diff options
Diffstat (limited to 'sysdeps/ieee754/ldbl-128ibm/math_ldbl.h')
| -rw-r--r-- | sysdeps/ieee754/ldbl-128ibm/math_ldbl.h | 64 |
1 files changed, 61 insertions, 3 deletions
diff --git a/sysdeps/ieee754/ldbl-128ibm/math_ldbl.h b/sysdeps/ieee754/ldbl-128ibm/math_ldbl.h index 051352f9f7..ccb646620e 100644 --- a/sysdeps/ieee754/ldbl-128ibm/math_ldbl.h +++ b/sysdeps/ieee754/ldbl-128ibm/math_ldbl.h @@ -1,6 +1,23 @@ -#ifndef _MATH_PRIVATE_H_ -#error "Never use <math_ldbl.h> directly; include <math_private.h> instead." -#endif +/* Manipulation of the bit representation of 'long double' quantities. + Copyright (C) 2006-2018 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 + <http://www.gnu.org/licenses/>. */ + +#ifndef _MATH_LDBL_H_ +#define _MATH_LDBL_H_ 1 #include <ieee754.h> #include <stdint.h> @@ -230,3 +247,44 @@ ldbl_nearbyint (double a) } return a; } + +/* Canonicalize a result from an integer rounding function, in any + rounding mode. *A and *AA are finite and integers, with *A being + nonzero; if the result is not already canonical, *AA is plus or + minus a power of 2 that does not exceed the least set bit in + *A. */ +static inline void +ldbl_canonicalize_int (double *a, double *aa) +{ + /* Previously we used EXTRACT_WORDS64 from math_private.h, but in order + to avoid including internal headers we duplicate that code here. */ + uint64_t ax, aax; + union { double value; uint64_t word; } extractor; + extractor.value = *a; + ax = extractor.word; + extractor.value = *aa; + aax = extractor.word; + + int expdiff = ((ax >> 52) & 0x7ff) - ((aax >> 52) & 0x7ff); + if (expdiff <= 53) + { + if (expdiff == 53) + { + /* Half way between two double values; noncanonical iff the + low bit of A's mantissa is 1. */ + if ((ax & 1) != 0) + { + *a += 2 * *aa; + *aa = -*aa; + } + } + else + { + /* The sum can be represented in a single double. */ + *a += *aa; + *aa = 0; + } + } +} + +#endif /* math_ldbl.h */ |