| 0,0 → 1,47 |
|---|
| /* |
| * ==================================================== |
| * Copyright (C) 1998, 2002 by Red Hat Inc. All rights reserved. |
| * |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| #if !defined(_SOFT_FLOAT) |
| |
| /* |
| Fast version of pow using Intel float instructions. |
| |
| double _f_pow (double x, double y); |
| |
| Function calculates x to power of y. |
| The function optimizes the case where x is >0.0 and y is finite. |
| In such a case, there is no error checking or setting of errno. |
| All other cases defer to normal pow() function which will |
| set errno as normal. |
| */ |
| |
| #include <math.h> |
| #include <ieeefp.h> |
| #include "f_math.h" |
| |
| double _f_pow (double x, double y) |
| { |
| /* following sequence handles the majority of cases for pow() */ |
| if (x > 0.0 && check_finite(y)) |
| { |
| double result; |
| /* calculate x ** y as 2 ** (y log2(x)). On Intel, can only |
| raise 2 to an integer or a small fraction, thus, we have |
| to perform two steps 2**integer portion * 2**fraction. */ |
| asm ("fyl2x; fld %%st; frndint; fsub %%st,%%st(1);"\ |
| "fxch; fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1);"\ |
| "fmulp" : "=t" (result) : "0" (x), "u" (y) : "st(1)" ); |
| return result; |
| } |
| else /* all other strange cases, defer to normal pow() */ |
| return pow (x,y); |
| } |
| |
| #endif |