From 8a0efa53e44919bcf5ccb1d3353618a82afdf8bc Mon Sep 17 00:00:00 2001 From: Christopher Faylor Date: Thu, 17 Feb 2000 19:39:52 +0000 Subject: import newlib-2000-02-17 snapshot --- newlib/libc/machine/i386/f_pow.c | 44 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 newlib/libc/machine/i386/f_pow.c (limited to 'newlib/libc/machine/i386/f_pow.c') diff --git a/newlib/libc/machine/i386/f_pow.c b/newlib/libc/machine/i386/f_pow.c new file mode 100644 index 000000000..ac7dcfe26 --- /dev/null +++ b/newlib/libc/machine/i386/f_pow.c @@ -0,0 +1,44 @@ +/* + * ==================================================== + * Copyright (C) 1998 by Cygnus Solutions. All rights reserved. + * + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* +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 +#include +#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 ("fldl 8(%%ebp); fyl2x; fld %%st; frndint; fsub %%st,%%st(1);" \ + "fxch; fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1);"\ + "fmulp" : "=t" (result) : "0" (y)); + return result; + } + else /* all other strange cases, defer to normal pow() */ + return pow (x,y); +} + -- cgit v1.2.3