From 4482ff226e4b286ab171f3c5841ae1f7e61780cd Mon Sep 17 00:00:00 2001 From: "Paul E. Murphy" Date: Mon, 8 Aug 2016 15:58:28 -0500 Subject: Merge common usage of mul_split function A number of files share identical code for the mul_split function. This moves the duplicated function mul_split into its own header, and refactors the fma usage into a single selection macro. Likewise, mul_split when used by a long double implementation is renamed mul_splitl for clarity. --- math/mul_splitl.h | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 math/mul_splitl.h (limited to 'math/mul_splitl.h') diff --git a/math/mul_splitl.h b/math/mul_splitl.h new file mode 100644 index 0000000000..8a39ce0553 --- /dev/null +++ b/math/mul_splitl.h @@ -0,0 +1,50 @@ +/* Compute full X * Y for long double type. + Copyright (C) 2013-2016 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 + . */ + +#ifndef _MUL_SPLITL_H +#define _MUL_SPLITL_H + +#include + +/* Calculate X * Y exactly and store the result in *HI + *LO. It is + given that the values are small enough that no overflow occurs and + large enough (or zero) that no underflow occurs. */ + +static inline void +mul_splitl (long double *hi, long double *lo, long double x, long double y) +{ +#ifdef __FP_FAST_FMAL + /* Fast built-in fused multiply-add. */ + *hi = x * y; + *lo = __builtin_fmal (x, y, -*hi); +#else + /* Apply Dekker's algorithm. */ + *hi = x * y; +# define C ((1LL << (LDBL_MANT_DIG + 1) / 2) + 1) + long double x1 = x * C; + long double y1 = y * C; +# undef C + x1 = (x - x1) + x1; + y1 = (y - y1) + y1; + long double x2 = x - x1; + long double y2 = y - y1; + *lo = (((x1 * y1 - *hi) + x1 * y2) + x2 * y1) + x2 * y2; +#endif +} + +#endif /* _MUL_SPLITL_H */ -- cgit 1.4.1