1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
/* long double round function.
IBM extended format long double version.
Copyright (C) 2004, 2006 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <sysdep.h>
#include <math_ldbl_opt.h>
.section ".toc","aw"
.LC0: /* 2**52 */
.tc FD_43300000_0[TC],0x4330000000000000
.LC1: /* 0.5 */
.tc FD_3fe00000_0[TC],0x3fe0000000000000
.section ".text"
/* long double [fp1,fp2] roundl (long double x [fp1,fp2])
IEEE 1003.1 round function. IEEE specifies "round to the nearest
integer value, rounding halfway cases away from zero, regardless of
the current rounding mode." However PowerPC Architecture defines
"Round to Nearest" as "Choose the best approximation. In case of a
tie, choose the one that is even (least significant bit o).".
So we can't use the PowerPC "Round to Nearest" mode. Instead we set
"Round toward Zero" mode and round by adding +-0.5 before rounding
to the integer value. */
ENTRY (__roundl)
mffs fp11 /* Save current FPU rounding mode. */
lfd fp13,.LC0@toc(2)
fabs fp0,fp1
fabs fp9,fp2
fsub fp12,fp13,fp13 /* generate 0.0 */
fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */
fcmpu cr6,fp1,fp12 /* if (x > 0.0) */
bnl- cr7,.L2
mtfsfi 7,1 /* Set rounding mode toward 0. */
lfd fp10,.LC1@toc(2)
ble- cr6,.L1
fneg fp2,fp12
fadd fp1,fp1,fp10 /* x+= 0.5; */
fadd fp1,fp1,fp13 /* x+= TWO52; */
fsub fp1,fp1,fp13 /* x-= TWO52; */
fabs fp1,fp1 /* if (x == 0.0) x = 0.0; */
.L0:
mtfsf 0x01,fp11 /* restore previous rounding mode. */
blr
.L1:
fsub fp9,fp1,fp10 /* x-= 0.5; */
fneg fp2,fp12
bge- cr6,.L0 /* if (x < 0.0) */
fsub fp1,fp9,fp13 /* x-= TWO52; */
fadd fp1,fp1,fp13 /* x+= TWO52; */
fnabs fp1,fp1 /* if (x == 0.0) x = -0.0; */
mtfsf 0x01,fp11 /* restore previous rounding mode. */
blr
/* The high double is > TWO52 so we need to round the low double and
perhaps the high double. In this case we have to round the low
double and handle any adjustment to the high double that may be
caused by rounding (up). This is complicated by the fact that the
high double may already be rounded and the low double may have the
opposite sign to compensate.This gets a bit tricky so we use the
following algorithm:
tau = floor(x_high/TWO52);
x0 = x_high - tau;
x1 = x_low + tau;
r1 = rint(x1);
y_high = x0 + r1;
y_low = x0 - y_high + r1;
return y; */
.L2:
fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */
fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */
fcmpu cr5,fp2,fp12 /* if (x_low > 0.0) */
lfd fp10,.LC1@toc(2)
bgelr- cr7 /* return x; */
beqlr- cr0
mtfsfi 7,1 /* Set rounding mode toward 0. */
fdiv fp8,fp1,fp13 /* x_high/TWO52 */
bng- cr6,.L6 /* if (x > 0.0) */
fctidz fp0,fp8
fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
bng cr5,.L4 /* if (x_low > 0.0) */
fmr fp3,fp1
fmr fp4,fp2
b .L5
.L4: /* if (x_low < 0.0) */
fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
.L5:
fadd fp5,fp4,fp10 /* r1 = x1 + 0.5; */
fadd fp5,fp5,fp13 /* r1 = r1 + TWO52; */
fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */
b .L9
.L6: /* if (x < 0.0) */
fctidz fp0,fp8
fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
bnl cr5,.L7 /* if (x_low < 0.0) */
fmr fp3,fp1
fmr fp4,fp2
b .L8
.L7: /* if (x_low > 0.0) */
fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
.L8:
fsub fp5,fp4,fp10 /* r1 = x1 - 0.5; */
fsub fp5,fp5,fp13 /* r1-= TWO52; */
fadd fp5,fp5,fp13 /* r1+= TWO52; */
.L9:
mtfsf 0x01,fp11 /* restore previous rounding mode. */
fadd fp1,fp3,fp5 /* y_high = x0 + r1; */
fsub fp2,fp3,fp1 /* y_low = x0 - y_high + r1; */
fadd fp2,fp2,fp5
blr
END (__roundl)
long_double_symbol (libm, __roundl, roundl)
|
