1 | /* Return positive difference between arguments. i386 version. |
2 | Copyright (C) 1997-2022 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 Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the 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 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <errno.h> |
20 | #include <fpu_control.h> |
21 | #include <math.h> |
22 | #include <math-narrow-eval.h> |
23 | #include <libm-alias-double.h> |
24 | |
25 | double |
26 | __fdim (double x, double y) |
27 | { |
28 | if (islessequal (x, y)) |
29 | return 0.0; |
30 | |
31 | /* To avoid double rounding, set double precision for the |
32 | subtraction. math_narrow_eval is still needed to eliminate |
33 | excess range in the case of overflow. If the result of the |
34 | subtraction is in the subnormal range for double, it is exact, so |
35 | no issues of double rounding for subnormals arise. */ |
36 | fpu_control_t cw, cw_double; |
37 | _FPU_GETCW (cw); |
38 | cw_double = (cw & ~_FPU_EXTENDED) | _FPU_DOUBLE; |
39 | _FPU_SETCW (cw_double); |
40 | double r = math_narrow_eval (x - y); |
41 | _FPU_SETCW (cw); |
42 | if (isinf (r) && !isinf (x) && !isinf (y)) |
43 | __set_errno (ERANGE); |
44 | |
45 | return r; |
46 | } |
47 | libm_alias_double (__fdim, fdim) |
48 | |