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authorWaldemar Brodkorb <wbx@uclibc-ng.org>2017-12-03 21:12:34 +0100
committerWaldemar Brodkorb <wbx@uclibc-ng.org>2017-12-03 21:12:34 +0100
commitedce88cfef2f2a62647c2ab9536ca29694fab292 (patch)
tree5cfc13c44a91bb8b983ee137de38e136289db81e /libm/x86_64/fesetround.c
parentc69db851309995c525b3993a10dc13dabdeb7b33 (diff)
x86_64: add fenv support from glibc
Diffstat (limited to 'libm/x86_64/fesetround.c')
-rw-r--r--libm/x86_64/fesetround.c44
1 files changed, 44 insertions, 0 deletions
diff --git a/libm/x86_64/fesetround.c b/libm/x86_64/fesetround.c
new file mode 100644
index 000000000..312bddf85
--- /dev/null
+++ b/libm/x86_64/fesetround.c
@@ -0,0 +1,44 @@
+/* Set current rounding direction.
+ Copyright (C) 2001-2017 Free Software Foundation, Inc.
+
+ 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, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <fenv.h>
+
+int
+fesetround (int round)
+{
+ unsigned short int cw;
+ int mxcsr;
+
+ if ((round & ~0xc00) != 0)
+ /* ROUND is no valid rounding mode. */
+ return 1;
+
+ /* First set the x87 FPU. */
+ __asm__ ("fnstcw %0" : "=m" (*&cw));
+ cw &= ~0xc00;
+ cw |= round;
+ __asm__ ("fldcw %0" : : "m" (*&cw));
+
+ /* And now the MSCSR register for SSE, the precision is at different bit
+ positions in the different units, we need to shift it 3 bits. */
+ __asm__ ("stmxcsr %0" : "=m" (*&mxcsr));
+ mxcsr &= ~ 0x6000;
+ mxcsr |= round << 3;
+ __asm__ ("ldmxcsr %0" : : "m" (*&mxcsr));
+
+ return 0;
+}