glibc/sysdeps/s390/fpu/s_lrint.c
Stefan Liebler e3f0762220 S390: Use convert-to-fixed instruction for lrint functions.
If compiled with z196 zarch support, the convert-to-fixed instruction
is used to implement lrint, lrintf, lrintl.
Otherwise the common-code implementation is used.
2019-12-11 15:12:22 +01:00

56 lines
1.9 KiB
C

/* lrint() - 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>
/* The sizeof (long int) differs between s390x (8byte) and s390 (4byte).
Thus we need different instructions as the target size is encoded there.
Note: On s390 this instruction is only used if build with -mzarch. */
# ifdef __s390x__
# define INSN "cgdbra"
# else
# define INSN "cfdbra"
# endif
long int
__lrint (double x)
{
long int y;
/* The z196 zarch "convert to fixed" (cgdbra) instruction is rounding
according to current rounding mode (M3-field: 0).
First convert x with suppressed inexact exception and check if the
resulting value is beyond the target limits (indicated by cc=3;
Note: a nan is also indicated by cc=3).
If the resulting value is within the target limits, redo
without suppressing the inexact exception. */
__asm__ (INSN " %0,0,%1,4 \n\t"
"jo 1f \n\t"
INSN " %0,0,%1,0 \n\t"
"1:"
: "=&d" (y) : "f" (x) : "cc");
return y;
}
libm_alias_double (__lrint, lrint)
#else
# include <sysdeps/ieee754/dbl-64/s_lrint.c>
#endif