1 | /* Round to integer generic implementation. |
2 | Copyright (C) 2019-2024 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Library General Public License as |
7 | published by the Free Software Foundation; either version 2 of the |
8 | License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Library General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Library General Public |
16 | License along with the GNU C Library; see the file COPYING.LIB. If |
17 | not, see <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #ifndef _ROUND_TO_INTEGER_H |
20 | #define _ROUND_TO_INTEGER_H |
21 | |
22 | #include <fenv_private.h> |
23 | |
24 | enum round_mode |
25 | { |
26 | CEIL, |
27 | FLOOR, |
28 | ROUND, |
29 | TRUNC, |
30 | NEARBYINT, |
31 | RINT |
32 | }; |
33 | |
34 | static inline fenv_t |
35 | set_fenv_mode (enum round_mode mode) |
36 | { |
37 | fenv_t fe = 0; |
38 | if (mode != RINT) |
39 | /* Save current FPU rounding mode and inexact state. */ |
40 | fe = fegetenv_register (); |
41 | |
42 | switch (mode) |
43 | { |
44 | case CEIL: |
45 | __fesetround_inline_nocheck (FE_UPWARD); |
46 | break; |
47 | case FLOOR: |
48 | __fesetround_inline_nocheck (FE_DOWNWARD); |
49 | break; |
50 | case TRUNC: |
51 | case ROUND: |
52 | __fesetround_inline_nocheck (FE_TOWARDZERO); |
53 | break; |
54 | case NEARBYINT: |
55 | /* Disable FE_INEXACT exception */ |
56 | reset_fpscr_bit (FPSCR_XE); |
57 | break; |
58 | case RINT: |
59 | break; |
60 | } |
61 | return fe; |
62 | } |
63 | |
64 | static inline void |
65 | reset_fenv_mode (fenv_t fe, enum round_mode mode) |
66 | { |
67 | switch (mode) |
68 | { |
69 | default: |
70 | __builtin_mtfsf (0xff, fe); |
71 | break; |
72 | case RINT: |
73 | break; |
74 | } |
75 | } |
76 | |
77 | static inline float |
78 | round_to_integer_float (enum round_mode mode, float x) |
79 | { |
80 | /* Ensure sNaN input is converted to qNaN. */ |
81 | if (__glibc_unlikely (isnan (x))) |
82 | return x + x; |
83 | |
84 | if (fabs (x: x) > 0x1p+23) |
85 | return x; |
86 | |
87 | float r = x; |
88 | |
89 | fenv_t fe = set_fenv_mode (mode); |
90 | if (x > 0.0) |
91 | { |
92 | /* IEEE 1003.1 round function. IEEE specifies "round to the nearest |
93 | integer value, rounding halfway cases away from zero, regardless of |
94 | the current rounding mode." However PowerPC Architecture defines |
95 | "Round to Nearest" as "Choose the best approximation. In case of a |
96 | tie, choose the one that is even (least significant bit o).". |
97 | So we can't use the PowerPC "Round to Nearest" mode. Instead we set |
98 | "Round toward Zero" mode and round by adding +-0.5 before rounding |
99 | to the integer value. */ |
100 | if (mode == ROUND) |
101 | r += 0.5f; |
102 | r += 0x1p+23; |
103 | r -= 0x1p+23; |
104 | r = fabs (x: r); |
105 | } |
106 | else if (x < 0.0) |
107 | { |
108 | if (mode == ROUND) |
109 | r -= 0.5f; |
110 | r -= 0x1p+23; |
111 | r += 0x1p+23; |
112 | r = -fabs (x: r); |
113 | } |
114 | reset_fenv_mode (fe, mode); |
115 | |
116 | return r; |
117 | } |
118 | |
119 | static inline double |
120 | round_to_integer_double (enum round_mode mode, double x) |
121 | { |
122 | /* Ensure sNaN input is converted to qNaN. */ |
123 | if (__glibc_unlikely (isnan (x))) |
124 | return x + x; |
125 | |
126 | if (fabs (x: x) > 0x1p+52) |
127 | return x; |
128 | |
129 | double r = x; |
130 | |
131 | /* Save current FPU rounding mode and inexact state. */ |
132 | fenv_t fe = set_fenv_mode (mode); |
133 | if (x > 0.0) |
134 | { |
135 | if (mode == ROUND) |
136 | r += 0.5; |
137 | r += 0x1p+52; |
138 | r -= 0x1p+52; |
139 | r = fabs (x: r); |
140 | } |
141 | else if (x < 0.0) |
142 | { |
143 | if (mode == ROUND) |
144 | r -= 0.5; |
145 | r -= 0x1p+52; |
146 | r += 0x1p+52; |
147 | r = -fabs (x: r); |
148 | } |
149 | reset_fenv_mode (fe, mode); |
150 | |
151 | return r; |
152 | } |
153 | |
154 | #endif |
155 | |