S390: Use convert-to-fixed instruction for llround functions.

If compiled with z196 zarch support, the convert-to-fixed instruction
is used to implement llround, llroundf, llroundl.
Otherwise the common-code implementation is used.

sysdeps/s390/fpu/s_llround.c

@@ -0,0 +1,42 @@
+/* llround() - 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/>.  */
+
+#if defined __s390x__ && defined HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT
+/* We only support s390x as on s390 a long long int refers to a register pair
+   of two 4byte registers instead of a 8byte register which is produced by the
+   instruction.
+   Note: On s390 this instruction would only be used if build with -mzarch.  */
+# include <math.h>
+# include <libm-alias-double.h>
+
+long long int
+__llround (double x)
+{
+  long long int y;
+  /* The z196 zarch "convert to fixed" (cgdbra) instruction is rounding
+     x to the nearest integer with "ties away from 0" rounding mode
+     (M3-field: 1) where inexact exceptions are suppressed (M4-field: 4).  */
+  __asm__ ("cgdbra %0,1,%1,4" : "=d" (y) : "f" (x) : "cc");
+  return y;
+}
+libm_alias_double (__llround, llround)
+
+#else
+# include <sysdeps/ieee754/dbl-64/s_llround.c>
+#endif

sysdeps/s390/fpu/s_llroundf.c

@@ -0,0 +1,42 @@
+/* llroundf() - 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/>.  */
+
+#if defined __s390x__ && defined HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT
+/* We only support s390x as on s390 a long long int refers to a register pair
+   of two 4byte registers instead of a 8byte register which is produced by the
+   instruction.
+   Note: On s390 this instruction would only be used if build with -mzarch.  */
+# include <math.h>
+# include <libm-alias-float.h>
+
+long long int
+__llroundf (float x)
+{
+  long long int y;
+  /* The z196 zarch "convert to fixed" (cgebra) instruction is rounding
+     x to the nearest integer with "ties away from 0" rounding mode
+     (M3-field: 1) where inexact exceptions are suppressed (M4-field: 4).  */
+  __asm__ ("cgebra %0,1,%1,4" : "=d" (y) : "f" (x) : "cc");
+  return y;
+}
+libm_alias_float (__llround, llround)
+
+#else
+# include <sysdeps/ieee754/flt-32/s_llroundf.c>
+#endif

sysdeps/s390/fpu/s_llroundl.c

@@ -0,0 +1,43 @@
+/* llroundl() - 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/>.  */
+
+#if defined __s390x__ && defined HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT
+/* We only support s390x as on s390 a long long int refers to a register pair
+   of two 4byte registers instead of a 8byte register which is produced by the
+   instruction.
+   Note: On s390 this instruction would only be used if build with -mzarch.  */
+# include <math.h>
+# include <math_private.h>
+# include <libm-alias-ldouble.h>
+
+long long int
+__llroundl (_Float128 x)
+{
+  long long int y;
+  /* The z196 zarch "convert to fixed" (cgxbra) instruction is rounding
+     x to the nearest integer with "ties away from 0" rounding mode
+     (M3-field: 1) where inexact exceptions are suppressed (M4-field: 4).  */
+  __asm__ ("cgxbra %0,1,%1,4" : "=d" (y) : "f" (x) : "cc");
+  return y;
+}
+libm_alias_ldouble (__llround, llround)
+
+#else
+# include <sysdeps/ieee754/ldbl-128/s_llroundl.c>
+#endif