49 lines
1.5 KiB
C
49 lines
1.5 KiB
C
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/* Set current rounding direction.
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Copyright (C) 2001-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <fenv.h>
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int
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__fesetround (int round)
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{
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unsigned short int cw;
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int mxcsr;
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if ((round & ~0xc00) != 0)
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/* ROUND is no valid rounding mode. */
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return 1;
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/* First set the x87 FPU. */
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asm ("fnstcw %0" : "=m" (*&cw));
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cw &= ~0xc00;
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cw |= round;
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asm ("fldcw %0" : : "m" (*&cw));
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/* And now the MSCSR register for SSE, the precision is at different bit
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positions in the different units, we need to shift it 3 bits. */
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asm ("stmxcsr %0" : "=m" (*&mxcsr));
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mxcsr &= ~ 0x6000;
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mxcsr |= round << 3;
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asm ("ldmxcsr %0" : : "m" (*&mxcsr));
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return 0;
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}
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libm_hidden_def (__fesetround)
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weak_alias (__fesetround, fesetround)
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libm_hidden_weak (fesetround)
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