libm/x86_64: implement some fenv functions

from glibc

Posted to uclibc:
http://lists.busybox.net/pipermail/uclibc/2010-December/044523.html

Signed-off-by: Natanael Copa <ncopa@alpinelinux.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/libm/x86_64/fclrexcpt.c b/libm/x86_64/fclrexcpt.c
new file mode 100644
index 000000000..4fc3bfbdc
--- /dev/null
+++ b/libm/x86_64/fclrexcpt.c
@@ -0,0 +1,52 @@
+/* Clear given exceptions in current floating-point environment.
+   Copyright (C) 2001 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <fenv.h>
+
+int
+feclearexcept (int excepts)
+{
+  fenv_t temp;
+  unsigned int mxcsr;
+
+  /* Mask out unsupported bits/exceptions.  */
+  excepts &= FE_ALL_EXCEPT;
+
+  /* Bah, we have to clear selected exceptions.  Since there is no
+     `fldsw' instruction we have to do it the hard way.  */
+  __asm__ ("fnstenv %0" : "=m" (*&temp));
+
+  /* Clear the relevant bits.  */
+  temp.__status_word &= excepts ^ FE_ALL_EXCEPT;
+
+  /* Put the new data in effect.  */
+  __asm__ ("fldenv %0" : : "m" (*&temp));
+
+  /* And the same procedure for SSE.  */
+  __asm__ ("stmxcsr %0" : "=m" (*&mxcsr));
+
+  /* Clear the relevant bits.  */
+  mxcsr &= ~excepts;
+
+  /* And put them into effect.  */
+  __asm__ ("ldmxcsr %0" : : "m" (*&mxcsr));
+
+  /* Success.  */
+  return 0;
+}