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ff8be6152b
Legacy encodings of SSE instructions incur AVX-SSE domain transition penalties on some Intel microarchitectures (e.g. Haswell, Broadwell). Using the VEX forms avoids these penatlies and keeps all instructions in the VEX decode domain. Use "%v" sequence to emit the "v" prefix for opcodes when compiling with -mavx. No functional changes intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Reviewed-by: Florian Weimer <fweimer@redhat.com> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
54 lines
1.6 KiB
C
54 lines
1.6 KiB
C
/* Set the FPU control word for x86.
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Copyright (C) 2003-2025 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 <math.h>
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#include <fpu_control.h>
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#include <fenv.h>
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#include <unistd.h>
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#include <ldsodefs.h>
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void
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__setfpucw (fpu_control_t set)
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{
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fpu_control_t cw;
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/* Fetch the current control word. */
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__asm__ ("fnstcw %0" : "=m" (cw));
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/* Preserve the reserved bits, and set the rest as the user
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specified (or the default, if the user gave zero). */
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cw &= _FPU_RESERVED;
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cw |= set & ~_FPU_RESERVED;
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__asm__ ("fldcw %0" : : "m" (cw));
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/* If the CPU supports SSE, we set the MXCSR as well. */
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if (CPU_FEATURE_USABLE (SSE))
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{
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unsigned int xnew_exc;
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/* Get the current MXCSR. */
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__asm__ ("%vstmxcsr %0" : "=m" (xnew_exc));
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xnew_exc &= ~((0xc00 << 3) | (FE_ALL_EXCEPT << 7));
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xnew_exc |= ((set & 0xc00) << 3) | ((set & FE_ALL_EXCEPT) << 7);
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__asm__ ("%vldmxcsr %0" : : "m" (xnew_exc));
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}
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}
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