1/* Set current rounding direction.
2 Copyright (C) 2001-2023 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 <fenv.h>
20
21int
22__fesetround (int round)
23{
24 unsigned short int cw;
25 int mxcsr;
26
27 if ((round & ~0xc00) != 0)
28 /* ROUND is no valid rounding mode. */
29 return 1;
30
31 /* First set the x87 FPU. */
32 asm ("fnstcw %0" : "=m" (*&cw));
33 cw &= ~0xc00;
34 cw |= round;
35 asm ("fldcw %0" : : "m" (*&cw));
36
37 /* And now the MSCSR register for SSE, the precision is at different bit
38 positions in the different units, we need to shift it 3 bits. */
39 asm ("stmxcsr %0" : "=m" (*&mxcsr));
40 mxcsr &= ~ 0x6000;
41 mxcsr |= round << 3;
42 asm ("ldmxcsr %0" : : "m" (*&mxcsr));
43
44 return 0;
45}
46libm_hidden_def (__fesetround)
47weak_alias (__fesetround, fesetround)
48libm_hidden_weak (fesetround)
49