1 /* long double round function.
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
28 .tc FD_3fe00000_0[TC],0x3fe0000000000000
31 /* long double [fp1,fp2] roundl (long double x [fp1,fp2])
32 IEEE 1003.1 round function. IEEE specifies "round to the nearest
33 integer value, rounding halfway cases away from zero, regardless of
34 the current rounding mode." However PowerPC Architecture defines
35 "Round to Nearest" as "Choose the best approximation. In case of a
36 tie, choose the one that is even (least significant bit o).".
37 So we can't use the PowerPC "Round to Nearest" mode. Instead we set
38 "Round toward Zero" mode and round by adding +-0.5 before rounding
39 to the integer value. */
42 mffs fp11 /* Save current FPU rounding mode. */
46 fsub fp12,fp13,fp13 /* generate 0.0 */
47 fcmpu cr7,fp0,fp13 /* if (fabs(x) > TWO52) */
48 fcmpu cr6,fp1,fp12 /* if (x > 0.0) */
50 mtfsfi 7,1 /* Set rounding mode toward 0. */
54 fadd fp1,fp1,fp10 /* x+= 0.5; */
55 fadd fp1,fp1,fp13 /* x+= TWO52; */
56 fsub fp1,fp1,fp13 /* x-= TWO52; */
57 fabs fp1,fp1 /* if (x == 0.0) x = 0.0; */
59 mtfsf 0x01,fp11 /* restore previous rounding mode. */
62 fsub fp9,fp1,fp10 /* x-= 0.5; */
64 bge- cr6,.L0 /* if (x < 0.0) */
65 fsub fp1,fp9,fp13 /* x-= TWO52; */
66 fadd fp1,fp1,fp13 /* x+= TWO52; */
67 fnabs fp1,fp1 /* if (x == 0.0) x = -0.0; */
68 mtfsf 0x01,fp11 /* restore previous rounding mode. */
71 /* The high double is > TWO52 so we need to round the low double and
72 perhaps the high double. In this case we have to round the low
73 double and handle any adjustment to the high double that may be
74 caused by rounding (up). This is complicated by the fact that the
75 high double may already be rounded and the low double may have the
76 opposite sign to compensate.This gets a bit tricky so we use the
79 tau = floor(x_high/TWO52);
84 y_low = x0 - y_high + r1;
87 fcmpu cr7,fp9,fp13 /* if (|x_low| > TWO52) */
88 fcmpu cr0,fp9,fp12 /* || (|x_low| == 0.0) */
89 fcmpu cr5,fp2,fp12 /* if (x_low > 0.0) */
91 bgelr- cr7 /* return x; */
93 mtfsfi 7,1 /* Set rounding mode toward 0. */
94 fdiv fp8,fp1,fp13 /* x_high/TWO52 */
96 bng- cr6,.L6 /* if (x > 0.0) */
98 fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
99 bng cr5,.L4 /* if (x_low > 0.0) */
103 .L4: /* if (x_low < 0.0) */
104 fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
105 fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
107 fadd fp5,fp4,fp10 /* r1 = x1 + 0.5; */
108 fadd fp5,fp5,fp13 /* r1 = r1 + TWO52; */
109 fsub fp5,fp5,fp13 /* r1 = r1 - TWO52; */
111 .L6: /* if (x < 0.0) */
113 fcfid fp8,fp0 /* tau = floor(x_high/TWO52); */
114 bnl cr5,.L7 /* if (x_low < 0.0) */
118 .L7: /* if (x_low > 0.0) */
119 fsub fp3,fp1,fp8 /* x0 = x_high - tau; */
120 fadd fp4,fp2,fp8 /* x1 = x_low + tau; */
122 fsub fp5,fp4,fp10 /* r1 = x1 - 0.5; */
123 fsub fp5,fp5,fp13 /* r1-= TWO52; */
124 fadd fp5,fp5,fp13 /* r1+= TWO52; */
126 mtfsf 0x01,fp11 /* restore previous rounding mode. */
127 fadd fp1,fp3,fp5 /* y_high = x0 + r1; */
128 fsub fp2,fp3,fp1 /* y_low = x0 - y_high + r1; */
133 long_double_symbol (libm, __roundl, roundl)