1 /* Install given floating-point control modes.  x86_64 version.
2    Copyright (C) 2016-2022 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 <fenv.h>
20 #include <fpu_control.h>
21 
22 /* All exceptions, including the x86-specific "denormal operand"
23    exception.  */
24 #define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
25 
26 int
fesetmode(const femode_t * modep)27 fesetmode (const femode_t *modep)
28 {
29   fpu_control_t cw;
30   unsigned int mxcsr;
31   __asm__ ("stmxcsr %0" : "=m" (mxcsr));
32   /* Preserve SSE exception flags but restore other state in
33      MXCSR.  */
34   mxcsr &= FE_ALL_EXCEPT_X86;
35   if (modep == FE_DFL_MODE)
36     {
37       cw = _FPU_DEFAULT;
38       /* Default MXCSR state has all bits zero except for those
39 	 masking exceptions.  */
40       mxcsr |= FE_ALL_EXCEPT_X86 << 7;
41     }
42   else
43     {
44       cw = modep->__control_word;
45       mxcsr |= modep->__mxcsr & ~FE_ALL_EXCEPT_X86;
46     }
47   _FPU_SETCW (cw);
48   __asm__ ("ldmxcsr %0" : : "m" (mxcsr));
49   return 0;
50 }
51