diff options
Diffstat (limited to 'sysdeps/i386/fpu/s_f32xsubf64.c')
| -rw-r--r-- | sysdeps/i386/fpu/s_f32xsubf64.c | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/sysdeps/i386/fpu/s_f32xsubf64.c b/sysdeps/i386/fpu/s_f32xsubf64.c new file mode 100644 index 0000000000..3f41acfdc9 --- /dev/null +++ b/sysdeps/i386/fpu/s_f32xsubf64.c @@ -0,0 +1,42 @@ +/* Subtract _Float64 values, converting the result to _Float32x. i386 version. + Copyright (C) 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/>. */ + +#include <math.h> +#include <fpu_control.h> +#include <math-narrow-eval.h> +#include <math_private.h> +#include <math-narrow.h> + +_Float32x +__f32xsubf64 (_Float64 x, _Float64 y) +{ + /* To avoid double rounding, set double precision for the subtraction. + math_narrow_eval is still needed to eliminate excess range in the + case of overflow. If the result of the subtraction is in the + subnormal range for double, it is exact, so no issues of double + rounding for subnormals arise. */ + fpu_control_t cw, cw_double; + _FPU_GETCW (cw); + cw_double = (cw & ~_FPU_EXTENDED) | _FPU_DOUBLE; + _FPU_SETCW (cw_double); + _Float32x ret = math_narrow_eval (x - y); + _FPU_SETCW (cw); + CHECK_NARROW_SUB (ret, x, y); + return ret; +} +libm_alias_float32x_float64 (sub) |