/*
|
/*
|
* ====================================================
|
* ====================================================
|
* Copyright (C) 1998, 2002 by Red Hat Inc. All rights reserved.
|
* Copyright (C) 1998, 2002 by Red Hat Inc. All rights reserved.
|
*
|
*
|
* Permission to use, copy, modify, and distribute this
|
* Permission to use, copy, modify, and distribute this
|
* software is freely granted, provided that this notice
|
* software is freely granted, provided that this notice
|
* is preserved.
|
* is preserved.
|
* ====================================================
|
* ====================================================
|
*/
|
*/
|
|
|
#if !defined(_SOFT_FLOAT)
|
#if !defined(_SOFT_FLOAT)
|
|
|
/*
|
/*
|
Fast version of pow using Intel float instructions.
|
Fast version of pow using Intel float instructions.
|
|
|
float _f_powf (float x, float y);
|
float _f_powf (float x, float y);
|
|
|
Function calculates x to power of y.
|
Function calculates x to power of y.
|
The function optimizes the case where x is >0.0 and y is finite.
|
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.
|
In such a case, there is no error checking or setting of errno.
|
All other cases defer to normal powf() function which will
|
All other cases defer to normal powf() function which will
|
set errno as normal.
|
set errno as normal.
|
*/
|
*/
|
|
|
#include <math.h>
|
#include <math.h>
|
#include <ieeefp.h>
|
#include <ieeefp.h>
|
#include "f_math.h"
|
#include "f_math.h"
|
|
|
float _f_powf (float x, float y)
|
float _f_powf (float x, float y)
|
{
|
{
|
/* following sequence handles the majority of cases for pow() */
|
/* following sequence handles the majority of cases for pow() */
|
if (x > 0.0 && check_finitef(y))
|
if (x > 0.0 && check_finitef(y))
|
{
|
{
|
float result;
|
float result;
|
/* calculate x ** y as 2 ** (y log2(x)). On Intel, can only
|
/* calculate x ** y as 2 ** (y log2(x)). On Intel, can only
|
raise 2 to an integer or a small fraction, thus, we have
|
raise 2 to an integer or a small fraction, thus, we have
|
to perform two steps 2**integer portion * 2**fraction. */
|
to perform two steps 2**integer portion * 2**fraction. */
|
asm ("flds 8(%%ebp); fyl2x; fld %%st; frndint; fsub %%st,%%st(1);" \
|
asm ("flds 8(%%ebp); fyl2x; fld %%st; frndint; fsub %%st,%%st(1);" \
|
"fxch; fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1);"\
|
"fxch; fchs; f2xm1; fld1; faddp; fxch; fld1; fscale; fstp %%st(1);"\
|
"fmulp" : "=t" (result) : "0" (y));
|
"fmulp" : "=t" (result) : "0" (y));
|
return result;
|
return result;
|
}
|
}
|
else /* all other strange cases, defer to normal pow() */
|
else /* all other strange cases, defer to normal pow() */
|
return powf (x,y);
|
return powf (x,y);
|
}
|
}
|
|
|
#endif
|
#endif
|
|
|
