1 /* nearbyint long double.
2 IBM extended format long double version.
3 Copyright (C) 2004, 2006 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
22 #include <math_ldbl_opt.h>
26 .tc FD_43300000_0[TC],0x4330000000000000
29 /* long double [fp1,fp2] nearbyintl (long double x [fp1,fp2])
30 IEEE 1003.1 nearbyintl function. nearbyintl is simular to the rintl
31 but does raise the "inexact" exception. This implementation is
32 based on rintl but explicitly maskes the inexact exception on entry
33 and clears any pending inexact before restoring the exception mask
36 PowerPC64 long double uses the IBM extended format which is
37 represented two 64-floating point double values. The values are
38 non-overlapping giving an effective precision of 106 bits. The first
39 double contains the high order bits of mantisa and is always rounded
40 to represent a normal rounding of long double to double. Since the
41 long double value is sum of the high and low values, the low double
42 normally has the opposite sign to compensate for the this rounding.
44 For long double there are two cases:
45 1) |x| < 2**52, all the integer bits are in the high double.
46 floor the high double and set the low double to -0.0.
47 2) |x| >= 2**52, Rounding involves both doubles.
48 See the comment before lable .L2 for details.
51 mffs fp11 /* Save current FPSCR. */
54 mtfsb0 28 /* Disable "inexact" exceptions. */
55 fsub fp12,fp13,fp13 /* generate 0.0 */
57 fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */
58 fcmpu cr6,fp1,fp12 /* if (x > 0.0) */
62 fadd fp1,fp1,fp13 /* x+= TWO52; */
63 fsub fp1,fp1,fp13 /* x-= TWO52; */
66 bnl- cr6,.L9 /* if (x < 0.0) */
67 fsub fp1,fp13,fp1 /* x = TWO52 - x; */
68 fsub fp0,fp1,fp13 /* x = - (x - TWO52); */
71 mtfsb0 6 /* Clear any pending "inexact" exceptions. */
72 mtfsf 0x01,fp11 /* restore exception mask. */
75 /* The high double is > TWO52 so we need to round the low double and
76 perhaps the high double. This gets a bit tricky so we use the
79 tau = floor(x_high/TWO52);
87 fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */
88 fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */
89 bge- cr7,.L9 /* return x; */
91 fdiv fp8,fp1,fp13 /* x_high/TWO52 */
93 fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
94 fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
95 fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
97 fcmpu cr6,fp4,fp12 /* if (x1 > 0.0) */
99 fadd fp5,fp4,fp13 /* r1 = x1 + TWO52; */
100 fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */
104 bge- cr6,.L6 /* if (x1 < 0.0) */
105 fsub fp5,fp13,fp4 /* r1 = TWO52 - x1; */
106 fsub fp0,fp5,fp13 /* r1 = - (r1 - TWO52); */
109 fadd fp1,fp3,fp5 /* y_high = x0 + r1; */
110 fsub fp2,fp5,fp8 /* y_low = r1 - tau; */
114 long_double_symbol (libm, __nearbyintl, nearbyintl)