1 /* Install given floating-point environment.
2 Copyright (C) 1997-2023 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 #include <fpu_control.h>
21 #include <assert.h>
22 #include <unistd.h>
23 #include <ldsodefs.h>
24 #include <dl-procinfo.h>
25
26
27 /* All exceptions, including the x86-specific "denormal operand"
28 exception. */
29 #define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
30
31
32 int
33 __fesetenv (const fenv_t *envp)
34 {
35 fenv_t temp;
36
37 /* The memory block used by fstenv/fldenv has a size of 28 bytes. */
38 assert (sizeof (fenv_t) == 28);
39
40 /* Install the environment specified by ENVP. But there are a few
41 values which we do not want to come from the saved environment.
42 Therefore, we get the current environment and replace the values
43 we want to use from the environment specified by the parameter. */
44 __asm__ ("fnstenv %0" : "=m" (*&temp));
45
46 if (envp == FE_DFL_ENV)
47 {
48 temp.__control_word |= FE_ALL_EXCEPT_X86;
49 temp.__control_word &= ~FE_TOWARDZERO;
50 temp.__control_word |= _FPU_EXTENDED;
51 temp.__status_word &= ~FE_ALL_EXCEPT_X86;
52 }
53 else if (envp == FE_NOMASK_ENV)
54 {
55 temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
56 /* Keep the "denormal operand" exception masked. */
57 temp.__control_word |= __FE_DENORM;
58 temp.__control_word |= _FPU_EXTENDED;
59 temp.__status_word &= ~FE_ALL_EXCEPT_X86;
60 }
61 else
62 {
63 temp.__control_word &= ~(FE_ALL_EXCEPT_X86
64 | FE_TOWARDZERO
65 | _FPU_EXTENDED);
66 temp.__control_word |= (envp->__control_word
67 & (FE_ALL_EXCEPT_X86
68 | FE_TOWARDZERO
69 | _FPU_EXTENDED));
70 temp.__status_word &= ~FE_ALL_EXCEPT_X86;
71 temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT_X86;
72 }
73 temp.__eip = 0;
74 temp.__cs_selector = 0;
75 temp.__opcode = 0;
76 temp.__data_offset = 0;
77 temp.__data_selector = 0;
78
79 __asm__ ("fldenv %0" : : "m" (temp));
80
81 if (CPU_FEATURE_USABLE (SSE))
82 {
83 unsigned int mxcsr;
84 __asm__ ("stmxcsr %0" : "=m" (mxcsr));
85
86 if (envp == FE_DFL_ENV)
87 {
88 /* Clear SSE exceptions. */
89 mxcsr &= ~FE_ALL_EXCEPT_X86;
90 /* Set mask for SSE MXCSR. */
91 mxcsr |= (FE_ALL_EXCEPT_X86 << 7);
92 /* Set rounding to FE_TONEAREST. */
93 mxcsr &= ~0x6000;
94 mxcsr |= (FE_TONEAREST << 3);
95 /* Clear the FZ and DAZ bits. */
96 mxcsr &= ~0x8040;
97 }
98 else if (envp == FE_NOMASK_ENV)
99 {
100 /* Clear SSE exceptions. */
101 mxcsr &= ~FE_ALL_EXCEPT_X86;
102 /* Do not mask exceptions. */
103 mxcsr &= ~(FE_ALL_EXCEPT << 7);
104 /* Keep the "denormal operand" exception masked. */
105 mxcsr |= (__FE_DENORM << 7);
106 /* Set rounding to FE_TONEAREST. */
107 mxcsr &= ~0x6000;
108 mxcsr |= (FE_TONEAREST << 3);
109 /* Clear the FZ and DAZ bits. */
110 mxcsr &= ~0x8040;
111 }
112 else
113 mxcsr = envp->__eip;
114
115 __asm__ ("ldmxcsr %0" : : "m" (mxcsr));
116 }
117
118 /* Success. */
119 return 0;
120 }
121
122 #include <shlib-compat.h>
123 #if SHLIB_COMPAT (libm, GLIBC_2_1, GLIBC_2_2)
124 strong_alias (__fesetenv, __old_fesetenv)
125 compat_symbol (libm, __old_fesetenv, fesetenv, GLIBC_2_1);
126 #endif
127
128 libm_hidden_def (__fesetenv)
129 libm_hidden_ver (__fesetenv, fesetenv)
130 versioned_symbol (libm, __fesetenv, fesetenv, GLIBC_2_2);