1 | /* Round to nearest integer. PowerPC64 version. |
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 | #define NO_MATH_REDIRECT |
20 | #define lroundf __redirect_llround |
21 | #define __lroundf __redirect___lround |
22 | #include <math.h> |
23 | #undef lroundf |
24 | #undef __lroundf |
25 | #include <libm-alias-float.h> |
26 | #include <math-barriers.h> |
27 | |
28 | long long int |
29 | __llroundf (float x) |
30 | { |
31 | #ifdef _ARCH_PWR5X |
32 | double r = __builtin_round (x); |
33 | /* Prevent gcc from calling llround directly when compiled with |
34 | -fno-math-errno by inserting a barrier. */ |
35 | math_opt_barrier (r); |
36 | return r; |
37 | #else |
38 | /* IEEE 1003.1 llroundf function. IEEE specifies "roundf to the nearest |
39 | integer value, rounding halfway cases away from zero, regardless of |
40 | the current rounding mode." However PowerPC Architecture defines |
41 | "roundf to Nearest" as "Choose the best approximation. In case of a |
42 | tie, choose the one that is even (least significant bit o).". |
43 | So we can't use the PowerPC "round to Nearest" mode. Instead we set |
44 | "round toward Zero" mode and round by adding +-0.5 before rounding |
45 | to the integer value. |
46 | |
47 | It is necessary to detect when x is (+-)0x1.fffffffffffffp-2 |
48 | because adding +-0.5 in this case will cause an erroneous shift, |
49 | carry and round. We simply return 0 if 0.5 > x > -0.5. Likewise |
50 | if x is and odd number between +-(2^23 and 2^24-1) a shift and |
51 | carry will erroneously round if biased with +-0.5. Therefore if x |
52 | is greater/less than +-2^23 we don't need to bias the number with |
53 | +-0.5. */ |
54 | |
55 | float ax = fabsf (x: x); |
56 | |
57 | if (ax < 0.5f) |
58 | return 0; |
59 | |
60 | if (ax < 0x1p+23f) |
61 | { |
62 | /* Test whether an integer to avoid spurious "inexact". */ |
63 | float t = ax + 0x1p+23f; |
64 | t = t - 0x1p+23f; |
65 | if (ax != t) |
66 | { |
67 | ax = ax + 0.5f; |
68 | if (x < 0.0f) |
69 | ax = -fabs (x: ax); |
70 | x = ax; |
71 | } |
72 | } |
73 | |
74 | long int ret; |
75 | __asm__ ("fctidz %0, %1" : "=d" (ret) : "d" (x)); |
76 | return ret; |
77 | #endif |
78 | } |
79 | #ifndef __llroundf |
80 | strong_alias (__llroundf, __lroundf) |
81 | libm_alias_float (__llround, lround) |
82 | libm_alias_float (__llround, llround) |
83 | #endif |
84 | |