S390: Use load-fp-integer instruction for roundeven functions.

If compiled with z196 zarch support, the load-fp-integer instruction
is used to implement roundeven, roundevenf, roundevenl.
Otherwise the common-code implementation is used.

1 files changed, 39 insertions, 0 deletions

diff --git a/sysdeps/s390/fpu/s_roundeven.c b/sysdeps/s390/fpu/s_roundeven.c
new file mode 100644
index 0000000000..95a83a70e8
--- /dev/null
+++ b/sysdeps/s390/fpu/s_roundeven.c
@@ -0,0 +1,39 @@
+/* roundeven() - S390 version.
+   Copyright (C) 2019 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, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifdef HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT
+# include <math.h>
+# include <libm-alias-double.h>
+
+double
+__roundeven (double x)
+{
+  double y;
+  /* The z196 zarch "load fp integer" (fidbra) instruction is rounding
+     x to the nearest integer with "ties to even" rounding mode
+     (M3-field: 4) where inexact exceptions are suppressed (M4-field: 4).  */
+  __asm__ ("fidbra %0,4,%1,4" : "=f" (y) : "f" (x));
+  return y;
+}
+hidden_def (__roundeven)
+libm_alias_double (__roundeven, roundeven)
+
+#else
+# include <sysdeps/ieee754/dbl-64/s_roundeven.c>
+#endif