 0x0000000da96ccb1bLL, | ||
33 | 0x0000000078d1b897LL, | ||
34 | 0x000000000422b029LL | ||
35 | }; | ||
36 | |||
37 | static const Xsig hiterm = MK_XSIG(0xb17217f7, 0xd1cf79ab, 0xc8a39194); | ||
38 | |||
39 | /* Four slices: 0.0 : 0.25 : 0.50 : 0.75 : 1.0, | ||
40 | These numbers are 2^(1/4), 2^(1/2), and 2^(3/4) | ||
41 | */ | ||
42 | static const Xsig shiftterm0 = MK_XSIG(0, 0, 0); | ||
43 | static const Xsig shiftterm1 = MK_XSIG(0x9837f051, 0x8db8a96f, 0x46ad2318); | ||
44 | static const Xsig shiftterm2 = MK_XSIG(0xb504f333, 0xf9de6484, 0x597d89b3); | ||
45 | static const Xsig shiftterm3 = MK_XSIG(0xd744fcca, 0xd69d6af4, 0x39a68bb9); | ||
46 | |||
47 | static const Xsig *shiftterm[] = { &shiftterm0, &shiftterm1, | ||
48 | &shiftterm2, &shiftterm3 }; | ||
49 | |||
50 | |||
51 | /*--- poly_2xm1() -----------------------------------------------------------+ | ||
52 | | Requires st(0) which is TAG_Valid and < 1. | | ||
53 | +---------------------------------------------------------------------------*/ | ||
54 | int poly_2xm1(u_char sign, FPU_REG *arg, FPU_REG *result) | ||
55 | { | ||
56 | long int exponent, shift; | ||
57 | unsigned long long Xll; | ||
58 | Xsig accumulator, Denom, argSignif; | ||
59 | u_char tag; | ||
60 | |||
61 | exponent = exponent16(arg); | ||
62 | |||
63 | #ifdef PARANOID | ||
64 | if ( exponent >= 0 ) /* Don't want a |number| >= 1.0 */ | ||
65 | { | ||
66 | /* Number negative, too large, or not Valid. */ | ||
67 | EXCEPTION(EX_INTERNAL|0x127); | ||
68 | return 1; | ||
69 | } | ||
70 | #endif /* PARANOID */ | ||
71 | |||
72 | argSignif.lsw = 0; | ||
73 | XSIG_LL(argSignif) = Xll = significand(arg); | ||
74 | |||
75 | if ( exponent == -1 ) | ||
76 | { | ||
77 | shift = (argSignif.msw & 0x40000000) ? 3 : 2; | ||
78 | /* subtract 0.5 or 0.75 */ | ||
79 | exponent -= 2; | ||
80 | XSIG_LL(argSignif) <<= 2; | ||
81 | Xll <<= 2; | ||
82 | } | ||
83 | else if ( exponent == -2 ) | ||
84 | { | ||
85 | shift = 1; | ||
86 | /* subtract 0.25 */ | ||
87 | exponent--; | ||
88 | XSIG_LL(argSignif) <<= 1; | ||
89 | Xll <<= 1; | ||
90 | } | ||
91 | else | ||
92 | shift = 0; | ||
93 | |||
94 | if ( exponent < -2 ) | ||
95 | { | ||
96 | /* Shift the argument right by the required places. */ | ||
97 | if ( FPU_shrx(&Xll, -2-exponent) >= 0x80000000U ) | ||
98 | Xll++; /* round up */ | ||
99 | } | ||
100 | |||
101 | accumulator.lsw = accumulator.midw = accumulator.msw = 0; | ||
102 | polynomial_Xsig(&accumulator, &Xll, lterms, HIPOWER-1); | ||
103 | mul_Xsig_Xsig(&accumulator, &argSignif); | ||
104 | shr_Xsig(&accumulator, 3); | ||
105 | |||
106 | mul_Xsig_Xsig(&argSignif, &hiterm); /* The leading term */ | ||
107 | add_two_Xsig(&accumulator, &argSignif, &exponent); | ||
108 | |||
109 | if ( shift ) | ||
110 | { | ||
111 | /* The argument is large, use the identity: | ||
112 | f(x+a) = f(a) * (f(x) + 1) - 1; | ||
113 | */ | ||
114 | shr_Xsig(&accumulator, - exponent); | ||
115 | accumulator.msw |= 0x80000000; /* add 1.0 */ | ||
116 | mul_Xsig_Xsig(&accumulator, shiftterm[shift]); | ||
117 | accumulator.msw &= 0x3fffffff; /* subtract 1.0 */ | ||
118 | exponent = 1; | ||
119 | } | ||
120 | |||
121 | if ( sign != SIGN_POS ) | ||
122 | { | ||
123 | /* The argument is negative, use the identity: | ||
124 | f(-x) = -f(x) / (1 + f(x)) | ||
125 | */ | ||
126 | Denom.lsw = accumulator.lsw; | ||
127 | XSIG_LL(Denom) = XSIG_LL(accumulator); | ||
128 | if ( exponent < 0 ) | ||
129 | shr_Xsig(&Denom, - exponent); | ||
130 | else if ( exponent > 0 ) | ||
131 | { | ||
132 | /* exponent must be 1 here */ | ||
133 | XSIG_LL(Denom) <<= 1; | ||
134 | if ( Denom.lsw & 0x80000000 ) | ||
135 | XSIG_LL(Denom) |= 1; | ||
136 | (Denom.lsw) <<= 1; | ||
137 | } | ||
138 | Denom.msw |= 0x80000000; /* add 1.0 */ | ||
139 | div_Xsig(&accumulator, &Denom, &accumulator); | ||
140 | } | ||
141 | |||
142 | /* Convert to 64 bit signed-compatible */ | ||
143 | exponent += round_Xsig(&accumulator); | ||
144 | |||
145 | result = &st(0); | ||
146 | significand(result) = XSIG_LL(accumulator); | ||
147 | setexponent16(result, exponent); | ||
148 | |||
149 | tag = FPU_round(result, 1, 0, FULL_PRECISION, sign); | ||
150 | |||
151 | setsign(result, sign); | ||
152 | FPU_settag0(tag); | ||
153 | |||
154 | return 0; | ||
155 | |||
156 | } | ||