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/* Implementation of gamma function according to ISO C.
Copyright (C) 1997, 1999, 2002, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <>, 1997 and
Jakub Jelinek <, 1999.
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
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 "quadmath-imp.h"
tgammaq (__float128 x)
/* We don't have a real gamma implementation now. We'll use lgamma
and the exp function. But due to the required boundary
conditions we must check some values separately. */
int64_t hx;
uint64_t lx;
__float128 res;
int sign;
GET_FLT128_WORDS64 (hx, lx, x);
if (((hx & 0x7fffffffffffffffLL) | lx) == 0)
/* Return value for x == 0 is Inf with divide by zero exception. */
return 1.0 / x;
if (hx < 0 && (uint64_t) hx < 0xffff000000000000ULL && rintq (x) == x)
/* Return value for integer x < 0 is NaN with invalid exception. */
return (x - x) / (x - x);
if (hx == 0xffff000000000000ULL && lx == 0)
/* x == -Inf. According to ISO this is NaN. */
return x - x;
/* XXX FIXME. */
res = expq (lgammaq (x));
return signbitq (x) ? -res : res;